FAIRBANKS - Moose and caribou are the preferred menu item for wolves in Interior Alaska, but new research shows salmon play a larger-than-expected role in their diet.
The study, the results of which appeared in the journal Ecological Applications, found that salmon comprises a third of the diet for some wolves in the Denali National Park and Preserve. On average, salmon make up about a sixth of the diet of wolves in the area.
"That's quite a bit for an animal that's supposed to be relying on ungulates," said Layne Adams, a biologist who co-wrote a paper about the study.
Biologists already knew that wolves in coastal regions commonly feed on spawned-out salmon. This was the first research on inland wolves eating the fish. The study focused on Toklat Springs, an area where chum and coho salmon spawn each fall after swimming up the Yukon, Tanana and Kantishna rivers.
"I think what it shows is the salmon subsidize the wolf population and hold it at a higher level than it would be if the salmon weren't there," said Adams, who has been studying wolves in Denali more than 20 years.
"If it wasn't for the salmon, a lot of those wolves would die."
Because they don't die, they end up consuming more moose and caribou. Moose and caribou densities in the northwest portion of the park, near where salmon spawn, were 78 percent lower than those in the rest of the study area.
"They'd rather be killing and eating moose than eating salmon, but if they're really hungry they can go find a salmon carcass," Adams said.
Researchers used bone samples of wolves that died in or near the park in 1986-2002, as well as blood samples from moose, sheep and caribou studies in the same area. Spawned-out chums were also collected from the Toklat Springs area.
The researchers then examined the ratios of nitrogen isotopes in wolf bones and compared them with the prey samples to obtain evidence of the diets of individual wolves.
The idea for the study was sparked by a comment a decade ago by Fairbanks pilot Dennis Miller, who flies salmon- and wolf-tracking surveys for the National Park Service. He was tracking wolves for Adams when the pilot called to say he didn't need radios to find one pack of wolves. It was always in the same place - Toklat Springs.
"It was no surprise that wolves ate salmon, but it made me think if they're hanging around there all the time they may be eating more salmon than we thought," Adams said.