Fur Seals: Back From The Brink But A Long Way To Go by Mary Jane Schramm

Fur Seals: Back From The Brink But A Long Way To Go by Mary Jane Schramm

     November along our Northern California coast brings crisp, crystalline air—a backdrop for rain-darkened clouds; long, deep ocean swells; and Dungeness crabs, ripe for harvest. In oceanographic terms, fall represents the “relaxation” season of the sea, before winter storms pummel the coast with waves like small mountains. General upwelling subsides, the lazy, north-flowing Davidson Current kicks in, and the sea enters a quiet period. The guano-spattered islets off Mendonoma and Marin no longer host seabird nests; the Farallon Islands fall nearly silent. A few humpbacks eke out a final meal before decamping to Mexico and Central America to find mates and bear their calves. 

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     But offshore, at the edge of the Continental Shelf, a migration is underway, ahead of the southbound gray whales: female and juvenile northern fur seals (Callorhinus ursinus). Having forsaken their Alaskan breeding grounds in the Pribilof and Aleutian islands, they are fattening up on fish and squid, headed south, some as far as Baja California. The edge of the Continental Shelf is their highway marker and “groaning board” thanks to localized nutrient upwelling. Perhaps to ensure the sexes don’t compete over a finite food supply, the males remain in more northerly waters. Survival of both to the next breeding season is their sole objective.

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     Northern fur seals resemble smaller California sea lions, with lush fur, blunt muzzles, and more attitude and teeth per pound than any other seal or sea lion around. These feisty animals dominate their surroundings, often challenging and displacing enormous elephant seals and majestic Steller sea lions on rookeries. See http://www.nmfs.noaa.gov/pr/species/mammals/seals/northern-fur-seal.html

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     FUR TRADE: Because of their soft, incredibly dense fur (around 360,000 hairs/sq. inch), European hunters in the 18th and 19th centuries harvested them with relentless efficiency, on land and at sea. Not content to decimate the Russian and American rookeries (around 1862 sealers took 150,000 fur seal skins from the Farallones in just three years!), at-sea hunting targeted female seals whose migration patterns were tragically predictable. Killing one seal “cow” often meant three dead seals: the female, her nursing pup, and the pup developing inside her (they have two-sided uteruses, allowing year-round pregnancies). Whole populations collapsed, until the North Pacific Fur Seal Convention of 1911 was signed by Great Britain (for Canada), Russia, Japan and the United States. Their numbers rebounded, but in the past few decades Pribilof seal pup production has declined by 50%. Possible causes include fisheries competition and entanglement, killer whale predation, and climate change. They are now listed as "vulnerable" under the U.S. Endangered Species Act. Hunting is illegal except for a limited subsistence hunt by native peoples. Estimates for the North Pacific are now just over a million. The World Conservation Union still considers the species at risk of future extinction due to the manifold threats it faces.

     SOUTHERN COLONIES: Fort Ross and San Francisco were bustling fur seal commerce centers, but by the early 20th Century the Farallon Islands colony was wiped out. However, in the mid-20th century, seals from the Pribilofs and Commander Islands recolonized San Miguel Island off Southern California. Their numbers increased robustly, to over 10,000. Some ventured north and, beginning in the 1970s, solitary “vagrants” from San Miguel were seen on the rugged Farallones once more. In 1996 Farallones sanctuary biologists and a Point Blue Conservation scientist found a single pup among older animals at West End Island: the first known breeding in 150 years. As boy met girl … and girl … and girl … (they form harems), exponential growth ensued: in summer 2017, 1,200 pups were born, the population now numbering around 2,500 individuals.

     ONE THREAT REMOVED: Marine sanctuary regulations prohibit petroleum development. Spills bring all sorts of grief to living things, especially fur seals, whether oil is inhaled, ingested, absorbed, or external. Oil mats fur, rendering it useless for retaining precious body heat (most marine mammals have thick blubber to remain warm). Caustic vapors can sear throat and lung tissues, causing emphysema and pneumonia. Ingested, it can cause fetal abortion and stillbirth. Legal protections from drilling-related spills are now in place, but leaks from ships and pipelines still take their toll. And other threats remain.

     Still, their future is promising. Once on the brink of extinction, these fur seals are now increasing, and conservationists are looking to their case history for lessons learned and guidance for new directions.

Photos Credit: NOAA

Learn more about the Farallones colony: 

https://news.nationalgeographic.com/2015/12/151222-california-fur-seal-farallon-islands-science/

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