Population viability analysis for captive breeding and reintroduction of the endangered Columbia basin pygmy rabbit

摘要

Captive breeding has become globally important in endangered species recovery, yet it is fraught with problems such as maintenance of genetic diversity, and adaptation to captivity. We studied survival and population dynamics of a captive population of endangered Columbia Basin pygmy rabbits Brachylagus idahoensis, from 2003 to 2007, to evaluate its potential for supporting reintroduction and recovery of wild extirpated populations in shrub-steppe ecosystems of eastern Washington, USA. We developed stochastic population viability analysis models in Vortex and RAMAS to assess performance and surplus production of the captive population. This pygmy rabbit population has low adult survival beyond 1 year and dependency on high juvenile recruitment for population growth. Low juvenile survival and high variability in stochastic growth rates result in high variability in annual productivity. Our analysis showed that the captive population at n=75 cannot sustain a steady annual harvest of >= 30 rabbits for reintroduction and supplementation without increasing the risk of quasi-extinction (n=30) to 59%. We conducted sensitivity analysis on maternity, carrying capacity and survival rates to identify critical values for model parameters that would lower extinction risk to the captive population when used as a source of rabbits for reintroduction. Increasing juvenile survival and recruitment into the first breeding class is the most effective method for enhancing the breeding program. Our population models suggest that captive breeding and recovery programs for short-lived lagomorphs present significant conservation challenges because of the need to rapidly grow such populations to overcome demographic and genetic challenges.