One last opportunity remains for the northern white rhinos. Small numbers have been kept and managed in captivity since the 1970s. The last eight northern white rhinos are in two zoos in Europe and the USA. Whilst the survival rates for captive white rhinos are good, reproduction rates are very low.
Despite the best efforts of captive-breeding programmes the success rate has been very poor, with just one calf born since 1985. As well as the obvious differences in natural diet and habitat it is thought that the unusual social conditions experienced by captive rhinos is a possible critical factor in their failure to breed at normal rates seen in the wild. Rhinos that have grown up together in captivity often develop sibling relationships, do not behave as potential mates, and so do not breed. These non-breeding individuals in zoos offer no hope for the future of the northern white rhino. Biologists predict that returning these captive animals to a wild African setting will encourage successful breeding.
The only four captive northern white rhino still capable of breeding reside in Dvur Králové Zoo in the Czech Republic. The Zoo’s two males and two females represent the last hope of survival not only for the subspecies, but for the valuable genes they carry. As the last known individuals of the northern subspecies, they have valuable and unique genes that are specifically adapted for the local habitats and environmental conditions of the former range. For example, these genes are likely to include resistance to local disease and parasites.
Because there are so few animals and because they are inter-related, it is likely that they will have to be ‘inter-crossed’ with southern white rhinos. Whilst the historical range of the southern white rhino was several thousand kilometres away, south of the Zambezi, thanks to conservation efforts they now number approximately 17,500, and the Ol Pejeta Conservancy already has a healthy and growing population of 12 animals.
Whilst it is hoped and planned that some pure-bred northern white rhino calves will result from the proposed project we must accept that inter-crossing with southern white rhinos as a more realistic plan. Inter-crossing will maximise the number of offspring born in the remaining breeding lifetimes of the last four northern white rhinos and in particular ensure that at least the genes and characteristics can be maintained within viable populations, and not be lost entirely.
