A population in peril

The Yukon's top ptarmigan biologist is depressed. The fat, white grouse Dave Mossop has spent more than 40 years studying are in dramatic decline. "There has been a major disruption in the boreal system," he said.

The Yukon’s top ptarmigan biologist is depressed.

The fat, white grouse Dave Mossop has spent more than 40 years studying are in dramatic decline.

“There has been a major disruption in the boreal system,” he said.

Ptarmigan populations follow a 10-year cycle, like all medium-size boreal creatures, including lynx, hares and foxes.

“And right now, we should be at a peak,” said Mossop.

“But it didn’t happen.

“The ptarmigan population didn’t come back up.”

Mossop fell in love with ptarmigan when he was 12.

The prairie boy was “a bird freak.”

And every now and then, these exotic white grouse would show up in the winter near his home.

“My childhood dream was to go north and study ptarmigan,” he said.

After studying biology at the University of British Columbia, he made the dream a reality and moved to the Yukon.

More than 40 years later, Mossop is one of the world’s leading ptarmigan experts.

He’s been tracking and counting the skittish birds for more than four decades.

Originally, Mossop wanted to learn how ptarmigan maintain their density without population explosions or extinctions.

But after realizing the birds follow a 10-year cycle, his mission changed.

“I started looking at ptarmigan cycles,” he said.

When Mossop started working in the territory, in the early ‘70s, he was the only government biologist.

Some years later, he was joined by another biologist who was studying gyrfalcons – a raptor that relies on ptarmigan for its food.

“We quickly realized we were looking at a community of life,” said Mossop.

“We had the top of the food chain and the bottom.”

The next question Mossop had was: How does a predator deal with a prey population that follows such a dramatic cycle, like the ptarmigan?

What he learned was hard to believe – gyrfalcons can actually track the number of ptarmigan each year.

When the ptarmigan are at a low, the gyrfalcons don’t breed. But when they’re at a peak, the raptors breed regularly.

“The results were so closely linked, it looked like we fudged them,” said Mossop.

Now, with the ptarmigan remaining at an all-time low, Mossop is also worried about the Yukon’s gyrfalcons.

“The predators have built their life cycle around the peaks,” he said.

With the ptarmigan not peaking, “we are already seeing a decline in the gyrfalcon population.

“It will affect everything.”

Native hunters have been asking Mossop why there aren’t any lynx and rabbits this year.

Even researchers in Europe have noticed a drop in the hare population, he said.

The last three ptarmigan population peaks have been smaller and smaller, said Mossop.

“But now, there’s basically nothing.”

Snowmobiles are a big disruption, he said.

Their effect on wildlife “is just devastating.”

But the ptarmigan’s decline is being caused by “something much broader than that,” said Mossop.

He blames climate change.

At the end of April, Mossop is heading back out on the land to count the birds that have shaped his life.

He counts ptarmigan on the Haines Pass, off the Dempster Highway and on the North Slope.

He also monitors the gyrfalcon population, but this is harder because he needs a helicopter.

“I have to beg money to keep these studies going,” he said.

“Every year it’s been a struggle.”

In the early ‘80s on the Haines Pass, Mossop built a tiny green shack with a wood stove.

That’s still where he and his volunteers hole up at night, after walking through the snow counting the camouflaged grouse.

Mossop loves his profession.

“I haven’t worked a day in my life,” he said with a laugh.

But these days, the job is getting harder.

“Other bird populations are also disappearing,” said Mossop.

“And I’m getting tired of all the bad news.

“It’s depressing.

“It’s a bad time to be interested in natural species.”

Contact Genesee Keevil at


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