New numbers for the migratory Porcupine caribou herd show it is still on the upswing and nearing the 200,000 mark.
The latest population estimate, based on a 2013 post-calving aerial photo census, pegs the herd at 197,000. That’s up from 169,000 in 2010 and 123,000 in 2001.
Porcupine Caribou Management Board chair Joe Tetlichi said he’s “comfortably surprised” by the increase, especially given the precarious position of other barren ground herds in the North.
With a range stretching from the Mackenzie River Delta across the northern Yukon and into Alaska – including the Arctic National Wildlife Refuge – the iconic Porcupine caribou herd varies its migration pattern from year to year, which is one reason for the good news, Tetlichi said.
“The herd was mostly on the Alaskan side for the last five years and there are not many caribou taken when it’s in Alaska,” he said.
About 65 per cent of the estimated 2,500 caribou harvested each year are taken by NWT hunters from Fort McPherson, Aklavik and Inuvik, Tetlichi said.
The Dempster Highway often provides easy access to the herd, so when it stays west of that corridor only residents of the Yukon’s remote community of Old Crow and a couple of Alaskan villages hunt it.
Another reason for the rise is the recent push to persuade Gwich’in and Inuvialuit hunters to take the bulls and leave the cows alone, Tetlichi said.
“We were looking for a bull-dominated harvest,” he said, referring to the new harvest plan agreed to several years ago by the communities that rely on the herd.
“Even before we started the harvest management plan, the people on the NWT side were already telling their hunters to not take cows,” he said.
Strong adult cow survival rates are paramount to a herd’s health, said Alaska government biologist Jason Caikoski.
“That’s really the main driver on whether these herds are growing, stable or declining, is that adult cow mortality – obviously the reproductive component of the herd,” he said in a telephone interview.
Although the Porcupine’s cow survival rate has definitely improved during the last decade, Caikoski said they’re not exactly sure why.
“It could be range condition, it could be a difference in predation, it could be possibly some climate effects,” he said.
The herd has also shifted its calving grounds east into Canada during the last three or four years for reasons unknown, he said.
“For most of the ‘80s and ‘90s and into the early 2000s, it was on the coastal plain of Alaska and it’s kind of been shifting to the east and calving is primarily occurring now between the Babbage River and the (Yukon-Alaska) border,” he said.
“I don’t know why that would change annual (cow) survival much because most of the mortality that occurs in cows is in late winter…but it possibly could.”
Although the Porcupine herd’s range overlaps in places with Alaska’s Central Arctic herd, both have been in a growth mode, nixing any theory the two may have mixed, he said.
The Central Arctic herd was also counted in 2013. The results haven’t yet been released but Caikoski expects the estimate to come in around 70,000 as it did in 2010.
Alaska’s other two large migratory herds aren’t faring so well. The Western Arctic and Teshekpuk Lake herds – which were also counted last summer – have been on the decline, he said.
The state tries to count all four herds every two to three years. The next Porcupine count is slated for 2015 or 2016, he said.
The herds are photographed after the calves are born in June or July when the caribou bunch up in tight groups to fend off “severe insects,” he said.
The Porcupine caribou herd was first counted in 1972. At the time it had 102,000 caribou. By 1989 it had grown to 178,000 but then began a decline that didn’t turn around until after 2001.
The NWT’s other two western Arctic migratory herds – Bluenose West and Cape Bathurst – are listed in stable condition after experiencing dramatic declines.