Demographic consequences of habitat loss and crowding in large carnivores : a natural experiment

Abstract

Habitat loss is one of largest threats to the persistence of large carnivore populations. However, because most large carnivores are long-lived, cryptic and wide-ranging, few studies examine the demographic consequences of habitat loss, and the resultant crowding that ensues, on these species. We used long-term data to examine the demographic responses of an African lion (Panthera leo) population to flooding-induced habitat loss in a seasonal wetland, the Okavango Delta, during a transition from low to high annual flooding patterns. We found that intraspecific competition reduced cub survival and that this effect was exacerbated by habitat loss and consequent crowding. The proportion of cubs recorded in the population also declined as crowding increased, and both the survival of cubs and proportion of cubs recorded declined as prey abundance decreased. Apparent sub-adult survival declined with increasing pride size, but this likely reflects emigration rather than mortality. Adult survival remained relatively constant throughout the study period, a population response which is important in buffering populations against short-term fluctuations in ecological conditions. As many large carnivore populations face future habitat loss, it is important that we understand the demographic consequences of habitat loss in order to better mitigate its effects in the future.