Porcupine Caribou herd has declined, according to latest population estimate

One of North America’s largest caribou herds — known for its over 2,400-kilometre migration across Arctic tundra, snow-covered mountains and roaring rivers to its calving grounds on Alaska’s coastal plain — is declining. 

The Porcupine Caribou Management Board released its latest population estimate for the barren ground caribou herd last week. It says the herd’s population is estimated to be 143,000, down from 218,000 in 2017, when biologists last conducted surveys.

Despite the decline, chair of the Porcupine Caribou Management Board, Joe Tetlichi says the decline was expected and the board doesn’t have to “put up the red flags yet.”

“The population goes up and down and we know that through Indigenous knowledge and scientific knowledge," Tetlichi said. “And we’ve had that same scenario back in 1989 to 2001 when we had an population estimate of 187,000. And then in 2001 we finally got a count and it was 123,000. So we know that it [goes] up and down.”

Biologist Mark Nelson with the Alaska Department of Fish and Game says nutrition could be playing a role in the current decline. 

“We compare the older animals, the younger animals and when there's a lot of nutrition on the landscape and everybody's fat and happy, the younger animals are giving birth at a rate very similar to the older animals.”

Nelson says in the last six to eight years the herd's younger females have been giving birth less often, signalling that nutrition could be an issue. And if birth rates remain low for several years, the herd is unlikely to grow. 

The management board’s latest annual report says research indicates that there has been a small decrease in lichen cover over the herd’s range.

In addition to birth rates, survival rates are also an important indicator of population health and what direction the herd size is trending.

The board's latest report says adult female survival was the lowest since 2015 and below the threshold for a stable or increasing herd, and calf survival was also lower than average. Both indicate the herd is in decline and will continue in that direction.

“From the Indigenous side, we've had our local experts out on the land saying that, you know, there's less cow caribou, they see less calves in the spring,” Tetlichi said. “So that's something that we really rely on.”

Collecting data on the herd’s size is important for informing the board’s management measures, but making as population estimate is not easy.

“We try to do the population count every two years, but everything has to line up,” Tetlichi said. 

In order to survey the herd, biologists sometimes have to wait years for the right conditions. Before last summer, the last time that happened was in 2017 when biologists were able to photograph the herd from an airplane and use those photos to estimate its size.