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.

A systematic map of demographic data from elephant populations throughout Africa: implications for poaching and population analyses

“…For both species, 58 reviewed studies provided data from individual recognition surveys in 31 ecosystems. In total, 2914 estimates were extracted, primarily from populations in: Addo Elephant National Park, South Africa (Whitehouse & Hall‐Martin 2000, Whitehouse & Kerley 2002, Gough & Kerley 2006), Hluhluwe–Imfolozi Park, South Africa (Kuiper et al 2018), Pilanesberg National Park, South Africa (Woolley et al 2008), Amboseli National Park and surrounding area, Kenya (Western et al 1983, Lee & Moss 1986, Moss 1988, 2001, Poole & Thomsen 1989, Poole 1989, Hollister‐Smith et al 2007, Lee et al 2011, 2013, 2016), Meru National Park, Kenya (Njumbi 1995, Onyango & Lesowapir 2016), Samburu and Buffalo Springs National Reserves, Kenya (Wittemyer 2001, Wittemyer et al 2005, 2013, Rasmussen et al 2008), Sweetwaters Game Reserve, Kenya (Ogola & Omondi 2005), Tsavo National Park, Kenya (Poole 1989, McKnight 2000), Dzanga Bai, Central African Republic (Turkalo et al 2013, 2017, 2018), Kasungu National Park, Malawi (Jachmann 1980, 1986), Kidepo Valley National Park, Uganda (Aleper & Moe 2006), Queen Elizabeth National Park, Uganda (Poole 1989), Mikumi National Park, Tanzania (Poole 1989), Tarangire National Park, Tanzania (Foley et al 2008, Foley & Faust 2010), and Odzala National Park, Congo (Querouil et al 1999). …”

Social integration of translocated wildlife: a case study of rehabilitated and released elephant calves in northern Kenya

“…Facilitating interactions of recently released orphans with orphans that have had time to accrue knowledge of the release site may be an important factor to consider as it may take time for orphans to integrate with wild residents (Figs. 7,8), and ecological knowledge gained from associations with other elephants is likely essential for avoiding predation and locating resources (Kuiper et al 2018;Goldenberg et al 2021). However, we note that these results should be interpreted with caution as the small sample size of individuals whose interactions were documented pre-release did not allow us to control for the effects of age and sex on pairwise interactions.…”

“…For example, elephant family groups that ventured together outside of a protected area during a drought had lower calf mortality, attributed to matriarch knowledge of the landscape (Foley et al 2008); groups with older matriarchs exhibited greater knowledge of other individuals within the population (McComb et al 2001); dominance relationships among females structured their landscape use during periods of resource constraint (Wittemyer et al 2007); and dominance relationships among males influenced their reproductive opportunities (Rasmussen 2005). Given this dependence on long-term bonds, characterizing the formation and nature of social interactions amongst rehabilitated orphans and the social integration process of rehabilitated elephants into wild populations may generate applied strategies that can be used in an iterative way to support future translocations (Kuiper et al 2018). Investigation into social interactions is thus a worthwhile avenue to increase the conservation value of these projects as the social relationships that released elephants form or maintain may determine their ability to survive, locate resources, and reproduce (Evans et al 2013).…”

Demographic responses of an insular elephant population to removal as a management intervention

“…At present, contraception and translocations are used to keep elephants from becoming overpopulated in some places, while supplementation of resources, demographic enrichment and control of illegal hunting aim to maintain or increase population sizes elsewhere (summarized in van Aarde et al, 2008; Hayward & Slotow, 2016). Measures of the effectiveness of interventions (usually only based on population growth from counts) unwittingly assume asymptotic dynamics that imply stability in population growth, structure and vital rates (e.g., Wood, 1999; Knight et al, 2001; Woolley et al, 2008; Booth & Dunham, 2016; Kuiper et al, 2018). Stability seldom, if ever, occurs in nature (Hastings et al, 2018).…”