Locomotory patterns and external morphology of the river otter, sea otter, and harp seal (Mammalia).

Abstract

Terrestrial and aquatic locomotion of the river otter (Lutra canadensis), the sea otter (Enhydra lutris), and the harp seal (Pagophilus groenlandicus) are successively described and analyzed in relation with the external characteristics of these species. Terrestrial locomotion, typical of land carnivores in Lutra and Enhydra, is different and extremely awkward in Pagophilus. In the water, only Lutra has to actively maintain itself at the surface; the other two species have been observed at the surface for long periods with no movements. There is an increased tendency from Lutra to Enhydra to Pagophilus toward enlarged highly specialized feet, approximating a perfect lunate border. Tail surface area decreases in the above order. The length and density of foot hairs decrease if compared with midback and tarsal regions and also from Enhydra to Lutra to Pagophilus.