62 



NORTH AMERICAN FAUNA 68 



times the hind feet are used to deliver paddling strokes similar to 

 the stroking movements employed when swimming on the back. 

 Progress on the surface appears to be slower when swimming on 

 the belly than while swimming on the back. 



The front feet are not used in swimming either on the surface 

 or beneath it. They are pressed palmside down against the chest 

 or folded across the chest when not in use to manipulate food or 

 to preen the fur or hold young (fig. 30). 



The tail is flattened in the horizontal plane and tapers only 

 slightly, so that it presents a broad surface for most of its length. 

 The tail of an adult female measured 317 mm. long, 44 mm. thick, 

 and 64 mm. wide near its base. In addition to its use in conjunction 

 with the hind flippers in underwater swimming, the tail is used as 

 a ''sculling oar." Slight alterations of positions are made when 

 the otter is floating on its back. Frequently I observed resting 

 otters floating in this position with front and hind feet folded on 

 the chest and abdomen. Normally the tail floats on the surface 

 while the otter rests, but if it wishes to make slight movements, for 

 example to face away from a light breeze, the tail is projected 

 downwards and by means of circular sideward movements the 

 body is rotated in the desired direction. Also, when captives were 

 eating and they wished to pivot about on the surface to avoid food 

 pilferage by other otters, the tail was used in sculling to assist the 

 stroking hind flippers. 



Swimming speed and agility 



The sea otter is a slow swimmer but it moves more rapidly 

 beneath the water than on its surface. Two methods were used 

 to measure swimming speed: (1) From the shore, otters traveling 

 from one area to another were timed as they passed beach points. 

 The distances were then measured on nautical charts and the 

 speed computed. (2) Otters were pursued with a motor-driven dory 

 while they swam beneath the surface. In clear water the otters 

 could sometimes be seen as they attempted to escape pursuit. 

 Presumably, at such times they moved at maximum velocity. The 

 speed of the dory was measured by timing its passage over a 

 known distance. 



Examples, surface speed: (1) An adult female swam parallel 

 to the coast of Kirilof Point on a nearly windless day. For the most 

 part she swam on her back but occasionally she rolled over and 

 "porpoised'^ (exposing the back, but not leaving the water) for 

 10 to 15 yards. During the observation period she made one food 

 dive and when she emerged ate the several urchins she had i 



