Yukon wildlife managers brought in temporary caribou hunting restrictions Monday that they hope will save the Porcupine caribou herd's numbers from further decline.

The new rules, effective immediately, require hunters to report all the caribou they kill in the Yukon, and to hunt bulls only. As well, licensed Yukon hunters are now limited to hunt just one bull per season.

Aboriginal hunters can still hunt as many bulls as they want, but they are now prohibited from killing cows in the hopes that more cows will produce more calves.

The Porcupine caribou herd is still considered the largest herd in the Yukon, but government wildlife officials estimate the herd to have between 90,000 and 100,000 animals — only half the size the herd was 20 years ago.

Without hunting restrictions in place, the herd's numbers could be cut in half again before 2020, said retired government biologist Doug Larsen, who sits on the Porcupine Caribou Management Board.

"If we can put these measures in place now, we can prevent that. We think we can prevent that; we hope we can prevent that from happening," Larsen told reporters Monday in Whitehorse.

Highway checkpoints

The interim rules will stay in place until various international groups agree on a management plan for the Porcupine herd.

The Porcupine Caribou Management Board, a joint entity comprising members from the federal Yukon and N.W.T. governments, as well as First Nations officials, is asking hunters not to hunt cows.

However, complying with the board's request is voluntary whereas the Yukon government has made the ban on hunting cows mandatory. Yukon government officials have said voluntary hunting bans have historically done little to reduce the decline in caribou numbers.

Caribou surveys suggest that Gwich'in and Inuvialuit hunters from the neighbouring Northwest Territories, as well as hunters from Alaska, account for 80 per cent of the 4,000 Porcupine caribou harvested each year.

The Yukon government will have manned checkpoints on the Dempster Highway to ensure all hunters report all their Yukon caribou kills, fish and wildlife director Dan Lindsey said.

"Our real interest is to try to get people to change, and having people up monitoring the site and [having] requirements to report the harvest, I think, is a big step initially," Lindsey said.

"We want to roll it out in a fair manner, so there's a range of warnings and tickets, with the most severe cases [going] to a court."

Violators will face warning tickets, or fines from $75 to $100, Lindsey said.

With files from Vic Istchenko