ELSEVIER Palaeogeography, Palaeoclimatology, Palaeoecology 149 (1999) 271–282

Taphonomy of pollen associated with predation

Y. Fernandez-Jalvo a,d,Ł, L. Scott b, C. Denys c

a Museo Nacional de Ciencias Naturales (CSIC), Jose Gutierrez Abascal 2, E-28006 Madrid, Spainb Department of Botany and Genetics, University of the Orange Free State, P.O. Box 339, SA-9300 Bloemfontein, South Africa

c Laboratoire des Mammiferes et Oiseaux, Museum National d’Histoire Naturelle, 55, rue Buffon, F-75005 Paris, Franced Institut des Sciences de l’Evolution, UMR 5554, CNRS-Paleontologie, Universite de Montpellier II Cc. 64, Pl. E. Bataillon,

F-34095 Montpellier Cedex 05, France

Received 10 December 1996; revised version received 6 October 1997; accepted 8 June 1998

Abstract

The pollen contents of owl pellets were studied in order to use them as modern analogues in the interpretation of fossilsediments which accumulated through predation. Firstly, experiments were conducted to follow pollen through a trophicpredation cycle and to observe any physical alterations. Neither pollen in mouse droppings nor that in raptor pellets showedany clear signs of damage as result of digestion by gastric juices. However, clear fracturing of grass pollen grains wereobserved in one case. The cause of fracturing is unknown and although chewing action of rodents may be consideredas one possibility, further research is necessary to study this phenomenon and its significance. Further, it was found thatchemical preparation of pellets to extract pollen resulted in the formation of high ratios of small organic nodules. A thinbut very resistant superficial debris covering was found on many pellet pollen grains, but it could not be firmly establishedif it is caused by digestive action in the stomachs of raptors or by the laboratory procedure. Further, the pollen compositionof pellets in the natural setting was studied to throw light on alterations on pollen assemblages in the predation process.The modern analogues show differences in pollen composition between accumulation sites and the pollen rain of the studyarea. They help to identify several problems of predation bias such as seasonal variations, and site locality, which shouldbe considered in environmental interpretations of fossil material. 1999 Elsevier Science B.V. All rights reserved.

Keywords: taphonomy; environment; pollen grains; predation; owl pellets; modern analogues; digestion

1. Introduction

Far from being the image of palaeobiologicalcommunities frozen in time, fossil materials are theresult of dynamic environmental systems and inter-relationships of organisms which can be observed innature today. New approaches of palaeontology aimto interpret the past in as much detail as possible in

Ł Corresponding author. Current address at a. E-mail:yfj@mncn.csic.es

order to explain the distribution of present environ-ments and climatic phenomena. Taphonomy offersa great contribution to this field by identifying theindependent events and processes which occurred inthe past which are not ascribed to climate, ecologyor sedimentology. Pollen from land sites, which isgenerally interpreted in terms of the current pollenrain in a region, may, however, be disturbed bynatural trophic sequences. Pollen is consumed byherbivorous small mammals and these in turn mayfall prey to predators. Even in the most generalist

0031-0182/99/$ – see front matter 1999 Elsevier Science B.V. All rights reserved.PII: S 0 0 3 1 - 0 1 8 2 ( 9 8 ) 0 0 2 0 6 - 5

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herbivores, palatability of plants may vary greatly,because some species of prey are ignored and othersheavily consumed (Marquis and Batzli, 1989). Sim-ilarly, the species composition of small mammalstaken by predators is biased when compared withtheir natural occurrence (Mikkola, 1983; Andrews,1990). Accumulations produced by predation may,therefore, contain pollen which can differ from thepollen rain of the area, and complicate subsequentenvironmental interpretations.

Pollen contents of owl pellets have previouslybeen studied in order to determine the effects onpollen composition of micromammal assemblagesaccumulated through processes of predation. Prelim-inary results (Fernandez-Jalvo et al., 1996; Scott etal., 1996) show different cases of pollen compositionbias due to predation, depending on the selectivefeeding of rodent species and the dietary preferencesor hunting behaviours of their predators. These re-sults show, on the other hand, that the interpretationof contemporary local landscapes at a fossil site,should rely on the combination of different envi-ronmental indications obtained through taphonomicobservations of inferred predators and taxonomicidentifications of their prey (micromammals) andassociated pollen spectra.

In view of the observation that fossil accumu-lations can be influenced by predation processes,factors determining the nature of pollen assemblagesassociated with predation, are studied in this paper.Owl pellets as modern analogues of fossil accumula-tions are investigated.

Firstly, experiments on pellets are reported inwhich the possible physical effects of digestion onpollen are investigated. The experiments were car-ried out with the aim of studying the effect of thetrophic sequence on pollen under controlled condi-tions. Even though pollen grains are strongly acidresistant, and it is unlikely that they will be damagedby stomach acids of predators, we, nevertheless, feltthat it was necessary to test this assumption withexperiments in order to observe pollen quality afterdigestion. Natural undamaged pollen was fed to micewhich in turn were ingested by raptors. Pollen frommouse droppings and raptor pellets were observedwith a scanning electron microscope (SEM), andchemical composition was analysed, to see signs ofdamage that could be related to digestion processes.

Secondly, we continue previous research onpollen composition in owl pellets in this paper bypresenting new palynological data which includepollen assemblages and measurements of their con-centrations in relation to seasonal variations. Dietarypreferences of spotted eagle owls at two differentsites are also compared. This approach may providenew perspectives on the dynamics of palaeobiolog-ical communities by shedding light on ecologicalinter-relationships. This in turn may be applied todetailed reconstructions of the local landscapes atpredation debris sites where large and small mam-mals remains are associated with pollen. In fossilsequences this may help to distinguish between as-semblage changes caused by either climate or tapho-nomic differences.

This work should be followed up by applyingthe observations on predation bias on fossil assem-blages. A beginning has been made with an Earlyand middle Pleistocene site in Spain with humanremains (Atapuerca, near Burgos), to test pollen con-tent and association with rodents. The investigationis in progress and preliminary results show possiblepollen bias due to sampling, taphonomic factors androdent palatability of plants. It is hoped that this ap-proach will cast more light on palaeoenvironmentalconditions of this important site.

2. Material

2.1. Experiments on digestion damage

Ultramicroscopic analyses of pollen grains inkestrel pellets (from Spain) and in spotted eagleowl pellets (from Clarens, South Africa) were doneto investigate the possible digestion effects related topredation. In order to observe possible damage dueto digestion, experimental work was carried out withnatural pollen, rodents and raptors. Natural pollenof Platanus, Quercus and Olea was obtained fromflowers with no chemical treatment. This pollen wasingested by 5 adult laboratory mice (Mus musculus;l.c. 129v, Pasteur) 7 months old provided by theUniversity of Montpellier. Another set of 43 mice(same species and 2 months old) were provided forthe second part of the experiment. Raptors involvedin the experiment were two barn owls (Tyto alba),

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one of them used as control, tawny owl (Strix aluco),long-eared owl (Asio otus), kestrel (Falco tinnuncu-lus) and black kite (Milvus migrans). These are wildraptors injured by cars or electric wires which arenursed in the Ornithological Park of Saintes-Mariesde la Mer (Camargue, France).

2.2. Pollen composition in pellets

More modern owl pellets have been analysedin order to increase our data base of their pollencontents. A new pellet from Ouwerf, Clarens (FreeState, South Africa), which is visited by spottedeagle owls, has been found in order to follow upprevious work at this site (Fernandez-Jalvo et al.,1996; Scott et al., 1996). Material from a nestingand hunting area of spotted eagle owls at the Kloof,another nearby site at Clarens, was studied in detail,also to compare the data from the two sites. Isolatedpellets from the cave site at Sterkfontein (Gauteng,South Africa), which were apparently produced bybarn owls, has also been collected.

The number of new pellets from the differentsites is, however, limited. The scarcity has beenascribed to a critical drought period during 1994and early 1995 which after a rodent plague causedthe rodent population to decline markedly virtuallydisappearing in 1995 over the large parts of SouthAfrica. This resulted in the disruption of huntingpractises of resident owls, forcing them to leave theirtraditional areas or to change their prey from smallmammals to birds and insects (G. Lockwood, pers.commun.). It was noticed that the pellet productionat the Kloof declined steadily over several monthsuntil none was available in December 1995. Onlyone was found at Ouwerf. Similarly, in the nearbyGolden Gate National Park, common roosting andnesting places where owls have frequently been seenby the Park personnel, yielded no pellets.

3. Methods

3.1. Experimental work

3.1.1. Pollen ingested by rodentsInitial experiments showed that pollen passed

through the digestive tracts of mice and was not

yet included in their excrements 1 h 30 min afteringestion time. The main experiment involved fiveadult mice. Four different pollen doses were given tothe mice: Platanus on the first day, oak on the secondone, olive on the third, and a mixed preparation ofthe three types on the fourth day. The natural pollenwas suspended in water to facilitate the ingestion.Solutions were highly concentrated in pollen, butbecause the aim of the experiment was not to countthe excreted pollen, proportions were not weighted.Each suspension, however, was prepared using thesame procedure to obtain similar concentration ofpollen. The pollen suspension was administered tothe mouths of to each mouse by a metric syringe toensure that each mouse drank the same quantity. Aspecial cage was made for the experiment with twodifferent floors. The upper one was fixed and con-sisted of a 5 mm mesh, large enough for droppingsto pass through, and small enough for the comfort ofthe mice. The second floor, with a mesh of 0.5 mmfor urine to pass through, was removable in order toenable the sampling of droppings. The five cleanedmice were left to fast outside the experimental cagefor 17 to 18 hours, receiving only water. After polleningestion the mice were placed in the experimentcage. The first sample of excrements appeared 1 h 30min and four further samples of droppings at hourlyintervals. Droppings were collected in separate pa-per envelopes, noting the date, pollen ingestion, timeof sampling and number of droppings. After thelast sampling, the mice were returned to their liv-ing cage which were previously cleaned and withoutfood, for one night. Droppings made during the nightwere collected the following day. The last samplewas taken during ingestion of the next pollen type.Stress caused by the ingestion process apparentlystimulated defecation. Subsequent analyses showedthat these last samples, around 24 hours after initialingestion, still had residual pollen.

3.1.2. Pollen ingested by predatorsSince raptors from the Ornithological Park in the

Camargue, near Montpellier (France), normally re-ceived a chicken diet, they were accustomed to adiet of mice which were not enriched in pollen. Thediurnal birds took mice on the first day, but the owlsonly after five days. A total of 48 adult mice wereacquired for the experiment to feed the raptors. It

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Fig. 1. SEM micrograph of nodules heavily covering pollengrains from a spotted eagle owl pellet from the Kloof site(Clarens, Free State, South Africa).

was observed that a minimum of three mice per rap-tor should be given. During the experiment, raptorswere placed in individual cages (1 ð 3 m). Micewere divided into three groups, fifteen had Platanuspollen, 16 had oak pollen and 17 had olive pollen.Three mice containing the same pollen type weregiven to each raptor every day, except for the barnowl used as control of the experiment that receivedmice non-enriched in pollen. The extra mice of eachset were given to the biggest bird, the black kite,which needed a bigger supply. Pellets were collectedeach day as soon as they were noticed during threedaily observations (morning, afternoon and evening).Pellets were wrapped in blotting paper and stored insealed plastic bags, marking the date, raptor, sam-pling time and pollen content.

3.2. Processing

The same processing procedure was used to ex-tract pollen from pellets collected during the exper-iment and the fieldwork in natural settings. Pellets,soil samples and sediments were placed in KOH(10%) at about 80ºC for 3 minutes, and washed andcentrifuged at least twice with distilled water. Thiswas followed by standard acetolysis treatment for3 minutes. Short centrifuging at about 3000 r.p.m.was carried out to improve pollen concentrations byremoving colloidal particles.

Residues were prepared for scanning electron mi-croscope (SEM) analysis. Pollens were separatedfrom the residue and mounted on SEM aluminium

stubs (50 mm of diameter). The samples were sputtercoated with gold or carbon, and examined using aJeol-6400 from the University of the Orange FreeState of Bloemfontein, a Jeol-6300F from the Uni-versity of Montpellier II, and a Philips XL20 fromthe Natural History Museum of Madrid (MNCN).Observations were made using secondary electronemission mode at 10 to 15 kV. The pollen slideswere also examined using a light microscope.

Some samples had also EDS chemical elementanalyses using a Cameca SX50 electron microprobeat the Natural History Museum of London, and aPhilips XL20 at the MNCN of Madrid.

4. Results and discussion

4.1. General

High ratios of small nodules of unknown compo-sition (Fig. 1) were found to be difficult to removefrom pellet preparations without destroying pollen.The nodules prevents the production of highly con-centrated pollen preparations, making pollen analysisof modern pellets time consuming even if they aremoderately rich. Therefore, only pellets extremelyrich in pollen were counted. The nodules are be-lieved to be products derived from the bodies ofprey, especially because they have not been observedon pollen from mouse droppings. Similar nodulesmay, however, show up in preparations of fossilremains and may serve as an indication that suchdeposits include products of owl pellets.

4.2. Pollen alteration

Apart from the small nodules, smooth superficialdebris coverings were often observed on some pollengrains by scanning electron microscope (Fig. 2a, b).These are apparently transparent because they are notnoticeable under a light microscope. The covering onpollen was observed on pollen residues obtained fromvirtually all the studied pellets from different raptors,whether they were artificially enriched with pollen inthe experiments, or natural. Samples were treated fur-ther with organic solvents like xylol and acid (HF) inorder to dissolve any organic matter but the coveringon pollen grains resisted this.

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Fig. 2. (a) SEM micrograph of an Olea pollen grain from black kite (Milvus migrans) from the experiment. The grain is completelycovered by the smooth layer of superficial debris. Mice containing olive pollen were ingested one day before the pellet was sampled.(b) SEM micrograph of a pollen grain completely covered by the smooth layer of superficial debris. The sample is coming from spottedeagle owl pellets from the Kloof site (Clarens).

We have also analysed the chemical element com-ponent of the covering using EDS microprobe anal-yses in order to investigate its origin and nature,but results are not conclusive. The biggest problemis the thinness of the covering layer which made itdifficult to analyse it exclusively and not the pollensurface, or even the SEM stub made in aluminium.This layer, however, has consistency, because whenit completely covers a pollen grain, the amount ofaluminium, which comes from the stub underneaththe pollen specimens, is lower (Fig. 3a, b). The de-termination of the chemical composition is, however,not conclusive as inconsistent results were obtainedwith chlorine occurring in some cases and phospho-rous in others.

Apart from intensity of digestion (pH) typicalof each raptor (Duke et al., 1976; Andrews, 1990),the covering seems to be also related with time inthe stomach. Pellets ejected one day after a givenmouse pollen set was ingested had more pollenscompletely covered. This may also be related withthe enzymatic activity. Studies on digestion withraptors have shown that after the first meal, the pHof the gastric juices are greatly reduced (Leprince etal., 1979). Experimental studies have shown that the

enzymatic activity is a powerful factor in digestiondamage (Denys et al., 1995) and its effects arerelated with time of digestion.

Previous ultramicroscopic analyses at the scan-ning electron microscope of pollens from kestrel pel-lets taken in natural conditions from Burgos (Spain)showed some surface cracking (Fig. 4a–d). Vacuumchamber of the SEM has been seen to crack somespecimens, such as rodent teeth (Denys, pers. com-mun.), though all pollen samples were analysed thesame day and SEM conditions were the same forall of them. We cannot, however, be sure that thecracking is not related to digestion.

One sample from a spotted eagle owl pellet fromthe South African site of Ouwerf (Owf. Dec ’93,in Fig. 5) showed a severe fracturing, apparentlyphysical in origin, affecting more than the 80% of thegrains. This unexpected fracturing (Fig. 6a) has onlybeen observed in this case and not in the six otherspotted eagle owl pellets which are represented inFig. 5. The question arises whether the fracturing inthis case is related to rodent chewing process, as theprey is graniverous (Table 1). No damage, however,was observed on the broken edges (Fig. 6b).

Experiments with mice that ingested natural

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Y. Fernandez-Jalvo et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 149 (1999) 271–282 277

Fig. 4. (a) SEM micrograph of a pollen grain of Quercus from kestrel (Falco tinnunculus) pellets taken in Burgos (Spain). Note thedistinct cracking on the grain surface. The arrow shows the area pictured in (c). (b) SEM micrograph. Detail of the cracking of theprevious picture. (c) SEM micrograph of the area pointed out in (a) showing a small cracking of the grain surface. (d) SEM micrographof a pollen grain of Quercus from kestrel pellets (Spain). The grain is affected by superficial cracking and is partially covered by asmooth layer of superficial debris which nature is unknown, but apparently related to digestion processes.

pollen, and raptors that ingested mice with pollenhave been conducted. Pollen recovered from mousedroppings and raptor pellets were all treated ina similar way as pollen samples from sediments.They were prepared for SEM analyses providingdocumentary evidence of the pollen. Unfortunately,pollen given to the mice in the experiment wassuspended in water, it was not chewed, and this pe-

Fig. 3. EDS chemical element analysis on a pollen grain from spotted eagle owl pellets from Kloof site uncovered (a) and from agrain completely covered (b) by the layer of superficial debris. Samples were sputter coated with carbon, and mounted on aluminiumstubs. Sulphur is assumed to be remains of the processing treatment. Note the lowest amount of aluminium in (b) covered pollen grain,compared with (a) non-covered pollen grain seemingly produced by the covering layer hindrance.

culiar fracturing could not be contrasted. Althoughthe prepared food given to laboratory mice includesgramineae, and the small size of the laboratory miceused for the experiment could produce some fractur-ing during chewing, few grass pollens were noticedin the dropping samples, and none was observedto be fractured. This is not conclusive, however,and probably the key to the problem is the rodent

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Fig. 5. Pollen diagrams from distinct pellets of spotted eagle owls owl (Bubo africanus) from Ouwerf (Owf) and Kloof (Kf) sites (Clarens) with indication of collectingdates. Slope sample represents the average pollen spectrum for the thickly vegetated area over 10 years (1980–1990; Scott and Vogel, 1992), where the owl was nesting.

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Table 1Taxonomic identification, diet and habitats of micromammals identified in the owl pellets (according to Lynch, 1983; Stuart and Stuart,1993)

Ouwerf Kloof Diet Habitat

Dec. ’93 Sept. ’94 May ’95 May ’95

Otomysirroratus

5 2 1 vegetarian dense stands of grass; in times of drought, they resort toring barking trees and shrubs; grassy hillsides

Aethomysnamaquensis

1 1 graniverous=herbivorous

rocks, open grassland

Mastomys spp. 1 omnivorous wide toleranceRhabdomys 2 omnivorous wide-range requires dense vegetationPronolagus sp. 1 grazer and leaves rocky outcrops and hills covered by grass and shrubs

species which produced the pellet (Owf. Dec ’93)with pollen fractured, Aethomys. Further investiga-tion with this or a similar taxon is needed.

4.3. Pollen composition of pellets in the naturalsetting

The new pellet sample from Ouwerf, Clarens(Owf. Dec ’95, Fig. 5) is similar to the previous onetaken from this site two years before. The pollen ofthese pellets, produced by spotted eagle owls (Buboafricanus) is almost exclusively grass pollen (Fig. 5),and small mammals identified (Table 1) are alsoassociated with grassland environments. The pelletswere collected just below the owl nest, situated ina precipitous wooded mountain slope (Fig. 7). Apollen spectrum, accumulated over 10 years (Scott,1989; Scott and Vogel, 1992) is richer in arborealpollen (Fig. 5). The pollen spectrum from the nest,used by the owls for years, contains pollen speciesfrom the surroundings, but it still shows predomi-nance of grass. This biased pollen spectra is consid-ered to be related to the diet of rodents (Table 1)captured in the higher-lying grassland slope (Fig. 8),where owls have been observed to be active (Fernan-dez-Jalvo et al., 1996; Scott et al., 1996). Similaritiesin pollen content observed between the old and thenew pellets from Ouwerf suggest that the grasslandslope is regularly visited by the owls for hunting.

Another site, also inhabited by spotted eagle owls,is the Kloof, near Clarens. This site is in a smallprotected valley where owls have their nest (Fig. 9)and roost on the rocks and in trees. The placementof the nest is similar to the one at Ouwerf, butat Ouwerf the higher-lying habitat is more open

Fig. 6. (a) SEM micrograph of pollen grains of Gramineae fromspotted eagle owl pellets taken from the nest at Clarens site. Notethe frequent fracturing of the pollen grains. (b) SEM micrograph.Detail of the fracture edge of the grass pollen with no apparentdamage.

and in the Kloof area the topography slightly ismore even (Fig. 10). More low bush is found in thevegetation above the Kloof nest. Numerous pellets

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Fig. 7. Emplacement of the spotted eagle owl nest in the woodedmountain slope of Ouwerf (Clarens). The arrow shows the posi-tion of the nest spot.

indicate a long term use of this area. All pelletswere taken on the first visit to the Kloof site inDecember 1994. Afterwards the site was visitedregularly and new pellets were removed. The pollenin two of them which were produced in May ’95,were analysed in detail (Fig. 5). Different pollencomposition was found in individual pellets at theKloof, and to some extent, these differences alsoaffect the micromammal species identified in thesepellets (Table 1). Because both pellets were producedin the same period, differences between Myrsine andAnthospermum pollen in individual pellets of Kloofhave to be related to prey dietary preferences. BothMyrsine and Anthospermum are typical shrubs on thesouth facing (shady slopes). The differences betweenKloof and Ouwerf pollen spectra is that the latterhas much more grass pollen, even in the nest debris.

Fig. 8. The spotted eagle owl hunting area at Ouwerf site(Clarens) is an open grassland slope above the nest spot.

This is an indication that the owls at Ouwerf huntedin the higher-lying grassland, although the season ofsampling may have played a role (see Section 4.5).The low number of grass pollen in the Kloof pelletsand nest debris may be an indication of huntingactivities in shrubby slopes and not above over theopen habitat or activity closer to the nest site (whichincidentally is surrounded by Myrsine shrubs). Thefact that the Kloof pellets formed in winter doesnot account for the low grass contents because thisratio is also found in the nest debris which representsseveral seasons.

4.4. Pollen concentration

Although the concentration values seem high(Table 2) in the Clarens pellets only the richestones were counted as explained above. The Decem-ber and January pellets are poor in pollen but the

Table 2Concentration estimates of different owl pellets calculated as 100grains per gram

Site Date Season Concentration

Kloof 26 Sept. ’94 spring 2Kloof 30 Dec. ’94 summer 1Kloof 30 Dec. ’94 summer 5Kloof 30 Dec. ’94 summer 13Kloof 28 Jan. ’95 summer 12Kloof a 23 May ’95 autumn–winter 72Kloof a 23 May ’95 autumn–winter 63Ouwerf a 11 Dec. ’95 summer 25

a Included in the pollen diagram (Fig. 5).

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Fig. 9. Location of the spotted eagle owl nest at the Kloofsite (Clarens) in a vegetated small valley. The arrow shows theposition of the nest spot.

autumn–winter ones (May) are rich in pollen. Thisis unexpected since the area receives summer rainwhich results in flowering and pollen production ofgrasses. But as mentioned above the weak springduring the drought phase rains and better rains inautumn probably accounts for this.

Virtually no pollen was found in the Sterkfonteinowl pellets. This is difficult to explain since thedates of their formation is unknown. It may berelated to seasonal factors or drought conditionswhich influenced flowering in the region or to otherfactors.

4.5. Seasonality

One of the Kloof pellets seem to be dominatedby flowers that probably flower in winter e.g. An-

Fig. 10. Open habitat on top of the limestone cliff of Kloof site.

thospermum, but the other is dominated by Myrsinewhich may flower in summer (Fig. 5). Both, how-ever, have very small flowers and the dominance ofthese types in the different sample can be related tothe inclusion of small dead flowers in the stomachcontents or fur of the prey, preserving the pollenbeyond the flowering season. As suggested above,the low grass pollen is not necessarily related to thewinter season in which they were collected becausethe nest debris assemblage does not support this.They differ from the summer pellets which comefrom Ouwerf (December, 1993 and 1995) and con-tain mainly grass pollen which flower in summer.It is possible that the studied pellets from Ouwerfcontain anomalously high grass proportions becausethey were formed in summer. However, the grassflowering time extends well into autumn so thatgrass pollen is probably still numerous in early win-ter. Further the nest debris suggest that in generalmore grass pollen reaches this nest than the one atthe Kloof and this effect is more likely related tohunting area than season.

5. Conclusion

The problem of pollen flux through a predationcycle is complex. The present results serve mainlyto recognise these complexities. Several factors ac-count in pollen composition from these types ofassociations, such as prey dietary preferences, raptorhunting area, prey availability and seasonality. Thispaper provides additional data that support previous

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results, and new observations that may help in in-terpreting fossil sites. It is clear, however, that pelletsampling and monitoring have to be extended inorder to calibrate this pollen bias, and to establishbetter correlations between rodent and pollen datafor palaeoenvironmental interpretations. In generalterms, the analyses of both mouse droppings andraptor pellets from the experiment show no damageto pollen quality, but further research is necessaryto address some of the questions that arose. For in-stance, it remains to be seen if the covering debrislayer on pollen and small nodules will show up infossil assemblages. If so this could be a criterion forrecognizing fossil pollen produced by predation.

Acknowledgements

We are very grateful to Mr. R. Lamouroux, di-rector of the Ornithological Park of Saintes-Mariesde la Mer (Camargue, Southern France) who kindlyprovided all predators, special cages and facilities, aswell as, to the Park assistants for constant help andguidance during the experiment. We thank to J.-P.Cour who helped to design the experiment and pro-vided natural pollen. Annie Orth and Catherine Mou-lia offered their valuable help and advice, and sup-plied mice, laboratories and instrumental to accom-plish the experiment. Laboratory, microscope andfield assistance was given by Marianna Steenkamp,Frederick Scott, Dr. Pieter van Wyk and ProfessorRudi Verhoeven of the University of the Free Stateand by Martin Wessels, J. Ferrier and J. Chambon.We also thank, T. Williams from the Departmentof Mineralogy of the Natural History Museum ofLondon (NHM), and to J. Bedoya from the MuseoNacional de Ciencias Naturales (MNCN), for help

and facilities in operating the microprobes and theSEMs. Thanks to J. Gonzalez de la Fuente from thePhoto Unit of the MNCN for the rapid and valuablework. This project received partial financial sup-port of the University of the Orange Free State, theFRD, the Institut des Sciences de l’Evolution (UMR-5554, CNRS), the DGICYT project no. PB90-O126-CO3-01, and the Fyssen Foundation.

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