The Bathurst caribou herd, considered to be the largest in the Northwest Territories, is estimated to have 31,900 animals this year. (CBC)

The Bathurst caribou herd in the Northwest Territories has shrunk drastically to one-quarter the size it was only three years ago, according to the latest survey by the N.W.T. government.

Final survey results from the N.W.T. Environment Department, released in Yellowknife on Thursday, estimate the population of the herd at 31,900, plus or minus 11,000, this year.

By comparison, the government's last survey in 2006 indicated 128,000 animals in the barren-ground caribou herd.

'Tough decisions' ahead, minister warns

The latest numbers also show the estimated number of breeding female caribou has dropped to 16,600 this year from 55,600 in 2006.

"Although caribou herds traditionally cycle, these low levels and rapid decline indicate tough decisions must be made for the herd to recover," N.W.T. Environment Minister Michael Miltenberger said in a release.

The Bathurst herd, the largest caribou herd in the territory, has been declining since the 1990s. In 1986, the herd numbered around 472,000.

But the numbers can be confusing: part of the Bathurst herd was split off after the 1986 count, creating the Ahiak herd.

Hunting, industry possible factors

The Ahiak herd has not been surveyed since 1996, when about 200,000 caribou were counted. That herd will be surveyed next year.

Territorial government biologists say factors behind the herd's decline could include overhunting, changes in the environment, and the impacts of industry.

For example, the territory's three diamond mines are located along the Bathurst herd's migration route, biologist Jan Adamczewski said.

Adamczewski said caribou must cross an ice road that is used by heavy trucks to transport supplies to the mines.

"Sometimes even a small disturbance increases their energy expenditures — they spend less time feeding — and you could start to affect the condition of the cow in the fall, in the breeding season," Adamczewski said.

'Big, big loss': Tlicho grand chief

As a result of the 2006 survey results, the N.W.T. government cut the number of caribou hunting tags allocated to hunters and hunting outfitters.

Last week, the Yellowknives Dene First Nation announced it would not hold a community caribou hunt this year because of the latest low numbers.

Miltenberger said his department will work with the Tlicho aboriginal government on a joint proposal for managing the Bathurst caribou herd.

Miltenberger said that plan could include more cutbacks in the number of caribou that can be hunted.

"It's a big, big loss. And when we met as chiefs, yes, you can say that the hunters will not go hunting," Tlicho Grand Chief Joe Rabesca told CBC News.

"We [may not] be allowed to kill caribou — we don't know that yet, but that's up for discussion. We're going to have a lot of meetings over it."

The department will also consult with other aboriginal governments and stakeholder groups in November.