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Thursday, March 30, 2023

Sea otter restoration sends ripples by the ecosystem

This text was initially featured on Hakai Journal, an internet publication about science and society in coastal ecosystems. Learn extra tales like this at hakaimagazine.com.

Gretchen Roffler recollects looking on the waterfront in Alaska’s Katmai Nationwide Park and Protect as three wolves got here into view, then disappeared behind some rocks. When the predators returned, all three had been gripping the identical limp sea otter between their jaws. Working collectively, the wolves tore the otter to items. “It was like a tug of battle,” says Roffler, a wildlife biologist with the Alaska Division of Fish and Recreation.

Roffler and her colleagues paid shut consideration; they wanted to doc the June 2021 occasion intimately. In any case, Roffler believes, this was “one of many first observations of wolves killing sea otters.”

Sea otters had been extirpated from Alaska in 1830, however their reintroduction over the previous few a long time has been extremely profitable. The marine mammal’s resurgence signifies that in Alaska sea otters and wolves are actually inhabiting the identical environments for the primary time within the fashionable scientific file. This assembly of historic predator and prey is having essential penalties—particularly for the area’s deer.

Scientists are likely to assume {that a} wolf inhabitants’s dimension is dictated by the supply of ungulate prey like deer and moose. However on the Alaska coast, scientists like Roffler are more and more documenting instances of coastal wolves munching on marine mammals. The truth is, on Nice Island, close to Glacier Bay Nationwide Park and Protect, Roffler and her colleagues’ evaluation of wolf scat has proven that the native wolves have nearly fully switched their food regimen from deer to sea otters.

Quite than the wolves leaving the deer alone, although, Roffler says that this new supply of vitamins has saved the wolf inhabitants so wholesome that it has worn out the area’s deer.

By fixing Alaska coastal wolves with GPS collars to see the place they had been touring and searching, and by analyzing wolf scat and hair samples collected between 2015 and 2021, Roffler and her colleagues retraced the modifications which have taken place.

Their analysis exhibits that sea otters first recolonized the world round Nice Island within the early 2000s, whereas wolves landed on the island in 2013. The deer inhabitants crashed in 2015, and by 2016 the wolves had been largely consuming sea otters.

Whereas wolves scavenging the occasional sea otter might not be sudden, Roffler says it’s stunning {that a} pack may utterly swap its food regimen and proceed to keep up a wholesome inhabitants on a small island devoid of deer. “We assumed what would occur is that the wolves would eat a number of deer and probably deplete the inhabitants, after which the wolves would both die off or depart,” she says.

The scientists are curious how widespread this type of prey switching has been in different areas alongside the coast the place sea otters have additionally rebounded. They’re additionally concerned with how wolves study to hunt sea otters—and whether or not it may be a conduct that may catch on between wolf packs.

Up to now, Roffler says it’s too quickly to foretell whether or not wolf populations rising fats on sea otters may spell hassle for deer elsewhere because it has on Nice Island, however they believe it could solely have an identical impact on different comparatively remoted small islands the place wolves have easy accessibility to sea otters.

Chris Darimont, a conservation biologist from the Raincoast Conservation Basis who was not concerned within the examine, says that in addition to serving to us perceive how the ecosystem is altering, this type of work additionally provides a window into historical past—earlier than the ocean otters had been worn out by hunters. “In a approach, we’re having a glimpse into the previous by learning one thing that’s recovering now.”

This text first appeared in Hakai Journal and is republished right here with permission.

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