Exposure to persistent organic pollutants and first-year survival probability in gray seal pups

Many studies have demonstrated that persistent organic pollutants are transferred from mother to pup during lactation in phocid seals, but none have been able to determine the significance of these findings for survivorship. The aim of this study was to investigate the relationship between blubber contaminant concentrations and first-year survival in gray seal pups. A mark-recapture framework was used to estimate survival probabilities and animals were "marked" using novel mobile phone tags. Individual and group covariates (sex, condition, and blubber contaminants) were embedded within a live-resighting model. The most significant covariates remained condition at weaning and sex (males in poor condition had the lowest survival probability), as was found previously, but there was also evidence indicating that higher blubber contaminants additionally decreased survivorship. The models' Akaike's Information Criteria (AICs) and their associated weights, point toward the tetrapolybrominated diphenyl ether congeners (dominated by BDE-47) as being the most important group of contaminants affecting survival probability, followed by the total dichlorodiphenyltrichloroethanes (DDTs) and pentapolychlorinated biphenyl congeners. These compounds were not the most abundant in the blubber, suggesting further studies into their toxicological effects in this species are necessary. The specific mechanisms driving the reduction in survivorship remain unknown.