More than 3,000 reindeer in the Northwest Territories have somehow disappeared, leaving herders scrambling to find them and prompting concerns about what threats the lost reindeer may pose to wild caribou.

The territory's only reindeer herd inhabits the northern part of the N.W.T., living unsupervised on Richards Island near Tuktoyaktuk in the summer. When ice forms in the winter, the herd's caretakers keep a close watch on the animals to ensure they don't wander away.

'The longer they're mixed with the caribou, the wilder they get.' —Lloyd Binder

But this winter, the herd crossed the ice from Richards Island to the mainland Beaufort Delta, dispersing before herders arrived for the season.

"It was a kick to the head, for sure, but I'm getting pretty used to that with this business," herd owner Lloyd Binder told CBC News.

"The previous owner said it's all about heartbreak, and I would say it's all about that and disappointment."

Since the beginning of December, Binder and another herder have been on snowmobiles, searching for the missing reindeer. As of last week, they had found 400 of the roughly 3,000 animals in the herd.

"Given good weather, every day we go out and check a new area of the herding range and see what we can find," he said.

"We basically wander around looking for tracks, and when we find them, we try and track them and then pick up whatever we find."

Reindeer, caribou a bad mix

Binder's business, Kunnek Resource Development Corp., assumed private ownership and management of the herd about 10 years ago.

The federal government first imported reindeer from Alaska to the Beaufort Delta in 1935.

A major concern for Binder is that the domesticated reindeer could begin mixing with wild caribou herds in the region.

"If the reindeer take off with the caribou … that is a different story. It can be pretty bad," he said.

"The longer they're mixed with the caribou, the wilder they get."

Intermixing with caribou also worries retired Yukon wildlife biologist Rick Farnell, who said diseases that are prevalent in the reindeer herd could endanger the already fragile caribou population.

"There's the threat of those animals intermingling with caribou and spreading a pretty virulent disease to wild caribou," Farnell said, adding that quick action must be taken to separate the reindeer from the caribou.