Captive Breeding and Reintroduction Evaluation Criteria: a Case Study of Peninsular Bighorn Sheep

Abstract: Captive breeding and reintroduction programs are rarely evaluated, and assessment criteria vary widely. We used the following criteria to evaluate a bighorn sheep ( Ovis canadensis ) augmentation program: (1) survival and recruitment rates in the captive population, (2) survival of released animals, (3) recruitment of released animals, (4) growth rate of the reintroduced or augmented population, and (5) establishment of a viable wild population. Captive bighorn survival and recruitment was high, averaging 0.98 (SD = 0.05) and 71.0% (SD = 19.4), respectively. Annual survival of free-ranging captive-reared bighorn ( n = 73, x = 0.80, SD = 0.11) did not differ (   Z = −0.85, p = 0.40; n = 14) from survival of wild-reared bighorn ( n = 43, x = 0.81, SD = 0.12). Recruitment was unusually low for both captive-reared (  x = 13.7%, SD = 0.24) and wild-reared ewes (  x = 13.7%, SD = 0.20). Although reintroduction did not result in population growth or establishment of a viable population, it helped prevent extirpation of the reinforced deme, preserved metapopulation linkage, and aided habitat preservation. Chronic low recruitment and low adult survivorship precluded achievement of criteria 3–5. Environmental conditions in the release area also appeared to hinder program success. Standard evaluation criteria for ongoing reintroductions allow for informative assessments and facilitate comparisons needed to refine reintroduction science as a recovery tool for threatened or endangered populations.