A huge Alaska caribou herd’s population is again in decline

The Western Arctic Caribou Herd is down to about 188,000 animals, after stabilizing at 244,000 two years ago. It may no longer be the largest in North America.

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Caribou from the Western Arctic Caribou Herd traverse the Noatak National Preserve in northwest Alaska in September 2012. (National Park Service)

One of the largest caribou herds in North America has declined by nearly a quarter in the past two years, hitting a population level that justifies new hunting restrictions.

The news was delivered last week at the annual meeting of the Western Arctic Caribou Herd Working Group, an advisory organization with representatives of villages dependent on the herd. The population estimate for the Western Arctic herd is 188,000, down from 244,000 two years ago.

The decline appears to be driven by deaths among adult females, said Alex Hansen, a Kotzebue-based biologist for the Alaska Department of Fish and Game.

Biologists don’t yet know how serious the decline is.

Hansen, speaking at the online meeting, noted that caribou populations can swing up and down and that the estimate itself contains an element of uncertainty. However, he said, “This just happens to be a pretty steep hill that we’re on right now.”

Several working group members expressed concerns. “This decrease, I mean, it’s huge. If this happens again two years from now, we’re really going to be in trouble,” said Tom Gray of Nome.

He and others argued for restrictions to limit hunting pressure on females. “This herd’s been here for thousands of years. Let’s not kill it in a few,” he said.

The decline might have knocked the Western Arctic herd into second place among Alaska’s herds. The most recent census of the Porcupine herd, which roams through the Arctic National Wildlife Refuge and in northeastern Alaska and in neighboring areas of Canada, estimated that population at about 218,000, Hansen said. However, that census and its relationship to the Western Arctic herd total is dated, Hansen said. It was taken in 2017, a year when the Western Arctic herd was estimated at 259,000 animals, he said.

The Porcupine and Western Arctic herds may now be the biggest in North America, as several Canadian herds have crashed.

Climate changes mean migration changes

The warming climate appears to have drastically changed the Western Arctic herd’s fall migration behavior — delaying it and, in many cases, limiting the distance they travel, according to a presentation by Kyle Joly, a National Park Service wildlife biologist who studies the herd.

In the past, the herd’s caribou regularly made early fall crossings of the Kobuk River, a major river in Alaska’s Northwest Arctic region that flows east to west along the Arctic Circle. But those crossings have become fewer.

From 2010 to 2015, the first six years of tracking collared animals by GPS tracking, an average of 82 percent crossed the river during the fall migration, Joly said. But from 2016 to 2019, only 34 percent did so, and in 2020, the percent that actually crossed the Kobuk hit a record low of 6 percent, Joly said.

The animals that still cross the river do so much later in the season than in previous years. Crossings used to start as early as late August or early September. Now, they’re occurring at the end of October or even early November, according to the data.

“The last four years have all been the latest migrations that we have on record,” Joly told the working group.

For subsistence hunters in the southern part of the herd’s range, the late crossing poses challenges, he said. If the animals are not reaching that area until November, they are in their hormone-charged rut phase, making their meat “stinky,” he said.

“We can talk about trying to focus on bulls,” Joly said, referring to hunting recommendations. “If the timing of migration is so much later, that’s going to make it more difficult.”

Caribou from the Western Arctic Caribou herd migrate south through the DeLong Mountains in the Western Brooks Range in Alaska’s Arctic in a 2012 file photo. A proposed road connecting a mining district to the rest of Alaska’s highway system would cut through foothills south of the Brooks Range — and through the Western Arctic Caribou Herd’s habitat. (National Park Service)

Joly’s past research shows that in the past, Western Arctic caribou populations have fluctuated in concert with the Pacific Decadal Oscillation, an oceanic climate cycle that switches from cold to warm. Additionally, other research in which he has participated shows alterations in the northward spring migration of various North American caribou populations that are also linked to oceanic cycles, the North Atlantic and Arctic oscillations as well as the PDO.

But there are concerns that the long-term warming, which is delaying the arrival of winter, is transforming the Western Arctic herd’s habitat and overtaking the temporary effects of the oceanic cycles.

“The fact is that climate change is happening so rapidly. Will the animals be able to adapt and come out of this trough, like they’ve come out of other troughs, with all of the change?” he said after the meeting.

The impacts of roads

Aside from climate change, human developing is affecting caribou movements. There is increasing evidence that roads inhibit caribou movements.

While most of the Western Arctic herd’s range is free from roads, there is a major exception: the 50-mile industrial road at the Red Dog Mine, one of the world’s largest zinc producers. The road links the minerals extraction area to the facility’s Chukchi Sea port.

The mine road cuts through territory where herd members make their annual migrations. Some of the tracked animals showed a distinct aversion to the road.

At the annual meeting, Joly showed an animation of those caribou movements. Once the animals hit the road, the animation showed, they wandered along its side toward the Chukchi Sea, and many of them headed back north before moving south, eventually.

It is an “obvious” impact, he told the working group, delaying southward migration by almost a month.

“The animals come down, they hit the road, they end up going to the coast,” Joly said. “That Red Dog road is impacting the timing and flow of migration.”

It’s a phenomenon described in a 2016 study that Joly co-authored, which described “slow crossers” and their behavior on both sides of the road.

Exactly why the caribou avoid crossing the road is still unknown, Joly said after the meeting. It’s possible that the road’s higher elevation, a result of construction methods intended to avoid permafrost thaw, make it look to caribou like a barrier, he said. There are also possible dust and noise considerations, he said.

Whatever the reason, the caribou reaction to the Red Dog Mine road has implications for any other road that would be built in the range.

The best-known road proposal in the Western Arctic Caribou Herd’s range is the 211-mile access route that the Alaska Industrial Development and Export Authority is seeking to build to the Ambler mining district in northwestern Alaska. That project won approval in the final days of the Trump administration.

But the approval is being challenged in court. A Dec. 1 plaintiff brief accused the federal government and AIDEA of using a “permit first, analyze later” strategy that overlooked serious environmental impacts of the project, including the need for over 40 gravel mines along the route.

Caribou could also be impacted by another set of roads being proposed by the state’s Arctic Strategic Transportation and Resources project, known as ASTAR. A newly published study led by Tim Fullman, a wildlife biologist with The Wilderness Society and a member of the Western Arctic Caribou Herd Working Group, predicts significant impacts to the caribou herd if ASTAR roads were to be built. The study concludes that the ASTAR roads would affect both fall and spring migrations, with uneven impacts for villages that depend on caribou hunting.