Rare Fur Seals Reclaim Place on Farallon Islands

[Guest guest]

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 glenmartin.