DEMOGRAPHY, EXTINCTION AND INTERVENTION IN A SMALL POPULATION - THE CASE OF THE SERENGETI WILD DOGS

The effects of ecological factors (prey, competitors, predators and di sease) and intervention (immobilization, radio-collaring, and vaccinat ion) on population size and demography were investigated in Serengeti wild dogs (Lycaon pictus), an endangered canid, between 1965 and 1991. Variation in ecological factors explained most changes in demography, but did not explain a decline in adult longevity. A significant reduc tion in pack life and individual longevity was coincident with the int roduction of routine intervention and consistent with pathogen-induced mortality. Survival varied significantly between categories of interv ention, and between individuals likely to have been exposed to differe nt degrees of social stress before intervention. The loss of all study packs in 1991 contrasted with the persistence of breeding packs outsi de the study area. The cause of the demise of most study packs is unkn own. Monte Carlo simulations demonstrated that population extinction w as unlikely to be the consequence of chance events alone. One explanat ion compatible with the evidence is an outbreak of viral disease induc ed by stress, possibly caused by intervention,