How do you protect an animal that won't stay put? The Porcupine Caribou Herd migrates back and forth across mountains, rivers and tundra, oblivious to national and international boundaries. Its range covers hundreds of thousands of square kilometres and 12 different management regimes.

A major step in protecting the caribou is protecting the most sensitive parts of their habitat, says Don Russell, director of the Canadian Wildlife Service in Whitehorse. Russell is part of the Porcupine Caribou Technical Committee, an international group of researchers and managers who have assessed the most crucial areas of the herd's range.

The group rated different parts of the range according to a set of criteria related to the herd's ability to survive and reproduce. The ratings are based on solid information about the Porcupine Caribou Herd, says Russell.

"With this particular herd, we've followed their movements pretty well constantly for the past 25 years, so we've got a lot of data."

Not surprisingly, the most sensitive habitat is the area used during the calving and post-calving period each June. The caribou calve as far as possible out onto the coastal plain, along the western half of the Yukon's North Slope and across the border in Alaska. This area offers the best combination of fresh green vegetation when they need it, within a week after calving, and fewer predators.

"In calving period they tend to be in really poor energy balance because they usually arrive on the calving grounds prior to green-up," Russell says. "They've left all the lichen-rich wintering areas, so they're on moss and whatever else they can fill their stomachs with, and they're in really poor shape. Half of the calves that are going to die in any given year will die in the first month."

The next most difficult time for the caribou is early summer and mid-summer, when insect harassment can prevent them from feeding adequately. Areas where they can escape insects are particularly important to cows and young calves trying to build fat and strength before winter.

"So once one identifies the sensitive habitats, the next question is, are the most sensitive habitats well protected?" says Russell. "In the Yukon, our calving and post-calving areas are pretty well protected in Ivvavik National Park and in the area called East of the Babbage, a special conservation area under the Inuvialuit land claim."

However, the Alaska calving and post-calving grounds, in the Arctic National Wildlife Refuge, are located in an area that developers want to see opened for oil exploration.

"It's probably the most important habitat of the herd, according to this analysis," says Russell. The Canadian government and groups interested in the Porcupine Caribou Herd's survival have lobbied hard in Washington to protect the Alaskan calving area.

"I guess if there's one area in the Yukon that could use more protection, it would be the Richardson Mountains in the midsummer insect period," he says. In July, when bot and warble flies are harassing the caribou, the high, cool Richardson Mountains offer relief from the temperature-sensitive insects as well as plenty of food for the caribou herd.

The Porcupine Caribou Technical Committee's habitat research has been published in a report entitled Sensitive Habitats of the Porcupine Caribou Herd. The first printing of 6,000 copies is almost gone, says Russell, many of them distributed in Washington as part of the effort to stop development in the Alaskan calving grounds.

The Sensitive Habitat report is also available on the Internet. This Internet site also offers an interactive model that allows the visitor to see how changing climatic conditions might affect the caribou.

For more information about the Porcupine Caribou Herd and its habitat, contact the Canadian Wildlife Service in Whitehorse at 393-6700.