The Art Of Bullying - behavior of northern fur seals

National Wildlife, August-Sept, 1999

As violent as life in a northern fur seal colony may be, even this territorial contest between males is really all about social harmony

A RICKETY WOODEN catwalk suspended a mere 10 feet above a rocky beach is one of the prime locations on Alaska's St. Paul Island for scientists to study northern fur seals. So that's where some field biologists go in summer to observe a breeding colony of the marine mammals, often evading territorial bulls with sharp teeth on the way to the ladder. Once on the catwalk, researchers are surrounded by the fur seals jam-packed around the structure. 'If you fall, no one can help you,' Colorado State University pathologist Terry Spraker warns newcomers to the site, which is strictly off-limits to the public. 'The bulls will tear you apart.' It is mid-July, the peak of the breeding season in the Pribilof Islands, 500 miles west of the Alaska mainland. Cold, dusky fog rolls in from the Bering Sea and shrouds the rookery. Barnyard noises emanate from thousands of dark, wet humps. Occasionally the chorus of bleats, barks and roars suddenly swells, whirlpools of movement spread with explosive energy and the rookery goes on full alert.

A sleek female emerges from the sea and runs a gauntlet of menacing jaws to reunite with her bleating pup. Other pups engage in free-for-all combat, lunging to nip folds of skin or flippers. A large bull rushes into the thicket of bodies, invading the established territories of breeding males. Enraged, several of them blast through masses of cowering females, trampling inattentive pups under their giant foreflippers, to sink their canines into the interloper's 500-pound bulk. His eyes wild, he endures punitive bites until he can scoot away, blood oozing from the lacerations. A bull grabs an escaping female one-fifth his size and throws her back into his territory: Stay put! Her torn skin exposes shredded muscle.

As all of this activity indicates, nearly all relationships among northern fur seals include aggression, fueled by the surging hormones of breeding season and made all the more potent by the size and athletic abilities of the combatants. Yet biologists studying the boistrous life of fur seal colonies have been discovering order rather than chaos, and economy of aggression rather than senseless bloodletting.

Callorhinus ursinus -- which roughly means 'bear with a beautiful nose' -- has been studied for more than a century, by scores of researchers. German naturalist Georg Wilhelm Steller first described the seals as 'sea apes' when he observed them in 1741 off the coast of what would become Alaska. Swedish naturalist Carolus Linnaeus praised their 'flesh succulent and tender; fat and skin useful.' The animals' long-sought breeding grounds in the Bering Sea were found by Russian navigator Gerasim Pribilof in 1786. The Russians soon relocated enslaved Native hunters from their homes on the Aleutian Islands chain well south of the Pribilofs to St. Paul and St. George Islands and put them to work killing the animals for their exquisite fur. After Russia sold Alaska, Pribilof residents continued the work as wards of the U.S. government. Millions of harvested pelts, with 300,000 soft hairs per square inch, filled first Russian and then American coffers with enormous profits. Russian and U.S. government scientists who spent summer months on the Pribilofs focused on the seals' population dynamics and life cycle to make sure the herds thrived. When the United States called a halt to its commercial seal harvest in the early 1980s, scientists were already studying many aspects of the animals' biology, including seal-on-seal violence.

Northern fur seals spend most of the year at sea, distributed sparsely over a vast area of the Pacific Ocean. Their range includes the Bering Sea in the north, offshore waters south to California and Japan and all points between. In winter and spring, the seals have been seen traveling singly or, more rarely, in pairs. This solitary life-style changes dramatically in summer and autumn, when the animals crowd onto a few oceanic islands. Approximately 70 percent of all northern fur seals migrate to the Pribilofs, located within one of the world's most productive marine ecosystems.

St. Paul Island, the largest in the archipelago, is home to nearly one million of the animals. The Bering Sea provides vast quantities of small schooling fishes and squid eaten by the seals. Fur seals of all ages use the island's shoreline for everything from mating, to rearing young, to simply surviving unscathed. All of that means aggressive interactions among seals with competing interests. Yet more violence does not beget greater success. Bluffs, threats, ritualized displays and mock duels turn out to be the rule; outbursts of grievous violence are the exception. Adult males arrive on the rookeries in late spring to establish territories before the females appear.

Powerful and robust, they are clad in a thick layer of blubber that nourishes them while they protect their domain and fast during the next two months. The breeding bulls defend resources critical to the females: birth sites on prime real estate. Breeding occurs on crowded beaches, mainly during a few weeks in July, and the success of a male fur seal is largely related to the number of times he mates. Since the opportunities are so condensed in space and time, the disparity between the 'haves' and 'have nots' is immense. A male that can defend several square yards of boulder-strewn beachfront at the right time of year might couple with as many as 50 females. A hundred yards away, on the periphery of the rookery, the same male could fail entirely, spurned by females that don't like the location.