Porcupine Caribou an indicator of wildlife sustainability in the Northern Yukon

What is Happening?

The Porcupine Caribou herd, a large population of migrating Grant's Caribou which ranges across the border between Alaska, Yukon and the Northwest Territories, has been an important part of northern Yukon's natural environment for thousands of years. It is the eighth largest herd in North America.

Source: Population estimates are from the Porcupine Caribou Management Board and the harvest data are from the Yukon Department of Renewable Resources.

GRAPH DATA

During the 1980s, the herd grew approximately 4.5% per year, numbering 178,000 by 1989 and almost doubling in size since the early 70s. Although the herd is considered physically healthy, by 1998 it had declined to 129,000. In 2001 the herd was estimated at 123,000 caribou.

Over the past 30 years, the reported harvest of the herd has ranged from 2,000 to 7,000 caribou with an annual average of about 2,900 per year. This estimate includes all non-Aboriginal and most, but not all, Aboriginal hunting.

Why is it Happening?

Despite having a comparable birth rate, the Porcupine Caribou Herd has not grown as quickly as other barren ground caribou herds. This suggests that the Porcupine herd experiences greater mortality than other barren ground caribou herds.

On an annual basis, the main predators on caribou are wolves and humans. Since the local wolf population is relatively low, they do not have a large effect on caribou populations, taking between three and five percent of the herd each year. Human hunters take between two and three percent of the herd each year. In total, about 16% of the adult cows die from natural causes each year.

Biologists are uncertain about the causes of suspected increasing "natural" mortality but they have noted a greater number of thaw days during spring migration periods since the herd has been in decline. These conditions change the structure of the snow and result in harsher traveling and feeding conditions for caribou. As well scientists have noted high variability in spring conditions, experiencing both early melt and very late melt. When environmental conditions such as late snow melt make it difficult for caribou to reach their coastal calving plains, as seen in 1987 and in the springs of 2000 and 2001, the caribou give birth in areas where predator numbers are higher. Predation rate and food availability are crucial during this period as 50% of annual calf mortality occurs in the first month after birth.

Porcupine Caribou Herd Calving Ground Distribution

Source: US Fish & Wildlife Service: Heavier snowfall in 1987 than 1985 prevents caribou from reaching calving grounds (green represents calving areas; dark green represents areas of highest use).

Scientists predict that global warming may cause the Northern Yukon to have greater snowfall in winter, faster melt period in spring and warmer summers. Warmer weather could lead to higher levels of insect harassment in summer; biologists created a model to predict the effects these changes will have on the caribou populations. Already, scientists are noting earlier snowmelts and a general increase in the biomass of green vegetation at calving areas. These conditions are associated with higher early calf survival. Elsewhere in the arctic, global warming models predict that the habitat of the Peary caribou on Bathrust Island will experience heavier snowfalls and more freezing rain. Conditions that were linked to Peary caribou mortalities in 1974-75 and in three successive winters between 1994 and 1997. In 1998, only 43 Peary caribou remained from a population of 2,400 in 1993 (Miller and Gunn 2003). Another arctic caribou species, the Arctic Island caribou, migrates across the ice from the islands to the mainland. Warmer weather means the ice melts earlier in the spring and freezes later in the fall making the crossings treacherous.

Why is it Significant?

Caribou are the main large ungulates ranging across the Northern Yukon, and the Gwitchin, Inuvialuit, and Inupiat, as well as non-Aboriginal residents from 13 communities in the Yukon, Alaska and Northwest Territories depend upon them for food and cultural well-being. Wolves, Grizzly Bears and Golden Eagles also rely on the herd as an important food source.

Human caribou harvest depends on the accessibility of the herd to hunters during the hunting season. At no time has the harvest exceeded 3% of the population, despite a human population increase of 20-30% in nearby communities over the last three decades.

Porcupine Caribou are most sensitive to disturbance while on their calving grounds and less so while on their winter range. There is potential for serious disturbance of important calving grounds on Alaska's North Slope if proposals to allow oil exploration in the Alaska National Wildlife Refuge are approved.

What is Being Done?

Since 1984, the Canadian government, the governments of the Yukon and Northwest Territories, several native groups, and the US government have concluded agreements or passed land claim legislation that has greatly increased the protection of the herd's habitat and put more control for herd protection in the hands of local governments.

In Canada, Vuntut and Ivvavik National Parks have been created to protect key habitats of the herd.

Research, in response to development proposals, enables managers to more accurately predict impacts of human activity within the range of the herd. Presently, biologists monitor caribou, caribou harvest levels, plant biomass and caribou birth rate and mortality. This helps to determine the relationships between these factors and climatic effects, and to estimate a sustainable human harvest.

In September 1999, Environment Canada and Yukon Renewable Resources announced a funding of $295,500 to support the Northern Climate Exchange, an innovative approach to looking at the impacts of climate change in the North that involves both traditional science and traditional knowledge. As well Environment Canada announced a contribution of $142,000 to the Impact of Climate Change on Migratory Caribou, a continent-wide assessment of the impacts of climate change on major migratory caribou herds in North America. Environment Canada is also presently funding a two year study ($120,000) to conduct a comparative assessment of calving grounds across North America through their Northern Ecosystem Initiative.

For more information contact: Don.Russell@ec.gc.ca

Check the following sites for additional information on this indicator:

• Ecological Monitoring and Assessment Network for Northern Canada (EMAN-North)
• Caribou - Hinterland Who's Who

The following Web sites are not under the control of Environment Canada (EC) and they are provided solely for the convenience of users. Environment Canada is not responsible for the accuracy, currency or the reliability of the content. Environment Canada does not offer any guarantee in that regard and is not responsible for the information found through these links, nor does it endorse the sites and their content. Users should be aware that information offered by non Government of Canada sites that are not subject to the Official Languages Act, and to which Environment Canada links, may be available only in the language(s) used by the sites in question.

• Yukon State of the Environment Report
• Arctic Borderlands Ecological Knowledge Co-op
• Taiga Net
• Beverly and Qamanirjuaq Caribou Herds
• Human Role in Reindeer/Caribou Systems
• US Fish & Wildlife Service - Arctic national Wildlife Refuge - Wildlife
• US Fish & Wildlife Service - Porcupine Caribou Herd Calving Area

For references used in this indicator click here.