Alaska’s northern fur seals find refuge on tip of volcano
Vents on
“The population growth of northern fur seals on Bogoslof has been extraordinary,” said
Geographically speaking, the island is not a particularly unusual place for the seals known for their thick coats to hang out. Most of the world’s roughly 1.1 million northern fur seals breed in the eastern
But why the seals chose volatile Bogoslof over the dozens of other uninhabited
“The surface is covered with these big, ballistic blocks, some as big as 10 meters (33 feet) in length that were exploded out of the vent,” said
The eastern
Fur seals were first spotted on Bogoslof in 1980, and
The animals stay on beaches, but on Bogoslof _ which is about a third the size of New York City’s
The center of the island supports a field of fumaroles, openings through which hot gases emerge. Some roar “like jet engines” and spurt mud geysers several meters high, Waythomas said. He has visited the last two summers.
“It was amazing, the sounds that were being produced,” he said.
Eruptions in 2016 and 2017 showered the landscape with rocks and killed all vegetation. They also shrank and grew the island. Explosions destroyed acres of Bogoslof only to have fragmented material blown from lava vents create new real estate. The island remains about 0.5 square miles (1.2 square kilometers).
Bogoslof is surrounded by deep water, and its seals eat squid and northern smoothtongue, a deep-water fish that looks like a smelt. Seals on
Females with pups on Bogoslof return from foraging faster than Pribilof mothers, possibly allowing their pups to receive more meals and wean at a larger size, Gelatt said. Bogoslof also is closer to winter feeding grounds south of the Aleutians, possibly allowing pups to reach the grounds with less risk from
Northern fur seals are distinct from harbor, ringed, bearded, ribbon and spotted seals in
The animals have a prominent role in the history of colonized
But by 1988, four years after the commercial harvest ended on
“That’s the million-dollar question,” Gelatt said. Competition for prey from the commercial fishing fleet, predation by killer whales, disease and ecosystem changes affecting seal or prey behavior are possibilities.
Volcanic activity on Bogoslof has been relatively stable, but Gelatt’s crew chose not to camp there during their weeklong August expedition, fearing a recurrence of explosions that could shoot boulders like bottle rockets. They instead made day trips from an anchored boat.
The crew tallied seals and assessed whether aerial images taken from unmanned aircraft could be used in future counts. As fewer seals breed on
“Barring other future catastrophic eruptions that could dramatically change the geography of the island, there is plenty of room for a lot more seals on Bogoslof,” Gelatt said.
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