Dynamics of a small re-introduced population of wild dogs over 25 years: Allee effects and the implications of sociality for endangered species’ recovery

Abstract

We analysed 25 years of demographic data on a small re-introduced population of endangered African wild dogs (Lycaon pictus) in Hluhluwe-iMfolozi Park (HiP), South Africa, to describe population and pack dynamics. As small populations of cooperative breeders may be particularly prone to Allee effects, this extensive data set was used to test the prediction that, if Allee effects occur, aspects of reproductive success, individual survival and population growth should increase with pack and population size. The results suggest that behavioural aspects of wild dogs rather than ecological factors (i.e. competitors, prey and rainfall) primarily have been limiting the HiP wild dog population, particularly a low probability of finding suitable mates upon dispersal at low pack number (i.e. a mate-finding Allee effect). Wild dogs in HiP were not subject to component Allee effects at the pack level, most likely due to low interspecific competition and high prey availability. This suggests that aspects of the environment can mediate the strength of Allee effects. There was also no demographic Allee effect in the HiP wild dog population, as the population growth rate was significantly negatively related to population size, despite no apparent ecological resource limitation. Such negative density dependence at low numbers indicates that behavioural studies of the causal mechanisms potentially generating Allee effects in small populations can provide a key to understanding their dynamics. This study demonstrates how aspects of a species' social behaviour can influence the vulnerability of small populations to extinction and illustrates the profound implications of sociality for endangered species' recovery.

Reproductive sharing and proximate factors mediating cooperative breeding in the African wild dog (Lycaon pictus)

“…Our results supported the findings of Creel and Creel (2002) and Somers et al (2008) that the probability of being socially dominant increases with female age, as all females in our population surviving to 6 years or older became dominant. In fact, there was an overall skewing of sex ratio for mature wild dogs to favor males (60%) despite there being near-gender parity in the pup age class.…”

Inbreeding, heterozygosity and fitness in a reintroduced population of endangered African wild dogs (Lycaon pictus)

“…Over the 7 year study period, the KZN wild dog population grew steadily through reintroductions and natural pack formations and from one protected area with two breeding packs comprising seven individuals to three protected areas with nine breeding packs and 88 dogs (Somers et al 2008). In all, a total of 257 individuals were identified and present in the KZN study population over our study interval.…”

The Demography and Dynamics of an Expanding, Managed African Wild Dog Metapopulation

“…Post-release population dynamics were determined from photographic records, radio-telemetry studies and opportunistic sightings (Mills, 1992;Maddock & Mills, 1994;Somers et al, 2008) (Table 1). Individual life histories were used to document changes in the structure and dynamics of each subpopulation, forming the basis of a database containing a timeline of all known individuals.…”