Abstract
Based on external morphometry of Canadian river otters (Lontra canadensis) kept in Hakone-en aquarium, proportions of body parts relative to body lengths were compared between five adults and one neonate. Proportions of head, mouth and anterior body of the neonate were larger than those of the adults. Forepaw, hind limb and tail were relatively smaller in the neonate than in the adults. The Canadian river otter showed different patterns from the sea otter (Enhydra lutris) in the development of body parts relevant to swimming: hind limb and tail proportions in the sea otter were similar between adult and young, and young sea otters had relatively large forepaws compared to adults. However, the forepaw, hind limb, and tail were relatively smaller in the river otter neonate than in the adults. Variation in the developmental patterns of the limb and tail can be explained by the necessity of locomotion in precocial and altricial young of these species in their early life stages.
