Rare fur seals reclaim place on Farallon Islands Animals fled 1834 slaughter; now they're back and breeding
Glen Martin, Chronicle Environment Writer Monday, September 11, 2006 The fur seal population on the Farallones is surging, an ... Northern Fur Seals. Chronicle graphic by John Mavroudis Farallon Islands. Chronicle Graphic A marine mammal that disappeared from California's North Coast more than 170 years ago has returned in force to the Farallon Islands. The Farallones once supported hundreds of thousands of breeding northern fur seals -- big marine predators with luxuriant pelts. Their thick, soft fur proved their undoing: In 1834, sealers slaughtered about 200,000 of the animals, delivering their pelts to Fort Ross in what is now Sonoma County. The rest of the seals fled, abandoning their rookeries for more than a century and a half. A few started returning in the early 1970s, but this year their numbers surged -- an indication of the islands' enduring vitality and proof that a sensitive species can revive under favorable circumstances. "We're ecstatic to see any marine mammal recovery, but it's especially gratifying when you're talking about a sensitive species like northern fur seals," said Clyde Morris, manager of the Don Edwards San Francisco Bay National Wildlife Refuge. "Their comeback is probably due to the high protection from human intrusion the Farallones receive." Fur seals shunned the Farallones, islands rigorously protected as a refuge and research site by the U.S. Fish and Wildlife Service, until a handful of young male seals rediscovered the islands about 30 years ago, said Bill Sydeman, the director of marine ecology at PRBO Conservation Science, the lead research group at the Farallones. "That's a typical pattern," he said. "Juvenile males will range far from established rookeries, visiting new sites for abbreviated periods of time." If females eventually show up, it's usually after the young males have extensively prospected the area, Sydeman said. That's just what happened in 1996, when the first female fur seals hauled up at the Farallones and produced a few pups. Since then, their numbers have grown -- and this year, 80 pups were born, almost triple last year's figure. "We're starting to see the beginning of exponential growth," Sydeman said. Adam Brown, a PRBO marine biologist stationed at the Farallones, said six fur seals lived on the refuge in 1998. That increased slowly through 2004, when there were 38, Brown said. "There were 90 in 2005, and last week we counted 188," he said. If the rate of increase continues to accelerate, Brown said, there could be up to 50,000 fur seals on the Farallones in less than a decade. "It's unclear if there are the habitat and prey base to support that many, but those kinds of numbers are at least possible," he said. Paradoxically, that sort of success could be a problem. If the big, voracious fur seals return to the Farallones in anything approaching their original numbers, it could harm other mammals and birds, experts say. Of particular concern, Sydeman said, are Cassin's auklets. The rare seabirds nest in the same kind of habitat fur seals prefer for their rookeries. "Cassin's auklets have suffered almost complete breeding failures for two consecutive years at the Farallones," Sydeman said, noting the lack of nesting success was likely due to excessively warm water temperatures and inadequate plankton production. "Any additional stress during the breeding season could have serious repercussions for them." Brown agreed that such concerns are justified. "Any time you introduce a top predator into a system, you can expect changes," he said. "Right now, they're not directly encroaching on the bird colonies, but that time probably isn't very far away. That said, it's wonderful to watch this unfold. New pinniped colonies aren't established every day." Unlike other West Coast pinnipeds such as harbor seals and sea lions, northern fur seals are pelagic by inclination, meaning they spend most of their lives drifting with the ocean currents. They log only a few weeks a year on isolated islands to whelp and rear their young. Pups are quickly weaned, joining their parents to ply offshore waters in quest of fish and squid. By contrast, elephant seals -- another charismatic marine mammal now aggressively colonizing California -- can spend several months in their rookeries, breeding and rearing their pups. Perhaps a million northern fur seals range the North Pacific, which includes California waters. The World Conservation Union, a group that keeps track of threatened species worldwide, considers the seal a vulnerable species at risk of extinction in the future. Most of the world's northern fur seals breed on the Pribilof Islands in the Bering Sea. Indeed, some of the seals now inhabiting the Farallones migrated from the Pribilofs, Brown said. "So far, we have counted nine seals, all females, that have Pribilof tags," he said. Smaller colonies are also found at Bogoslof Island in the Aleutian chain, and San Miguel Island off Santa Barbara. Colonies of relatively modest size are also established on several islands in Russian territorial waters. Though the global fur seal population may seem substantial, say biologists, their numbers are down drastically from the 1970s. This year, about 850,000 adult and juvenile fur seals were on the Pribilof Islands -- a 46 percent decline from the mid-1970s, Sydeman said. "The declines at the Pribilofs have been tracking at about 5 percent a year," he said. "2002 saw the lowest number of animals since 1919. It's pretty worrisome." Some scientists have hypothesized that the Pribilof declines might be linked to commercial fishing for pollack, a fur seal staple. Federal regulators say further research is needed. Though they avoid human contact, fur seals do not lightly suffer harassment from people or other marine mammals. "I just got back from working with some of the pups at the Pribilofs," said Tom Gelatt, the leader of the Alaskan Ecosystems Project at the National Marine Mammal Laboratory, a facility of the National Oceanic and Atmospheric Administration. "They come right at you," Gelatt said. "They're real ankle-biters." Brown said he has witnessed bull fur seals chasing sea lions away from the new colony at the Farallones. "They're probably the top-dog pinniped in the North Pacific," Brown said. "At least, they really act that way." Northern fur seals Status: The seals are rare and considered a species vulnerable to extinction by the World Conservation Union. Numbers of the seals are rising at the Farallon Islands but dropping at the Pribilof Islands, an established breeding ground. Description: The seals have large, bare flippers. Their soft, thick fur covers the rest of their body. Their pelts can have 46,500 squares per square centimeter. They have very large eyes that give them good night vision. Adult males can weigh 600 pounds; females weigh between 60 and 110 pounds. Their fur color ranges from reddish brown to black. Range: Their range includes the Bering Sea, waters of northern Japan and down to Southern California in the Pacific Ocean. Diet: They primarily dive for squid and fish, including walleye pollack, Pacific salmon and herring. Breeding: Adult males are usually at least 10 years old. Females usually return to breeding islands in June and have their first pups when they are 5 to 6 years old. Source: National Marine Mammal Laboratory E-mail Glen Martin at [EMAIL PROTECTED] __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! 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