Morphological changes to black-footed ferrets (Mustela nigripes) resulting from captivity

Abstract

Captive breeding of endangered species carries risks associated with small population size and domestication. The black-footed ferret (Mustela nigripes) was among the first endangered species bred in captivity. We documented morphological changes to the species after >10 years of captive breeding. We measured 9 dental or cranial traits on 109 skulls; 85 specimens were collected prior to captivity and 24 specimens were of captive-born animals. Skulls of captive animals were 5–6% smaller than skulls from precaptive animals and were 3–10% smaller than skulls of animals collected near the founding population, suggesting that changes occurred in captivity rather than from sample bias in the founders of the captive population. Skull size did not correlate with inbreeding coefficients of captive animals, eliminating the possibility that black-footed ferrets were smaller because of the effects of inbreeding depression or overdominance. Although reintroduced animals were smaller than historical animals, we recommended no alterations to the current management because intentional selection for body size might further reduce genetic variation in a genetically impoverished species. We hypothesize that reintroduced individuals will return to historical body sizes rapidly, owing either to release of environmental stresses or to natural selection for larger size.