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Wolves Prefer Salmon to Deer?

Anne Minard
for National Geographic News
September 3, 2008
 
Move over, grizzly bears. "Fishing wolves" in coastal British Columbia are also looking to snatch some salmon, and will eat the fish almost exclusively when they are available, new research reveals.

Biologists analyzed years of data from gray wolves' feces to monitor what the animals were eating.

The team found that the coastal predators, like many other wolves, rely on deer most of the time in the spring and summer.

But during several months in the fall, the wolves ignored deer to focus on migrating salmon.

"What is unusual is this huge seasonal shift to salmon. They were forgoing deer to target salmon," said study leader Chris Darimont at the University of Victoria in Canada.

Study co-author Thomas Reimchen added in a press release that the results are as much about salmon as about wolves.

"Salmon continue to surprise us, showing us new ways in which their oceanic migrations eventually permeate entire terrestrial ecosystems," he said.

"In terms of providing food and nutrients to a whole food web, we like to think of them as North America's answer to the Serengeti's wildebeest."

Seafood Buffet

Researchers already knew that wolves occasionally eat salmon, because biologists have found evidence of the fish in wolf droppings and had even seen the wolves fishing.

But the "comfortable, orthodox" theory, Darimont said, is that wolves are first and foremost linked to populations of ungulates—four-legged, hoofed mammals such as elk and deer.

"I would say it's pretty much central to most of the wolf literature," he said.

Even the authors believed salmon would be an alternative prey, reserved for times when deer were scarce.

Darimont said he and his team were "absolutely shocked" to find that the wolves seemed to prefer salmon in the fall, when the fish are migrating upstream to spawn.

"The deer are there," he said. "They could persist on deer."

Ecologically speaking, Darimont is most excited about the fact that the wolves' food choice is driven by the abundance of salmon, not the scarcity of deer. On reflection, he added, this strategy makes good sense.

"[Salmon is] safe, it's nutritious, it's spatially constrained. This buffet from the sea comes to them. They don't have to search dozens of kilometers for deer. And it's predictable. Those are some awesome qualities in a resource."

The study, which was published online this week in the open-access journal BMC Ecology, was partially funded by the National Geographic Society's Committee for Research and Exploration.

(National Geographic News is part of the National Geographic Society.)

Relics of the Past?

David Mech is a research biologist whose 40-plus-year investigation of wolves in the Great Lakes region (see map) helped fuel the predominant theory that wolves and ungulates are inextricably connected.

Mech said he found the new results interesting but not surprising.

"I would call it more of an exception," he wrote in an email. "This is certainly not the first exception reported."

Mech pointed out that, in the Arctic, wolves often prey on Arctic hares, particularly in the summer. And in Ontario, Canada, wolves have depended on beavers when ungulates were scarce.

"On [Lake Superior's] Isle Royale last year or the previous, wolves ate a lot of apples, as reported by Rolf Peterson," he said, referring to another well-known wolf expert.

"I consider these trite exceptions to the generalization that most of the time, wolves—and even Darimont's wolves—are dependent on ungulates," Mech said.

Still, Darimont sees British Columbia's fishing wolves as relics of a time when the association between wolves and prey other than deer was much more mainstream.

"People forget, but it wasn't too long ago when both salmon and wolves co-occurred over much, much greater portions of North America and even Europe. This fishing wolf would have existed from southern California up to Alaska," he said.

Wolves' fishing behavior was noted in the journals of Lewis and Clark and other early North American naturalists, he said.

"It's like we're stepping back in time and being able to observe how this predator-prey system would have worked and existed all the way down the coast of North America."

Salmon Threats

Darimont, who is also affiliated with the Raincoast Conservation Foundation, worries that today's wolf-salmon association is imperiled.

"There's this huge biomass of energy and nutrients"—salmon—"heading back to reproduce for future generations, basically serving a whole ecosystem, feeding bears wolves, songbirds, insects," he said.

But highly efficient coastal fishing boats may take 90 percent of fish before they make it up the river to spawn, he said.

"In the context of conservation, if we are interested in the maintenance of this incredible resource, then we ought to seriously reduce exploitation levels."

Darimont said he personally avoids farmed salmon, because the process threatens natural populations with disease. (Related: "Farmed Salmon Decimating Wild Salmon Worldwide" [February 12, 2008].)

As for wild-caught salmon, he said, "consider that every bite of salmon you take, that's one less for wolves and songbirds … and many of these animals don't have options."
 

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