Aj?. J. Ecol. 1982, Volume 20, pages 279-287 Pelage and moult in the springhare Pedetes cupensis in Botswana T. M. BUTYNSKI* Department of’wildlije, National Parks and Tourism, Gaborone, Botswana Summary Springhares were collected monthly between August 197 1 and August 1973 in the Republic of Botswana. Pelages of foetal, juvenile and adult springhares are described. Moult pattern is of the caudad type in both the juvenile and adult moult. In a sample of 326 springhares, 64% of the juveniles and 19% of the adults were in moult. Time of juvenile moult was directly correlated with body weight (age). Incidence ofjuvenile moult was highest during the wet season, but occurred in all months. Peak months for adult moult were December and January. No springhares were in adult moult during July or August. Adult moult showed significant positive correlations with monthly total rainfall, mean air tempera- ture, mean forage protein and day length at mid-month. No sexual dimorphism was found for pelage, moult pattern or season of moult. Lactation appeared to hinder moult. At the population level adult moult in springhares occurs seasonally but at the level of the individual the adult moult appears to be a chronologically flexible phenomenon which is delayed or retarded during times of stress and initiated or accelerated when conditions are favourable. Resume Des lievres sauteurs ont ete recoltes chaque mois entre aodt 197 1 et aodt 1973 en Republique du Botswana. Les pelages des foetus, des jeunes et des adultes sont decrits. Le schema de mue est de type “caudal” tant chez lesjuveniles que chez les adultes. Dans un echantillons de 326 lievres, 64% des juveniles et 19% des adultes etaient en mue. La periode de mue chez les juveniles prksente une relation positive avec le poids du corps (iige). La mue des jeunes est la plus frequente pendant la saison des pluies mais peut se rencontrer toute l’annee. Les mois de mue principaux pour les adultes sont decembre et janvier, et il n’y en a jamais en juillet-aodt. La mue des adultes montre une correlation positive significative avec les chutes de pluies mensuelles, la temperature moyenne de l’air, la moyenne proteinique du fourrage et la duree du jour au milieu du mois. On n’a pas observe de dimorphisme sexuel du pelage, du procesus ou de la periode de mue. La *Present address: New York Zoological Society. Bronx Park, Bronx, New York 10460, U.S.A. Correspondence: Kibale Forest Project, P.O. Box 409, Fort Portal, Uganda. 0141-6107/82/12004279 $02.00 0 1982 Blackwell Scientific Publications
Transcript
Aj?. J. Ecol. 1982, Volume 20, pages 279-287
Pelage and moult in the springhare Pedetes cupensis in Botswana
T. M. BUTYNSKI* Department of’wildlije, National Parks and Tourism, Gaborone, Botswana
Summary Springhares were collected monthly between August 197 1 and August 1973 in the Republic of Botswana. Pelages of foetal, juvenile and adult springhares are described. Moult pattern is of the caudad type in both the juvenile and adult moult. In a sample of 326 springhares, 64% of the juveniles and 19% of the adults were in moult. Time of juvenile moult was directly correlated with body weight (age). Incidence ofjuvenile moult was highest during the wet season, but occurred in all months. Peak months for adult moult were December and January. No springhares were in adult moult during July or August. Adult moult showed significant positive correlations with monthly total rainfall, mean air tempera- ture, mean forage protein and day length at mid-month. No sexual dimorphism was found for pelage, moult pattern or season of moult. Lactation appeared to hinder moult.
At the population level adult moult in springhares occurs seasonally but at the level of the individual the adult moult appears to be a chronologically flexible phenomenon which is delayed or retarded during times of stress and initiated or accelerated when conditions are favourable.
Resume Des lievres sauteurs ont ete recoltes chaque mois entre aodt 197 1 et aodt 1973 en Republique du Botswana. Les pelages des foetus, des jeunes et des adultes sont decrits. Le schema de mue est de type “caudal” tant chez lesjuveniles que chez les adultes. Dans un echantillons de 326 lievres, 64% des juveniles et 19% des adultes etaient en mue. La periode de mue chez les juveniles prksente une relation positive avec le poids du corps (iige). La mue des jeunes est la plus frequente pendant la saison des pluies mais peut se rencontrer toute l’annee. Les mois de mue principaux pour les adultes sont decembre et janvier, et il n’y en a jamais en juillet-aodt. La mue des adultes montre une correlation positive significative avec les chutes de pluies mensuelles, la temperature moyenne de l’air, la moyenne proteinique du fourrage et la duree du jour au milieu du mois. On n’a pas observe de dimorphisme sexuel du pelage, du procesus ou de la periode de mue. La
*Present address: New York Zoological Society. Bronx Park, Bronx, New York 10460, U.S.A.
Correspondence: Kibale Forest Project, P.O. Box 409, Fort Portal, Uganda.
lactation semble empCcher la mue. Au niveau de toute la population, la mue des lilvres adultes se produit saisonnierement mais au niveau individuel elle semble Ctre un phenomene chronologiquement flexible qui est reporte ou retard6 en cas de stress et provoque ou accelere quand les conditions sont favorables.
Introduction Ling (l970), in his comprehensive review of pelage and moult in wild mammals, indicated a need for additional information on moult in tropical and equatorial wild mammals. In a more recent survey of the literature only three papers were found which dealt with moult in African mammals (Meester, 1958; Viljoen, 1975; Baxter, 1977).
The pelage of the springhare P e d ~ t c ~ cupensis (Forster) and the process and season of its moult were studied in the Republic of Botswana from August 1971 until August 1974 as part of a broader ecological study of this interesting and economically important species (Butynski, 1973).
Springhares are large ( 3 kg), saltatorial, bipedal rodents inhabiting flat, short- grass areas of the southern third of Africa (Coe, 1969; Dorst & Dandelot, 1970; Kingdon, 1974). They arc strictly herbivorous and nocturnal, spending the day within burrows. During this study no seasonal peaks in the reproduction of springhares were noted (Butynski, 1979).
Study areas, methods and definitions The Kalahari Study Area was located in the Kutswe Game Reserve and southern portion of the Central Kalahari Game Reserve (23-24"s 24-25"E). Rainfall over the Kalahari Study Area can deviate 70% from the annual mean of 400 mm. The vegetation consists primarily of scattered shrubs and tall grasses. Most springhares, however, are associated with circular (0.1-1 .O km in diameter), flat-bottomed, seasonally flooded depressions called 'pans'. These are charac- terized by compact, clayey calcareous soils, bordering sand dune formations, a dense, short, grass cover, and a paucity of woody vegetations (Dawson & Butynski, 1975).
The Eastern Botswana Study Area was 180 km to the southeast on the outskirts of Gaborone (24-25"s 25-26"E). The mean yearly rainfall on the Eastern Study Area is 500 mm with a variation of up to 30%. Most of the area is covered by annual grasses and bush. A good grass cover persists during the wet season but the area is nearly devoid ofgrass during the dry season (Butynski, 1975, 1978).
Mean monthly maximum and minimum air temperatures range from 37 and 11°C in January and December, to 27 and -3°C in June and July. Frosts occur from May to October and may be severe.
Springhares were located at night with the help of a spotlamp and were shot with a 12-gauge shotgun. An attempt was made to collect all individuals en- countered. The sampling method is assumed to be random; there is no evidence to suggest that any sex, age or reproductive class was differentially susceptible to collection.
The mean monthly sample size from September 1972 to July 1973, for both areas combined, was 29.5 50.25 springhares. In addition, two springhares were collected in August 1073. Observations were made on the moult patterns of six captive springhares and on springhare study skins in the National Museums of
Pelage and moult in the springhare 28 1
Rhodesia, of which 308 were collected from various localities in Botswana and 63 from Rhodesia. Pelts and moults were classified as either juvenile or adult (see criteria below), and the percentage of new pelage was estimated. Sketches were made and photographs were taken of springhares in moult for later reference.
An accurate criterion for estimating age was not available for springhares so body weight was used to indicate relative age. A body weight of 2.6 kg was used as the division between juveniles and adults (Butynski, 1979; Butynski & Hanks, 1979).
In this paper, ‘rainfall’ is the mean monthly rainfall based on 30 years of data (1 939-1 969) for Gaborone (Botswana Meteorological Services). ‘Air temperature’ is the mean daily air temperature for each month as derived from nine years of data (1958-1967) for Gaborone (Siderious, 1972). ‘Forage protein’ is the percentage protein in springhare stomach contents collected in this study during each month from August 1971 through August 1973 (n=542) . ‘Day length’ is taken from the Smithsonian Meteorological Tables (List, 1966) and represents the number of daylight hours at mid-month.
Springhares were classified as ‘in moult’ if any pelage replacement was detected. The ‘juvenile moult’ removes the juvenile pelage and brings in the first adult pelage. All subsequent moults are termed ‘adult moults’. A ‘moult line’ occurs where shedding pelage meets the new pelage. Movement of the moult line from the beginning to the end of moult provides a ‘moult pattern’.
Hair type, pelage stage, and moult pattern were classified according to Danforth (1 9 2 9 , Negus ( 1 958) and Stodart (1 9 6 9 , respectively.
Results Preliminary analysis of the data indicated that neither locality of collection nor sex of the individual influenced pattern of moult, body weight at first moult or season of moult. All of the springhares examined, therefore, were considered to be from one population and for some ofthe analyses the data have been combined.
Pelage types The gestation period of the springhare is approximately 77 days (Rosenthal & Meritt, 1973; Velte, 1978). Fur starts to appear at about 17 days before birth (Butynski, 1978). T h e a f t e r the pelage of the foetus develops rapidly. Dense brown fur first appears on top of the head and then on the tail, nape, hips and rump. At birth the entire dorsal portion of the body is covered with a dense brown fur which, except on the ears, tail, and outer parts ofthe legs, is overlain by longer, black guard hairs. The belly, neck, genitalia, insides of the legs and soles of the feet are nearly naked. F. F. Velte (pers. comm.) remarked that the underparts do not possess a good fur covering until at least three weeks after birth.
Springhares between 1-7 weeks of age were not observed. They first emerged from the burrow and became available to the collector at about 7 weeks of age (body weight > 1.3 kg) (Butynski & Mattingly, 1979). Thus, it is not known whether the pelage classified here as ‘juvenile’ represents the first pelage or is preceded by one or more moults.
In the juvenile pelage, the upper parts of the body, the lower half of the ears, and the first 20 cm of the tail are brown. The underfur on the back is relatively thick and 25-33 mm in length. The proximal half of these hairs is a dull cream
282 T. M . Butjwski
colour and the distal half is glossy brown. A sparse covering of 35-mm long black guard hairs overlays the underfur of the back. The brown fur on the tail is coarser and duller than that on the body, is 50-60 mm in length and lacks the cream colour on its proximal half, Fur on the last 20 cm of the tail, upper half of the ears, and soles of the hind feet is black, as are the vibrissae. The only other black fur occurs as a large, clearly defined area on the underside of the base of the tail. Underparts and insides of the legs vary in colour, depending upon the subspecies, from white to light orangc. Belly fur is 20-30 mm in length, fine in texture and sparse. Guard hairs are lacking from the tail and those parts of the body covered with white fur.
Adult pelage is similar to juvenile pelage but coarser and generally darker. The underfur on the back is grey at its base rather than cream-coloured, and the black fur at the base of the tail and on the bottoms of the hind feet changes to light grey or cream.
Moult pattern The moult line in springhares is distinct only where brown fur is overlain with guard hairs. In springhares, therefore, the moult line cannot be used to determine moult pattern, or occurrence of moult on parts of the body where guard hairs are lacking.
Springhares have a ‘caudad’ moult pattern (Stodart, 1965). No differences were found in the patterns of moult between either juvenile and adult or between male and female springhares. Pelage replacement begins on the face, muzzle and base of the anterior side of the ears. The moult line then becomes ‘U-shaped’ (bottom of ‘U’ in the centre of the back and nearest the rump) and progresses over the top of the head, nape and front half of the back. The U-shaped moult line is usually evident until completion of the moult at the base of the tail, but may become straight, jagged or indistinct.
Relationship hetween body weight and moult In a sample of 183 springhares, all of which had some juvenile pelage, the lightest animals in moult weighed I .7 kg. None of the sixteen individuals weighing less than 1-7 kg had begun the juvenile moult. Thirteen per cent of the springhares weighing between 1.7 kg and 2.1 kg, and nearly 90*/0 of those weighing between 2.2 kg and 2.9 kg, were in juvenile moult. Most springhares completed the juvenile moult before attaining a weight of 2 3 kg, although some were nearly 3.0 kg. Therefore, juvenile moult commenced after springhares started to feed outside their burrows (body weight > 1.3 kg) and before most reached sexual maturity (body weight > 2.6 kg).
Springhares occasionally entered into the first adult moult at a weight of 2.6 kg, but most weighed between 2.7 kg and 2.9 kg.
Relative ratcs and Jieqi.renc,j) of moult There were no significant differences between the percentages of juvenile males (55% of49)andjuvenilefemales(73% of45)in moult (~2=2.67 , d.f.= 1 , P>O.IO), or between adult males (22Yo of 122) and adult females ( I 5% of 1 10) in moult 01’ = 2.22, d.f. = 1 . P > 0.14). These data indirectly suggest that there was no sex
Pelage and moult in the springhare 283
difference in the amount of time required to moult (i.e. rate of moult) or the frequency at which moult occurs. A highly significant difference existed, however, between percentages ofjuveniles (64%, n = 94) and adults (19%, n = 232) in moult kZ=63.49, d.f. = I , P<O.OOOl). Thus, there appears to be an age differ- ence in either the rate of moult (slower in juveniles) and/or in the frequency at which moult occurs (more frequent in juveniles).
In the collection of the National Museums of Rhodesia the percentage of juvenile specimens in juvenile moult was cocsiderably smaller (26% n= 122) than in the sample obtained during the present study (64%). However, the percentage of adults in moult in the two collections was similar (15% v. 19%, n=257). No immediate reason can be given for this anomaly.
The lowest incidence of adult moult was in non-pregnant adult females, 78% of which were lactating. Only one of twenty-six non-pregnant adult females was in moult whereas sixteen of eighty-four pregnant females were in moult. However, this difference is not significant (x2=2.45, d.f. = 1, P< 0.10).
Whether or not a springhare was collected was apparently independent of the degree to which it had undergone moult. The relative rate of movement of the moult line from the head towards the tail was determined by comparing the number of collected springhares occurring within each of ten 10% categories of pelage replacement (i.e. category 1 for animals with >0-9% new pelage; category 2 for 10-19% new pelage, etc.). If the rate of movement of the moult line was the same during the entire moult, one would expect each category of pelage replace- ment to be equally represented in the sample. A sample of 165 moulting spring- hares indicated that the rate of pelage replacement was fairly constant over the anterior 90% of the body. Fifty-three (32%) of the moulting springhares, however, exhibited moult lines within the posterior 10% of the body. This indicated that the rate of moult over the posterior 10% of the body was approximately four times slower than over the anterior 90% of the body.
Time,from beginning to end of moult Time required to moult varied considerably among individuals and possibly between juveniles and adults. A juvenile female captured at a weight of 1.2 kg began the juvenile moult 10 weeks later at a weight of 1.7 kg and completed the moult in 30 days at a weight of 2-0 kg. Three adult females, each with 80% of the adult moult completed, required an additional 4, 7 and 10 weeks, respectively, to complete the final 20% of the moult. Another adult female required six weeks to undergo the complete adult moult. The effect of captivity on the moulting process is unknown.
Time of moult and environmentalfactors Monthly percentages of springhares in juvenile moult and in adult moult Y were transformed by log, ( Y + 1) and their degree of association with four environ- mental factors tested by least square linear regression.
The juvenile moult occurred at all times of year (Table 1). There is evidence of an increase in juvenile moult activity from January through April when 53-71% of the juveniles were in juvenile moult. The monthly percentages of juvenile springhares undergoing juvenile moult showed significant positive correlations
284 T. M. Butynski
Table 1. Monthly distribution o f springhares in juvenile and adult moults in Botswana and Rhodesia, and monthly values for total rainfall, mean air temperature, mean forage protein, and mid-month day length
Month Total Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec ormeans
with rainfall (r=0.619, d.E= 10, P<0.025), air temperature (r=0.600, d.f.= 10, P<0-025), and forage protein (r=0-582, d.f.= 10, P<0-025), but not with day length (r=0.472, d.f. = 10, P >().lo).
During 1972-73 the adult moult was confined to the period between November and May, inclusive. Peak months for adult moult were December and January when more than 4Oo/o of those springhares in adult pelage were moulting. Study skins in the National Museums of Rhodesia showed that some members of the Botswana population underwent adult moult in June, September and October during some years (Table 1 ). No springhares were found in adult moult in July or August.
Monthly percentages of' adult springhares in adult moult yielded highly signifi- cant positive associations with rainfall. air temperature, forage protein and day length (Fig. 1 ). Springhares in adult moult exhibited higher correlation coefficients and levels of significance with these environmental variables than did springhares in juvenile moult.
Discussion This study found a positive correlation between juvenile moult in springhares and body size (age). Such a relationship has also been observed in muskrats Ondatra zihelhica (Errington, 1939), meadow voles Microtus pennsylvanicus (Goin, I943), California voles Microtu.\ c*al(/brnicus (Ecke & Kinney, 1956), brown rats Rattus norvegicus (Mohn, 1958), and hispid cotton rats Sigrnodon hispidus (Chipman, 1965).
Although physical condition and reproductive effort in springhares appears to be.unrelated to seasonal environmental changes (Butynski, 1979) this is not the
Pelage and moult in the springhare 285
4 7 ( 0 )
3- 0 0
2- 0
.- ! 0 - O 1 ' 5 :O 45 $0 7: 9'0 105 o t z i $ o l k 1 ' 8 $0 2: 214
Rainfall (mm) Temperature (OC) .2" J)' A
0
log ( Y +I ) = 1.080X - 10.999 (rz0.767, df=lO, Pe0.005) ( r ~0.913, df ;lo, k0 .005)
I I I I I I I I I 10.0 11.5 13.0 14.5 16.0 17.5 19.0 20.5 10.5 11.0 11.5 12.0 12.5 13.0 13.5 14.0
Protein (%) Day-length ( h )
Fig. 1. Relationship between the percentages of springhares in adult moult Y and (a) total rainfall, (b) mean air temperature, (c) mean forage protein, and (d) day length at mid-month during each of twelve consecutive months. Sample sizes as in Table 1. See text for definitions.
case for the adult moult. The highly significant correlations of adult moult with rainfall, air temperature, forage protein and day length suggest that timing of this moult evolved to circumvent the period of the year when temperature and rainfall are lowest, and nutrients scarcest. The replacement of adult pelage occurs at a time when environmental conditions are most favourable (Butynski, 1978) as has been found for a number of mammalian species in many environments (Ling, 1970,1972).
In springhares, fat deposition occurs throughout gestation and fat reserves are drained during lactation (Butynski, 1978). Clearly, lactation is the most stressful phase of the springhare reproductive cycle. The low occurrence of adult moult in lactating females strongly suggests that lactation hinders the moult process. Lactation also has been interpreted as interrupting, arresting or preventing the completion of moult in a number of rodents, including squirrels Sciurus spp. and Tamias spp. (Allen, I894), spiny pocket mice Heteromys spp. (Goldman, 19 1 l), prairie dogs Cynomys spp. (Hollister, 19 16), deer mice Peromyscus maniculatus (Collins, I923), pocket gophers Thomomys umhrinus (Morejohn & Howard, 1956), R. norvegicus (Mohn, 1958), S. hispidus (Chipman, 1965) and pocket mice Perognathus parvus (Speth, Pritchett & Jorgensen, 1968; Speth, 1969).
Although adult moult in springhares occurs seasonally, there is, nonethe- less, considerable individual variation in the inception, progression and duration of moult, particularly among adult females. This variability does not necessarily indicate a reduced sensitivity to environmental stimuli at the individual level. In fact, the opposite is more likely the case. Moult in springhares appears to be a chronologically flexible phenomenon which is delayed or retarded during times of
286 T. M . Butjmrki
stress, and initiated or accelerated when conditions are favourable. Ling (1970) mentioned several cases in which the related factors of physical condition and reproductive state are known to act alone or in combination to block or promote moult in mammals.
From a review of the literature, Ling (1970) concluded that moult in mammals is ‘. . .an inherent characteristic co-ordinated with respect to season by photo- period but modified locally by such indirect factors as temperature and behaviour and, more directly, by nutrition’. The present study of a tropical rodent found nothing to contradict these conclusions.
Acknowledgments I wish to acknowledge the co-operation and financial assistance of the Botswana Department of Wildlife, National Parks and Tourism, the United States Peace Corps, and Michigan State University. Deepest appreciation goes to Alec Campbell, Lindsey Birch, Gregory Mann, Jeffery Dawson, ‘Kutswe’ Aaron, Carol Fisher Wong and Dr. Wolfgang von Richter for their assistance in the field. I wish also to thank Jan Kalina and Drs George Petrides, Rollin Baker, John King and Duane Ullrey, all of Michigan State University, for their critical reading of this paper. I am indebted to Dr Raey Smithers and the National Museums of Rhodesia for original data on Pedetcjx
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