15.4 Trends in barren-ground caribou population size in tundra-taiga ecosystems

Last Updated: 
June 9, 2015

This indicator measures the trend in population sizes of barren-ground caribou (Rangifer tarandus groenlandicus) herds in the NWT. Information on Peary caribou (R. t. pearyi) and boreal caribou (R.t. caribou) is presented in the SPECIES AT RISK focal point.

Barren-ground caribou
Barren-ground caribou.

Population estimates are calculated and tracked to monitor the status of caribou herds (size and whether a herd is increasing, stable, or declining).

Barren-ground caribou in the NWT, as in Alaska and other jurisdictions, are managed at the herd level, with herds defined by fidelity to distinct calving grounds. Nine migratory caribou herds have part or their entire range in the NWT: Porcupine, Tuktoyaktuk Peninsula, Cape Bathurst, Bluenose-West, Bluenose-East, Bathurst, Beverly, Ahiak and Qamanirjuaq. The Dolphin-Union herd is unique in the world, and is morphologically similar to both the barren-ground caribou and the Peary caribou (Rangifer tarandus pearyi).

For some large NWT barren-ground herds like the Beverly and Bathurst, population estimates are derived from photographic surveys in June when female caribou are concentrated on the calving grounds. Prior to the early 1980s, calving ground surveys were visual, but photographic surveys were found to be more accurate, particularly for counting larger groups of caribou. Caribou in other NWT herds like the Tuktoyaktuk Peninsula, Cape Bathurst, Bluenose-West and Bluenose-East herds, as well as most Alaskan herds, are counted from aerial photographs taken over large post-calving aggregations that form for insect relief.

The information for this indicator is obtained from ENR surveys that are conducted by biologists, with involvement of community members and in partnership with neighbouring wildlife agencies. Surveys of the Beverly, Ahiak and Qamanirjuaq, Dolphin, Wager Bay and Lorillard herds are led by the Government of Nunavut. Surveys of the Porcupine herd are led by the Alaska Department of Fish and Game and Yukon Department of Environment.

Map of barren-ground caribou herds
Map of barren-ground caribou herds that are entirely or partially in the NWT. Range derived from satellite locations of females from the 1990s to 2000s. Range distribution for each herd is dynamic and changes slightly annually. This map is provided for illustrative purposes only.

NWT Focus

Caribou are an important source for food, clothing, and cultural identity for Aboriginal people in the NWT, and one of the NWT’s most important wildlife resources.

Some factors that affect caribou are difficult to control (e.g. weather) but human activities such as hunting and industrial development can be managed. When herds are declining or at low numbers they are less resilient to environmental change and hunter harvest than when herds are increasing or at high numbers. This information allows managers and users to identify which management actions are appropriate to ensure that caribou harvesting remains sustainable.

Current view: status and trend

Recent barren-ground caribou surveys indicate that the Porcupine herd is increasing, the Tuktoyaktuk Peninsula herd is in slow decline, the Cape Bathurst herd remains small but is increasing, the Bluenose-West herd remains small but stable.  However, both the Bluenose-East herd and the Bathurst herd are declining further despite management efforts to reverse the trend.  The Beverly, Ahiak, and Qamanirjuaq herds are possibly in decline, but surveys are not done frequently enough to determine the rates of change with high certainty.     

Population estimates
Barren-ground caribou population estimates, 1982-2014. Note: Timing of the decline is unclear for the Beverly, Ahiak and Qamanirjuaq herds.

Porcupine herd

Shown on map in dark grey.

Range is west of the Mackenzie River. Shared with Yukon and Alaska.

Numbers are from Alaska Department of Fish and Game, and Yukon Department of Environment.

 

 

Tuktoyaktuk Peninsula herd

Shown on map in brown.

Numbers are from ENR, GNWT, estimated based on post-calving surveys.

Error bars are 95% CI. Note the difference in herd size with the much larger Porcupine herd.

 

 

 

Cape Bathurst herd

Shown on map in green.

Numbers are from ENR, GNWT, estimated based on post-calving surveys.

Error bars are 95% CI. Note the difference in herd size with the much larger Porcupine herd.

 

 

Bluenose-West herd

Shown on map in beige. 

Numbers are from ENR, GNWT, estimated based on post-calving surveys.

Error bars are 95% CI. Note that prior to 2000, Bluenose-West and Bluenose-East were estimated together. Population estimates for Bluenose-West prior to 2000 were re-calculated in 2008 using raw data.  

 

 

Bluenose-East herd

Shown on map in blue.

Numbers are from ENR, GNWT, estimated based on post-calving surveys.

Error bars are 95% CI. Note that prior to 2000, Bluenose-West and Bluenose-East were estimated together. Population estimates for separate Bluenose-East prior to 2000 are not available.

A reconnaissance survey in Spring 2014 showed this herd declined further since the last population survey in 2013.

 

Bathurst herd

Shown on map in yellow.

Numbers are from ENR, GNWT, estimated based on calving survey surveys. Error bars are SE.

A reconnaissance survey in Spring 2014 showed this herd declined further since the last population survey in 2012.

 

 

Beverly herd

Shown on map in dark red.

Numbers are from Government of Nunavut and ENR, GNWT, estimated based on calving survey surveys. Error bars are SE.

There were very few caribou on the traditional Beverly calving ground in 2009. Recently, most of the remaining collared Beverly females have been using a calving ground further north along the Queen Maud Gulf area. In 2011, the latest survey of Beverly was performed on both their traditional calving ground near Beverly Lake and on the calving ground near Queen Maud Gulf.

 

Ahiak herd

Shown on map in red.

Numbers are from Government of Nunavut and ENR, GNWT estimated based on calving surveys. Error bars are SE.

The Ahiak herd population number had been estimated only once in the past (1996) using only four transects. In 2011, the Ahiak herd was estimated by surveying their current calving ground in the vicinity of Adelaide Peninsula.  

 

 

Quamanirjuaq herd

Shown on map in pink.

Numbers are from Government of Nunavut, estimated based on calving survey surveys.

 

 

 

Dolphin-Union herd

Shown on map in mauve.

Numbers are from Government of Nunavut.  Animals of this herd have characteristics of both Peary (R. t. pearyi) and Barren-ground caribou (R. t. gooenlandicus). Error bars are SE.  The last two estimates are done by surveys along an area of concentration on southern Victoria Island.

 

 

Wager Bay and Lorillard herds are not tracked on this indicator as these herds are in Nunavut entirely.  Population numbers can be obtained from the Government of Nunavut.

Tracking Population Change

There are many natural factors that can influence population changes in caribou, including insect harassment, quality of forage in spring, summer and fall, depth of snow in winter, levels of predation, and other climate and range dynamics. Traditional and scientific sources provide evidence of caribou populations naturally increasing and decreasing on a periodic basis. These changes may be due to the influence of fluctuating climatic patterns1.

Human activities on barren-ground caribou ranges have changed in the last sixty years (see focal point HUMAN ACTIVITIES). Oil and gas exploration and development, as well as mineral exploration and mining, occur to varying degrees across barren-ground caribou ranges. Human harvesting patterns have also changed from dispersed harvesting to more concentrate harvesting in areas near communities or with improved road access to caribou. Winter roads have made remote areas more accessible, and technologies such as snowmobiles, aircrafts and all-terrain-vehicles (ATVs) have changed how caribou are hunted.

The cumulative impact of these human activities on caribou herds is not well understood, but it must be assessed in the context of continuing natural variation in weather and foraging conditions.

Looking forward

When caribou herds are declining, the GNWT surveys the herds more often and other monitoring is also increased. Management actions take on greater significance. Declining or small herds are less resilient to hunting and disturbance than herds that are increasing or larger. The overall goal is to manage activities  that humans can influence (e.g. harvesting, resource development) so that herds can recover from natural declines. Due to widespread community concerns over declining barren-ground caribou herds, the caribou strategy was updated (A Barren-ground Caribou Management Strategy for the Northwest Territories for 2011-20153) to increase barren-ground caribou monitoring and management actions. Long-term management and monitoring strategies are described in the publication Caribou Forever: Our Heritage, Our Responsibility2

Looking around

Caribou herds (both barren-ground and Peary) have declined in the past decades in most of northern North America4. Caribou herds increased from lows in the mid-1970s to peaks in the 1990s, and declined in the 2000s. However, exceptions can occur to this pattern. For example, the time of declines and peaks may be different in some Alaskan and northern Quebec herds. The Leaf River herd in Quebec/Labrador has increased while the neighbouring George River herd has decreased.

Find out more

Technical Notes

  • Data prior to 1980s was collected using visual surveys. Photographic surveys were used from the 1980s onward. 

 

Found an error or have a question? Contact the team at NWTSOER@gov.nt.ca.


References:

Ref. 1 Zalatan R., A. Gunn, and G. Henry. 2006. Long-term Abundance Patterns of Barren-ground Caribou Using Trampling Scars on Roots of Picea mariana in the Northwest Territories, Canada. Arctic, Antarctic, and Alpine Research 38:624-630

Ref. 2. Department of Environment and Natural Resources. 2006. Caribou Forever – Our Heritage, Our Responsibility. A Barren-ground Caribou Management Strategy for the Northwest Territories 2006 – 2010.

Ref. 3. ENR. 2011. A Barren-ground Caribou Management Strategy for the Northwest Territories 2011-2015

Ref. 4. Federal, Provincial, Territorial, Governments,.2010. Canadian biodiversity: ecosystem status and trends 2010. Canadian Councils of Resources Ministers, Ottawa, ON.

Ref. 5. Nagy, J.A, D.L. Johnson, N.C. Larter, M.W. Campbell, A.E. Derocher, A. Kelly, M. Dumond, D. Allaire, and B. Croft. 2011. Subpopulation structure of caribou (Rangifer tarandus L.) in arctic and subarctic Canada. Ecol. Appl. 21: 2334-2348.