323 



Leslie E. McDonald, D.V.M., Ph. D., Associate Dean and Professor of Physi- 

 ology and Pharmacology, College of Veterinary Medicine, Athens, Ga. 



*Alvin F. Moreland, D.V.M., Associate Professor and Head, Division of Com- 

 parative Medicine, University of Florida, Gainesville, Fla. 



♦Wallace M. Wass, D.V.M., Ph. D., Professor and Head, Department of Vet- 

 erinary Clinical Sciences, College of Veterinary Medicine, Iowa State University, 

 Ames, Iowa. 



A Thriving Hebd 

 (By John A. Guinan) 



On the grim, mist-shrouded Pribilof Islands ofE the coast of Alaska, an annual 

 ritual that predates recorded history is taking place once again. 



The Northern Fur Seals have arrived at the rookeries on these lonely islands. 

 The snowdrifts along the rocky beaches and rough volcanic hillsides have not 

 melted completely when, in late May and early June, the big breeding bulls begin 

 to appear. Heavy with fat from the long winter's feeding, belligerent and full of 

 fight, the bulls or "beachmasters" lumber ashore. Each establishes his individual 

 territory — about 30 to 50 feet in diameter — which another bull enters at his peril. 



Mature male or "bull" fur seals are much larger than the females or "cows." 

 The fur seal cows average about 100 pounds in weight, but the great breeding 

 bulls weigh from 400 to more than 600 pounds. The yoimg of these fascinating 

 creatures are called "pups." 



Soon it is summer on the tiny islands where no tall tree grows, but where for 

 this brief season hundreds of varieties of wildflowers of rare color and beauty 

 burst into bloom. 



About mid-June, the cows begin to arrive. Until this time, once their territories 

 had been established, the bulls have slept or rested from their long sea journey. 

 When the contest for their harems begins, however, there is no rest for the big 

 beachmasters. Polygamous to an amazing degree, each gathers in as many docile 

 cows as possible ; the number varies from one or two to a hundred, but the aver- 

 age is about 40. Day and night, the air is filled with the bleating of females and 

 young, and with the roars of the mighty males as each bull defends his harem 

 against all comers. Battles between males are savage. From now until the end 

 of the breeding season, the bulls live without food and get little sleep, gradually 

 losing the layers of fat uith which they came ashore. 



Almost as soon as the harems are formed, the pups conceived the year before 

 begin to appear, and soon after a pup is born the mother is bred again. One 

 pup per cow is the rule, and the young are carried for an entire year before 

 binth. Not all cows bear young each season ; the proportion is about 80 percent. 



The pups are precocious, their eyes wide open. They are active and have a 

 coat of hair. It will be some weeks before any fur appears. They are entirely 

 dependent on the mother's milk for food. The cow generally stays close to her 

 youngster for several days, then leaves to go to sea for food. The mother may 

 be away for a week, her trip taking her as far as a hundred miles from the 

 rookery, but when she returns, the pup makes up for lost time. It takes on 

 several times more milk than would a human infant of the same body weight — 

 up to a gallon of rich, creamy milk at a feeding. The little stomach swells like 

 a toy balloon as the pup drops off for a long sleep. The mother seal will feed 

 only her own pup and, despite her lengthy absence, the miles she travels, and 

 the thousands of pups in a rookery, she finds her own. 



Baby fur seals venture to the water at about four weeks. Even though they 

 can swim at birth, they have very little endurance. Their first trips to the cold 

 water are taken with trepidation. 



The cow seals nurse their young for about three months, and no human disturbs 

 them. By now, the weather is taking a turn for the worse, and the pups are left 

 abruptly to shift for themselves. Early mortality is high. Many pups succumb on 

 the island before migration ; others are prey to killer whales or big sharks ; still 

 more are lost in storms at sea. Yet more than enough yoimg seals survive each 

 year to keep the herd at its maximum healthy size. 



Around the edges of the breeding rookeries range the younger bulls, varying 

 in age from six to eight years but not yet strong enough to compete with the 

 fully matured beachmasters. Now and then they may steal a wayward wife 

 or two, or even take over the harem of a disabled monarch. But most of the 



♦Member, A.V.M.A. Council on Research's Panel on Euthanasia. 



