48 



NORTH AMERICAN FAUNA 74 



Fig. 32, Pelage and surface topography of adult Pacific walruses: upper — lateral surface 

 of the chest and abdomen of a 15-\ ear-old female; lower — dorsal surface of the neck and 

 shoulders of a 24-year-old male. (Photos by F. H. Fay) 



parallels that of the reproductive organs (Krylov 1967). Other investigators (e.g.. 

 Brown 1868; Loughrey 1959). however, have regarded them only as scars. Since 

 bosses ha\'e not yet appeared in sexually mature male Pacific walruses up to 18 

 years old that were reared in captivity (E. D. Asper. T. Otten. personal com- 

 munication), the argument for secondar\- sexual character is weakened. The 

 evidence for scarring (presumably from tusk-strikes) as a causative factor is much 

 weaker, however, because the females and immature males also are hea\'ily 

 scarred but have no bosses. Furthermore, the bosses on adult males show scar 



