140 



NORTH AMERICAN FAUNA 74 



Fig. 95. Calf, about 13 months old, in a herd of adult males at Round Island, Bristol 

 Bay in June 1972. (Photo by B. Hines) 



individuals of this age are capable of feeding on benthic invertebrates. 



According to the St. Lawrence Islanders, the 17- to 18-month-old young 

 accompanied by an adult usually have only milk in the stomach, but some 

 contain both milk and invertebrates; a few have only invertebrates. Although I 

 was not able to confirm this, I examined the stomach of a 22-month-old animal, 

 which contained a mixture of milk and soft-shelled (molting) brachyuran crabs 

 of the genus Chionoecetes. 



Two 24-month-old animals that I examined had only benthic invertebrates in 

 their stomachs, as did several examined by Chapskii (1936), Brooks (1954), 

 Mansfield (1958fl), and Loughrey (1959). However, Nikulin (1941) and Freiman 

 (1941) found one 26- to 27-month-old animal that had only milk in its stomach 

 and another that had both milk and mollusks. 



On two occasions, I observed 34- and 35-month-old animals suckling. Since 

 the adults that they were with had no other younger animals with them, I 

 assume that both of these were parent-offspring pairs that had remained 

 together longer than the usual 2-year period. 



In summary, the data available suggest that (1) calves are dependent on milk 

 alone in at least the first 5 months after birth, (2) some calves may begin to eat 

 invertebrates infrequently by the time they are 6 months old, (3) a few are 

 proficient at benthic feeding by the end of their first year, but (4) they usually 

 continue to suckle, at least as a dietary supplement, for several months longer, 

 (5) their milk intake probably declines radically toward the end of the second 



