Wolves slowing down the Mulchatna caribou herd rebound, says ADF&G biologist

Nov 10, 2017

Neil Barten breifed the Nushagak Fish and Game Advisory Committee about recent predation on caribou calves, and how the state is moving to expand the intensive wolf control area to 10,000 sq. miles, covering most of Unit 17B.

Caribou in the upper Mulchatna in June.
Credit ADF&G

The Mulchatna caribou herd is struggling to rebuild itself to even the lower end of the state’s 30,000-80,000 objective population size. After reaching a peak of nearly a quarter million animals in the late 1990s, the herd crashed hard and within a decade was estimated to be only around 20,000 strong.

Predators, mainly wolves, are holding back the herd’s growth. That’s the message ADF&G wildlife biologist Neil Barten delivered to the Nushagak Fish and Game Advisory Committee meeting in October as he addressed the state’s plan to expand the intensive predator control area in Unit 17B.

The state does not have a current estimate on the herd size. Last year a photo census put the number at 27,000, down a bit from the year before. This year ADF&G was weathered out of a good aerial census, which involves flying the massive range of the Mulchatna herd.

“We had too many inclement weather periods,” Barten said. “About the time the caribou would aggregate, they’d disperse again. It just didn’t happen for us.”

ADF&G staff were able to collar about 80 calves not long after they were born this spring. Roughly half were in the “southern calving grounds” in the Bonanza Hills, and the other half in the “northern calving grounds” near Nishlik Lake. Neither fared well, said Barten.

“The group that calved up at the Bonanza Hills, out of the 38 or 40 collars we put out, I think right now we’re still holding on to five of them,” he said. “The rest all died of various causes – bears, wolves, and golden eagles, but wolves being the majority of the predation that we could determine. The group by over by Nishlik Lake did a little better. The last we checked we probably 35 percent of those were still alive.”

Mulchatna caribou.
Credit ADF&G

The bull-to-cow and calf-to-cow ratios are both a little below the management plan, too, but Barten said otherwise the Mulchatna caribou appear to be healthy.

“The range is in good condition, the animals are telling us that. We’ve got early pregnancy, high pregnancy, and good fecundity. What we are missing out on is the calf survival, and that’s something I think we can hopefully do something about.”

If wolves are the primary predator, then doing something about calf survival involves increasing the harvest of wolves. An intensive predator management program that has been in place since 2011 allows same-day airborne wolf hunting from February through April inside an area about 2700 square miles. It has not been a very successful effort, said Barten, probably because of poor winter weather.

“If you want to get wolves with aerial gunning, you have to have good tracking snow, and then you have to snow where you can land to retrieve the wolves, and we just haven’t had much of that.”

Last spring afforded pretty decent conditions, but aerial hunters only took three wolves. Local hunters on snowmachine took 65 in Unit 17, a decent uptick.

ADF&G is planning to increase the size of the wolf control zone to close to 10,000 square miles to include more of the actual areas used by the herd during calving season. This, said Barten, is the next logical step in its Board of Game-backed mandate to boost Mulchatna caribou by taking more wolves.

If allowing for intensive wolf hunting in a larger area over the next three years does not help, things could get pretty aggressive.

“There’s a point the Board of Game may request that the Department do Department-removal, which would be using helicopters to take out wolves and remove them,” Barten said.

dave@kdlg.org or 907-842-5281

Credit ADF&G