Functional correlates of differences in bone density among terrestrial and aquatic genera in the family Mustelidae (Mammalia)

Summary

Increasing body density by increasing bone density has been cited as a means by which semiaquatic mammals are able to control their buoyancy in water. In order to investigate the relationship of bone density to buoyancy and the degree of morphological adaptation to a semiaquatic existence, we examined limb-bone densities in a single mammalian family. Among genera within the Mustelidae, i.e., weasels and their relatives, there is an apparent trend toward increasing limb-bone density associated with a gradation from a terrestrial to an aquatic way of life. However, the association of increasing bone density with increasing adaptation to an aquatic environment is tempered by the realization that increasing body size may also influence bone density in larger, terrestrial mammals. These results are in accordance with previous data on bone density in other mammalian orders and suggest that a new hypothesis which encompasses historical, physiological, and behavioral information would be best suited to explaining differences in this morphological relationship.