A caribou herd in northwestern Alaska has been the state's largest for several years, but its population is on a downward slide and now it may have lost that status.

The Western Arctic Caribou Herd, which peaked in 2003 at 490,000 animals, is likely down to about 200,000 today, and some hunting restrictions could be in the offing, according to experts from the Alaska Department of Fish and Game.

The population estimate is far from exact, said Lincoln Parrett, a Fairbanks-based Fish and Game biologist who briefed the Western Alaska Caribou Herd Working Group, which met this week in Anchorage. Technical problems thwarted efforts to complete an aerial population survey this summer, he said; biologists will try again next summer.

The 2013 census put the herd size at 235,000 animals, down from 325,000 in the 2011 census.

If the new 200,000-animal estimate proves accurate for the Western Arctic herd, it would about match the most recent estimate for the size of the Porcupine Caribou Herd, which straddles the far-north Alaska-Canada border. It is possible that the thriving Porcupine herd has now grown bigger than the Western Arctic herd, Parrett said.

The Porcupine herd may even now be the largest herd in North America, Parrett said. Two Canadian herds, the Leaf River Caribou Herd in Quebec and the Qamanirjuaq Caribou Herd in Nunavut and Manitoba, might also be contenders for that title, "but neither have been counted in a while, and could easily be smaller," he said in an email.

The good news about the Western Arctic herd, Parrett told the working group, is that the rate of decline appears to have slowed since 2013. Animals appear to be in good shape, and mortality rates for adult females -- a factor critical to herd demographics -- are not as high now as was seen in recent years, he said.

The bad news is that the current annual hunt of about 13,000 caribou from the herd may soon be too much.

Up to now, the hunt "played a very small role in demographics," Parrett said. "But that may be changing in the future if the herd size continues to decline."

Members of the working group, a panel representing the region's caribou-dependent villages and other stakeholders, appeared to be preparing for some new hunting limits.

"In years to come, we're going to have some hard decisions to make," said Tom Gray, a working group member, during Thursday's session.

Some new rules already went into effect this year. Those stopped the harvest of calves, halted the nonresident harvest of cows and put more limits on nonresident harvest of bulls.

There is not yet an explanation for the decline. Parrett discussed some hypotheses at the three-day working group meeting. Unusual weather, possibly linked to climate change, is one suspect, he said.

"People are noticing on-the-ground changes," Parrett said.

Many animals were lost in one recent winter in which there was rain that iced up the landscape and created a barrier to vegetation that caribou eat, he said.

"It was obvious to the people working in the area that that rain-on-snow event had a big effect on the caribou," Parrett said.

So far, there isn't evidence that pressure from predators is a major factor, but if the herd's population continues to decline, the predators' role might loom larger, Parrett said.

While habitat fragmentation from logging and other development has hurt caribou herds elsewhere in North America -- dramatically so in parts of Canada -- that does not seem to be a problem for the Northwestern Alaska herd, Parrett said. For the Western Arctic herd, "The range is largely still intact," he said. "This is wilderness, compared to everywhere else in the world."

Village residents are worried about pressure from non-local hunters, and a study by University of Alaska Fairbanks researchers found that locals cited aircraft disturbances and non-local harvest as the top two factors hurting the herd.

Still, non-local hunting accounts for less than 5 percent of the total harvest, Parrett said.