Alaska-Canada caribou herd rebounds, survey shows

A caribou herd shared by Alaska and northwest Canada has rebounded after a near one-third decline, according to a photo census announced Wednesday by the Alaska Department of Fish and Game.
State biologists said the Porcupine Caribou Herd has grown to an estimated 169,000 animals.
"People on both sides of the Alaska-Canada border are pleased," said Jason Caikoski, an assistant area biologist.
The numbers announced this week are in line with a preliminary estimate released in January. That estimate was announced early so Canadian officials could consider the new herd size when they updated the Porcupine Harvest Management Plan and Yukon hunting regulations.
The herd is a crucial source of food for subsistence hunters along the border. It also figures into national political discussions of opening up the coastal plain of the Arctic National Wildlife Refuge to petroleum drilling. The coastal plain is the herd's traditional calving grounds.
Environmental groups say the herd's concentrated calving area makes young animals vulnerable if petroleum development displaces the herd. Sarah James, a Gwich'in elder from Arctic Village, said 15 villages on both sides of the border rely on the herd and are united against development near calving grounds.
"I know we're doing the right thing with caribou," she said.
The herd's 800-mile round-trip between calving and wintering grounds gives it the distinction of the longest land-mammal migration on the planet. U.S. Fish and Wildlife Service spokesman Bruce Woods said individual caribou in the herd have been recorded walking as many as 3,000 miles in one year. The herd uses an area the size of Wyoming in the Arctic National Wildlife Refuge, Yukon Territory and Northwest Territories.
The herd peaked in 1989 at 178,000 caribou, but four photo surveys between 1992 and 2001 documented a decline to 123,000 caribou, a drop of more than 30 percent.
Department spokeswoman Cathie Harms said biologists detected no change in reproductive rates, only a decline in adults.
"It could have been caused by a variety of things," she said, including predators, poor nutrition or severe weather. Even insects can figure into a decline if they drive caribou to seek relief and end up making them expend too much energy.
Several other northern caribou herds declined at the same time, she said.
Documenting the comeback was itself a challenge. Since 2001, factors combined to prevent aircraft from recording accurate photos, including foul summer weather, smoke from forest fires and the herd's failure to congregate in tight enough numbers.
"There's just a million ways you can't get a photo census," Harms said.
The department in July found conditions ideal for the photography.
"Caribou were aggregated well, and most of the aerial photos are good quality," Caikoski said. "We accounted for all of the active radio collars in the herd, which means we likely didn't miss many caribou during the survey."
Counting caribou in the photographs began in December.
The herd was named for a major river in its range. Sometime in April, the caribou head north toward the calving grounds. The route depends on snow and weather conditions.
By early June, pregnant females reach the calving areas and give birth. The rest of the herd joins the cows and calves to forage.
In late June and early July, when mosquitoes hatch, caribou gather in groups numbering in the tens of thousands. To escape insects, they move along the coast, onto ice fields, and to uplands in the Brooks Range, according to the Fish and Wildlife Service. The herd leaves the coastal plain by mid-July, heading east and south toward its wintering area.
A spokesman for the Yukon Department of Environment said the herd's higher numbers likely will result in higher bag limits and other changes for hunters under Canada's caribou herd management plan.
Both subsistence and Yukon licensed hunters had been limited to bulls, with the latter limited to one animal, said Dennis Senger from his office in Whitehorse. That could double before the fall hunting season, he said.