EDITORIAL

The encouraging news on the translocation of four northern white rhinos from Dvur Králové Zoo to the Ol Pejeta Conservancy in Kenya (see below, p. 168) becomes even more significant in the light of the recent proposal that the northern and southern forms of Ceratotherium should be recognised as two full species. If Colin Groves and his colleagues (below, p. 171) are right, the world’s rarest rhinoceros species is not the Javan, with its small but relatively stable population in Ujung Kulon (plus a few survivors in Vietnam), but the northern white, now presumed extinct in the wild and with just eight individuals surviving in captivity (of whom the four now at Ol Pejeta are probably the only ones still reproductively viable).

The Groves et al. paper (which may be read in full at www.plosone.org/article/info:doi/10.1371/journal.pone.0009703) makes a persuasive case for the taxonomic change, arguing that the two taxa ‘differ absolutely in numerous respects’ both morphologically – ‘they can be differentiated externally apparently without error’ – and genetically – ‘genetic analysis suggests that they have been separate for more than a million years’. The authors conclude that ‘we have no option but to consider them specifically distinct.’ As Kees Rookmaaker points out (below, p. 171), the paper ‘clearly shows the importance of taxonomy for policy in conservation’. (Importance, yes, but in conservation terms this sort of revision frequently means trouble: readers will recall a number of recent similar cases of the ‘splitting’ of large, charismatic mammals – African elephant, gorilla, orang-utan, clouded leopard – which, because ‘species’ as a concept somehow carries more weight than ‘subspecies’, seem to have the main effect of giving us all something more to worry about.)

In view of recent claims that conservationists regularly underestimate the number of individuals needed to safeguard a species against extinction [see, e.g., IZN 56 (6), 361–2], the two males and two females at Ol Pejeta seem a hopelessly small nucleus from which to rebuild a viable population. However, similar forlorn hopes have succeeded in the past – Père David’s deer, Przewalski’s horse, Arabian oryx and European bison are just a few examples of large ungulates whose numbers have bounced back from a tiny group of founders. Not from one as small as four, though – offhand, the Mauritius kestrel is the only species I can think of which has survived that degree of brinkmanship. But a more hopeful parallel in the present case is that of the southern white rhino: in the late 19th century it was thought to be extinct until a small number (as few as 20 by some accounts) were found living in the Hluhluwe region of Natal, South Africa. Effective measures to preserve them were initiated, and the subsequent century-long success story has led to today’s population of at least 10,000 (published estimates of the total differ widely). Given a fighting chance, it seems, white rhinos are very good at breeding back from the brink. The Ol Pejeta project gives the northern subspecies (species?) such a chance.

Nicholas Gould