1980, 44 elephant seals with shark-inflicted in- 

 juries were observed (Table 2). Most of the ele- 

 phant seals bearing recent shark wounds were 

 adults. Males incurred the highest injury rate. 

 Even the largest adult bulls, measuring more 

 than 4.9 m and weighing between 1,800 and 

 2,700 kg were observed with shark bites (see Fig- 

 ure 2a). This may be due to the male habit of 

 spending more time in the water near the rook- 

 ery during the breeding season than females. 



Table 2.— Shark-bitten northern elephant seals 

 observed on Ano Nuevo Island and the Ano Nuevo 

 Mainland. 



Shark bites were located on diverse areas of 

 the body but rarely on the head (Fig. 2). Possibly, 

 frontal attacks were less successful or head bit- 

 ten seals simply did not survive the encounter. In 

 many cases, large pieces of blubber were missing 

 or hung loosely from the animal. Some seals lost a 

 foreflipper or hindflipper and in one case most of 

 the proboscis. Some animals were bitten several 

 times. 



The majority of injured seals survived and re- 

 cuperated rapidly. Infected wounds were rarely 

 observed. Only three elephant seals died on the 

 island or on the mainland following shark injury. 

 In September 1976, an S^-mo-old female was 

 found dead with numerous deep lacerations and 

 teeth marks covering her body. In December 

 1977, a 1-wk-old pup washed up with its entire 

 sacral region amputated just below the umbili- 

 cus. In February 1978, a large 7-yr-old male died 

 on the island's main breeding beach from mas- 

 sive shark wounds incurred within the previous 

 24 h. The most serious wounds consisted of two 

 large oval chunks of flesh missing from the left 

 side of the thoracic region (Fig. 2e). The bites 

 measured 61 and 69 cm wide, 61 cm high, and 30 

 cm deep. No bite penetrated the body cavity al- 

 though some muscle was removed and a rib was 

 partly exposed. 



Most female elephant seals bitten by sharks 

 shortly before giving birth failed to wean their 

 pups successfully. One female gave birth to a 

 stillborn and returned to sea immediately. Seven 



females either abandoned their pups shortly 

 after parturition or they were unable to care for 

 them adequately. Four of these pups died; the 

 eventual status of the other three pups could not 

 be determined. The three females who were suc- 

 cessful in weaning their pups appeared to have 

 sustained the least serious injuries. All injured 

 females remained in the harem for a much short- 

 er period than normal. No injured female was 

 observed to copulate, as uninjured females do, 

 just before returning to sea. Thus, most injured 

 females not only failed to produce a pup during 

 the year of injury, but if they failed to copulate, 

 they did not reproduce in the subsequent year as 

 well. 



Discussion 



The data on stomach contents of white sharks 

 presented in this paper is conclusive evidence 

 that this shark preys on elephant seals and har- 

 bor seals in southern and central California wa- 

 ters. 



We hypothesize that shark-inflicted injuries to 

 northern elephant seals at Ano Nuevo were 

 caused primarily by white sharks. This hypothe- 

 sis is supported by: 



1) Data from a white shark that washed ashore 



at Ano Nuevo Bay whose stomach contained 

 the remains of an elephant seal (Table 2). 



2) Observation of white sharks in the area. 



Twice during the summer of 1970 seal re- 

 searchers saw white sharks measuring 

 about 4.5 m from a dinghy 100 m south of 

 the island. Party boat operators and fisher- 

 men reported seeing white sharks in this 

 area several times during the last decade. 

 Anglers report that white sharks occasion- 

 ally attack large lingcod, Ophidon elonga- 

 tus, when they are caught on hook and line; 

 the sharks surface and circle boats, espe- 

 cially when fishing stops (Miller and Col- 

 lier 1980). 



3) An observed white shark attack of a northern 



elephant seal near Ano Nuevo Island. This 

 occurred on 1 February 1981. 



4) The large size of shark bites. This indicates 



that they were caused by large sharks. 

 White sharks may also be responsible for 

 injuries to elephant seals on other rookeries 

 in California (Ainley et al. 1981) and in 

 Mexico (Townsend 1885; B. Le Boeuf, pers. 

 obs.). 



893 



