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Porcupine caribou herd reaches record numbers

Population definitely a high, future decline ‘inevitable’: biologist
After declining to 123,000 animals in 2001, a new survey by the Yukon government and the Alaska Department of Fish and Game estimates the Porcupine caribou herd to be between 202,000 and 235,000 animals, a record high population. (U.S. Fish and Wildlife Service/Wikimedia Commons)

The Porcupine caribou herd has reached record numbers, according to a new survey by the Yukon government and the Alaska Department of Fish and Game.

The new population estimate puts the herd at between 202,000 and 235,000 animals with 95 per cent certainty. This is significantly higher than the herd’s previous peak population of 178,000 animals in 1989, said Alaska Fish and Game biologist Jason Caikoski.

Caribou go through natural cycles of growth and decline, Caikoski said, related to the balance of births versus deaths, calf mortality rate and recruitment from other caribou herds. At a certain point, increasing caribou populations tend to tip and then begin to decline, he said, although what causes these tipping points is poorly understood.

Boom times

The Porcupine caribou count has been going on since the 1970s — a very short study, in terms of biological time, Caikoski said. At that time, the herd numbered only about 100,000 animals, but steadily increased to its 1989 peak before steadily declining to 123,000 animals in 2001. The herd has been growing steadily since then at a rate of between three to four per cent annually, with an average yearly growth rate of 3.7 per cent.

This growth rate is actually relatively low, in terms of what biologists see in other barren grounds caribou herds, Caikoski said, and makes the Porcupine caribou somewhat unique amongst their species, which tend to cycle up and down much more rapidly.

“To put it in perspective … growing at three to four per cent a year is very modest. We see growth rates of up to 10 per cent in other herds,” he said. “They (the Porcupine) are not as eruptive and don’t crash as hard as other herds.”

So how big can the herd really get? Nobody is really sure, Caikoski said. There are, certainly, larger herds — the Western Arctic herd in Alaska grew to nearly 500,000 animals at its most recent peak before crashing, he said, but that doesn’t mean the Porcupine can get that large. Factors that limit growth, such as habitat type, predation and weather all affect caribou populations.

“The top end is the big unknown,” he said. “Presently, the animals are really robust, with healthy calves and good body condition … but these things can tip over pretty fast.”

“We don’t really know the reason why survival is really good right now … (but) we do know survival is higher than average.”

“We’re at a high point right now, for sure,” said Yukon biologist Mike Suitor. “The herd is healthy, very fat. Reproductively, they seem to be doing very well.”

However, Suitor said, a decline is inevitable “in the not-too-distant future.”

The inevitable bust

That could be a problem, Suitor said. On Dec. 22, the United States signed a bill into law which officially opened up the Arctic National Wildlife Refuge (ANWR) to oil exploration and drilling. The Porcupine caribou traditionally calve in 1002 Area, a piece of coastal tundra within ANWR, and conservationists, biologists and Gwich’in people on both sides of the border are concerned about the impact that will have on the herd’s long-term health.

A recent paper by biologist Brad Griffith of the Alaska Cooperative Fish and Wildlife Research Unit found that drilling in the Porcupine caribou calving ground would likely reduce calf survival rates in the herd by 8.2 per cent.

The herd can sustain a 4.6 per cent reduction in calf survivability before it begins to negatively impact the population, Griffith said.

“I don’t think anyone can say for sure what might happen (if development occurs) in the calving grounds,” Suitor said. “But we know that caribou need to calve where caribou need to calve… the need to go where the proper conditions for them are.”

When the Porcupine caribou decline, their population shrinks on average 3.3 percent per year, Suitor said. If the herd is already in decline when development begins and are disturbed by this human activity, “one could assume” that the population decline would be accelerated, although the precise impact would be impossible to predict.

Caikoski said sometimes the caribou do not use 1002 Area at all, calving by choice closer to or on the Yukon border, and no one is really sure why. Many things can impact caribou survival rates besides the calving grounds, he said, including weather conditions and changes in the landscape.

“I think the jury is still out on what kind of effect a disturbance would have on that herd,” Caikoski said.

A recent survey of 13 North American barren ground caribou populations found that all the herds were either in decline or had stabilized at lower-than-average numbers — with the notable exception of the Porcupine herd, who are still growing, said Suitor.

“Some of those herds have declined by 90 per cent,” he said. “The Baffin herd is probably the worst-case example.”

Given this decline, the barren grounds caribou as a whole may be classified as a threatened species in the next few years, Suitor said.

Gwich’in concern

Opening ANWR to oil exploration has been the subject of much debate. The herd, which migrates thousands of kilometres each year between the Northwest Territories, Yukon and northeastern Alaska, is important to the Gwich’in, who traditionally rely on the animals for food and clothing. The Gwich’in consider their relationship to the caribou sacred, and refer to the calving ground of the Porcupine caribou as ‘the sacred place where life begins.’

Gwich’in leaders have expressed extreme sadness and disappointment at the bill’s passing.

The Gwich’in have been campaigning to protect the caribou calving grounds for more than 30 years, said Pauline Frost, the Yukon’s environment minister and a Vuntut Gwitchin First Nation member.

Frost said that “like everyone” she was happy to see the Porcupine herd growing, despite trends in other caribou populations. However, the First Nation and Canadian government need to “be at the table” with the Americans to ensure the herd’s proper management now that the bill has passed and ANWR is open.

“We know (the Americans) are advancing development for economic reasons in ANWR…. We want to get to the table with them and have a conversation about sustainable resource extraction in the region,” she said.

Canada and the U.S. have a 1987 treaty which recognizes the need to protect the Porcupine caribou and their habitat, Frost said. The government and First Nations will want “some kind of commitment” from the Americans that extraction will be done without compromising the herd and that development is properly managed with that treaty commitment in mind.

“We have a lot of experience in land and resource management…. Really we want to look at best practices and what we can do here to protect this iconic herd,” she said.

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