Inbreeding and density‐dependent population growth in a small, isolated lion population

Abstract

In South Africa, more than 30 small, enclosed game reserves have reintroduced lions over the last two decades, which now house more than 500 individuals. There is a high risk of inbreeding in these fragmented, fenced and isolated populations, which may be compounded by a lack of management guidelines. A population of 11 founder lions Panthera leo was reintroduced to Madikwe Game Reserve in 1995, and this population has in turn become a source for reestablishing other populations. Only four lineages were reintroduced, founder males were related to founder females, and since 1997, only one male lineage maintained tenure for 49 years, resulting in breeding with direct relatives. Interventionist management to limit lion population growth and inbreeding in Madikwe has taken the form of translocating, trophy hunting and culling of mainly sub adult lions. Despite this management, inbreeding started 5 years after reintroduction. Reproductive performance and thus population growth in Madikwe were dependent on the overall lion population density. When lion density was low, females first gave birth at a significantly younger age and produced larger litters, resulting in a high population growth rate, which decreased significantly when lion density in the park reached carrying capacity, that is, 61 lions. This might have profound consequences for future reestablishment of lion populations when restocking new reserves: our study illustrates the need for founder populations of reintroduced endangered predator species to be as large and genetically diverse as possible, and thereafter new genetic material should be supplemented. The development of such management guidelines is becoming very important as large predator populations become increasingly fragmented and managed as metapopulations.

Key factors and related principles in the conservation of largeAfrican carnivores

“…Even the risk of inbreeding in isolated protected areas has been solved via metapopulation management (Kettles & Slotow , Trinkel et al. ).…”

Rapid Growth Rates of Lion (Panthera leo) Populations in Small, Fenced Reserves in South Africa: A Management Dilemma

“…For example, in Madiwke GR only four lineages were reintroduced, founder males were related to founder females and since 1997 only one male lineage maintained tenure for nine years, resulting in breeding with direct relatives (Trinkel et al 2010). Thus managers should consider reducing tenure lengths of males on reserves to mimic a more natural turnover rate and while this may not have much effect on growth rates, it should result in genetically more diverse populations and would thus more closely mimic natural populations.…”

“…By largely avoiding systematic contraception to induce these effects, and focussing more on the removal of excess lions, the situation has developed where there is no longer much opportunity for the translocation of lions to new areas (Kettles & Slotow 2009) and where euthanasia has become a vital management option. Furthermore this approach has led to high levels of inbreeding (Trinkel et al 2008(Trinkel et al , 2010 and seriously questions the conservation value (Slotow & Hunter 2009) of the over 700 lions involved. The first step to remedy this situation would be for managers to use one of the approaches outlined above to reduce population growth, with preference to the Kruger NP approach due to ecological similarities.…”

“…One of the major management challenges has been high reproductive and survival rates and the potential for overpopulation (Kilian 2003;Funston 2008;Lehmann et al 2008;Kettles & Slotow 2009;Slotow & Hunter 2009). Previous studies of lion population growth in these reintroduced populations in South Africa have focused on lions in one small reserve at a time and often only for a few years immediately following introduction (Hunter 1988;Kilian 2003;Druce et al 2004;Lehmann et al 2008;Kettles & Slotow 2009;Trinkel et al 2010). Here, we collated time series data from 14 small reserves to quantify population parameters affecting growth rate and potential drivers of changes in these parameters.…”

“…However, in recent decades lions have been reintroduced into over 40 small (<1000 km 2 ), fenced areas, including private reserves, conservancies, protected areas, national and provincial parks, hereafter referred to as 'reserves' (reviewed by Funston 2008;Slotow & Hunter 2009). These lion reintroductions have been successful on the individual reserve level; however, the introduced lions are all intensively managed (Hayward et al 2007a;Hunter et al 2007) and increasingly genetically compromised (Trinkel et al 2008(Trinkel et al , 2010, the net effect of which reduces their conservation value on a regional scale (Slotow & Hunter 2009). It has been suggested that small reserves in South Africa need to move away from intensive management in isolation towards a managed metapopulation approach (Funston 2008;Slotow & Hunter 2009;Hayward & Kerley 2009;Trinkel et al 2010).…”