Zoo populations of endangered species are becoming increasingly more important, especially when their wild equivalents are facing substantial threats. The eastern black rhino is threatened by illegal poaching in sub-Saharan Africa that may counteract the successful population increases in protected reserves seen over recent years. Therefore, zoo collections are important to protect the species, but it is vital that these animals maintain demographic and genetic viability so that populations retain characteristic features apparent in wild populations.
10% of the global population of eastern black rhinos is kept in Europe but this study represents the first evaluation of the sustainability of this population. Using Population Viability Analysis (PVA) and population management software, data taken from the European Association of Zoos and Aquariums (EAZA) studbook were used to assess the genetic and demographic sustainability.
We compared this to wild counterparts from eight managed wild populations in Kenya. We found that the European population growth rate is 1-2% per annum, which is below the 5% annual target and lower than the 6-8% increase seen in wild populations. Factors such as longer periods between calves and females not reproducing until later in life, or not at all, could contribute to this under-performance.
Pedigree analysis of the population discovered that over a third of the European collection are related to only five wild caught founders leading to reproductive skew. The combination of a small number of breeding females and reproductive skew could make maintaining genetic and demographic viability difficult in the future. Therefore, it has been recommended that measures to combat these issues are of great important to sustainably manage small zoo populations.
Edwards, K. L., Walker, S. L., Dunham, A. E., Pilgrim, M., Okita-Ouma, B., & Shultz, S. 2015. Low birth rates and reproductive skew limit the viability of Europe’s captive eastern black rhinoceros, Diceros bicornis michaeli. Biodiversity and Conservation, 1-22.