Reproduction 



Motivated by a strong homing instinct, bulls 

 usually return to the rookery of their birth to 

 establish a territory which they will defend, 

 whether or not they are joined by females. A 

 female seal or group of seals occupying a terri- 

 tory is called a harem. Harems vary in size from 

 1 to over 100 females; the average is about 40. 

 Location determines the size of a bull's territory 

 and his harem and the rapidity with which he 

 will acquire females. Generally, locations near 

 the water attract the most females but there are 

 many exceptions. Locations that appear almost 

 identical to the human eye either may be crowded 

 with seals or completely unused. Females seek 

 a location rather than cL specific male. The most 

 vigorous efforts of a bull are not sufficient to 

 retain a female that is determined to leave. 



On the Pribilof Islands in 1962, 12,674 harem 

 bulls were counted in addition to 11,759 bulls 

 without harems. 



Age determinations have been made for seals 

 up to 26 years of age. Tagged seals 21 years old 

 were recovered in 1962. The maximum life span 

 is believed to be about 30 years. Most fur seals 

 have their first pups when 4 to 6 years of age. 

 Few bear young after age 18 or 19. Some 70 

 percent of the adult females in the Pribilof herd 

 in any one year bear young. 



A large proportion of the fur seal pups are 

 born during the first three weeks of July. Females 

 give birth to one pup usually a day after first 

 coming ashore on the rookery. Five days later 

 they are impregnated, usually in a single mating, 



and sometime in the following week make a trip 

 to sea to feed. Feeding excursions may last 5 

 to 14 days, but average 8 days. Females nurse 

 only their own offspring, which they recognize 

 by a combination of location, sound, and smell. 

 The pup must obtain enough of the rich milk, 

 containing about 45 percent fat, to survive be- 

 tween the widely spaced feedings. During the 

 nursing period the pup's stomach occupies most 

 of the body cavity. A well-fed pup in September 

 resembles a football with flippers! No food other 

 than milk is taken by the pup before it leaves 

 the island in the fall at weaned age of 3 or 4 

 months. By the time the young are ready to 

 leave the rookery in November, the larger ones 

 weigh over 30 pounds. Nursing ends abruptly 

 when the female leaves the islands to migrate 

 southward. The pups must then begin finding 

 their own food in the form of fish and squids. 

 After several months at sea they may not have 

 gained or may even have lost weight, but their 

 contours are more nearly those of an adult. 



A much-repeated fallacy is that young fur 

 seals are taught to swim. The pups can swim 

 from the moment of their birth, and none ever 

 receives lessons from its mother. At first they 

 swim rather awkwardly with head high out of 

 the water but soon gain in skill and endurance. 



During the first day or two after birth of her 

 pup the female will attempt to protect it and will 

 sometimes carry it in her mouth. Thereafter, 

 the female flees from an intruder without making 

 any attempt to protect her pup. A pup that 

 falls into a crevice in rocks dies because the 

 mother will not retrieve it. 



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