Natural disasters and primate populations:: The effects of a 2-year drought on a naturally occurring population of ring-tailed lemurs (Lemur catta) in southwestern Madagascar

We examine demographic patterns from a long-term study (1987-1996) of the population of ring-tailed lemurs in the Beza-Mahafaly Special Reserve, in southwestern Madagascar In particular we focus on the effects that a severe drought in 1991 and 1992 had on the population. The population of adult animals peaked in 1991 but decreased rapidly during the subsequent drought and immediate postdrought years. In the 1992 birth season (and second year of the drought) infant mortality reached 80%, and 20.8% of all adult females in the reserve died. The following year adult female mortality reached a high of 29.9%. Juvenile mortality in 3 intensively studied groups was 57% during the second year of the drought. We compare these data with infant, juvenile, and adult female mortality in non-drought years. We are not able to calculate adult male mortality, as they often emigrate from the reserve to the adjacent forest; however in the same 3 intensively studied groups, 89% of the males disappeared during the 2 immediate postdrought years. By 1996 the population had begun to recover after the decline that correlated with the drought conditions. Annual reproduction, high birth rates (.80-.86 annually), early sexual maturity and dietary adaptability may be contributing factors to the recovery. Effects of and recovery from this type of natural disaster in the Beza Mahafaly ring-tailed lemur population parallel responses of some species of macaques and baboons with respect to the adaptability of edge species.