Do small mammals affect plant diversity?Do small mammals affect plant diversity? Field studiesin...

University of Münster

Department of Behavioural biology

Diploma thesis

Presented by

Christina Keller

- April 2005 -

Do small mammals affect plant diversity?

Field studies in Namaqualand, South Africa, a biodiversity-hotspot

University of Münster

Department of Behavioural biology

Diploma thesis

Presented by

Christina Keller

- April 2005 -

Do small mammals affect plant diversity?

Field studies in Namaqualand, South Africa, a biodiversity-hotspot

Contents I

1.1. Abstract...........................................................................................................1

1.2. Zusammenfassung.........................................................................................2

2. Introduction .......................................................................................................3

3. Subjects, Material and Methods.......................................................................9

3.1. Study area....................................................................................................9

3.2. Animals ......................................................................................................11

3.3. Correlation between small mammals and plants........................................14

3.3.1. Trapping............................................................................................14

3.3.2. Vegetation survey .............................................................................14

3.3.3. Soil samples .....................................................................................16

3.3.4. Altitude..............................................................................................17

3.3.5. Rainfall..............................................................................................17

3.3.6. Statistics ...........................................................................................17

3.4. Food Preference tests................................................................................18

3.5. Plant biodiversity around bush Karoo rat nests ..........................................19

3.6. Fence line...................................................................................................20

4. Results .............................................................................................................22

4.1. Correlation between small mammals and plants........................................22

4.1.1. Comparison between winter and summer.........................................22

4.1.2. Winter trapping season .....................................................................24

4.1.3. Summer trapping season..................................................................26

4.1.4. Correlation between plant cover and small mammals.......................29

4.1.5. Soil survey ........................................................................................29

4.1.6. Cluster-analyses ...............................................................................32

4.1.7. General linear model.........................................................................32

4.2. Food Preference tests................................................................................34

Contents II

4.2.1. Pilot study .........................................................................................34

4.2.1.1. Striped mouse (R. pumilio) ....................................................34

4.2.1.2. bush-Karoo rat (O. unisulcatus).............................................34

4.2.2. Second set of tests ...........................................................................35

4.2.2.1. Striped mouse (R. pumilio) ....................................................35

4.2.2.2. bush-Karoo rat (O. unisulcatus).............................................36

4.3. Plant biodiversity around bush Karoo rat nests ..........................................37

4.4. Fence line...................................................................................................38

5. Discussion .......................................................................................................39

5.1 Correlation between small mammals and plants.........................................39

5.2. Food-preference-tests................................................................................42

5.2.1. Pilot study .........................................................................................43

5.2.2. Second set of tests ...........................................................................43

5.3. Plant diversity around bush-Karoo rat nests...............................................44

5.4. Other factors that might influence plant biodiversity...................................45

5.5. Fence line...................................................................................................47

6. Conclusions.....................................................................................................50

7. References .......................................................................................................51

8. Appendix ..........................................................................................................57

9. Acknowledgements.........................................................................................66

Abstract 1

1.1. Abstract

The conservation of species is one of the most important duties of our century.

Basic ecological knowledge is essential in order to perform it. Conservation is

particularly effective in hotspots of biodiversity, because many species can be

protected here at the same time in a relative small area. One of these biodiversity

hotspots is the Succulent Karoo in southern Africa, which holds an extraordinary

high number of plant species. Small mammals are abundant in the Succulent

Karoo and might be of crucial importance as herbivores in this ecosystem. For the

first time the influence of small mammals on plant diversity was investigated in my

study. It is known from earlier studies that herbivores can increase floral diversity

by reducing dominant plant species and thus providing space for subdominant

species, which would be outcompeted otherwise. In a correlative study I tested if

this mechanism might exist in the Succulent Karoo. The plant diversity in 10

ecological different study sites in Goegap Nature Reserve was correlated with the

number of small mammals living there. Additionally two rodent species

(Rhabdomys pumilio and Otomys unisulcatus) were taken as example-species

and tested in food-preference-tests for a preference for subdominant or dominant

plant species. Additionally the influence of O. unisulcatus on the plant community

surrounding their nests was also investigated. I found several positive correlations

between plant diversity and the number of individuals and especially the species

number of small mammals. The direct surroundings of occupied O. unisulcatus

nests showed a significantly higher plant diversity than control areas, although

food-preference tests revealed that O. unisulcatus prefers subdominant food-

plants. In the contrary R. pumilio preferred dominant food-plants. All in all this

results indicate a distinct influence of small mammals on plant diversity. The

results of my study are of great importance for conservation programs in the

Succulent Karoo in which small mammals should be included in the future.

Zusammenfassung 2

1.2. Zusammenfassung

Artenschutz ist eine der wichtigsten Aufgaben unserer Zeit. Für seine

Durchführung ist ökologisches Basiswissen zwingend erforderlich. Besonders

effektiv ist Artenschutz an Schwerpunkten der Artenvielfalt (Biodiversität), denn

hier lassen sich viele Arten gleichzeitig und auf kleinem Raum schützen. Einer

dieser Biodiversitätshotspots ist die Sukkulentenkaroo im südlichen Afrika, die sich

im Besonderen durch ihre extrem artenreiche Flora auszeichnet. Kleinsäuger sind

hier als Pflanzenfresser von großer Bedeutung. Erstmals wurde in dieser Studie

der Einfluss von Kleinsäugern auf die Artenvielfalt der Pflanzen in der

Sukkulentenkaroo untersucht. Es ist aus andern Studien bekannt, dass

Pflanzenfresser einen positiven Einfluss auf die Diversität ihrer Futterpflanzen

haben können, indem sie dominante Pflanzenarten reduzieren und auf diese

Weise Platz für subdominante Arten schaffen, die andernfalls verdrängt würden.

Ob dies in der Sukkulentenkaroo der Fall ist wurde mit einer korrelativen Studie

untersucht. Die Pflanzendiversität an 10 ökologisch verschiedenen

Untersuchungsgebieten im Goegap Nature Reserve wurde mit den dort lebenden

Kleinsäugern in Zusammenhang gebracht. Zusätzlich wurde mit Futter-Präferenz-

Tests exemplarisch an zwei Nagerarten (Rhabdomys pumilio, Otomys unisulcatus)

getestet ob sie dominante Futterpflanzen bevorzugt fressen. Bei einer dieser Arten

wurde außerdem ihr Einfluss auf die Pflanzendiversität in unmittelbarer Umgebung

ihres Nestes untersucht. Es wurden mehrfach positive Korrelationen zwischen der

Anzahl der Kleinsäugerindividuen und besonders der Anzahl ihrer Arten und der

Pflanzendiversität gefunden. Dieser Zusammenhang war im Winter deutlicher als

im Sommer. Im Vergleich zu unbewohnten Gebieten wurden in unmittelbarer

Umgebung von bewohnten Otomys unisulcatus-Nestern signifikant mehr Pflanzen

gefunden, obwohl Futter-Präferenz-Tests zeigten, dass diese Art subdominante

Pflanzenarten bevorzugt. Rhabdomys pumilio hingegen bevorzugte dominante

Futterpflanzen. Diese Ergebnisse zeigen einen deutlichen Einfluss von

Kleinsäugern auf die Diversität der Pflanzen ihrer Umgebung. Der ökologische

Hintergrund ist von großer Bedeutung für Artenschutzprogramme in diesem

gefährdeten Gebiet, in die Kleinsäuger in Zukunft einbezogen werden sollten.

Introduction 3

2. Introduction

The phenomenon of biodiversity is one of the most fascinating in biology. In this

study biodiversity is understood as the number of different species in a certain

area without regards to endemism or abundance. When Darwin first described the

process of evolution, biologists began to understand the scientific basis of

diversity. In the process of adaptive radiation and adaptation to ecological niches,

evolution created numerous different species of plants and animals. But these

species are not distributed evenly over the planet.

In 2000 Myers et al identified 25 hotspots of biodiversity. These areas were

chosen for their species richness, endemism, taxonomic uniqueness, unusual

ecological or evolutionary phenomena and global rarity. Myers et al. saw the

identification of diversity hotspots as a tool for the improvement of conservation

management. All the hotspots are facing extreme threats from human interference.

As conservation budgets are insufficient given the number of species threatened

with extinction it is highly important to be able to support the greatest number of

species at the least cost. This is much easier after identifications of biodiversity-

hotspots, since all hotspots together cover only 11.8 percent of the planet’s land

surface, but include no less then 44 percent of the worlds plants and 35 percent of

terrestrial vertebrates. Myers included only terrestrial ecosystems. Examples of

these hotspots are Madagascar, Brazil’s Atlantic forest and the Tropical Andes.

Identifying biodiversity is the first step understanding is the second. Several

authors established hypotheses trying to explain gradients of biodiversity.

Biodiversity is for example often connected with the number of available niches

and the strength of genetic drift (Ihlenfeldt 1994, Connell 1964). According to

Jürgens et al. (1999) a high population turnover can decrease the competition for

an ecological niche in plants. Normally competition for resources limits the sharing

of the same ecological niche by several species, but if species have a short

lifespan, this exposure to competition is of relative short duration. In addition there

is always space for new recruits to become establish. This can lead to increased

biodiversity.

Another potential mechanism to create or maintain diversity is the predation

hypothesis first formulated by Paine (1966). By keeping the abundance of their

prey in check and thus prevent competitive exclusion, predators can maintain a

Introduction 4

higher diversity of prey species than would occur in their absence (Paine 1966,

1971). Already Darwin realised in 1859 that the diversity in a meadow decreases if

cutting is stopped. Paine (1966) investigated connections between predators and

their prey on a reef. He found that the removal of predators (i.e. the sea star

Pisaster ochraceus) led to decreased diversity of their prey, mussels (e.g. Mytilus

californianus) in this case. Lubchenco (1978) noticed the same phenomenon in

tidal pools. Here, the presence of snails led to higher diversity of algae species, as

predicted by the predation hypothesis. But the number of algae species decreased

again when the snail population exceeded a limit, causing the extinction of the

preferred food plants. The diversity of the prey, here the algae, reached a

maximum under the influence of a medium population density of predators, here

the snails. An interesting aspect of Lubchencos study is the extension of Paine’s

predation hypothesis by including plants as prey species. In contrast to the study

by Lubchenco (1978) Harper (1969) found that herbivores decrease plant

diversity. This variable result may be due to the fact that herbivores can only

increase the diversity of plants if they preferentially feed on the competitive

dominant plant species, preventing them from displacing subdominant plant

species. They decrease plant diversity if they prefer the subdominant plant

species. In conclusion herbivores can potentially do both, increase or decrease

plant diversity (Lubchenco 1978).

This study focuses on the rich plant diversity in Namaqualand, part of the

Succulent Karoo, a biodiversity hotspot. The Succulent Karoo is situated on the

West Coast of South Africa and Namibia. Namaqualand is the part of the

Succulent Karoo, which lies in South Africa. This area is a semi-desert to desert

environment. The temperatures can reach over 40° in summer and can be below

0° in winter. During daytime the temperature fluctuations are also very high. The

average annual rainfall is between 50 and 400 mm depending on the area

(Cowling et al. 1999), with rain falling mainly in winter (June to August).

Compared to other desert ecosystems Namaqualand has many unique

biological features (Cowling et al. 1999). The rainfall is rare, but highly predictable

(Desmet & Cowling 1999). Droughts are very rare and have a disastrous effect on

the plants that are not adapted to it. There is nearly every year enough rain for

plants to germinate, grow and to produce seeds that can establish successfully

afterwards. Thus plants are not forced to invest in robustness or longevity, abilities

Introduction 5

that are crucial in other deserts with droughts lasting for years. The high

population turnover in plants in the Succulent Karoo, especially after droughts, is

one reason for the high plant diversity here (Jürgens 1999).

Usually, a semi-desert is not expected to be among the 25 most diverse

places in the world. Connell (1964) suggested that diversity is associated with the

stability within a system, because in a stable environment less energy is required

for homeostasis. He pointed out that diversity increases if species have higher

productivity due to more available energy. The Succulent Karoo however is not a

very stable environment, at least not compared to equatorial rain forests. There

are high temperature fluctuations during the day and rainfall is usually restricted to

the winter months.

Determining the reasons for the extraordinary high number of plant species

in the Succulent Karoo can be of great importance for its conservation. If herbivore

predators have a positive influence on plant diversity, it would be essential to

include these animals in conservation programs for plants. The conservation of

plants, and nature in general, is extremely important in this area because the

plants are a tourist attraction and tourism is an important economic factor in

Namaqualand. Furthermore, maintenance of plant biodiversity is also important for

the local farmers, as livestock feeds on a large variety of plant species, mainly

succulents and annuals. Grass is nearly absent in the Succulent Karoo, and a

decrease of biodiversity (e.g. because of overgrazing) is characterized by an

increase in abundance of unpalatable shrub species (i.e. Galenia africana, Todd &

Hoffman 1999).

Another reason why desert ecosystems are increasingly important for

conservation is global warming. Because there is a strong likelihood of a rapid

increase in temperature all over the world, the genetic stock held by desert

ecosystems might be of enormous importance for mankind in the future (Cowling

et al. 1999). The current rate of extinction is a loss we can ill afford. Additionally,

the Succulent Karoo is an inadequately protected biome (Hilton-Taylor & Le Roux

1989).

Botanically the Succulent Karoo is part of the Greater Cape Flora (Jürgens

et al. 1991). The Succulent Karoo is home to about 1954 endemic plant species,

making it the world’s richest succulent flora (Lombard 1999). Characterised by an

open dwarf shrubland (Milton et al. 1997), the vegetation is dominated by leaf-

Introduction 6

succulents and numerous species of highly abundant ephemeral geophytes

flowering in spring (Cowling et al. 1999). Namaqualand harbours probably 10% of

the succulent species in the world (Van Jaarsveld 1987). One of the most

abundant families is the Mesembryanthemaceae (also called Aizoaceae), which

are overwhelmingly concentrated in the Succulent Karoo (Hartmann 1991). In

contrast to other winter rainfall-deserts, leaf succulents with a shallow rooting

system dominate the vegetation. This rooting system makes the plants very

vulnerable for droughts (Cowling et al. 1999). To grow in the cool winter-

temperatures some plants have low temperature-optima for photosynthesis

(Rossa & von Willert 1998).

Namaqualand can be divided in smaller regions based on geology,

topography, amount and season of rainfall. Goegap Nature Reserve, where this

study was conducted, falls within the Hardeveld or Namaqualand Rocky Hills

(Hilton-Taylor 1996) extending from Steinkopf in the north to Bitterfontein in the

south. The vegetation cover here is relatively dense compared to other regions of

Namaqualand. The landscape in the Hardeveld can be divided into hills (local

name: koppies), plateaus and plains. Different soil features characterize each of

these regions. On koppies there is usually shallow soil, as sand is continually

removed by water. Wind and water deposit finer soil particles on plains and along

drainage lines. The soil of plains is deeper and supports different plant

communities.

There are various species of small mammals occurring in Namaqualand.

Some of them are endemic. In fact 85% of South Africa’s endemic mammal

species are small (Gelderblom 1995). Especially in the Hardeveld, the region of

Namaqualand where this study was conducted, the population densities of small

mammals can be extraordinary high (Schradin & Pillay 2005; Jackson 1999), while

large mammals are relatively rare in species and numbers. Most of the small

mammals are muroid rodents, like the striped mouse (Rhabdomys pumilio), the

bush-Karoo-rat (Otomys unisulcatus) and several species of gerbils. But elephant

shrews and mole rats are also represented with some species.

There are no obvious reasons for the extraordinary number of plant species

in the Succulent Karoo, but several hypotheses might apply. The plants in this

area are food for many herbivores. Thus, the plants can be regarded as prey and

the herbivores as their predators or consumers. The present study investigates if

Introduction 7

the predation-hypothesis can be applied to the Succulent Karoo, and if the

presence of small mammals as the dominant plant predators can at least partly

explain the high number of plant species.

It is suggested that small mammals of the Succulent Karoo have an

influence on the plant diversity in their surroundings. According to Andrews and

O`Brien (2000) small mammal distribution is representative for the distribution of

mammals in general. Thus, bigger herbivores such as zebras and antelopes were

not included in this study.

Furthermore, small mammals have the advantage of a small range of action

in comparison to larger mammals, like ungulates. This is highly useful for a study

like this where small-scale differences in species assemblage and population

densities were investigated.

In detail, I tested the following hypotheses:

1. The presence of small mammals as plant predators correlates with plant

diversity.

2. Small mammals as plant predators affect competition between plant species by

preferably feeding on dominant or subdominant plant species. According to

Lubchenco (1978) herbivores increase plant diversity if they prefer dominant

plant species. In this case they provide space for subdominant species that

would otherwise be outcompeted.

3. The effect of small mammals on plant diversity is supposed to be greatest in

the direct surrounding of their nests, especially in case of central place foragers

like O. unisulcatus (bush-Karoo rats). This would predict differential diversity

around occupied nests of bush-Karoo rats compared to abandoned areas.

While small mammals might have an influence on plant diversity, the

evolution and maintenance of plant biodiversity is very likely also dependent on

many other factors. While the focus of this study was on the role of small

mammals in this process, data regarding several other ecological factors were

collected, as well. In the first place some edaphic (soil concerning) parameters

were investigated that are hypothesised to have a great influence on species

diversity. The focus was on soil nutrients. The concentration of the ions from

sodium, potassium, calcium, manganese, magnesium and iron were measured. In

Introduction 8

addition the pH-value in the soil solution was measured. The nutrient status and

pH are important edaphic factors for characterisation of Succulent Karoo soil

(Lechemere-Oertel & Cowling 2001). Curiously, Succulent Karoo seedlings

accumulate more biomass if they grow in nutrient-poor soil in comparison to

nutrient-rich soil (Lechemere-Oertel & Cowling, 2001). Another recorded factor

was altitude. In the Andean forests, for example, there is a general tendency for

plant diversity to decrease with increasing altitude (Gentry 1988). These data on

edaphic parameters were used for descriptive statistical analyses (Cluster

analysis) to create hypotheses and predictions for future research into the

understanding of plant biodiversity in the Succulent Karoo.

In addition a possible impact of large ungulate herbivores on plant- and

small mammal diversity was investigated. The history of grazing by domestic

animals in Namaqualand dated back more than 2000 years (Smith 1999). The

keeping of livestock especially goats and sheep is common in the Succulent

Karoo, which might have a great influence on this biome. According to the

predation-hypothesis it can be expected that, like small mammals, livestock might

have an influence on plant diversity. Maybe very high stocking rates have a

negative effect on small mammal diversity because overgrazed rangelands show a

lack of cover for predator avoidance (Joubert & Ryan 1999). In this context Milton

et al. (1994) found that there is a progressive degradation of rangelands resulting

in irreversible changes in diversity and abundance of Karoo vegetation. Although

several studies found no differences in plant diversity between a reserve and a

lightly grazed, neighbouring farm (Todd & Hoffman 1999 inter alia), I investigated

this topic again by comparing plant biodiversity between a farm, which had a

history of overgrazing by livestock, and a nature reserve. I tested the following

prediction:

4. There is an effect of grazing on the number of plant/small mammal species.

Subjects, materials and methods 9

3. Subjects, Materials and Methods

3.1. Study area

The study was conducted in June-December of 2004 in Goegap Nature Reserve.

This reserve is near the town Springbok in the northwest of South Africa (Northern

Cape). Goegap Nature Reserve is situated in the middle of Namaqualand, which

is part of the Succulent Karoo. It is situated in the Namaqualand Rocky Broken

Veld (Acocks 1988) also called Hardeveld (Hilton-Taylor 1996). The area is

semiarid. Rain falls mainly in winter and the annual average is 160mm (Rösch

2001). The vegetation type is Succulent Karoo (Milton et al. 1997), dominated by

leaf succulent shrubs and many ephemeral species, mainly flowering in spring.

This biome is a bioregion of exceptional succulent plant diversity and endemism

(Hilton-Taylor 1996).

Within Goegap Nature Reserve ten areas differing with regards to structural

and floristic features were chosen for the main project (s. 3.3.). To avoid a bias in

the dataset it was important to choose more or less homogenous places, which

were ecologically different from each other. The areas were designed to be

representative for the plant assemblage of five different management units that

were identified in Goegap Nature Reserve by Rösch (2001). The distribution of the

ten areas is showed on the map (Fig. 1) while their characteristics are listed in

Table 1.


Figure 1: Goegap Nature Reserve with the ten investigated areas, the neighbouring farm and two public roads. The main road of the reserve is also shown. The map shows the distribution of the ten areas in the reserve. The two transects where the Fence line (s. 3.6.) was conducted are marked with an F. Reference: Software MapSource, South Africa

Table 1: Overview about the ten investigated areas; Rainfall: 0-50mm/year = sparse, 100-150mm/year = moderate, >150mm/year = plenty; all edaphic factors, altitude, soil texture and plant cover: results from this study (s. 4.1.3.) organic soil components in % referring the dry weight; soil: + = yes, - = no

Areasaltitude (m o. NN) rocky sandy rainfall Winter Summer

organic soil components (%)

c (Na) mg/l

c (K) mg/l

c (Mg) mg/l

c (Ca) mg/l

1 954.2 + + moderate 10 10 2.20 5.15 13.01 5.89 48.142 935.96 + - moderate 1 5 0.93 1.16 5.78 4.70 13.723 934.9 + - sparse 0 1 0.97 2.68 10.81 3.10 11.244 895.35 + - sparse 40 25 0.44 1.03 1.89 1.94 7.235 855.3 + - sparse 40 45 2.27 65.68 23.40 23.85 95.516 873.63 + - sparse 0 1 0.98 10.78 10.26 2.87 8.957 901.85 + - moderate 35 40 1.47 7.54 4.53 5.50 86.128 977.3 + - moderate 50 60 1.69 4.10 6.09 2.37 14.549 1062 + + plenty 40 50 2.28 1.94 2.15 3.48 17.5410 1109.85 - + plenty 80 50 2.95 3.70 1.26 6.79 33.67

soil plant cover (%) Edaphic factors


3.2. Animals

Ten different small mammal species were trapped during the study. The only

exclusively diurnal species was the striped mouse (Rhabdomys pumilio). The

striped mouse is a muroid rodent (Brooks 1982; Dewsbury & Dawson 1979) with

an adult mass range of 40-85g (Schradin 2003) in both sexes. It occurs in many

parts of southern Africa, including grasslands, marsh, forest, desert and the

Succulent Karoo (Kingdon 1974). In the Succulent Karoo R. pumilio lives in social

groups of one breeding male, 1-4 breeding females and their nonreproductive,

adult offspring (Schradin & Pillay 2003). Group-members sleep together in one

nest (Schradin & Pillay 2004), built in bushes. Sometimes they occupy old nests of

bush Karoo rats (Schradin in press). In spite of their group-living organisation

striped mice forage alone during the day (Schradin in press). Their diet is

omnivorous and contains herbage, fruits, insects and seeds (Curtis & Perrin 1979;

Kerley 1992).

The bush-Karoo rat (Otomys unisulcatus) is a rodent endemic to the sub-

arid regions of southern Africa (Skinner & Smithers 1990). It is confined to the

Karoo region of the South West Arid Zone (Davis 1974; Skinner & Smithers 1990)

and is often associated with the courses of ephemeral streams and rivers

(Shortridge 1934; Diekmann 1979). O. unisulcatus is a medium sized rodent with

an adult mass range of 70-135g (Pillay 2001). It has a shaggy pelage, which is ash

grey dorsally and buff white ventrally. (Pillay 2001) Its nest is a large stick lodge up

to 1.0m in diameter and up to 1.5m high (Schradin in press). It is usually situated

at the base of shrubs such as Zygophyllum retrofractum or under large rocks

(Dieckmann 1979, pers. observ.). They are constructed of sticks, twigs and

flowering ephemerals, sometimes enclosing the shrub completely (Dieckmann

1979; Plessis & Curley 1991). Passages are made within the dense shrub. A small

nest of finer material is constructed at the centre of the large structure in a shallow

burrow or depression. They always contain some green material if the nest is

occupied (Dieckmann 1979, pers. observ.). The literature disagrees concerning

the activity period of the bush Karoo rat. It is described as diurnal (Plessis & Kerley

1991, Plessis et al. 1990) or as crepuscular (inter alia Skinner & Smithers 1990).

O. unisulcatus is exclusively herbivorous (Kerley 1992; (Brown & Willan 1991).

Shrubs dominate their diet (Plessis et al. 1990). The feeding on highly hydrated

plant material is critical to the rat’s survival (Brown & Willan 1991). Mostly the


litters consist of 2 semi-precocial young that are weaned as early as eight days of

age (Pillay 2001). Interestingly the bush Karoo rat is not physiologically well

adapted to the arid environment it lives in (Du Plessis et al. 1989; Pillay et al.

1994). O. unisulcatus uses behavioural adaptations to cope with xeric conditions

such as building stick lodges and feeding on succulent plants to get access to

water.

One of the numerous nocturnal species was the Namaqua-Rock mouse

(Aethomys namaquensis). A. namaquensis is restricted to the central Karoo in the

Northern Cape Province. This rat like rodent has an average body mass of 50g. Its

fur is reddish brown to yellowish light brown with a white underpart. The tail is

longer than the body and happens to have dandruffs. A. namaquensis lives in

small colonies in rocky areas, where they hide in nests under rock crevices or in

burrows under shrubs. Their diet consists of seeds from grass and other plants. A.

namaquensis gives birth to 3-5 pups in summer month (Stuart &Stuart 2001).

The smallest of the trapped species was the pygmy mouse (Mus

minutoides). This mouse is widely spread over different habitats in southern Africa

and weighs just about 6g. Its fur is grey to reddish brown with a white underpart.

Not much is known about the social behaviour of this species. In this study more

than one animal was trapped in tha same place mostly. more than one animal in

one place. The birth weight of the up to seven pups is under 1g. They are often

born in self-dug burrows, but deserted burrows from other species or other

hideouts are also used (Stuart &Stuart 2001).

Three species of Gerbils were trapped, two pygmy gerbils (Gerbillurus

vallinus, Gerbillurus paba) and the short tailed-gerbil (Desmodillus auricularis).

The last is much heavier than the pygmy gerbils weighing about 50g compared to

25-35g. D. auricularis also has got a tail which is shorter than the body, which is

most uncommon for gerbils. The fur colour of the three species is nearly equal

varying from reddish brown to grey. All species have a white belly. In contrast to

the other species D. auricularis has got white patches at the base of its ears. The

diet of gerbils consists of seeds and sometimes insects. All these gerbils occur in

dry, sandy areas with G. paeba being most common. These nocturnal animals dig

their own burrows. G. vallinus lives in colonies whereas G. paeba build small

groups and D. auricularis is solitary or monogamous (Stuart &Stuart 2001).


In addition to all these rodents three elephant shrew species were trapped

(order Macroscelidae). Macroscelidae belong to the clade Afrotheria, which also

includes aardvarks, elephants, hyraxes, golden moles, tencres and serenians

(Murphy et al. 2001). The round-eared elephant shrew (Macroscelides

proboscidreus) has a long pelage that is light grey-brown on the dorsum, yellow-

brown on the flanks and white on the ventrum (Corbet & Hanks, 1968). M.

proboscideus has long slender legs and a long, narrow, semi-flexible snout

(Nowak 1991). The average adult body mass is 45g. M. proboscideus is endemic

to Africa and native to Namibia, southern Botswana and the Cape Province of

South Africa (Corbet & Hanks 1968; Nowak 1991). According to Nowak (1991) the

round-eared elephant shrew is mainly diurnal and just sometimes crepuscular or

nocturnal. In this study no elephant shrew was ever trapped during the day. So it

is likely, that the animals switched their schedule to avoid the threat of diurnal

predators like birds of prey (i.e. jackal buzzards, Buteo rufofuscus), which are

common in the study area. Their diet is dominated by insects along with roots,

berries (Nowak 1991), herbage and seeds (Kerley 1992). It lives on sandy and

thornbrush plains and seeks shelter in burrows under bushes (Nowak 1991) or

rock crevices (Dieckmann 1979). The animals breed in August and September. M.

proboscideus is mainly solitary according to Nowak (1991), but it is also

suggested to be monogamous (Rathbun pers. commun.) Once a year 1-2

precocial young are born, that are nearly immediately able to move. They are

weaned at 16-25 days and reach sexual maturity after about 43 days (Rathbun &

Fons).

The two Rock-elephant shrew species, the Smith-Rock-Elephant shrew

(Elephantulus rupestris) and the Cape-Rock-Elephant-shrew (Elephantulus

edwardii) are more common in rocky areas as the name implies. There are heavier

than M. proboscideus, weighing 65g and 50g, respectively. These two species are

difficult to distinguish from each other in the field. In contrast to E. edwardii, E.

rupestris has a clear white eye ring, a larger brown pelage at the neck, and a very

hairy tail. They have various fur colours (Stuart &Stuart 2001). In other aspects

they are similar to M. proboscideus.


3.3. Correlation between small mammals and plants

3.3.1. Trapping

To determine the diversity of small mammals, trapping was performed at

the ten different sites. Thirty locally hand-made Shearman-traps (26 x 9 x 9cm)

were placed 10m apart, in a line. The trapping transects were 290m long. Each

Trap contained bait and a piece of cotton wool, to avoid trap-death caused by

frost. The bait was a mixture of bran flakes, currants, sea salt, salad oil and

peanutbutter. Prebaiting was done for two days in the afternoon before trapping.

One day before trapping, no prebaiting was performed. Small mammals were

trapped in each area for four days. On the first two trapping days trapping

occurred in the afternoon, three hours before and three hours after sunset

followed by a day without trapping. On the last two trapping days trapping was

performed in the morning three hours before until three hours after sunrise. This

time schedule was chosen in order to trap the diurnal as well as the nocturnal

animals. Traps were checked every 90min to avoid the occurrence of trap deaths

and to open traps for other small mammals present at the transects. Trapped

animals were marked individually with hair dye (method from Weiß et al. 1996),

weighed and sexed. Trapping was done twice, July/August (winter) and the

second one during October/November (summer). No trapping was performed in

the rain or after a temperature drop of more than 5°C from one night to the other.

3.3.2. Vegetation survey

Vegetation analyses were performed after first trapping in August and

before second trapping in October. The surveys were distributed evenly along the

trapping-transect.

At each transect, plant species in and around five squares (each 2x2m)

were determined. All plant species present, the number of individuals per species

and the ground cover was noted. The mean ground cover in five vegetation

surveys was used for statistics (s. 3.2.7.)The seedlings found in spring were not

classified, as they were not present during the preceding trapping session. Plants

were divided in annual and perennials species. The number of individuals was

categorized as follows (after the Braun-Blanquet Method as described Wilmanns

1998).


r = 1 - 2 Individuals

+ = 3 - 10 Individuals

1 = 11 - 100 Individuals

2m = > 100 Individuals

If one species covered more than 5% of the ground the following classification

was used.

2a = 5 - 12,5 %

2b = 12,5 - 25 %

3 = 25 - 50 %

4 = 50 - 75 %

5 = > 75 %

Figure 2: Field assistant performing a vegetation analysis in a 2x2m square in area 8


3.3.3. Soil samples

Three samples of soil (100g) were collected in each area from a depth of

3cm. Samples were taken on open positions, not under shrubs or rocks. Collection

took place after a period without rainfall in the beginning of November. The

parameters pH-value and elemental composition (Na +, K +, Mg2+, Fe+, Mn2+) were

measured. The soil was air dried and sifted through a mesh with a mesh-size of

2mm.

To measure pH-value 10g of soil from each area was mixed with 25 ml

dH2O and measured with a pH-Meter (pH 91, WTW).

For the determination of the elemental composition with an AAspectrometer

(Unicom 939), an extract from 2.5g soil was produced. Two extracts and three

blind tests were analysed for each area. The soil was mixed with 50ml NH4Cl

(1mol/l) and left untouched for 4h. Afterwards the extracts were shaked for 2h on

an automatic shaker (Schüttelmaschine LS20, Gerhardt) and left untouched over

night. The extract was filtered. To measure Ca and Mg 10ml of extract was mixed

with 1ml buffer (7.6g KCl + 2.5ml 37%HCl in 200ml dH2O.). For the measurement

of Fe and Mn, three standards were prepared with 1ppm, 2ppm and 5ppm of Fe

and Mn. For the measurement of the other elements, four standards were

prepared with the following composition:

1. 1ppm Na, 2ppm K, 2ppm Ca, 0.1ppm Mg

2. 2ppm Ca, 5ppmCa, 5ppm K, 0.2ppm

3. 5ppm Na. 10ppm K, 10ppm Ca, 0.5ppm Mg

4. 10ppm Na, 20ppm K, 20ppm Ca, 1ppm Mg

Standards were used to calibrate the AAspectrometer. Samples were

diluted if necessary to fit in the range of the standards. Extracts were measured

with a Unicom 939 AAspectrometer.

To measure the percentage of organic components in the soil, two samples

(≈ 4g) were dried in a cabinet desiccator (Heraeus thermicon P) over night,

weighed (Mettler Type AE 163, accuracy of 0,001g ), cooled down to 20° in an

Exicator and stored in a muffle furnace (Heraeus Function line Typ 12) for 15h. In

the first 2h the oven heated the samples up to 400° temperature remained here for

3h. Than the oven heated the samples up to 600° in another 2h and kept them on

this temperature for 6h. Afterwards the samples needed 2h to cool down to 20°


and were weighed again. The weightloss in reference to the weight after drying

was calculated.

3.3.4. Altitude

The altitude of each transect in the ten areas was measured with a GPS

(eTrex Venture, GARMIN International, USA) at the start- and end-point. The

mean value was used for statistics (s. 3.3.7.).

3.3.5. Rainfall

The mean value of rainfall from the years 1998 to 2002 was taken

(information provided by Goegap Nature Reserve) with nine gauging stations

distributed in the whole Nature Reserve. The rainfall in the trapping areas was

assumed according to the nearest gauging station. No measurements had been

taken in the years 2003 and 2004.

3.3.6. Statistics

Correlations between the number of plant species and the number of small

mammal species and total number of small mammals were calculated as the

Spearman-Rank-correlation coefficient (rs). Results were corrected with

Bonferroni.

The influence of the number of small mammal species, the total number of

trapped animals, the soil characteristics, and the altitude on plant diversity were

calculated with a general linear model with the program Statistika. First all data

were tested for their normal distribution with a KS normality test. The data did not

differ significantly from the normal distribution. Plant diversity was taken as

dependent factor and all other factors were considered independent. No

interactions between the factors were taken into account. In a step-wise procedure

the independent factors with the highest p-value were left out one by one until all

remaining factors were significant.

To compare the different areas a Cluster-analysis was calculated. The

following factors were included in the Cluster-analysis for winter and summer:

small mammal number, small mammal species number, ground cover and number

of plant species. In addition the altitude and some soil characteristics were

included, as there were, the percentage of organic components and the


concentration of the ions Na+, K+, Mg2+, Ca2+. The statistic program SPSS was

used. Differences were considered significant if their probability of occurring by

chance was less than 0.05 (two tailed).

3.4. Food-preference tests

This experiment was performed with two species, bush-Karoo-rats (O.

unisulcatus) and striped mice (R. pumilio). Ten rats and eleven mice were tested.

Striped mice were chosen as a representative, medium sized, diurnal species

(Schradin, Pillay 2004) and bush-Karoo-rats were chosen as a representative,

larger, crepuscular species (Brown & Willan 1991).

Animals were trapped for food-preference-tests as described above.

Trapping was performed in Goegap Nature Reserve and, in case of bush-Karoo-

rats, on the neighbouring farm. Trapped animals were sexed, weighed and

marked with hair dye and/or eartags to identify them in case of recapture. Each

animal was used only once. The animals were put into a cage with sand as

substrate and pieces of six plant species. The plant pieces were all 3cm long but

of different weight, because equating weight would have led to immense

differences in surface and length (some plant species were succulent). It was

assumed that similar length ensures similar conditions for each plant species

better than similar weight. An equal number of dominant and subdominant plant

species were provided. The determination of dominance of plant species in areas

were the species lived was based on the previous studies (s. 3.3.). Plants were

freshly collected and stored in a refrigerator in airtight plastic bags containing wet

tissue paper. Plant species were arranged in a row on the short side of the cage.

Dominant species altered with subdominant species. Order was changed

systematically every experiment. The animals were left alone in a quiet room.

Beginning at 1h, the cage was checked every 30min. The experiment was

terminated when visible damage was done to one or more plant pieces, or a

maximum of 4h had elapsed. Tissue paper was positioned on top of the cage to

provide cover. Immediately after the experiment animals were released at the

place of capture. Plant species were weighed (Mettler Type AE 163, accuracy of

0,001g) before and after testing to determine the weight loss. To consider the

weight loss due to evaporation eight controls experiments were conducted. Here

the same procedure was used, but without an animal in the cage. The median of


the eight control experiments was subtracted from the measured weight loss in all

experiments. In the event of negative results due to this subtraction the weight

loss was assumed to be 0. Tests were performed during the active period of the

species. In the first set of tests Euphorbie spec., Mesembryanthemum

guerichianum and Leipoldtia pauciflora were used as dominant plant species for

O. unisulcatus, Osteospermum sinuatum, Cheiridopsis denticulata and Aptosimum

spinescens were used as subdominant plant species. For R. pumilio Zygophyllum

retrofractum, Lycium cinereum and Leipoldtia pauciflora were used as dominant

plant species and Galenia africana, Lessertia dfiffusa and Rhus spec. as

subdominant species.

Because the first set of tests (pilot study) revealed that a mixture of

perennial and annual plant species can cause a bias in the dataset, a second set

of tests was performed, including only perennial plant species. In the second set

of tests two plant species were left out for each small mammal species. O.

unisulcatus was tested with Euphorbie spec, and Leipoldtia pauciflora as dominant

plant species and Osteospermum sinuatum and Aptosimum spinescens as

subdominant plant species. R. pumilio was tested with Zygophyllum retrofractum

and Leipoldtia pauciflora as dominant plant species and Galenia africana and

Rhus spec. as subdominant species.

The weight loss of the dominant/subdominant plant species in percentage

referred to the weight at the beginning of the experiment was added. Dominant

species were compared to subdominant species with the Wilcoxon matched pairs

rank sign test. For in depth analyses, the Friedman test for multiple paired

comparisons was used, followed by a Wilcoxon-Wilcox test as post test.

3.5. Plant biodiversity around occupied and unoccupied bush Karoo rat

nests

The vegetation around occupied nests of bush-Karoo-rats (Otomys unisulcatus)

was compared to that around unoccupied nests. Always one occupied and one

unoccupied nest in areas as similar to each other as possible were investigated.

The two nests of each pair were situated as close to each other as it was possible

to ensure that the inhabitants of the occupied nest did not influence the area

around the unoccupied one. Changes in the landscapes (i.e. riverbeds, rocks)

were taken into account. One pair was situated on an adjoining farm (cf. 3.6.); all


other pairs (11) were in Goegap Nature Reserve. The diversity of plant species

around the nests was compared with the Wilcoxon matched pairs rank sign test.

The sample size was twelve pairs. Occupied nests were identified by fresh

droppings and fresh plant material, as indicators. Vegetation survey was

performed in a 10m radius around the nests. The same methods for data

recording were used that were described above (cf. 3.3.3.).

3.6. Fence line

The number of small mammal species on both sides of a fence between a farm

and the Goegap Nature Reserve was determined (Fig. 1). The farm has not been

used for stocking for two years, but great differences relative to the nature reserve

were still obvious in the assemblage of plant species. Trapping was performed in

a 290m transects as described above. The two trapping transects were situated

parallel to the fence. To exclude an influence of the fence itself and to avoid

trapping small mammals from the nature reserve on the farm or vice versa, that

were attracted by the traps themselves, traps were placed 20m away from the

fence.

Figure 3: Fence between Goegap Nature Reserve (left side) and a neighbouring farm (right

side)


Eleven vegetation analyses on each side were performed to compare the

plant diversity. The vegetation analysis was done as described above. Squares

were distributed almost evenly along the transects. The numbers of plant species

in the eleven pairs of squares were compared with the Wilcoxon matched-pairs

signed-rank test. The number of small mammal species and the number of

trapped small mammal individuals were compared descriptively as sample sizes

were too small for statistics.

Results 22

4. Results


4.1.1. Comparison between winter and summer

Significantly more plant species were found in summer (p=0.007; T=1). The

comparison between the plant cover of summer and winter revealed no significant

difference (p=0.514; T=17).

70 small mammal individuals were trapped in winter compared to 119

animals in summer (p=0.007; T=0). In the first trapping season (August/November)

ten species of small mammals were trapped. In the second trapping season

(October/November) nine species of small mammals were trapped. The species

were the same as in winter without the brush-tailed Hairy-footed Gerbil (G.

valinus). There was no significant difference concerning the number of species

(p=0.334; T=4). The detailed trapping data from winter and summer can be found

in Tables 4 and 5 (Appendix).

Results 23

Area 1 2 3 4 5 6 7 8 9 10

3 2 3 1 1 4 4 42 2 2 2 1 2 4 6 45 6 4 2 9 17 12 158 12 2 7 8 12 28 26 16

4 2 2 9 11 710 1 5 4 8 10

1

11

2 12 12 6

2 31 4

12 6

2 73 8

2 3 28 2 4

2 21 2

1 35 4 2

A. namaquensis

M. proboscideus

E. edwardii

E. rupestris

D. auricularis

R.pumilio

M. minutoides

O. unisulcatus

sM-species

sM-number

G. peaba

G. valinus

Table 2: Summary about the trapped small mammal species in the ten investigated area, their

number (sM-species) and the number of trapped individuals of all species combined (sM-

number). First value stands for winter, second for summer.

Results 24

4.1.2. Winter trapping season

The number of plant species in the ten investigated areas showed a significant

positive correlation with the total number of trapped animals (p=0.032; rs= 0.732;

Fig. 4) and with the number of small mammal species occurring there (p=0.004;

rs=0.895; Fig.5).

Winter

sM-species

0 1 2 3 4 5

pla

nt

sp

ec

ies

to

tal

0

5

10

15

20

25

Figure 4: Correlation between the number of plant species and the total number auf trapped small mammals (sM-number) in ten different areas. Spearman-Rank-Correlation-test: p=0.032; rs= 0.732

Figure 5: Correlation between the number of plant species and the number auf occurring small mammal species (sM-species) in ten different areas. Spearman-Rank-Correlation-test: p=0.004; rs=0.895

Winter

sM-number

0 2 4 6 8 10 12 14 16 18

pla

nt

sp

ecie

s t

ota

l

0

5

10

15

20

25

Results 25

93.1% of the plant species in winter were perennial. The number of

perennial plant species showed a nearly significant correlation with the total

number of small mammals (p=0.056; rs=0.713; Fig. 6) and a significant correlation

with the number of small mammal species (p=0.002; rs=0.882; Fig. 7). A

correlation between small mammals and annual plant species was not calculated,

because they were nearly absent in winter. In half of the areas there were no

annuals at all and in the other areas there were only one or two species.

Winter

sM-number

0 2 4 6 8 10 12 14 16 18

pere

nn

ial

pla

nt

sp

ecie

s

0

5

10

15

20

25

Figure 6: Correlation between the number of perennial plant species and the total number of small mammals (sM-number) in ten different areas. Spearman-Rank-Correlation-test: p=0.056; rs=0.713

Results 26

4.1.3. Summer trapping season

The total number of plant species did neither correlate with the number of

small mammal species (p=0.12; rs=0.559; Fig. 8) nor with the total number of

trapped small mammals (p=0.598; rs=0.334; Fig 9).

Figure 8: Correlation between the number of plant species and the total number of trapped small mammals (sM-number) in ten different areas. Spearman-Rank-Correlation-test: p=0.12; rs=0.559

Summer

sM-number

0 5 10 15 20 25 30

pla

nt

sp

ec

ies

to

tal

5

10

15

20

25

30

35

40

Winter

sM-species

0 1 2 3 4 5

pere

nn

ial

pla

nt

sp

ecie

s

0

5

10

15

20

25

Figure 7: Correlation between the number of perennial plant species and the number of occurring small mammal species (sM-species) in ten different areas. Spearman-Rank-Correlation-test: p=0.002; rs=0.882 The red point represents two areas with the same values.

Results 27

There was no significant correlation between perennial plant diversity and the total

number of trapped small mammals (p=0,12; rs =0,612; Fig. 10). However the

number of perennial plants species and the number of small mammal species

showed a significant positive correlation (p=0.03; rs=0.763; Fig. 11). Compared to

the winter there were considerable more annual species in this season (Wilcoxon

matched pairs rank sign test; p=0,005 t=0). There was no significant correlation

between annual plant species and small mammals, neither with the number of

small mammal species (p=0.859; rs= 0.032) nor with the total number of small

mammals (p=0.815; rs= -0.110).

Figure 9: Correlation between the number of plant species and the number of occurring small mammal species (sM-species) in ten different areas. Spearman-Rank-Correlation-test: p=0.598; rs=0.334 The red point represents two areas with the same values.

Summer

sM-species

0 1 2 3 4 5 6 7

pla

nt

sp

ec

ies

to

tal

5

10

15

20

25

30

35

40

Results 28

Summer

sM-species

0 1 2 3 4 5 6 7

pere

nn

ial

pla

nt

sp

ec

ies

0

5

10

15

20

25

Figure 10: Correlation between the number of perennial plant species and the number of trapped small mammal (sM-number) in ten different areas. Spearman-Rank-Correlation-test: p=0.12; rs=0,612

Figure 11: Correlation between the number of perennial plant species and the number auf occurring small mammal species (sM-species) in ten different areas. Spearman-Rank-Correlation-test: p=0.03; rs=0.763

Summer

sM-number

0 5 10 15 20 25 30

pere

nn

ial

pla

nt

sp

ecie

s

0

5

10

15

20

25

Results 29

4.1.4. Correlation between plant cover and small mammals

The Spearman-Rank-Correlation-test revealed that plant cover correlated with the

number of trapped small mammals in the ten areas, as well as with the number of

trapped small mammal species. The correlations were significant for winter (plant

cover–sM-number: p=0.014, rs=0.741; plant cover–sM-species: p= 0.004, rs=0.811)

and summer (plant cover–sM-number: p=0.002, rs=0.844; plant cover – sM-

species: p= 0.038, rs=0.660).

4.1.5. Soil survey

Data of the soil survey are included into the cluster-analyses (4.1.6) and here

described descriptively. The pH-values of the ten areas had a range from 5.7 to

8.5 (Fig. 12). The lowest pH-values were found in the highest areas (9, 10).

Soil survey

Areas

0 1 2 3 4 5 6 7 8 9 10 11

pH

0

2

4

6

8

10

Figure 12: pH-value of the ten areas, measured with dH2O as solvent.

Results 30

The percentage of organic component in the soil samples had a range from 0.92 to

2.97 % (Fig. 13).

Soil survey

Areas

0 1 2 3 4 5 6 7 8 9 10 11

Org

an

ic c

om

po

nen

ts i

n %

0,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

Figure 13: Organic components of soil samples from the ten areas in % from the oven-dry mass. The median from 2 samples is given.

Results 31

The concentration of Fe2+ was too low to be measured. Mn2+ concentrations were

also very low and had a range from 0.076 mg/l to 0.382 mg/l. The concentrations

of the other ions are given in Figure 14.

Soil survey

Areas

0 1 2 3 4 5 6 7 8 9 10 11

Concentration of Ions in mg/l

0

20

40

60

80

100

Natrium Calcium Magnesium Kalium

Figure 14: Concentration of the ions from Na, Ca, Mg, K in the soil of the ten areas. Mean value of two soil solutions is given.

Results 32

4.1.6. Cluster-analysis

The following factors were included in the Cluster-analysis for winter and summer:

small mammal number, small mammal species number, ground cover and number

of plant species. In addition the altitude and some soil characteristics were

included, as there were, the percentage of organic components and the

concentration of the ions Na+, K+, Mg2+, Ca2+. Three Clusters were identified with a

hierarchic Cluster-analysis. Areas 8, 9 and 10 belonged to the first cluster, area 5

stood alone in the second one and areas 1, 2, 3, 4, 6 and 7 were in the third

cluster. The areas in the first cluster were characterised by high values concerning

small mammals and plants, whereas the second cluster (area 5) had very high

concentrations of soil nutrients. The areas in the third clusters had moderate values

in most of the factors (Tab. 3).

4.1.7. General linear model

The general linear model for winter revealed a significant result (p<0.05, F=5.87).

Floral diversity was explained by the number of small mammals (p=0.0006,

F=29.86) and by the concentration of Manganese in the soil (p=0.0034, F=16.94).

The model for summer was also significant (p<0.0001, F=48.27), and the only

remaining significant factor explaining plant diversity was the number of small

mammals species (p=0.000008, F=81.31).

Cluster - analysis

Winter Summer Edaphic factors

Cluster

number of

plant species

sM-

number

sM-

species

plant

cover (%)

number of

plant species

sM-

number

sM-

species

plant

cover (%)

Altitude

(m)

organic

particles (%)

c (Na)

mg/l

c (K)

mg/l

c (Mg)

mg/l

c (Ca)

mg/l

1 n=3 Mean 18.33 14.67 4.00 56.67 25.33 23.33 4.67 53.33 1049.72 2.31 3.25 3,17 4.21 21.91

SD 4.51 2.52 0 20.82 5.77 6.43 1.15 5.77 67.12 0.63 1,15 2.57 2.30 10.29

2 n=1 Mean 9.00 2.00 1.00 40.00 11.00 8.00 1.00 45.00 855.30 2.27 65,68 23.40 23.85 95.51

SD . . . . . . . . . . . . . .

3 n=6 Mean 8.67 4.00 1.50 14.33 21.00 6.83 1.67 13.58 915.98 1,16 4,72 7.71 4.00 29.23

SD 5.54 3.52 1.38 18.40 10.32 5.00 0.82 15.77 30.45 0.60 3,88 4.29 1.59 31.79

Results

33

Table 3: Mean value and standard deviation of all factors included in the hierarchic cluster-analyses. Cluster 1 includes the areas 8, 9 and 10. Cluster 2 includes area 5 alone and Cluster 3 consists of the areas 1, 2, 3, 4, 6 and 7.

Results 34

4.2. Food-Preference-tests

4.2.1. Pilot study

4.2.1.1. Striped mouse (R. pumilio)

The Friedman-test revealed an overall significant difference in how much was

eaten from the four different plant species (p=0.0001). The following Wilcoxon-

Wilcox-test showed that Lycium cinereum (dominant) and Lessertia diffusa

(subdominant) are different from Leipoldtia pauciflora (dominant) and Rhus spec.

(subdominant) concerning the consume by R. pumilio. The other plant species

were not different from each other.

4.2.1.2. Bush-Karoo rat (O.unisulcatus)


eaten from the four different plant species (p=0.004). However the following

Wilcoxon-Wilcox-test showed no differences between certain plant species.

Figure 15: bush-Karoo rat (Otomys unisulcatus) with ear tag in a cage in which the food-preference test were performed

Results 35

4.2.2. Second set of tests

4.2.2.1. Striped mouse (R. pumilio)

R. pumilio showed a significant food preference for the dominant plant species Z.

retrofractum and L. pauciflora in comparison to subdominant plant species G.

africana and Rhus spec. (data for dominant species and subdominant species

combined; Wilcoxon matched pairs rank sign test; T=6; p = 0.007). The median

percentage of eaten dominant plants was 18.10 and 11.04 for subdominant plants,

respectively (Fig. 16).

Food-preference-test R. pumilio

dominant plants subdominant plants

ea

ten

pla

nt

pie

ce

s i

n %

0

10

20

30

40

50


eaten from the four different plant species. The following Wilcoxon-Wilcox-test

showed that Z. retrofractum is different from all other plant species concerning the

consume by R. pumilio. The dominant shrub Z. retrofractum was the preferred

food-plant. The other plant species were not different from each other.

Figure 16: Comparison of the quantity R. pumilio ate from two dominant /subdominant plant species provided in a food-preference-test. Data were corrected for evaporation by control experiments. t=6; p = 0.007

Results 36

4.2.2.2. Bush Karoo rat (O. unisulcatus)

O. unisulcatus showed a significant food preference. In contrast to the striped mice

they preferred the subdominant plants Osteospermum sinuatum and Aptosium

spinescens to the dominant plant species L. pauciflora and Euphorbia spec. (data

for dominant species and subdominant species combined; Wilcoxon matched

pairs rank sign test; T=1; p = 0.002). The median percentage of eaten

subdominant plants was 95.33 and 3.41 for dominant plants (Fig. 17).

Food-preference-tests O.unisulcatus

dominant plants subdominant plants

ea

ten

pla

nt

pie

ces i

n %

0

20

40

60

80

100

120

140


eaten from the four different plant species. The following Wilcoxon-Wilcox-test

showed that O. sinuatum is different from all other plant species concerning the

consume by O. unisulcatus. The other plant species were not different from each

other. O. sinuatum was the preferred food-plant.

Figure 17: Comparison of the quantity of dominant and subdominant plants eaten by O. unisulcatus provided in a choice test. Data were corrected for evaporation by control experiments. T=1; p = 0.002

Results 37

4.3. Plant biodiversity around bush Karoo rat nests

The effect of bush-Karoo rats on their direct environment was investigated by

counting the plant species in a circuit of 10m around occupied and unoccupied

bush-Karoo rat nests.

The comparison between the surrounding of occupied and unoccupied

bush-Karoo-rat nests (Fig. 18) showed a significant difference concerning the

number of plant species found in a circuit of 10m. Significantly more plant species

were found around occupied nests (Wilcoxon matched pairs rank sign test;

T=16.5; p = 0.05).

.

Figure 18: Comparison between the number of plant species in a circuit of 10m around occupied and unoccupied nests of O. unisulcatus. Median and original data are given. A line connects the data of one pair of nests in the same area. T=16.5; p = 0.05

BKR-nests

unoccupied occupied

number of plant species

0

5

10

15

20

25

30

Results 38

4.4. Fence line

A significant difference concerning the plant diversity in Goegap Nature

Reserve and the farm was found (Wilcoxon matched pairs rank sign test T=2.5;

p = 0.01; Fig. 19). In nine of eleven pairs there were more plant species on the

farm. Median number of plant species on the farm was 7 compared to 6 in the

Nature Reserve.

There were too few small mammals trapped for statistical comparisons. On the

Farm one G. paeba and three A. namaquensis were trapped. In the nature reserve

four R. pumilio and one G. paeba were trapped. Trapping data can be found in

Table 6 (Appendix).

Fence line

vegetation surveys

0 1 2 3 4 5 6 7 8 9 10 11 12

nu

mb

er

of

pla

nt

sp

ec

ies

0

2

4

6

8

10

12

14

16

18

Nature reserveFarm

Figure 19: Comparison between the number of plant species on both sides of a fence between Goegap Nature Reserve and a farm. I made 11 pairs of vegetation surveys on the same level. T=2.5; p = 0.01

Discussion 39

5. Discussion

Conservation (i.e. the maintenance and protection of natural habitats) is one of the

main challenges and duties of our time, as it also functions to protect our own

endangered habitat. An important part of conservation is the protection of species.

All species in an ecosystem are connected to each other in a more or less direct

way (Begon et al. 1998). The extinction of one species often has severe

consequences for other species in its ecosystem (Begon et al. 1998). Humans are

also involved given the fact that earth itself is the biggest known ecosystem.

Biodiversity is also of immense value with regards to adaption. No matter if from

human interference or more natural caused, our environment will change during

the following decades. With a more variable genpool it will be much easier for life

to adapt to these changes. Given the current rate of extinction and the explosion of

human population density, conservation is of increasing importance. In places

where many species live in a small area, conservation is most effective (Myers et

al. 2000). One of these places is the Succulent Karoo with its extraordinary floral

diversity (Myers et al. 2000). To provide effective conservation methods for plant

diversity, it is essential to find out which factors influence or maintain biodiversity.

Herbivore animals feeding on plants might be one of these factors. In the

Succulent Karoo small mammals are of special importance, because they have

high population densities here and larger herbivores are relatively rare. The

influence of small mammals on plant diversity was investigated in this study for the

first time.


Previous studies on the influence of predators on biodiversity revealed

contradictory results with predators either increasing (Paine 1966, Lubchenco

1978) or decreasing (Harper 1969; Lubchenco 1978) the diversity of their food-

plants. This difference might be due to whether the preferred prey species belongs

to the dominant or subdominant species in each case. It is crucial to know about

this because predators are only assumed to increase the diversity of their prey if

they prefer dominant prey species, making space for subdominant species, which

would otherwise be outcompeted (Lubchenco 1978). This predation-hypothesis

was first described by Paine (1966) and has so far been tested only in habitats

Discussion 40

with average biodiversity. To my knowledge my study is the first to test the

predation hypothesis on a biodiversity hotspot: the Succulent Karoo (Myers et al.

2000).

I found that plant diversity correlated significantly with the number of

trapped small mammals and the number of their species in winter (July/August).

This was true for the total number of plant species and for the perennial plant

species separately. In summer (November/December) only the association

between perennial plant species and the number of small mammal species

showed a significant, positive correlation. A correlation between perennial plant

species and the number of trapped small mammals however could not be

demonstrated. These results support the predation-hypothesis and indicate that

small mammals could increase biodiversity in the Succulent Karoo. However I

cannot be sure in this stadium, whether the relation I found was due to an

influence of small mammals on plants or the other way around. Maybe small

mammals have a positive influence on plant diversity, but not from reducing

dominant plant species. Indirect ways of influence are possible. Small mammals

digging burrows might for example increase plant diversity, because their burrows

store water during rainfall and keep it available for plants. However, only three of

the 10 trapped small mammal species burrowed (the three gerbil species).

Furthermore it is possible that other factors, such as altitude and edaphic factors

(see 3.3.4, 3.3.5 and 3.3.6) influenced plants and small mammals in a similar way,

although this is highly unlikely, because of the results the general linear model

revealed.

In winter plant biodiversity correlated more strongly with the number of

small mammal species than with the total number of small mammals, and in

summer the only significant correlation I found was also with to the number of

small mammal species and not with the total number of trapped individuals. The

stronger influence of small mammal species on plant diversity is probably due to

the range of their diet. One small mammal species alone affects possibly only a

few plant species that it prefers as food-plants. Many small mammal species

together, however, are likely to have a more variable diet and therefore a stronger

influence.

Additionally different species feed on different parts of their food plants (e.g.

seeds, leaves, roots). Therefore a plant species eaten by only one small mammal

Discussion 41

species might not be influences severely because the damage is done to only one

part of the plant. Many small mammal species together however might have a

much stronger influence, even if they have a low population density.

One reason for the stronger correlation between small mammals and plants

in winter might be the smaller cruising radius small mammals typically have in

winter (Schubert 2005). The larger the cruising radius of herbivores is, the smaller

should be the effect on plants in their surrounding, because the influence of a

single individual is spread over a larger area. It is also possible that small

mammals choose their habitat based on the diversity of their food plants, which is

why the correlation between small mammals and plant diversity would be stronger

in winter, when food is a more limited factor than in the early summer.

The Succulent Karoo is a seasonal environment with abundant plant growth

by ephemerals in spring, which is also the breeding season of most small

mammals (Schradin & Pillay 2005; Jackson 1999). In my study as well I found

both a higher abundance of small mammals and annual plant species at the

beginning of summer. The correlation between small mammals and annual plant

species could not be calculated for the winter-trapping-season season because

annuals were nearly absent during this season (Cowling 1999). Even in summer

when there were numerous annuals there was no significant correlation. Obviously

small mammals and annuals have no remarkable influence on each other.

Possibly the short time-span in which the two can interact plays a part here. Most

of the annual plant species in Namaqualand are ephemeral and have a lifespan of

only a few months. Small mammals on the one hand do not have enough time to

reduce certain dominant or subdominant plant species significantly because

annuals occur in great numbers for a relatively short period in spring and vanish

quickly when it gets dry in summer. On the other hand, due to their short lifespan,

annuals are not important for the over-winter survival of small mammals. Annuals

are essential for their breeding season, but small mammals cannot rely on annuals

over the whole year. This reduces the influence of annual plant species on the

species composition of small mammals.

In the future it would be good include other small mammal species that

were not sampled in my study. With different types of traps for example it would be

possible to trap small mammal species that do not enter the Shearman traps I

used. Whistling rats (Parotomys brantsii, Parotomys littledalei) and subterranean

Discussion 42

species like mole rats (Bathyergus janetta, Cryptomys hottentotus) belong to this

group. Dassie rats (Petromus typicus) are probably not attracted by the bait I used.

Another aspect that has not been taken into account in my studies is that insects

certainly also are important herbivores (Zeller 2002) and to my knowledge there

are no studies on their influence on biodiversity in Namaqualand or anywhere else.

Another constraint of this study could be the unevenly distribution of the ten

areas within the nature reserve. For methodological reasons the distances

between the areas are very different (Fig. 1). The areas were chosen in order to

be ecologically different, but nevertheless it cannot be excluded that the data from

some areas are more similar to each other than others, because of the varying

distance between them.

The correlations I found support the hypothesis that small mammals affect

floral diversity. However it cannot be said at the moment if there is a causal

connection between small mammals and plants. A clear statement would require

further investigations using an experimental approach. There are several fenced

monitoring plots in Goegap Nature Reserve. The fence protects the plants growing

inside the plots from bigger herbivores but not from small mammals. To prove the

influence of small mammals on plant diversity it would be useful to fence these

plots in a way that also excludes small mammals. A comparison between these

fenced plots and adjacent unprotected areas over several years and during

different seasons would make it possible to test the influence of small mammals

on plant biodiversity experimentally.

5.2. Food-preference-test

If small mammals influence plant biodiversity in the way predicted by the

predation-hypothesis it would be expected that at least some of them prefer

dominant plant species. Dominant plant species are not seriously threatened even

if they are the preferred food-plants. Being eaten just prevents them from

displacing subdominant plant-species. A preference for subdominant food-plants

however could lead to their extinction.

Discussion 43

5.2.1. Pilot study

The pilot study revealed that R. pumilio preferred the two plant species

Lessertia. diffusa and Lycium. cinereum. Lessertia. diffusa is an annual plant

species and therefore just available for the mice in spring and early summer. This

is also true for L. cinereum. Although this is a perennial shrub it foliates only in

spring. R. pumilio seems to prefer this fresh food in general. The same seems to

apply to O. unisulcatus. Nine out of the ten animals I tested preferred

Mesembryanthemum guerichianum, which was the only annual plant species in

the test. This can be easily explained by the higher nutrient value of annuals in

comparison with perennials (Oftedal 2002). To exclude the preference for fresh

plant material, only perennial shrubs, which are available throughout the year,

were used in the second set of tests.

5.2.2. Second set of tests

The influence of herbivores on their food-plant’s diversity depends

decisively on the preference of herbivores for dominant or subdominant plants

(Lubchenco 1978). In fact both of the tested species, O. unisulcatus and R.

pumilio, showed a significant preference. Interestingly the two preferences did not

point in the same direction. Whereas R. pumilio preferred the dominant food-plants

in the tests, O. unisulcatus favoured the subdominant plant species. This result

implies a positive influence from R. pumilio on plant diversity and a negative one

from O. unisulcatus as explained above (see 5.1.).

The choice of the tested plant species was done randomly. So it can be that

some species were chosen that are not included in the animals’ diet or are even

unpalatable. To be unpalatable is an effective strategy for plants to protect

themselves from being eaten. This way subdominant or formerly subdominant

plants can resist their palatable competitors that would probably outcompete them

otherwise. This can be seen most clearly on rangeland, where plants that are

unpalatable for livestock can spread unchecked. One of these plants is the shrub

Z. retrofractum, which is unpalatable for livestock, but the preferred food-plant of

R. pumilio. Z. retrofractum leaves contain toxic substances in their sap but not all

leaves are toxic to the same extend (pers. commun. du Toit, state botanist,

Northern Cape Province). R. pumilio might be able to feed specifically only on the

non-toxic very small leaves and seeds (size of a pinhead), which bigger ungulates

Discussion 44

like goats and sheep are unable to do. Livestock cannot choose the few palatable

leaves out of the large number of leaves growing on one branch. Z. retrofractum is

a dominant plant species and its population density can only be regulated by small

mammals. This can be of great interest for the farmers in Namaqualand, who

prefer to have palatable plants on their land, but support Z. retrofractum without

meaning to by high stocking rates, i.e. reducing its palatable competitors. Small

mammals are often seen as pests and their profitable side is overlooked.

There is certainly a need for food-preference-tests with other herbivore

species and it would be beneficial to repeat them with more plant species on R.

pumilio and O. unisulcatus. This would lead to a more general understanding of

the influence herbivores have on their food-plants in the Succulent Karoo.

5.3. Plant biodiversity around bush-Karoo rat nests

To measure a possible effect of small mammals on biodiversity directly, the plant

diversity around occupied/unoccupied nests of O. unisulcatus, was determined. O.

unisulcatus is a central place forager and therefore especially qualified for this

study. They feed in the direct surroundings of their nests so that an influence of a

rat’s presence can be determined by investigating the area around an occupied

nest. The population density of O. unisulcatus was not as high as usual, because

a drought during the previous year made them locally extinct on the study site,

which they only started to colonise again (from a neighbouring farm) in 2004, when

this study took place. Therefore there were occupied and abandoned areas, which

could be compared to each other. These circumstances were for example not true

for R. pumilio, which have a different foraging strategy and roam their homerange

searching for food. A study on R. pumilio was also made impossible by the fact

that it builds its nest in bushes in such a way that one cannot see them from

outside. Although several nesting sites were known from other studies, a study

was not possible because in the concerning area the population density was so

high that it was impossible to find unoccupied areas for comparison.

While the results of the food-preference-tests indicated that O. unisulcatus

might have a negative influence on plant diversity, the vegetation surveys around

the nests suggested the opposite. As the study was designed to have occupancy

as the only difference between the compared nests, the higher diversity around

Discussion 45

occupied nests could be due either to rats increasing plant biodiversity or rats

choosing nesting sites with higher plant biodiversity. I cannot say which possibility

is correct with this correlative study. Additionally, there might be other factors,

unrecognised by me, influencing the presence of rats and plant diversity in the

same way. Should the rats choose their nesting site according to floral diversity,

the duration of occupancy in the moment of investigation might affect the result.

Since the food-preference-tests implied a negative influence of O. unisulcatus, it is

possible that a recently occupied nest has a high plant diversity in its

surroundings, because the animals have chosen the nesting site according to

plant diversity. The surroundings of a nest that has been exposed to the potentially

negative influence of O. unisulcatus for a long time could have reduced plant

diversity. It is known, however, that many nests are used for several years (Brown

& Willan 1991; Schradin unpublished data). Therefore, it is not likely that O.

unisulcatus do lasting damage to their environment by, for example, causing the

extinction of subdominant plant species because they would not be able to live in

the same region for years in that case.

The high plant diversity around occupied nests of O. unisulcatus can also

be reconciled with the results of the food-preference tests in another way. It is

possible that other small mammals, which in contrast to O. unisulcatus prefer

dominant food-plants, but also prefer to stay next to O. unisulcatus, compensate

for the negative influence of O. unisulcatus. R. pumilio for example use

unoccupied nests of O. unisulcatus (Schradin in press). In this case I measured

not the direct effect of O. unisulcatus on the surroundings of their nests, but the

influence of other small mammals that are associates with O. unisulcatus.

5.4. Other factors that might influence plant biodiversity

The pH-values of the soil samples from the ten areas showed little variation.

Only the areas 9 and 10 had remarkably low pH-values. These two areas were at

a much higher altitude compared to the others and are also most distant from

them, which is a probable explanation for this deviation. Areas 9 and 10 also have

high percentages of organic particles in the soil that are known to decrease pH-

value because of their humic substances (Gisi 1997).

The highest percentage of organic components in the soil was found in

areas 1, 5, 9 and 10. Area 10 consists mainly of big rocks, so the soil samples

Discussion 46

were taken from the sandy patches in between. Probably organic soil particles are

concentrated in these places. The same could be true for the areas 1 and 9, which

are both situated on the foot of a hill, where wind and rain might deposit organic

particles. Area 5 did not only have a high percentage of organic soil components,

but also high concentrations of different metal ions. The area is situated next to an

old cooper mine. Strong winds, which are quite common in Namaqualand, often

blew grey dust from the mining dump to area 5. Most probably this is the reason

for the high concentrations of metal ions. The high concentration of organic

particles however remains surprising. In spite of high nutrient concentrations and

the organic particles in the soil, there was no extraordinarily high plant diversity or

plant cover in area 5. The sparse vegetation in areas 3, 4 and 6 can explain the

low percentage of organic components there.

The Cluster-analysis that included additional measured factors showed

clearly that small mammals and plants are more abundant in areas 8, 9 and 10 (cf.

Tab. 2). These areas are also at the highest average altitude and have the highest

average percentage of organic particles in the soil. The plant diversity might

directly affect the organic soil particles and the small mammal number and species

number, or the other way around. The altitude, however, is independent from plant

diversity. It is surprising on the first view that biodiversity seems to increase with

increasing altitude, because in the Andean forests the opposite effect can be

found (Gentry 1988). On the second view one can see that areas 8, 9, and 10 also

have moderate or plenty rainfall (cf. Tab. 1). Higher areas seem to have a

tendency to get more rainfall, which would explain the high plant diversity. Clouds

coming from the Atlantic rain out on the higher slopes whereas they often just pass

by in lower regions. For this reason the Kamiesberg area, the bioregion with the

highest altitude in Namaqualand, has got the highest average annual rainfall of all

bioregions here (Cowling 1999).

The general linear model showed that plant diversity could be explained by

small mammal diversity in winter and in summer. Concerning this result I can now

exclude the alternative explanation that other factors influenced plants and small

mammals in the same way and caused the correlation I found. Combining this

result with the others I can say now that small mammals indeed affect plant

diversity in Namaqualand. It was, however, surprising that plant diversity in winter

can also be explained by the concentration of manganese in the soil. Manganese

Discussion 47

is an essential nutrient for plants, but this is also true for other nutrients. It is even

more surprising that this connection between manganese and plant diversity was

only found in winter. So the importance of manganese seems to vary within the

year.

5.5. Fence line

The comparison between the floras of a Nature Reserve with those of a

neighbouring farm showed a significantly higher diversity on the farm. The plants

of the farm have been exposed to the influence of goats, sheep and cattle for

many years. If the stocking had a positive influence on the diversity of plants, this

could be due to livestock preferring dominant plant species and thereby keeping

them away from outcompeting subdominant food-plants. Because herbivores

decrease the diversity of their food-plants if they prefer subdominant plant species

(Lubchenco 1978) and the farm had a higher plant diversity in comparison to the

ungrazed nature reserve, it is unlikely that there is a preference for subdominant

plants.

The edibility of the plants was however unaccounted for in this study.

Possibly many of the subdominant plant species are unpalatable and therefore not

eaten by ungulates. This possibility requires further investigation. A high

reproduction of unpalatable plants (e.g. Galenia africana) was found in several

studies (Todd & Hoffman 1999).

Furthermore, one can think of other ways for livestock to increase

biodiversity. Their dung for example might be an advantage for plants growing on

farmland. The investigated farm has not been grazed for nearly 2 years and thus

might be in a phase of regeneration in which many pioneer-plants increase the

population density.

The season in which the study was conducted might also be of importance.

The vegetation surveys were done in spring and many annual plant species were

included in the investigation. Grazing has a particularly negative influence on

different shrubs, which were reduced by livestock. Unpalatable plants, like Z.

retrofractum and G. africana are left behind with sandy patches between them. On

these sandy patches a great number of annuals can be found in spring. Because

the investigated farm was not grazed in 2004, annual plant species could easily

Discussion 48

establish themselves. Probably the study would have had another result if it had

been conducted in winter.

Besides stock farming, other factors might be responsible for the species

richness on the farm. The farmers planted some trees for example and the areas

on the two sides of the fence differed in heterogeneity. The study area on the farm

was much more heterogeneous. Although there was a plain area and a sandy and

rocky area on both sides, there also was a waterhole on the farm. Water is of

enormous importance for plants, especially in arid regions. So it is likely that this

water hole had a positive effect on the plants of the farm. For methodological

reasons it was not possible to conduct this study in a more homogeneous area. It

would be important to repeat this study in a more appropriate area. This would

also be interesting with regards to small mammals. Joubert and Ryan (1999)

mentioned that the species composition on high stocking rate rangeland is a

subset of the species occurring in areas with lower stocking rates. In my study

there was neither a remarkable difference in small mammal species number nor in

number of trapped individuals. Only species composition differed. G. paeba was

trapped on the farm and on the nature reserve. This species is one of the most

abundant ones in the Hardeveld (this study) and seems to be very tolerant

regarding its habitat. As G. paeba is nocturnal (Stuart & Stuart 2001) and lives in

burrows, one can imagine that it is not so dependent on plant cover because there

is no need to hide from birds of prey, which are mainly diurnal and no shrubs are

required as nesting sites. G. paeba was also trapped on highly overgrazed

rangeland in other studies (Joubert & Ryan 1999). It does not seem to be a good

indicator species. A. namaquensis was also trapped on the farm. This species is

highly dependent on rocky areas (Stuart & Stuart 2001), but was trapped here

near the reeds at the mentioned water hole. Next to this place is a heap of stone

wreckage that might have been used by the mice as substitute for rock crevices.

R. pumilio was only trapped in the Nature Reserve, which had considerably more

shrubs providing cover and nesting sites.

When trapping for food choice tests on the farm and investigating bush-

Karoo rat nests, I also trapped several O. unisulcatus, a few R. pumilio and one

Mus minutoides on the farm right next to my transect. Additionally it is known from

earlier studies that O. unisulcatus and Macroscelides proboscideus live in the

nature reserve next to the fence (Schradin unpublished data). It is surprising that

Discussion 49

these species were not trapped during the actual fence-line-study (four trapping

days/nights). Possibly the trapping sites were not optimally chosen. Should this

study be reproduced in another place, it is advisable to increase the number of

trapping days. Although a clear statement about the effect of grazing on plant

diversity cannot be given in the end, the study still has value if one considers it to

be a pilot study for following investigations, which can hopefully be conducted

under better circumstances.

Conclusions 50

6. Conclusions

The results of my studies, though being mainly correlative, indicate an influence of

small mammals on plant diversity in the Succulent Karoo. This knowledge could

make it easier in the future to protect this biodiversity-hotspot. Conservation is

hardly possible without knowing the ecological background. From this study it is

now clear that it is not enough to protect the threatened plant species directly. It is

also necessary to consider small mammals in conservation programs, even if they

are not threatened themselves. Additionally, further investigations are urgently

needed, especially experimental ones that exclude small mammals from certain

areas and allow a direct comparison between areas influenced and protected from

small herbivorous mammals.

References 51

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Appendix 58

8. Appendix

Table 4: Trapping data from the winter-trapping season

species number date time area station weight (g) sex

M. minutoides 1 6.7.2004 20:05 1 30 - -

M. minutoides 2 8.7.2004 08:06 1 28 - -

A. namquensis 0 6.7.2004 19:55 1 15 -

A. namquensis 1 5.7.2004 19:55 1 29 - m

A. namquensis 1 8.7.2004 06:31 1 29 - m

E. rupestris 1 8.7.2004 07:53 1 7 - m

G. paeba 1 5.7.2004 21:20 2 14 - -

G. paeba 2 5.7.2004 21:30 2 29 - -

G. paeba 3 6.7.2004 20:22 2 10 - -

G. paeba 4 9.7.2004 06:45 2 4 27 -

M. proboscideus 1 5.7.2004 20:20 2 28 - f

M. proboscideus 2 5.7.2004 20:25 2 30 - f

G. paeba 6 10.7.2004 21:28 4 27 23 -

G. paeba 7 11.7.2004 19:42 4 29 24 -

R. pumilio 1 10.7.2004 19:45 4 11 32 -

R. pumilio 1 10.7.2004 21:12 4 11 - -

R. pumilio 1 11.7.2004 21:12 4 9 37 -

R. pumilio 1 14.7.2004 07:00 4 7 30 -

G. valinus 1 10.7.2004 21:13 4 15 26 m

G. paeba 1 15.7.2004 21:10 5 19 29 -

G. paeba 2 19.7.2004 06:25 5 5 26 -

G. paeba 1 20.7.2004 21:00 7 4 25 -

G. paeba 2 20.7.2004 21:05 7 10 27 -

G. paeba 2 21.7.2004 19:20 7 4 27 -

G. paeba 3 20.7.2004 21:10 7 12 26 m

G. paeba 4 20.7.2004 21:17 7 24 27 m

G. paeba 5 20.7.2004 21:17 7 27 30 m

G. paeba 12 21.7.2004 20:50 7 5 24 f

G. paeba 17 23.7.2004 06:20 7 19 27 -

G. paeba 18 23.7.2004 06:30 7 30 27 m

G. paeba 20 28.7.2004 06:30 7 1 25 -

R. pumilio 1 21.7.2001 16:43 8 3 52 m

R. pumilio 1 21.7.2004 18:10 8 3 m

R. pumilio 1 28.7.2004 09:35 8 2 50 m

R. pumilio 1 28.7.2004 11:10 8 2 m

R. pumilio 2 23.7.2004 11:00 8 1 37 m

O. unisulcatus 1 20.7.2004 18:12 8 2 106 m

G. paeba 6 20.7.2004 21:45 8 13 27 -

G. paeba 7 20.7.2004 21:50 8 19 25 f

G. paeba 8 20.7.2004 22:02 8 24 25 f

G. paeba 9 21.7.2004 19:40 8 26 30 m

G. paeba 10 21.7.2004 19:47 8 9 30 -

G. paeba 11 21.7.2004 20:00 8 2 26 -

G. paeba 13 21.7.2004 21:15 8 30 25 f

G. paeba 14 21.7.2004 21:25 8 19 28 -

G. paeba 15 21.7.2004 21:30 8 13 25 -

- = no data available m = male f = female X =animal escaped before it could be marked Recapture

Appendix 59


G. paeba 16 21.7.2004 21:36 8 5 28 -

G. paeba 16 23.7.2004 06:50 8 24 25 -

G. paeba 19 23.7.2004 06:59 8 21 26 -

M. proboscideus 1 20.7.2004 21:55 8 24 23 f

M. proboscideus 2 21.7.2004 20:03 8 1 49 f

M. proboscideus 3 28.7.2004 06:50 8 11 40 f

G. paeba 1 4.8.2004 10:45 9 29 55 m

G. paeba 1 31.7.2004 19:43 9 8 27 m

G. paeba 1 4.8.2004 06:12 9 4 24 m

G. paeba 2 31.7.2004 21:05 9 29 20 f

G. paeba 3 3.8.2004 06:09 9 5 28 m

G. paeba 3 4.8.2004 06:20 9 6 27 m

G. paeba 4 3.8.2004 07:46 9 4 25 -

G. paeba 5 4.8.2004 06:12 9 3 26 -

G. paeba 6 4.8.2004 06:26 9 8 25 m

G. paeba 7 4.8.2004 06:37 9 25 22 -

E. edwardii 3 31.7.2004 18:02 9 26 55 -

E. edwardii 4 31.7.2004 18:10 9 30 54 f

E. edwardii 4 4.8.2004 07:55 9 28 53

M. proboscideus 1 29.7.2004 19:30 9 5 41 m

M. proboscideus 1 31.7.2004 19:38 9 5 40 m

M. proboscideus 1 3.8.2004 06:14 9 9 45 m

M. proboscideus 1 4.8.2004 06:31 9 13 46 m

M. proboscideus 1 4.8.2004 07:50 9 2 43 -

M. proboscideus 2 29.7.2017 19:37 9 12 54 f

M. proboscideus 2 31.7.2004 19:34 9 2 45 f

M. proboscideus 2 3.8.2004 07:54 9 13 57 f

M. minutoides 1 29.7.2004 19:56 10 3 10 m

M. minutoides 2 31.7.2004 20:06 10 3 10 -

M. minutoides 0 4.8.2004 07:04 10 28 12 -

A. namaquensis 1 29.7.2004 18:31 10 28 - f

A. namaquensis 1 31.7.2004 18:35 10 28 47 f

A. namaquensis 1 31.7.2004 20:42 10 28 46 f

A. namaquensis 2 29.7.2004 18:40 10 29 39 f

A. namaquensis 2 29.7.2004 20:27 10 26 44 f

A. namaquensis 2 31.7.2004 18:36 10 29 38 f

A. namaquensis 2 3.8.2004 06:43 10 27 40 -

A. namaquensis 2 4.8.2004 07:04 10 29 43 f

A. namaquensis 2 4.8.2004 08:22 10 27 46 f

A. namaquensis 3 29.7.2004 18:40 10 29 39 m

A. namaquensis 3 29.7.2004 20:40 10 29 50 m

A. namaquensis 3 31.7.2004 18:36 10 30 47 m

A. namaquensis 3 31.7.2004 20:46 10 29 46 m

A. namaquensis 3 31.7.2004 21:22 10 23 44 m

A. namaquensis 3 3.8.2004 08:37 10 28 46 m

A. namaquensis 4 29.7.2004 20:10 10 17 52 m

A. namaquensis 4 3.8.2004 08:06 10 1 58 m

A. namaquensis 5 29.7.2004 20:27 10 28 57 m

A. namaquensis 5 31.7.2004 20:20 10 11 51 m

A. namaquensis 6 29.7.2004 21:35 10 28 46 -


Appendix 60


A. namaquensis 6 31.7.2001 20:34 10 25 39 -

A. namaquensis 7 31.7.2004 20:25 10 17 46 f

A. namaquensis 7 3.8.2004 08:16 10 10 46 f

A. namaquensis 7 4.8.2004 08:59 10 21 45 f

A. namaquensis X 29.7.2004 20:20 10 22 - -

E. edwardii 1 3.8.2004 06:30 10 1 50 m

E. edwardii 1 4.8.2004 06:50 10 3 52 m

E. edwardii 2 29.7.2004 21:20 10 3 52 -

E. edwardii 2 31.7.2004 16:38 10 1 60 -

E. rupestris 1 29.7.2004 18:18 10 25 74 f

E. rupestris 1 3.8.2004 08:25 10 20 64 f

E. rupestris 1 4.8.2004 07:04 10 30 65 f

E. rupestris 2 31.7.2004 18:33 10 23 59 -

E. rupestris 2 3.8.2004 08:30 10 21 58 f

E. rupestris 0 4.8.2004 08:10 10 20 63 m

Table 5: Trapping data from the summer-trapping season


A. namaquensis 0 8.11.2004 22:24 1 10 30 -

A. namaquensis 0 10.11.2004 04:40 1 13 33 -

A. namaquensis 20 7.11.2004 22:18 1 9 28 f

A. namaquensis 30 8.11.2004 22:19 1 9 57 -

E. rupestris 0 7.11.2004 20:58 1 9 25 f

E. rupestris 20 7.11.2004 17:48 1 9 61 m

E. rupestris 20 10.11.2004 06:00 1 30 64 m

E. rupestris 20 11.11.2004 07:36 1 12 65 -

E. rupestris 30 7.11.2004 17:55 1 12 73 f

E. rupestris 30 7.11.2004 20:55 1 7 - -

E. rupestris 30 8.11.2004 18:02 1 5 73 f

E. rupestris 30 8.11.2004 19:07 1 7 - -

E. rupestris 30 8.11.2004 21:05 1 10 - - E. rupestris 30 10.11.2004 07:30 1 5 78 -

E. rupestris 30 11.11.2004 06:05 1 4 80 -

E. rupestris 100 8.11.2004 18:03 1 10 28 f

E. rupestris 100 8.11.2004 21:00 1 9 29 f

E. rupestris 100 10.11.2004 06:01 1 9 30 -

E. rupestris 100 11.11.2004 06:10 1 9 34 -

E. rupestris 200 10.11.2004 04:37 1 10 31 f

E. rupestris 200 11.11.2004 06:08 1 7 25,5 -

R. pumilio 0 10.11.2004 07:50 2 30 44 m

R. pumilio 0 11.11.2004 07:50 2 29 48 m

R. pumilio 561 11.11.2004 09:00 2 30 48 m

G. paeba 0 11.11.2004 05:00 2 4 16,5 f

G. paeba 2 7.11.2004 22:41 2 19 30 m

G. paeba 2 11.11.2004 05:11 2 17 34 -

G. paeba 4 7.11.2004 22:44 2 21 33 m

G. paeba 4 8.11.2004 22:50 2 21 30 -

G. paeba 4 11.11.2004 05:05 2 7 34 -

G. paeba 10 11.11.2004 05:14 2 25 29 m


Appendix 61


G. paeba 20 7.11.2004 22:36 2 11 16 m

G. paeba 30 7.11.2004 22:47 2 30 25 f

G. paeba 100 8.11.2004 22:42 2 7 29 -

G. paeba 200 8.11.2004 22:46 2 11 15 m

G. paeba 300 10.11.2004 04:54 2 11 18 m

G. paeba 300 11.11.2004 05:09 2 11 18 -

G. paeba 300 11.11.2004 06:00 2 11 - -

G. paeba X 10.11.2004 05:00 2 30 29 -

G. paeba X 11.11.2004 05:17 2 26 28 -

G. paeba 3 18.10.2004 06:17 3 27 32 -

R. pumilio 1 19.10.2004 04:39 3 4 36 f

O. unisulcatus 1 15.10.2004 19:25 4 5 113 m

O. unisulcatus 2 18.10.2004 06:32 4 5 91 f

G. paeba 0 15.10.2004 21:00 4 19 8 f

G. paeba 1 15.10.2004 21:10 4 26 13 m

G. paeba X 18.10.2004 04:55 4 7 - -

G. paeba 2 18.10.2004 04:58 4 9 23 -

G. paeba 2 19.10.2004 05:05 4 23 27 m

G. paeba 3 18.10.2004 06:17 4 27 32 -

G. paeba 7 19.10.2004 04:58 4 10 26 f

M. proboscideus 1 19.10.2004 05:10 4 30 32 f

G. paeba 0 2.11.2004 10:31 5 15 14 -

G. paeba 0 3.11.2004 10:28 5 11 14 f

G. paeba 20 2.11.2004 10:34 5 17 33 f

G. paeba 30 2.11.2004 09:10 5 5 16 m

G. paeba 30 6.11.2004 04:50 5 5 15 -

G. paeba 100 2.11.2004 10:39 5 23 28 f

G. paeba 100 5.11.2004 04:55 5 17 31 -

G. paeba 200 5.11.2004 04:48 5 3 15 m

G. paeba 300 5.11.2004 04:58 5 30 22 m

G. paeba 800 6.11.2004 03:17 5 17 31 m

G. paeba 10 6.11.2004 05:00 5 28 30 f

G. paeba 2 21.10.2004 22:14 7 25 33 -

G. paeba 2 22.10.2004 22:10 7 28 31 m

G. paeba 2 25.10.2004 06:10 7 3 30 m

G. paeba 6 24.10.2004 04:28 7 9 33 f

G. paeba 10 25.10.2004 04:31 7 7 30 f

G. paeba 11 25.10.2004 04:40 7 21 28 m

M. proboscideus 0 25.10.2004 06:20 7 17 37 m

M. proboscideus 1 21.10.2004 19:04 7 1 30 f

M. proboscideus 1 24.10.2004 04:20 7 4 32 f

M. proboscideus 1 25.10.2004 06:05 7 1 37 f

M. proboscideus 2 21.10.2004 20:55 7 19 51 f

M. proboscideus 2 24.10.2004 04:35 7 19 53 f

M. proboscideus 3 21.10.2004 21:00 7 28 52 f

M. proboscideus 3 24.10.2004 04:40 7 30 53 f

M. proboscideus 4 21.10.2004 21:00 7 29 41 m

M. proboscideus 6 21.10.2004 22:08 7 9 38 m

M. proboscideus 7 22.10.2004 20:45 7 4 38 m

M. proboscideus 7 24.10.2004 07:19 7 4 42 m


Appendix 62


R. pumilio 0 22.10.1004 17:54 8 11 55 m

R. pumilio 0 24.10.2004 09:17 8 2 52 m

R. pumilio 0 25.10.2004 07:55 8 12 50 m

R. pumilio 1 21.10.2004 17:56 8 30 46 m

R. pumilio 2 21.10.2004 19:20 8 29 44 f

R. pumilio 2 22.10.2004 17:50 8 30 41 f

R. pumilio 2 22.10.2004 19:15 8 30 41 -

R. pumilio 2 24.10.2004 07:36 8 28 35 f

R. pumilio 2 25.10.2004 07:50 8 29 41 -

R. pumilio 3 24.10.2004 07:52 8 2 55 m

R. pumilio 4 24.10.2004 09:17 8 4 60 f

R. pumilio 5 25.10.2004 06:55 8 1 59 -

R. pumilio 6 25.10.2004 06:55 8 2 60 f

R. pumilio 7 25.10.2004 09:20 8 11 59 m

R. pumilio 8 25.10.2004 09:25 8 29 41 f

R. pumilio 9 25.10.2004 09:25 8 29 18 f

R. pumilio 10 25.10.2004 09:13 8 5 15 m

R. pumilio 11 24.10.2004 09:16 8 27 14 -

O. unisulcatus 0 25.10.2004 06:37 8 15 100 m

O. unisulcatus 1 22.10.2004 18:01 8 2 114 m

O. unisulcatus 2 22.10.2004 21:12 8 2 121 m

O. unisulcatus 3 24.10.2004 06:16 8 29 131 f

O. unisulcatus 4 24.10.2004 07:45 8 10 102 -

O. unisulcatus 5 25.10.2004 06:40 8 13 105 f

G. paeba 0 21.10.2004 22:30 8 30 31 -

G. paeba 0 24.10.2004 04:58 8 19 34 f

G. paeba 3 21.10.2004 22:38 8 4 29 f

G. paeba 4 22.10.2004 21:10 8 15 28 -

G. paeba 5 22.10.2004 22:28 8 27 25 f

G. paeba 5 21.10.2004 21:20 8 29 33 f

G. paeba 7 24.10.2004 04:54 8 26 27 m

G. paeba 7 25.10.2004 04:55 8 27 28 m

G. paeba 8 24.10.2004 05:02 8 17 30 m

G. paeba 8 25.10.2004 04:59 8 26 32 m

G. paeba 9 24.10.2004 05:08 8 2 28 f

G. paeba 12 25.10.2004 05:08 8 5 25 f

M. proboscideus 5 21.10.2004 21:20 8 29 33 f

M. proboscideus 8 25.10.2004 06:49 8 9 45 m

M. minutoides 0 30.10.2004 05:03 9 28 18 -

R. pumilio X 26.10.2004 17:37 9 1 49 -

R. pumilio 0 29.10.2004 07:47 9 29 juv. -

R. pumilio 1 26.10.2004 19:10 9 22 38 f

R. pumilio 1 27.10.2004 17:40 9 26 37 f

R. pumilio 1 29.10.2004 07:39 9 17 - -

R. pumilio 1 30.10.2004 09:00 9 17 34 -

R. pumilio 10 27.10.2004 17:28 9 2 57 f

R. pumilio 11 27.10.2004 17:30 9 5 24 m

R. pumilio 12 27.10.2004 18:58 9 10 62 m

R. pumilio 12 30.10.2004 07:18 9 10 62 -

R. pumilio 13 27.10.2004 18:58 9 11 65 m


Appendix 63


R. pumilio 13 29.10.2004 07:44 9 23 - -

R. pumilio 13 29.10.2004 09:00 9 23 - -

R. pumilio 13 30.10.2004 07:25 9 23 59 -

R. pumilio 13 30.10.2004 08:55 9 11 58 -

G. paeba 1 26.10.2004 20:42 9 17 13 -

G. paeba 1 27.10.2004 21:06 9 19 13 f

G. paeba 1 30.10.2004 04:48 9 15 15 -

G. paeba 2 26.10.2004 20:46 9 23 13 -

G. paeba 2 27.10.2004 21:16 9 28 15 m

G. paeba 2 29.10.2004 04:56 9 25 18 -

G. paeba 2 30.10.2004 05:00 9 27 17 f

G. paeba 3 26.10.2004 20:50 9 25 13 m

G. paeba 3 27.10.2004 21:14 9 26 16 -

G. paeba 3 29.10.2004 04:54 9 21 15 -

G. paeba 4 26.10.2004 22:02 9 3 11 m

G. paeba 4 27.10.2004 20:55 9 4 13 m

G. paeba 4 27.10.2004 22:00 9 3 11 -

G. paeba 4 29.10.2004 04:35 9 4 15 -

G. paeba 4 30.10.2004 06:04 9 3 16 -

G. paeba 5 26.10.2004 22:00 9 1 29 f

G. paeba 5 29.10.2004 04:29 9 1 30 -

G. paeba 5 30.10.2004 06:07 9 5 29 -

G. paeba 5 30.10.2004 04:32 9 5 30 f

G. paeba 6 26.10.2004 20:35 9 3 36 f

G. paeba 8 26.10.2004 22:06 9 4 32 f

G. paeba 8 27.10.2004 20:46 9 3 34 f

G. paeba 8 27.10.2004 22:02 9 7 - -

G. paeba 8 29.10.2004 04:37 9 5 35 -

G. paeba 8 29.10.2004 05:59 9 5 36 -

G. paeba 8 29.10.2004 07:30 9 4 34 -

G. paeba 8 30.10.2004 04:39 9 7 37 -

G. paeba 9 26.10.2004 22:12 9 10 29 f

G. paeba 9 27.10.2004 21:00 9 15 30 f

G. paeba 9 29.10.2004 04:44 9 15 34 -

G. paeba 9 30.10.2004 04:45 9 12 34 f

G. paeba 20 30.10.2004 04:54 9 21 17 m

E. edwardii 7 26.10.2004 19:20 9 28 77 f

E. rupestris 4 27.10.2004 17:26 9 1 38 f

E. rupestris 3 30.10.2004 04:28 9 1 67 m

E. rupestris 3 30.10.2004 06:17 9 30 65 m

E. rupestris 10 27.10.2004 20:45 9 1 79 f

E. rupestris 0 29.10.2004 06:06 9 30 80 f

M. macroscelides 1 26.10.2004 19:05 9 7 45 f




M. macroscelides 10 27.10.2004 21:10 9 21 18 m

M. macroscelides 10 29.10.2004 04:50 9 19 21 -




Appendix 64




M. minutoides 1 27.10.2004 22:27 10 25 9 -

M. minutoides 2 27.10.2004 22:29 10 27 9 m

M. minutoides 3 29.10.2004 05:36 10 27 13 m

M. minutoides 70 30.10.2004 05:19 10 4 14 m

A. namaquensis 1 26.10.2004 22:28 10 1 - -

A. namaquensis 1 29.10.2004 05:14 10 2 52 -

A. namaquensis 2 26.10.2004 20:59 10 1 54 -

A. namaquensis 2 27.10.2004 21:28 10 1 59 -

A. namaquensis 2 27.10.2004 22:17 10 1 - -

A. namaquensis 2 29.10.2004 06:16 10 2 60 -

A. namaquensis 2 30.10.2004 05:14 10 1 56 f

A. namaquensis 6 26.10.2004 21:12 10 28 54 f

A. namaquensis 7 26.10.2004 19:34 10 11 53 f

A. namaquensis 7 27.10.2004 21:37 10 11 56 f

A. namaquensis 7 29.10.2004 05:25 10 17 57 -

A. namaquensis 7 26.10.2004 21:08 10 11 - f

A. namaquensis 7 30.10.2004 05:35 10 21 57 -

A. namaquensis 10 27.10.2004 21:44 10 30 24 f

A. namaquensis 11 29.10.2004 05:19 10 11 33 f

A. namaquensis 20 30.10.2004 05:24 10 7 28 m

A. namaquensis 30 30.10.2004 05:40 10 26 29 f

E. rupestris 3 26.10.2004 22:35 10 18 67 m

E. rupestris 1 27.10.2004 17:55 10 21 63 f

E. edwardii 2 26.10.2004 19:25 10 1 71 f

E. edwardii 7 27.10.2004 19:15 10 2 74 f

E. edwardii 7 29.10.2004 06:20 10 4 80 f

E. edwardii 7 30.10.2004 05:31 10 16 78 f


Appendix 65

Table 6: Trapping data from the fence-line study


G. paeba 1 10.8.2004 19:56 Farm 26 24 m

G. paeba 1 11.8.2004 19:54 Farm 26 25 m

A. namaquensis 1 10.8.2004 21:22 Farm 18 50 f

A. namaquensis 1 11.8.2004 21:15 Farm 19 49

A. namaquensis 1 14.8.2004 08:00 Farm 19 - -

A. namaquensis 2 10.8.2004 21:22 Farm 19 37 -



A. namaquensis 2 13.8.2004 11:20 Farm 19 - -





A. namaquensis X 11.8.2004 19:18 Farm 21 52 -

G. paeba 2 10.8.2004 21:05 Goegap 19 27 f

G. paeba 2 14.8.2004 06:47 Goegap 13 30 f

R. pumilio 429 13.8.2004 09:20 Goegap 15 62 m






Acknowledgements 66

9. Acknowledgements

A lot of people made their contribution during this diploma thesis.

First, I want to thank Prof. Norbert Sachser, who gave me the possibility to make

this external diploma thesis and had the trust to send me half around the world in

order to do it. Most of all I have to thank my supervisor Dr. Carsten Schradin. He

showed a really exceptional engagement for my diploma thesis and me and even

lent me his beloved Landrover to collect my data. The data collection would not

have been possible without the help of my field assistants. My special thanks go to

Philipp Widmann and Annette Wiedon for bearing my bad mood during many

trapping nights and the effective help with dragging traps and mountain climbing.

For further field assistance I thank Eva Krause, Madeleine Scriba, Melanie

Schubert, Carola Schneider and Brigitte Britz. The whole team from the research

station in Goegap Nature Reserve owes my great thanks for a lot of social support

and motivation during difficult times. I got a lot of useful tips and lessons in

distinguishing E. rupestris from E. edwardii from Galen Rathbun and therefore also

send my thanks to California.

For the warm reception back in Münster and a lot of advises I thank the

whole team of the Department of Behavioural Biology. Most support came from

Oliver Ambreé, who spent a great deal of time helping me to solve all my little

problems. For the correction of my English I thank Prof. Dr. Michael Hennessy. For

their patience and competent help for an ignorant zoologist, who tried to analyse

soil samples, I thank Dr. Nicole Armbrüster and Hildegard Schwitte. For providing

a scale and managing to bring it to South Africa I thank Prof. Dr. von Willert.

I also have to thank Jens Mecklenborg for providing his laptop and

bolstering me, along with many other friends and family members. Especially I

want to mention my flatmate Jörg Holle, who had to deal with an interim tenant for

six month and was still so generous to provide me an extra desk. I also thank

Ruben Böhmer for constantly telling me that everything can be managed.

I would like to thank the Northern Cape Department of Agriculture, Land Reform,

and Environment for their permission to conduct my studies in Goegap Nature

Reserve, and the staff of Goegap for their assistance.

For financial support I thank the University of the Witwatersrand,

Johannesburg and especially Prof. N. Pillay the Frauenförderung of the University

of Münster and my parents, who supported me during my whole course of studies.

Erklärung

Hiermit versichere ich, die vorliegende Arbeit selbstständig verfasst und keine

anderen als die angegebenen Quellen und Hilfsmittel verwandt zu haben.

Münster, den 30.04.2005

. Christina Keller

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