Factors Associated with Reproductive Success in Captive Vancouver Island Marmots (Marmota vancouverensis).

Simple Summary: The Vancouver Island marmot (Marmota vancouverensis) is Canada's most endangered endemic mammal and is found exclusively on Vancouver Island in British Columbia. In the 1990s, the wild population drastically declined to fewer than 100 animals, primarily due to habitat alterations. In 1997, a conservation breeding-for-release program was established to supplement wild marmot populations as part of the National Recovery Plan. Retrospective analyses of captive breeding studbook records since 2000 indicate that among animals of proven fertility, the proportion of breeding pairs weaning a litter of pups is only 53%, which is less than optimum to support the reintroduction of animals to increase the wild population. Factors associated with the female were found to have the greatest impact on the odds of successfully weaning a litter, including age of the female and her previous success, although the age of the male also had an effect. A comparison of adrenal function between new and established breeding pairs, and successful and unsuccessful breeding pairs, indicated lower fecal glucocorticoid metabolite concentrations in established and successful pairs. This suggests that certain pairings are associated with lower stress than others, possibly reflecting social buffering of the stress response. The results of these analyses will be used to inform the captive management breeding program as it continues to supplement the wild populations of this endangered species. The Vancouver Island marmot (Marmota vancouverensis) is Canada's most endangered endemic mammal. In 1997, a conservation breeding-for-release program was established to supplement wild marmot populations. Retrospective analyses of captive breeding studbook records since 2000 indicate the age of the sire and the dam significantly impacted the odds of successfully weaning a litter. Dams and sires between 5 and 7 years of age had more than double the odds of reproductive success compared to older animals. Successful reproduction by the dam in the previous year also doubled the odds of successfully weaning a litter in subsequent years. Assessment of adrenal function via fecal glucocorticoid analyses indicated established breeding pairs had decreased stress compared to new pairs (5.74 ± 0.28 ng/g vs. 7.60 ± 0.34 ng/g; p < 0.0001). Pairs that were ultimately successful at weaning pups in a breeding season had decreased stress compared to unsuccessful pairs (6.05 ± 0.34 ng/g vs. 7.22 ± 0.28 ng/g; p = 0.0006). These endocrine results suggest social buffering via familiarity and breeding/pair bond formation may be decreasing stress in established and successful pairs, respectively. The results of this study will be used to assist in the captive breeding management of this species to optimise numbers of animals produced to supplement the wild populations. [ABSTRACT FROM AUTHOR]