ECOLOGY AND BIOLOGY OF THE PACIFIC WALRUS 



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(65) 



Fig. 129. Age composition of male 

 (upper) and female (lower) wal- 

 ruses that died from intraspecific 

 trauma on the Punuk Islands in 

 1961, 1974, and 1976-78. (From 

 F. H. Fay, B. P. Kelly, and L. M. 

 Shults, unpublished data) 



20 



0- 



(69) 



j1 



II 



Li 



I I I I I I I M I I 



10 



20 



30 



40 



Age ( years) 



animals that lay on and around them on the haulout. Because none of the 

 animals had any evident bullet wounds, we judged that all of the deaths were 

 from natural causes. Most of the carcasses were of adult females; only a few of 

 the males were adults (Fig. 129). 



We examined by necropsy 29 of the carcasses that had been relatively well 

 preserved by being covered with ice and snow until just before our arrival. Of 

 those, 16 were calves 5 to 6 months old, each of which showed the following 

 primary pathological conditions: extreme contusion and hemorrhage of the 

 cervical musculature, vertebral dislocation, and cerebrospinal hemorrhage 

 (Fig. 130). Several also showed extensive hemorrhagic congestion of the lungs, 

 with extravasation of blood into the thoracic cavity; one showed intestinal 

 prolapse. None was flattened, hairless, or had any premortem bone fractures. 

 None was damaged externally, though most were bleeding from the nostrils. The 

 condition of their lungs and the one case of prolapse suggested the possibility of 

 severe compression; the state of their cervical musculature and spinal cord 

 indicated also extreme torsion of the spine in that region. These conditions 

 strongly suggested that the calves had been rolled and trampled to death by 

 larger animals (i.e., adult walruses). 



The conditions in the 13 older animals were remarkably similar to those in the 

 calves. At least nine had died in the same way; two females probably had died 

 from prolapse of the uterus and intestine; one adult male apparently had suffered 

 a fatal concussion from being struck on the head by a blunt object; the cause of 

 death of the 13th animal was not determined. As in the calves, the implication 

 was of their having been rolled and compressed, as might have occurred in a 

 "stampede" situation. 



On one occasion (1979), we found numerous aborted fetuses scattered among 

 the larger carcasses. Presumably, these were expelled also as a result of trauma. 



