Variable inbreeding effects across life-history stages in a captive carnivorous mammal population

Studies evaluating inbreeding depression and purging in captive populations often focus on a single life-history stage, commonly juvenile survival, using it as a binomial response variable to model inbreeding effects. Through the use of a statistical procedure known as survival analysis, and focusing on four life stages, we examined the effects of inbreeding and other demographic and life-history variables on the survival of the bush dog Speothos venaticus captive population. Through generalized linear mixed models, we assessed the impact of these variables upon litter sizes and proportional viability of pups within a litter. We found a negligible effect of inbreeding on survival in two viability periods up to weaning age. On the other two life stages, up to the age of sexual maturity, inbreeding assumed a negative effect on survival. Individual inbreeding led to decreased litter size, whereas maternal age negatively affected litter sizes and the proportional viability of pups within the litter. Partial purging could have removed some genetic load in this captive population; however, our results indicate that even in populations maintained in benign conditions of captivity, deleterious effects of inbreeding are differentially expressed across life-history stages. Our results also underscore that investigating a single life-history stage could lead to erroneous conclusions about inbreeding and purging effects, misguiding management of captive populations.