Demography and population dynamics in the elephants Loxodonta africana of Addo Elephant National Park, South Africa: is there evidence of density dependent regulation?

Abstract

Density dependence of the Addo Elephant National Park (South Africa) elephants Loxodonta africana was assessed using a long-term data set. Estimated carrying capacity is 0.1–0.5 elephants km−2 but stocking rates have been up to 4 elephants km−2. Population growth rate was found to be positively correlated with increasing density. There was no relationship between birth rate, the age of first calving or calf sex ratio and elephant density but there was a positive relationship between birth rate and rainfall during conception year. Mortality rates, particularly for juveniles, were low, and mean inter-calf interval was 3.3 years. There is no evidence of density dependent regulation in this population, despite the population being consistently above the estimated sustainable carrying capacity and a loss of phytomass and biodiversity. This is interpreted in light of the characteristics of the aseasonal habitat, succulent thicket vegetation and the ability of elephants to utilize accumulated vegetation biomass. These findings indicate that density dependence should not be considered as an option in the control of elephant numbers in this Park, or where elephant resources are not seasonally limited.