Whenever the debate heats up over energy development in the Arctic National Wildlife Refuge (ANWR), the Central Arctic Herd is often used as proof that caribou and oil wells can get along just fine. This herd calves in the Prudhoe Bay area, and has increased fivefold in size since oil was first pumped out of the ground there.

Development in ANWR would center on what is known as the 10-0-2 lands, the calving grounds of the Porcupine Caribou Herd, and for thirty years there has been debate over how development in this sensitive area would affect the herd.

People in favour of development in ANWR point to the Central Arctic Herd, and say there is no need to worry about the caribou. But other evidence shows that comparing these two herds, and their calving grounds, can be like comparing apples and oranges.

Don Russell, a biologist with the Canadian Wildlife Service, has studied the Porcupine herd for decades. He says there are lessons to be learned from the Central Arctic Herd, and they do not bode well for the Porcupine Herd.

For one, as development at Prudhoe Bay has expanded over the years, it has encroached on more heavily used calving areas to the west. In turn, the caribou have moved off of this prime calving habitat to more marginal areas inland.

Biologists like Russell already knew that calving caribou generally do not like development, and recent research shows that this holds true for the Central Arctic Herd. After analyzing vegetation in the original and the displaced calving areas, a researcher found that the vegetation in the new area was of much poorer quality.

At calving time, caribou go for the green. The cows need fresh green growth to feed themselves and produce milk for their young. Moving to an area with poorer habitat makes no sense for a caribou, unless it is the only way to get away from energy development.

Fortunately for the Central Arctic Herd, it has room to shift inland and still stay on the coastal plain. This is not the case for the Porcupine herd. In the 10-0-2 area, the coastal plain is narrower so the caribou must climb up into the foothills and mountains if they move very far inland.

At these higher elevations there are more predators such as golden eagles, grizzlies, and wolves. Also the vegetation is of poorer quality there and the Porcupine caribou typically take in a large amount of the annual protein in their diet while on the coastal plain.

Cows from the Porcupine herd will put up with a lot of crowding to stay in the areas with the best forage. Caribou densities are four times higher in the 10-0-2 area than they are on the calving grounds of the Central Arctic Herd.

Russell points out other reasons why the two herds are not readily compared. The Porcupine Herd is large and must migrate over a huge area to find enough to eat. The Central Arctic Herd is much smaller, numbering only 27,000 animals at the last census, and does not wander as far during the course of a year.

He says the Central Arctic Herd is better compared to the neighbouring Teshekpuk Lake herd as both of them were about the same size in the early 1970s and increased at the same rate until the mid 1980's. Since then the Central Arctic herd has increased fivefold while the Teshekpuk herd has increased sevenfold.

The Central Arctic Herd has an annual growth rate of about 10 percent compared to 13 percent for the Teshekpuk herd, which has no development in its range. Russell says that these numbers could be interpreted to show that the Central Arctic Herd has paid a price for development, as it might be even larger today if there were no oil wells and pipelines in its range.

"You can say that there has been a three percent cost to development, and that is with a herd that is low density on its calving ground and has a wide coastal plain in its calving area," says Russell.

Even during the boom years from the mid-1970's to 1990, the Porcupine herd only increased at a rate of 4.5 percent, and since then it has decreased in size. Along with this low productivity, the herd's high dependency on its narrower strip of coastal plain must also be taken into account.

"The Porcupine Caribou Herd has half the ability of the Central Arctic Herd to increase in size and it really has no place to go if it is displaced, so the effect on its productivity will probably be much more acute," says Russell.

For more information on the Porcupine Caribou Herd contact the Canadian Wildlife Service at 393-6700 or www.taiga.net.