Pelage coloration in pinnipeds: functional considerations

Pinnipeds vary in adult pelage color and pattern ranging from uniform white to black or brown and from solid coloration to subtle spotted or bold markings. Moreover, pelage color often differs by sex and age with neonates having radically different color and patterning from those of adults. We explored the functional significance of these patterns in 34 species of pinniped using comparative phylogenetic analyses. We found strong evidence to support the hypothesis of background matching on land because species in which adults or pups have white pelage live in Arctic regions and are subject to terrestrial predation. We also found evidence supporting the hypothesis of background matching at sea because spotted species forage in well-lit shallow waters on-shelf and dark pinnipeds forage in deep dark waters off-shelf. Neonates are black for species lacking terrestrial predators on islands or in caves where selection on crypsis is relaxed. Distinctive markings may be used for intraspecific communication. Sexually dichromatic pinnipeds are highly polygynous and copulate on land, suggesting a role for male coloration in contests for access to females. Functional differences in the coloration of pinnipeds and cetaceans reveal differences in underlying selection pressures, in particular those derived from pinnipeds' amphibious lifestyle.