At its peak, the movement of the George River caribou herd was a spectacle to rival the great migrations of the Serengeti plain. Huge numbers of caribou swept through Labrador each winter, providing native groups with their cultural identity and a crucial source of food.

Less than 20 years ago, the herd was estimated at close to 800,000 individuals. But shortly afterward it reached a tipping point. It grew too big for its range and began to collapse. The latest official estimate puts the size of the George River caribou herd at barely 74,000 animals.

"People have a real sense of urgency that something needs to be done," said Darryl Shiwak, First Minister of the Nunatsiavut government, which represents the Inuit of Labrador. "It's their meat for most of the year."

While the specific numbers are doubted by some native leaders, the trend is clear. And the precipitous decline raises difficult questions about how to balance conservation with traditional rights - and whether it's wise, or even possible, to stop the decline.

Caribou go through cycles and the George River herd has crashed before, bottoming out about a century ago and remaining low for decades. Previous declines have led to famine among the native population, and while that wouldn't happen now, there is concern over how low the numbers of caribou will go.

"It's going to be devastating," said Stephen Loring, an anthropologist with the Smithsonian National Museum of Natural History, who noted that other traditional food sources are becoming less readily available.

"They're up the creek if they don't have caribou," said Dr. Loring, who has done field work with the Innu of Labrador "Country food is just a gazillion times better than anything you can get in the store."

The George River herd was first surveyed by Tom Bergerud, the former chief biologist of Newfoundland and Labrador, who pegged it at 15,000 animals in the 1950s. Now retired, he warned that the caribou will have to reach a natural equilibrium with their predators before starting to claw their way back.

"The wolves will [disappear] again; they can't live without the caribou," Dr. Bergerud said. "You'll break out of this [crash] for sure when the wolves are gone. The wolves were gone at 15,000. We don't have to go that low if the natives will shoot only the males."

That is a contentious point. The natives who have long relied on the caribou view themselves as good guardians who use the resource respectfully. They don't necessarily trust what they hear from the government in St. John's and want a greater voice in the management of the herd. Official appeals to set aside treaty rights and hunt fewer animals have met with limited success.

As the herd declines, calls for action can be expected to grow louder. But numerous experts - people who are keenly sympathetic to the plight of caribou-dependent natives - stress the limited ability of humans to stop the crash.

Micheline Manseau, an associate professor in the University of Manitoba's Natural Resources Institute, believes population fluctuations should be viewed as a "natural phenomenon" instead of a crisis demanding intervention. "We don't want to manage them so much they lose what is natural," she said. "You have to be quite careful thinking [we] can control this. You have to be sure we don't screw it up."

The issue has gained widespread urgency in recent years as caribou herds have plummeted across the North. The declines have led conservation groups such as the Canadian Boreal Initiative to call for a greater focus on habitat protection, while scientists are trying to determine if there are overarching factors common to all herds under stress.

Although the root causes are up for debate, declines among the various herds have shown a familiar pattern.

The caribou typically come under pressure due to some relatively minor factor, such as a big fire that reduces their food supply or a parasite that weakens the animals. Calves are born smaller and in fewer numbers. The population starts to fall, increasing the impact of predation by humans and other animals. A slow decline accelerates. Anecdotal evidence starts to accumulate, but scientific censuses can take years to confirm the decline.

In the case of the George River herd, it took firm evidence of a precipitous decline for the government to clamp down on hunting by non-natives. It recently banned out-of-province sportsmen, halved residents' bag limit to one and ended the transferable-licence system that had allowed some people to kill dozens of animals. Newfoundland and Labrador Environment and Conservation Minister Charlene Johnson said the new rules should result in a kill of about 5,000 caribou this year. This does not include the native hunt, which she estimated at about 4,000 in a typical year.

"Because this is very socially and culturally important, we wanted to have a hunt ... albeit very limited," she said.

Anne Gunn, a retired biologist who worked with caribou in the North for 30 years, believes hunting restrictions can slow the decline and help raise the odds of a recovery.

"Once caribou reach low numbers, you're kind of poised; it can go either way," said Dr. Gunn, who is still active with the CircumArctic Rangifer Monitoring and Assessment Network, a collaborative body that studies caribou and reindeer. "What we do during these periods of low numbers can have an effect on the rate of recovery."

She warned that managing a rebound is a long and difficult process and stressed the need to get all parties to the table. This allows every source of knowledge to be tapped and gives everyone a feeling that they have a voice, reducing the chance that people will push hard to hunt again too quickly.

George River stakeholders all agree on the need for co-management of the herd. But defining how that will work and getting everyone onside will be difficult.

"It's better to sit down and negotiate instead of trying to superimpose a foreign set of regulations," said Chris Montague, president of NunatuKavut, formerly the Labrador Métis Nation, which will halve its hunt this year to fewer than 200 animals, though Mr. Montague suspects the government has overstated the herd's decline.

Innu Nation representative Richard Nuna is similarly skeptical. "We need answers before we can even suggest a quota for Innu people," he said. "We need information from the past censuses and on how these censuses were conducted."

Mr. Shiwak of the Nunatsiavut government said he and other Inuit leaders are consulting their people on whether to undertake a voluntary reduction in hunting. For now, how low the herd will go and how long it will stay there is anybody's guess. And experts differ on whether the cyclical history is enough to assume that the caribou will bounce back again.

Dr. Gunn is also concerned that the decades-long cycle of the caribou means it will be attempting to recover in a world considerably different from the one it inhabited previously. Climate change and development both pose a threat.

Jim Schaeffer, a biologist at Trent University in Peterborough, Ont., argues that whatever else is done, the caribou will need room.

"This is the most mobile land animal on the planet," he said. "If we want to have that kind of magnificent migration, space is what we're going to have to provide."

A dissenting voice comes from Dr. Bergerud, who calls the caribou "a very adaptable animal ... not disturbed by people."

"They can come back if you manage wolves and you manage hunters," he said. "When everybody says, 'How few can you get?' I say, 'One, as long as it's a pregnant female.'"