Morphological differences of hindlimb levers between wild and farmed American mink (Neovison vison) and implications for reintroduction of mustelids

Reintroduction is an important strategy to restore or re-establish wild populations of endangered species. Pre-release training is a necessary step to ensure post-reintroduction survival. However, studies reported contradicting outcomes after pre-release training of juveniles and adults. This study used farmed and feral American mink (Neovison vison) to analyze the influence of captive breeding on the morphology, structure and efficiency of the two major hindlimb levers, the femur and tibia pivoted by hip and knee joints that are essential for locomotion. Results showed that captive breeding did not alter the sexual dimorphism of the two levers that are related to survival in the wild. Captive-bred mink showed slightly altered morphology of the femur and fundamental structure of the hindlimb levers that improved efficiency, but this resulted in reduction of performance related to foraging in both terrestrial and aquatic environments, especially for females. These findings suggest that reintroduction of mustelid as exampled by the mink here should focus on juveniles because the skeletal alterations associated with captive rearing were recorded only among adults and are irreversible in adulthood. In contrast, captive-reared juveniles showed no skeletal alterations and would be expected to recovery from any atrophy of the muscular system caused by captive rearing for shorter durations. Our results support the application of pre-release training of juveniles in enriched environments as a method for alleviating structural alteration of appendages and enhancing locomotion to increase survival probability in complex habitats.