THE SEA OTTER IN THE EASTERN PACIFIC OCEAN 63 



gathered while she continued on course at the surface. In 44 

 minutes she covered exactly 1 nautical mile, thus her speed was 

 2.3 km. per hour (1.4 knots). (2) An adult female, carrying a sleep- 

 ing pup on her chest, moved hurriedly and steadily on the surface 

 from an area where a rising wind caused rough water. The wind 

 was from her side, so she was neither swimming with or against 

 it. She passed over a measured distance of about 800 m. in 20 

 minutes, or at the rate of 2.4 km. per hour (1.5 knots). (3) After 

 emerging from a food dive with a fish (weighing about 0.5 kg.), 

 an adult male swam on his back while he consumed the fish and 

 moved with moderate speed to another area. His departure from 

 the feeding area was apparently prompted, to some degree at 

 least, by the presence of three Glaucous-winged Gulls (Larus 

 glaucescens) which swam beside or flew above him while they 

 retrieved discarded fish scraps. The otter was able to outdistance 

 the birds that alighted beside him on the water. In 675 seconds 

 he traversed a measured distance of 300 m. at an average speed 

 of 1.6 km. per hour (0.9 knots). 



The top speed of our dory was approximately 11 km. per hour 

 (6 knots). On many occasions we chased sea otters in order to 

 catch them in a dip net. When the water was clear and smooth, 

 we could watch the otters swimming beneath the surface as they 

 attempted to escape. It appeared that their top speed for brief 

 intervals, less than 1 minute, was not more than 9.25 km. per hour 

 (5 knots) and probably somewhat less. When we were unable to 

 see otters beneath the surface, we often overran them. Occasionally 

 during escape attempts, otters would porpoise clear of the water 

 ahead of the boat. When this was done they were most readily 

 captured. 



Thus it appears that when an otter moves from one area to 

 another on the surface, its near maximum sustained rate of travel 

 may approach 2.5 km. per hour and the underwater, briefly main- 

 tained (up to about 1 minute), maximum escape speed is about 

 9 km. per hour. This compares with a near maximum, briefly 

 sustained (3 to 5 minutes), escape speed of the northern fur seal, 

 which we pursued in a vessel having a maximum speed of 26 km. 

 per hour (14 knots), of about 18.5 km. per hour (10 knots). A 

 Pacific bottlenose porpoise ( Tursiops gilli) sustained a speed of 29 

 km. per hour (16.1 knots) for 7.5 seconds (Lang and Norris, 1965). 



Although a slow swimmer, the sea otter is remarkably agile. 

 On one occasion I plunged the dip net directly in the path of an 

 otter as it swam just ahead of the dory and at a depth of about 

 1/2 ni- The otter, unable to avoid entering the net, rolled forward, 



