30-40 days; they are in the process of returning to 

 sea to feed. As their number decUnes, juveniles of 

 both sexes begin to haul-out in increasing numbers. 

 They have been at sea for 4 months or more. Cen- 

 sus counts of total northern elephant seals are lower 

 at this time than at any other time of the year (Le 

 Boeuf and Bonnell 1980). 



Observations and Methods 



Most of the observations were made during an ex- 

 pedition to Mexican islands aboard the MV Mirage 

 from 20 to 31 August 1986. Islands surveyed in- 

 cluded Isla de Guadalupe, Islas San Benito, Cedros, 

 San Martin, and Los Coronados. We censused north- 

 ern elephant seals at all sites and, in doing so, 

 recorded the incidence of fresh wounds. On 2 

 September 1986, we censused and recorded wounds 

 on northern elephant seals at Ano Nuevo Island off 

 central California. Similar observations and cen- 

 suses were conducted weekly at Ano Nuevo Island 

 during October and November, when peak numbers 

 of juveniles are observed. 



Censuses and inspection for wounds were made 

 from an inflatable 6 m boat, approximately 10 m 

 from seals lying on sandy beaches near the water's 

 edge, or from on foot to get closer to the animals. 

 WTien possible, we inspected both sides of all seals; 

 we made no attempt to turn animals over to inspect 

 the ventrum or to arouse them to better inspect 

 them for wounds. Approximately half of the animals 

 counted were seen from only one side. Thus, the 

 counts of wounded animals we present are clearly 

 underestimates of the true figure. We noted the 

 location of all wounds and estimated their size and 

 freshness. 



We examined preserved specimens of Isistius 

 housed in the Marine Vertebrates Division of the 

 Scripps Institution of Oceanography (SIO). 



Results 



We observed fresh wounds on 20 juvenile northern 

 elephant seals on three of the five island groups in- 

 spected in August and September (Table 1); there 

 were no elephant seals on Isla San Martin. Four ad- 

 ditional wounded juveniles were observed on Ano 

 Nuevo Island later in the year. All wounds were 

 fresh, as indicated by their bloody color, and, with 

 one exception, they were of similar size and shape 

 (Fig. 1). The wounds were round and hollowed-out 

 craters; the margin of each wound was smooth. 

 Each wound was about 5-6 cm wide and 3-5 cm deep. 

 One wound, although like the others in most 

 respects, had a flap of skin and blubber still attached. 

 No fresh crater wounds were observed on adult and 

 subadult males. 



Most animals had one wound. Wounds were 

 located on various parts of the body (Fig. 1): the side 

 posterior to the flippers, on the ventrum or the back 

 and to either side or on the midline, on the chest 

 and neck, and just behind the ear. Two animals had 

 two wounds and one had three. One animal had two 

 fresh, identical wounds on the dorsal midline at the 

 level of the foreflippers, separated by approximately 

 3 cm. Another had two wounds 0.3 m apart on its 

 left side. One animal had three wounds: two on the 

 abdomen and one on the ventral surface of the neck. 



The incidence of fresh wounds was highest on 

 northern elephant seals inhabiting Isla de Guada- 

 lupe (8.4% of the juveniles censused) followed by Isla 

 Cedros and Islas San Benito (Table 1). No wounded 



Table 1 .—Proportion and percentage of fresh crater wounds on northern elephant 

 seals censused on various Mexican and Caiifornlan islands during August and 

 September 1986. 



^Over 90 juveniles were counted but only 57 were observed close enough to document wounds. 



388 



