Demography and social dynamics of an African elephant population 35 years after reintroduction as juveniles

Abstract

Given their vulnerability to local extinction, the reintroduction of megafauna species (often long-lived, ecologically influential and highly social) is an increasingly relevant conservation intervention. Studies that evaluate past megafauna reintroductions are both critical and rare. Between 1981 and 1996, 12 cohorts of a total of 200 juvenile (<5 years old) African savannah elephants Loxodonta africana africana were reintroduced to Hluhluwe-iMfolozi Park (HiP), South Africa, after 100 years of absence. Here, we model the population's long-term growth. We also present data on the current (2016) age class distribution and social dynamics of the population based on a year of intensive vehicle-based monitoring of 16 collared adult females and their family groups. Exponential population growth (7.1% annual increase) between 1996 and 2014 suggests reintroduction success but has created concerns about overpopulation (with contraception of females implemented since 2014 to suppress reproduction). The age class distribution has normalized as the juveniles have aged; reproductive females (>10 years old) composed 30% of the population in 2016. The population remains relatively young and forecasts suggest high potential for sustained growth over the next decade. The first calf was born to a reintroduced female in 1990 and since then mother–calf units have gradually developed into semi-independent multi-generation families (7–15 individuals in size in 2016). The size of observed cow–calf groups was highly variable (mean = 21.4 individuals, range: 7–109), with repeat observation of individual collared females revealing fusion and fission among different family groups through time, as is typical of more natural elephant populations. Synthesis and applications. From an unusual founder population of reintroduced juvenile elephants, we document rapid population growth and the development of normal sociality over 35 years. While this may be an encouragement for megaherbivore reintroductions in general, the potential for exponential population growth must be carefully considered when ecologically influential species are introduced to closed systems. Our study provides key long-term insights for elephant translocations, which are becoming increasingly necessary due to overpopulation in some areas and local extinction in others.