Thousands of "visitors" from Alaska's 40 Mile caribou herd have crossed the border into the Yukon in recent weeks, and U.S. wildlife officials hope the herd's Canadian foray will become a regular occurrence.

The bulk of the 40 Mile herd is currently west of Dawson City and officials are keeping a close eye on about 200 stragglers near Eagle, Alaska, saidCathy Harms, spokeswoman for the AlaskaDepartment of Fish and Wildlife.

"It looks like several thousand are in Canada at this time," Harms told CBC News in an interview from Fairbanks.

"They seem to like to go that direction this time of year, so we're thinking that this may be the norm now."

Historically, the herd would spend its annual migration crossing from Alaska, where it would spend its calving season, to wintering grounds in the Yukon.

The herd consisted of about 600,000 caribou roaming the Yukon and Alaska at the turn of the 20th century, according to the Yukon Fish and Wildlife Management Board.

Overhunting, poor weather and a growing wolf populationreduced the herd to about 5,000 animals, but that increased toabout 20,000 between 1970 and 1990. Conservationists launched a recovery program in 1995 to restore the 40 Mile herd in its former range.

Harms said the herd is much healthier now and is starting to roam further afield.

"As the herd gets larger, it reinhabits more of its traditional range and it migrates farther than it did before,"she said.

"When it wasn't crossing the border, it was more related to the size of the herd. It had shrunk to the point where it wasn't using much of its traditional range and it was just pretty much staying in Alaska all the time."

Harm said biologists in Alaska set this year's 40 Mile caribou hunting levels at 850 animals. Hunters in the state shot 600 caribou earlier this year and Harms said she expects the quota to be filled later this winter as the animals cross back into Alaska.

She doesn't think that hunting has anything to do with the caribou's Canadian visit.

"I wouldn't say they're trying to avoid hunters as much as the herd is now large enough that it occupies enough of its traditional range, which includes Canada, so it's spread out more," she said.

Even with hunters harvesting caribou on the U.S. side of the border, Harms expects the herd to grow somewhat this year.