15.5 Trends in range expansions of mammals

Last Updated: 
June 10, 2015

This indicator tracks mammal species that are extending their range in the NWT, using information from residents and visitors. It is also used to track the status of mammals in the NWT General Status Ranking Program1.

Raccoon relaxing
Raccoon relaxing

The indicator helps track mammals that are new to the NWT and expanding using three categories:

Vagrant species occurring infrequently and unpredictably in the NWT. These species are outside their usual range and may be in the NWT due to unusual weather occurrences, an accident during migration, or unusual behaviour by a small number of individuals.

New: range extension into NWT  species newly discovered in the NWT, for which there is evidence of recent range extension. This definition helps to track “true” new species to the NWT, as their pattern of distribution changes.

Range extension within NWT  species already present in the NWT, for which there is evidence of recent extension into habitats or ranges not previously occupied during a period reasonable for the species (e.g. since last glaciation). This definition helps to track changes in mammal distributions in the NWT due to factors including population increases, climate change or habitat changes. Reductions in range size of NWT mammals can be tracked using the SPECIES AT RISK focal point.

NWT Focus

Changes in the northern environment may favour expansion of southern mammals into our northern ecosystems. Species composition in an NWT ecoregion can provide an indicator of ecosystem change, including habitat and climate change.

Official species lists have been compiled for the NWT General Status Ranking Program since 2000. Species lists include all mammals. Updates on range expansions of mammals in the NWT are only possible due to the contribution of NWT residents and visitors interested in NWT biodiversity.

Current View: Status and Trend

Common Name Scientific species name Category Comments
Even-toed ungulates  
Wood Bison Bison bison athabascae Range extension within NWT Extention from Taiga Plains to Taiga Shield ecozone: Herd in Mackenzie Bison Sanctuary has been ranging further north since 2001, mostly along Hwy 3 past (west and north) Behchoko.
Muskox Ovibos moschatus Range extension within NWT Extension from Southern Arctic to Taiga Shield ecozone: Mainland population of muskox north of Great Bear Lake has been expanding west and southwest since the 1950s2.
Elk Cervus elaphus (C. candensis) New – range extension into NWT By 2003, residents in Trout Lake report occasional elk south of Great Slave Lake, Liard area and Nahanni National Park Reserve; one male was harvested on 23 September 2005 in Dehcho1.
Mule Deer Odocoileus hemionus New – range extension into NWT Extension into the NWT: Mule deer were in the Fort Smith area by 19593. Information of this species in the NWT is scarce.
White-tailed Deer Odocoileus virginianus Range extension within NWT Extension from Taiga Plains (south) into Taiga Plains (north) and Taiga Shield ecozone: Unknown when they first arrived in the NWT. First reported in 1959-60 in the Dehcho, then in the 1940s in Hook Lake area, and from Fort Liard to Fort Simpson. Observed occasionally in Hay River area and along Slave River for many years4. Much more common in all of these areas in recent years (comment written in 2001)3.  In 1996, the northernmost animal in North America was harvested crossing the Mackenzie River just north of Norman Wells (Taiga Plains)4. The northernmost harvested deer is now (2007) north of the Arctic circle, near Little Chicago on the Mackenzie River north of Fort Good Hope (Taiga Plains). This species is also in the Taiga Sheild; a doe was harvested near Yellowknife in 2007.
Coyote Canis latrans Range extension within NWT Extention from Taiga Plains to Taiga Shield exozone: Species present in low numbers mainly in the South Slave region. At least one family group has established itself in Yellowknife since 2001.
Cougar Puma concolor Range extension within NWT Extension from Taiga Plains (south) into Taiga Plains (north): Documented in fur records as early as 1919 in the extreme southern edge of the NWT. Between 1 to 9 have been sighted every year since 19905. Some individuals are seen as far north as the North Slave, Sahtu, and near Inuvik and Aklavik6.
Grizzly Ursus arctos Range extension within NWT Extension from Southern Arctic to Northern Arctic. Vagrant into Taiga Shield: Grizzlies have been reported on Banks and Victoria islands at least since the 1980s. Evidence of grizzly presence was recorded as far north as Melville Island in 2003 and 20047. Male grizzlies1 have been noted outside their range near Yellowknife.
 Polar Bear  Ursus maritimus  Vagrant Vagrant into Taiga Plains: One female and 2 cubs reported and destroyed about 500 km south of their range in Deline (Sahtu) in 2008. Polar bears are also reported more on land and near communities in the Inuvialuit Settlement Region6.
Northern Raccoon Procyon lotor Vagrant Vagrant into the NWT: Only one individual was reported from Fort Smith in 20031. The nearest population is near Fort McMurray, AB.
Source: Information from the NWT General Status Ranking Program and as referenced.

Detecting true range extensions can be difficult for less-studied species. For example, three species of bats (long-legged myotis, eastern red bad, and big brown bat) were discovered in the NWT in 2006, but because there had been very few studies on NWT bats prior to that year, it is not known whether these were new range extensions or the species had been present before but not noted.

Looking forward

As people report species of mammals that they have rarely been seen or never seen before, the knowledge on NWT mammals and their distribution is increasing. Overall, it appears that some species are seen further north than before. This slow movement northward is not occurring at a constant rate. Some years more observations of range expansions are reported than in other years. This may be due to a variety of reasons such as milder winters, hot summers, and increased reporting. Vagrancy, where animals are seen a long distance from where they normally occur, is normal in mammals. Individuals, especially young ones, will try new territories and explore new habitats, and can travel further than expected. It remains difficult to detect when there is an increase in vagrancy and when populations are established in a new area, hence to detect a range extension. ENR staff and interested community members in the North have a great role to play in monitoring range extensions by recording and reporting details on animals that are “out of place.”

Find out more

Other focal points

  • See VEGETATION for other indicators related to climate and new species of plants in the NWT. 


Ref 1. Working Group on General Status of NWT Species.  2014. NWT Species Infobase. Yellowknife, GNWT.

Ref. 2. Veitch A.M. 1997. An aerial survey for muskoxen in the Northern Sahtu Settlement Area, March 1997. Environment and Natural Resources, Yellowknife, NT.

Ref. 3. Bob Decker /HR /RWED. 2001. E-mail RE: White-tailed deer. (and other deers).

Ref. 4. Veitch A.M. 2001. An unusual record of a White-tailed Deer, Odocoileus virginianus, in the Northwest Territories. Canadian Field-Naturalist 115:172-175.

Ref. 5. Gau,R., R. Mulders, T. Lamb, and L. Gunn. 2001. Cougar (Puma concolor) in the Northwest Territories and Wood Buffalo National Park. Arctic 54:185-187.

Ref 6. Communities Inuvialuit Region. 2005. Unikkaaqatigiit – Putting the Human Face on Climate Change: Perspectives from the Inuvialuit Settlement Region. Joint publication of Inuit Tapiriit Kanatami, Nasivvik Centre for Inuit Health and Changing Environments at Université Laval and the Ajunnginiq Centre at the National Aboriginal Health Organization. Ottawa, ON.

Ref. 7. Doupe J.P., J.H. England, M. Furze, and D. Paetkau. 2007. Most northerly observation of a grizzly bear (Ursus arctos) in Canada: photographic and DNA evidence from Melville Island, Northwest Territories. Arctic 60:271-276.

Ref 8 . Lausen, C. 2006. Bat survey of Nahanni National Park Reserve and surrounding areas, NWT.  Prepared for Parks Canada and Canadian Paks and Wilderness Society, NWT Chapter. 39 pp.