Inbreeding depression in captive bighorn sheep

We estimated the extent of inbreeding depression for juvenile survival in 589 captive-born bighorn sheep, and, unlike an earlier report, found no evidence of significant inbreeding depression. There did not appear to be any overall effect of year of birth, place of birth, subspecies, sex or ancestral inbreeding upon the viability of inbred animals as compared to non-inbred animals. However, for the first few years of data, there was lower survival for inbred than non-inbred offspring. After this period, there was an increase in the viability of inbred offspring, probably reflecting a general improvement in husbandry conditions in the zoos. It should be emphasized that the lack of significant inbreeding depression does not necessarily imply that there may not be inbreeding depression for other traits or in a less benign or more natural environment for juvenile viability.