340 



Marine Mammals 



The sea Otter (Enhydra lutris) is unique among marine mammals and is 

 similar to birds in that it lias no insulatnig blubber layer. It is also similar to 

 birds in that the otter is protected from environmental temperatures by an air 

 blanket trapped among the dense fur fibers of its pelt. If the water in which 

 the sea otter lives is polluted by any foreign substance that causes the fur 

 to mat or otherwise lose its water-repellent character so that water reaches 

 the skin, body temperature is lost and the otter soon dies of exposure. 



Accidental exposure of two sea otters to a small but unknown amount of oil 

 (probably diesel) in an experimental holding pool on Amchitka Island resulted 

 in fur matting, progressively severe distress, emergence from the water, and 

 death by exposure within several hours (K. W. Kenyon, unpublished data). 

 The oil in this case formed a visible sheen, comparable to that sometimes present 

 in harbor areas where gulls appear unaffected by it. Similar or greater petro- 

 leum pollution in the marine environment would prove fatal to any sea otter 

 that came in contact with it. 



The northern fur seal (Callorhinus nr sinus) is insulated from the chilly 

 marine environment by both blubber and fur. Fur seals differ from all other 

 marine mammals except the sea otter because water does not penetrate the 

 dense underfur of its pelt during life. The insulation furnished by the fur is 

 inferred to be necessary to proper thermoregulation in the fur seal and any 

 substance destroying this insulating bai-rier could result in death by exposure. 



Accidental exposure of a less than year-old fur seal on the Oregon coast 

 in 1959 led to the animal being brought to the Depoe Bay Acquarium. It was 

 very thin and weak, and virtually covered with oil. Solvents were usetl under 

 the direction of a veterinarian to remove the oil and the cleaned seal was washed 

 with soap and water. At first it would not eat, so it was force-fe<l. The animal 

 recovered completely and was, in 1971, still an exhibit at the aquarium (Personal 

 communication to K. VV. Kenyon from W. Kukaska, 1971). The presence of 

 petroleum did not damage the seal permanently. It may also be inferred that 

 the presence of a large amount of petroleum on the animal interfered in some 

 way with the animal's ability to obtain food and that it would have died from 

 a combination of starvation and exposure if it had not been rescued. 



Of the 3,769 seals taken during pelagic sealing studies of the Marine Mammal 

 Biological Laboratory, Seattle, during the 1964 to 1971 seasons, one was observed 

 to have "half of the belly matted with grease" (Fiscus and Kajimura, 1967). 

 Among 107 fur seals taken at sea in May 1969, off Washington and British 

 Columbia, 12 (11 percent) were contaminated with oil. Of those, S were taken 

 almost directly off the mouth of the Strait of Juan de Fuca. This indicates that 

 fur seals that enter busy shipping lanes may become contaminated by oil (Per- 

 sonal communication to K. W. Kenyon from I. MacAskie, 1971). Among hundreds 

 of thousands of fur seals harvested and observed on the Pribilof Islands breeding 

 grounds, not one seal having oil on its i)elage has been recorded. One dead fur 

 seal, less than 1 year old, found on a Washington beach, was brought to the 

 Marine Mammal Biological Laboratory in about 194S. An area amounting to about 

 % of its body surface was heavily matted with crude oil. The apparent cause of 

 death was starvation. 



Three conclusions are indicated: (1) In most open sea areas where fur seals 

 are found on migration, they infrequently come in contact with petroleum prod- 

 ucts, although, when they enter busy shipping lanes, oil contamination may occur ; 

 (2) The absence of seals contaminated by oil on the breeding grounds suggests 

 that either contaminated animals do not survive to return to the grounds or 

 that none become contaminated during migration, or that they become clean 

 enroute; (3) Information on seal mortality due to any cause is severely limited 

 because fur seals usually occur well offshore, the body is of greater specific 

 gravity than water, and the dead animals sink and thus would rarely be found on 

 beaches. 



Two dead habor seals (Phoca vitulina) that w-ere heavily coated all over with 

 crude oil have been reported. One was found in Tacoma Harbor and the other in 

 Tacoma Narrows, Puget Sound, in about 1952. It was presumed that both liad 

 died because of the oil on their bodies but no positive determination was made. 

 The source of th(> oil was ascribed to intentional ship discharges, but no definite 

 linkage was established. 



A yearling harbor seal was found completely covered witli crude oil about 

 1952. When it was brought to the Tacoma Aquarium from a beach in Tacoma 

 Harbor, it was thin and weak. The seal was carefully cleaned, and with care and 



