Oil Development and Caribou Science

The Porcupine Caribou Range in Alaska's Arctic National Wildlife Refuge

By Doug Urquhart. Secretary/Treasurer, Porcupine Caribou Management Board

"Oil Development can coexist with complete protection for the caribou."
Press Release, Office of Senator Frank Murkowski of Alaska, May 19,1995.

"... after construction of a road system near Milne Point, mean caribou abundance declined by more than two-thirds within 2 km and nearly tripled 4-6 km from roads... Logically, roads comprising an oilfield complex that are on average less tha n 3 km apart may depress area wile calving activity."
Distribution and Productivity of the Central Arctic Herd in Relation to Petroleum Development, Alaska Department of Fish and Game Research Final Report, December 1994.

When congress passed the Alaska National Interest Lands Conservation Act (ANILEA) in 1980, in section '1002' of the act, it instructed the U.S. Fish and Wildlife Service to investigate the potential impacts of oil development on wildlife on the coastal pl ain of the Arctic National Wildlife Refuge.

Biologists with the U.S. Fish and Wildlife Service and the Alaska Department of Fish and Game have been working in this for the past 15 years and the following is a summary of their findings which has been reviewed by several biologists.

Each caribou herd has its own, discrete calving area. Prudoe Bay and other operating oilfields on the North Slope are within the calving grounds of the Central Arctic Herd. This herd was quite small (only about 5,000) when oil development first started in the mid-1970s (Cameron and Whitten 1979), but impacts from development were soon noted. Calving within the Prudoe Field had already largely ceased by the time oil first began flowing south (Whitten and Cameron 1985), and the dense network of pipelines, r oads, oil wells and production facilities at Prudoe blocked mid-summer movements along the arctic coast (Whitten and Cameron 1983). Cow and calf caribou also avoided the Trans Alaska Pipeline Corridor (Cameron et al. 1979) but continued to cross it succes sfully from late summer through spring, when calves were older and the herd was south of the intensely developed oilfields (Whitten and Cameron 1983).

In spite of these impacts, the Central Arctic Herd thrived during the early years of oil development and grew to about 14,000 by 1983. Bythe time development expanded into the Kuparuk area during the 1980s, the petroleum industry had begun to consolidate facilities so that the newer oilfields disturbed less space. Also, some pipelines were raised Higher above ground and separafedfromroads with heavy traffic.*These new designs allowed ciribouto move more freely than at Prudoe Bay, and caribou continued to use the Kuparuk and Mane Pt. Oil fields. Nevertheless, caribou with newborn calves still avoided developed areas, even when there was little traffic (Dau and Cameron 1986, Cameron et al. 1992). Over time, the Kuparuk and Milne Fields became more heavily d eveloped, and caribou used them less and less (Cameron at al. 1992; Smith et al. 1994).

By the late 1980s, growth of the Central Arctic Herd slowed, and the herd stabilized at about 23,000. There are now indications that caribou which spend more time in or near the oilfields are not faring as well as other members of the Central Arctic Herd which seldom encounter development (Cameron 1995). Avoidance of roads and pipelines during calving may be causing caribou to abandon preferred habitats and possibly to overuse some undisturbed habitats (Nellemann and Cameron, unpubl.). It is possible that chronic disruption of summer movements forces caribou to use habitats with less nutritious forage and prolongs their exposure to biting insects.

The United States Congress is debating whether or not to allow North Slope oil development to expand onto the coastal plain of the Arctic National Wildlife Refuge. The potential lease area lies within the calving grounds of the Porcupine Caribou Herd. Thi s large, migratory herd moves between the U.S. and Canada is vital to the traditional subsistence cultures of numerous native villages in both countries. Over the past 25 years, the Porcupine Herd has fluctuated between about 100,000 and 180,000 animals, with a current population of about 160,000.

Before authorizing oil leasing within the Arctic National Wildlife Refuge, Congress should consider that the Porcupine Caribou Herd is much more concentrated on its calving ground than the smaller Central Arctic Herd and may therefore be more vulnerable t o disturbance. Although calving has occurred historically over a fairly targe area of the North Slope in Alaska and the Yukon Territory, most calves are usually born in a smaller region that includes much of the area being considered for oil development ( Fancy and Whitten 1991). During late June and early July, essentially all cows and calves and many bulls of the Porcupine Herd use the potential development area every year.

Calf survival is generally high when the Porcupine Herd calves in the traditional coastal plain area that includes the potential oil lease area (Fancy and Whitten 1991, Whitten et al. 1992). Rapid, nutritious plant growth often occurs in this area during calving (National Biological Service, unpubl.). The coastal plain calving area is also relatively free of predators, and calf survival declines when late snow melt forces caribou to calve in nearby mountains and foothills where wolves, grizzly bears and g olden eagles abound (Whitten et al. 1992). The Porcupine Herd is already large and near its historic population high. If petroleum development were to displace it from part of its traditional calving grounds, suitable alternative habitat might not be avai lable. Consequently, the Porcupine Herd might not fare as well as the Central Arctic Herd apparently did during the early years of Prudhoe Bay.

Porcupine caribou normally herd in much larger groups than Central Arctic Herd caribou. Studies in the Prudhoe Bay and Kuparuk oilfields show that larger groups (100 or more caribou) have difficulty crossing roads and pipes ( Smith and Cameron 1985). Grou ps of several thousand caribou occur throughout the summer in the Porcupine Herd, and from mid-June through July, group sizes in the tens of thousands are common.

In summary, development of the Prudoe Bay oil field displaced caribou and disrupted their movements. Similar long-term displacement now appears to be occurring elsewhere, even in the "state-of-the-art" Kuparuk and Milne Pt. Oil fields. Mitigation measures proposed for Arctic Refuge oil fields will likely be even less effective in allowing access to critical habitats for the larger, more densely aggregated Porcupine Herd. The caribou resources at risk in the Arctic National Wildlife for petroleum developme nt far exceed those found at Prudhoe Bay. Development of the coastal plain may well cause a long-term decline in calf survival, thereby decreasing population size over time, with serious consequences for many residents in both Canada and the U.S.


Cameron, R.D. 1995. Distribution and productivity of the Central Arctic Herd in relation to petroleum development: case history studies with a nutritional perspective. Fed. Aid in Wildl. Rest. Final Rept. Ak. Dept. Fish and Game. Juneau. 35pp.

Cameron, R.D., and K R.Whitten. 1979. Seasonal movements and sexual aggression of caribou determined by aerial survey. J. Wildl. Manag. 43:626-633.

Cameron, R.D., tR Whitten, W.T. Smith, and D. D. Roby. 1979. Caribou distribution and group composition associated with construction of the Trans-Alaska Pipeline. Can. Field-Natur. 93:155-162.

Cameron, R.D., D.J. Reed, J.R. Dau, and W.T. Smith. 1992. Redistribution of calving caribou in response to oil field development on the arctic slope of Alaska. Arctic. 45:338-342.

Dau, J.R., and R.D. Cameron. 1986. Effects of a road system on caribou distribution during calving. Rangifer, Special Issue No. 1:95-101.

Fancy, S.C., and K.R. Whitten. 1991. Selection of calving sites by Porcupine Herd caribou. Can. J. Zool. 69:1736-1743

Nellemann; C., and R. D. Cameron. No date. Terrain preferences of calving caribou exposed to petroleum development, Submitted to Arctic.

Smith, W. T., and R. D. Cameron. 1985. Reactions of large groups of caribou to a pipeline corridor on the arctic coastal plain of Alaska. Arctic. 38:53-57

Smith, W. T., R. D. Cameron, and D. J. Reed. 1994. Distribution and movements of caribou in relation to roads and pipelines, Kuparuk Development Area,1978-1990. Ak. Dept. Fish and Game, Wildl. Tech. Bull. 12. 54pp.

Whitten, K. R., and R. D. Cameron. 1983. Movements of collared caribou, Rangifer tarandus, in relation to petroleum development on the arctic slope of Alaska. Can. Field-Natur. 97(2):143-146.

Whitten, K. R., and R.D. Cameron. 1985. Distribution of caribou calving in relation to the Prudoe Bay oilfield. In: Martell, A. M., and D. E. Russell, eds. Proceedings of the First North American Caribou Workshop, Whitehorse, Yukon. Ottawa: Canadian Wildl ife Service. 33-39. < p> Whitten, K. R., G. W. Garner, F. J. Mauer, and R. B. Harris. 1992. Productivity and early calf survival in the Porcupine caribou herd. J. Wildl. Manag. 56:201-212