Population dynamics, catastrophes and stability

Abstract

Three main external factors are important in the regulation of wild animal populations: food supply, predation and disease. The first two have been considered often, but population regulation by disease has received considerably less attention. Indeed, disease can play a dramatic role, as is demonstrated by the effect of the myxomatosis virus on rabbits. Yet, these catastrophes are rare events and can be studied only occasionally in wild animal populations, although some epidemics have been reported in, for example, white-tailed deer (Marburger and Thomas 1965), howler monkey (yellow fever; Chivers 1969, Mittermeier 1973), African elephant (in Manyara Mycoplasma pneumonia caused the death of approximately 23% of the elephant population in 1977; Weyerhaeuser 1982), or jackal and wild dog (Serengeti, probably due to rabies; J.G. Grootenhuis, personal communication). Whether disease has to be regarded as a population regulatory factor in mammals is not clear, but models and some observations strongly suggest that it is possible (Anderson and May 1979, 1985, May and Anderson 1979, Anderson 1981, Leader-Williams 1982). In birds disease is possibly more important (Anderson and May 1979; see also Potts et al. 1984). In this chapter I will discuss the impact of diseases on mortality, but first, I will discuss the impact of predation.