Environment and reproduction in tree squirrels with special reference to the genus Paraxerus

  • S. Viljoen
Part of the Biology and Environment book series (SBES)

Abstract

Environmental variables strongly influence reproduction in squirrels living in temperate zones where winter is a highly inclement period. However, even in tropical (Emmons, 1975) and subtropical squirrels (Viljoen, 1975), breeding is seasonally related to the environment. No single environmental factor exerts complete control over reproductive activity; for example, changes in light regime are accompanied by alterations in other environmental influences. Nutrition, inclement weather, rainfall and photoperiod are interrelated variables that have all been mentioned as factors affecting sciurid breeding seasons. Little experimental work has been done, however, and when discussing these factors separately, one must keep in mind that they do not stand in isolation. Some examples of the complexity of environmental influences on breeding patterns are evident from studies on the bush squirrel, Paraxerus cepapi cepapi, at Naboomspruit (24°35′ S, 28°47′ E) in South Africa (Viljoen, 1975). Rainfall commences in September, and the first females come into oestrus soon after. At this time, which coincides with or is just slightly after the spring equinox, there is a green flush of vegetation and flowers are abundant. In the male of this species the scrota show a sharp increase in size in June just before the winter solstice, when temperatures are at their lowest and rainfall is at a minimum. This coincides with the end of the period of food abundance. Scrotal shrinkage is apparent in late December and January during the rainy season, when maximum temperatures are at their highest and just after day-length has started to decrease. The number of vesicular follicles per ovary is low from April to August (1.3 ± 1.6 in May, n = 6) and much higher from September to December (22.8 ± 3.3 in September, n = 3). Corpora atretica show a reverse trend. Therefore, in South Africa, the seasonal availability of food has probably influenced the evolution of breeding periods in tree squirrels, but this factor is not easily separated from rainfall and day-length.

Keywords

Shrinkage Malaysia Nigeria Mast Congo 

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References

  1. Allen, D. L. (1942). Population and habits of the fox squirrel in Allegan County, Michigan, Am. Midl. Nat., 27, 338–79CrossRefGoogle Scholar
  2. Brown, L. G. and Yeager, L. E. (1945). Fox squirrels and grey squirrels in Illinois, Bull. Ill. nat. Hist. Survey, 23, 449–536Google Scholar
  3. Brown, L. N. and McGuire, R. J. (1975). Field ecology of the exotic Mexican red-bellied squirrel in Florida, J. Mammal., 56, 405–19CrossRefGoogle Scholar
  4. Delany, M. J. (1972). The ecology of small rodents in tropical Africa, Mammal Rev., 2, 1–42CrossRefGoogle Scholar
  5. Dolbeer, R. A. (1973). Reproduction in the red squirrel (Tamiasciurus hudsonicus) in Colorado, J. Mammal., 54, 536–40PubMedCrossRefGoogle Scholar
  6. Emmons, L. H. (1975). Ecology and behaviour of African rain forest squirrels, Ph.D. Thesis, Cornell University, Ithaca, N.Y.Google Scholar
  7. Ferron, J. and Prescott, J. (1977). Gestation, litter size and number of litters of the red squirrel (Tamiasciurus hudsonicus) in Quebec, Can. Field Nat., 91, 83–4Google Scholar
  8. Hanney, P. (1965). The muridae of Malawi, J. Zool., 146, 579–633Google Scholar
  9. Happold, D. C. D. (1966). Breeding periods of rodents in the Northern Sudan, Rev. Zool. Bot. afr., 74, 357–63Google Scholar
  10. Jewell, P. A. and Oates, J. F. (1969). Breeding activity in prosimians and small rodents in West Africa, J. Reprod. Fert., Suppl6, 23–38Google Scholar
  11. Kemp, G. A. and Keith, L. B. (1970). Dynamics and regulation of red squirrel (Tamiasciurus hudsonicus) populations, Ecology, 51, 763–79CrossRefGoogle Scholar
  12. Kingdon, J. (1974). East African Mammals, Vol. IIB, Academic Press, LondonGoogle Scholar
  13. Kirkpatrick, C. M. (1955). The testis of the fox squirrel in relation to age and seasons, Am. J. Anat., 97, 229–55PubMedCrossRefGoogle Scholar
  14. Knopf, F. L. and Balph, D. F. (1977). Annual periodicity of Uinta ground squirrels, Southwest. Nat., 22, 213–24CrossRefGoogle Scholar
  15. Lester, D. T. (1967). Variation in cone production of red pine in relation to weather, Can. J. Bot., 45, 1683–91CrossRefGoogle Scholar
  16. McKeever, S. (1963). Seasonal changes in body weight, reproductive organs, pituitary, adrenal glands, thyroid gland and spleen of the Belding ground squirrel (Citellus beldingi), Am. J. Anat., 113, 153–73PubMedCrossRefGoogle Scholar
  17. Mallinson, J. J. C. (1975). Notes on a breeding group of Sierra Leone striped squirrels, Int. Zoo Ybk, 15, 237–40CrossRefGoogle Scholar
  18. Michener, G. R. (1977). Effect of climatic conditions on the annual conditions and hibernation cycle of Richardson’s ground squirrels and Columbian ground squirrels, Can. J. Zool., 55, 693–703CrossRefGoogle Scholar
  19. Millar, J. S. (1970). The breeding seasons and reproductive cycle of the western red squirrel, Can. J. Zool., 40, 471–3CrossRefGoogle Scholar
  20. Millar, J. C. G. (1972). Certain aspects of the ecology of the American grey squirrel Sciurus carolinensis (Gmelin) in the Cape Province, unpublished manuscript, Cape Department of Nature ConservationGoogle Scholar
  21. Muul, I. and Lim, B. L. (1974). Reproductive frequency in Malaysian flying squirrels Hylopetes and Pteromyscus, J. Mammal., 18, 20–5Google Scholar
  22. Nixon, C. M. and McClain, M. W. (1975). Breeding seasons and fecundity of female grey squirrels in Ohio, J. Widl. Mgmt, 39, 426–38CrossRefGoogle Scholar
  23. Nixon, C. M., McClain, M. W. and Donohoe, R. W. (1975). Effects of hunting and mast crops on a squirrel population, J. Wildl. Mgmt, 39, 1–25CrossRefGoogle Scholar
  24. Prakash, I. (1960). Breeding of mammals in Rajasthan desert, India, J. Mammal., 41, 386–9CrossRefGoogle Scholar
  25. Pudney, J. (1976). Seasonal changes in the testis and epididymis of the American grey squirrel, Sciurus carolinensis, J. Zool., 179, 107–20PubMedCrossRefGoogle Scholar
  26. Purohit, K. G., Kametkar, L. R. and Prakash, I. (1966). Reproductive biology and post-natal development in the northern palm squirrel, Funambulus pennanti Wroughton, Mammalia, 30, 538–46CrossRefGoogle Scholar
  27. Rahm, U. (1970). Note sur la reproduction des sciuridés et murides dans la forét équatoriale au Congo, Rev. suisse Zool., 77, 635–46CrossRefGoogle Scholar
  28. Reddi, A. H. and Prasad, M. R. N. (1968).The reproductive cycle of the male Indian palm squirrel, Funambulus pennanti Wroughton, J. Reprod. Fert., 17, 235–45CrossRefGoogle Scholar
  29. Robinson, D. J. and Cowan I. McT.(1954).An introduced population of the grey squirrel (Sciurus carolinensis Gmelin) in British Columbia, Can. J. Zool., 32, 261–82CrossRefGoogle Scholar
  30. Rowlands, I. W. (1938). Preliminary note on the reproductive cycle of the red squirrel (Sciurus vulgaris), Proc. zool. Soc. Lond., 108, 441–3Google Scholar
  31. Rusch, D. A. and Reeder, W. G. (1978). Population ecology of Alberta red squirrels, Ecology, 59, 400–20CrossRefGoogle Scholar
  32. Sadleir, R. M. F. S. (1969). The Ecology of Reproduction in Wild and Domestic Mammals, Methuen, LondonCrossRefGoogle Scholar
  33. Seth, P. and Prasad, M. R. N. (1969). Reproduction cycle of the female five-striped Indian Palm squirrel Funambulus pennanti (Wroughton), J. Reprod. Fert., 20, 211–22CrossRefGoogle Scholar
  34. Shorten, M. (1951). Some aspects of the biology of the grey squirrel (Sciurus carolinensis) in Great Britain, Proc. Zool. Soc. Lond., 121, 427–59CrossRefGoogle Scholar
  35. Smith, C. C. (1968). The adaptive nature of social organization in the genus of tree squirrels, Tamiasciurus, Ecol. Monogr., 38, 31–63CrossRefGoogle Scholar
  36. Smithers, R. H. N. (1972). The Mammals of Botswana, National Museums of Rhodesia, SalisburyGoogle Scholar
  37. Thompson, D. C. (1977). Reproductive behaviour of the grey squirrel, Can. J. Zool., 55, 1176–89CrossRefGoogle Scholar
  38. Viljoen, S. (1975). Aspects of the ecology, reproductive physiology and ethology of the bush squirrel, Paraxerus cepapi cepapi, M.Sc. thesis, University of PretoriaGoogle Scholar
  39. Viljoen, S. (1977a). Factors affecting breeding synchronization in an African bush squirrel Paraxerus cepapi cepapi, J. Reprod. Fert., 50, 125–127CrossRefGoogle Scholar
  40. Viljoen, S. (1977b). Behaviour of the bush squirrel, Paraxerus cepapi cepapi,Mammalia, 41, 119–66CrossRefGoogle Scholar
  41. Viljoen, S. (1977c). Feeding habits of the bush squirrel Paraxerus cepapi cepapi (Rodentia: Sciuridae), Zool. afr., 12, 459–67CrossRefGoogle Scholar
  42. Viljoen, S. (1978). Notes on the western striped squirrel, Funisciurus congicus congicus (Kuhl 1820), Madoqua, 11, 119–28Google Scholar
  43. Walker, R. F. and Frawley, L. S. (1977). Gonadal function in underfed rats. II. Effect of oestrogen on plasma gonadotrophins after pinealectomy or constant light exposure, Biol. Reprod., 17, 630–4PubMedCrossRefGoogle Scholar
  44. Yahner, R. H. and Svendsen, G. E. (1978). Effects of climate on the circannual rhythm of the eastern chipmunk, Tamias striatus, J. Mammal., 59, 109–15CrossRefGoogle Scholar

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© Mrs S. Viljoen 1981

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  • S. Viljoen

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