Translocation, Hybridization, and the Endangered Black‐Faced Impala

Abstract

Species become endangered primarily through population decline-for example, because of extensive poaching. Conservation generally begins with protection from causes of decline. Subsequent steps may include (1) translocation to protected areas, especially where the cause of decline is local overhunting and/or habitat loss, and (2) establishment of international restrictions on trade. Paradoxically, such well-intentioned efforts can create new threats for the species. Translocation, or the intentional movement and release of animals in the wild, can be an important conservation tool, used to increase the number of individuals, genetic variability, and gene flow and to redistribute populations to areas of optimal habitat (Franzmann 1988; Griffith et al. 1989; Gripps 1991; Caughley 1994). Efforts to save endangered species have involved translocation from the natural range to similar areas nearby, where causes of decline are absent (Conant 1988). On the other hand, translocations involving introduction of exotic species generally result in serious problems for management and conservation (Scheffer 1994; Arano et al. 1995). Hybridization is likely when translocation allows contact between closely related taxa (Robinson et al. 1991; Rhymer & Simberloff 1996). For rare endemics, the threat posed by genetic swamping may be as great as that of population decline. Restrictions placed on importation of endangered species and products (e.g., hunting trophies) to other countries represent an attempt to reduce the value of endangered species as commodities by prohibiting trade in and use of these animals. In some circumstances, these controls actually hinder management and conservation of endangered species within their native countries. The case of the black-faced impala (Aepyceros melampus petersi) in Namibia illustrates potential problems inherent in translocation and import restrictions. We explore two of these problems: (1) loss of unique genotypes due to translocation-caused contact between previously allopatric taxa and (2) economic disincentives, caused by a U.S. ban on imports, for private landowners to maintain pure herds of black-faced impala. Black-faced impala are an endangered subspecies (World Conservation Union 1973; U.S. Department of the Interior 1980), differing from common impala (Aepyceros melampus melampus) in body size, coloration, facial markings, and habitat (Swart 1967; Haltenorth & Diller 1986; Skinner & Smithers 1990). Blackfaced impala are endemic to a small region in northwestern Namibia and southwestern Angola (Gaerdes 1965; Smithers 1983; East 1989). Recent reports indicate that they are nearly extinct in Angola (Huntley & Matos 1992; World Conservation Union 1992). In Namibia the natural range of the black-faced impala (Fig. 1) is in Kaokoland (Opuwo district), a communal area on the Angolan border (Swart 1967; Joubert 1971). Kaokoland is a remote, arid, mountainous region inhabited by nomadic pastoralists, the Ovahimba and Herero (Jacobsohn 1990). Kaokoland was previously renowned for its wildlife (Bigalke 1958) and set aside as a protected reserve in 1928, when it was part of Etosha National Park. At the same time it served as a reserve for the Himba and Herero (Owen-Smith 1972; Malan 1974). In 1970 Kaokoland lost its protected status. Today, little remains of its wildlife. Hunting pressure increased during the war between the South West Africa People's Organization and the South African Defense Force, when the latter issued thousands of rifles and ammunition to local people (Walker 1978; Owen-Smith 1986; Hall-Martin et al. 1988; Lindeque 1990). During this time, Kaokoland was devastated by the worst drought on record; in addition to wildlife, more than 80% of the cattle died (Owen-Smith 1986; Loutit & Owen-Smith 1989).