15.6 Trends in number of introduced and alien mammals, birds and fish

Last Updated: 
June 10, 2015

This indicator tracks introduced and alien mammals, birds, and fish in the NWT. These species are best known and most studied.

Fish introductions, or stockings, have been used in the NWT to enhance the fishing potential of a small number of lakes, providing greater opportunities for sport fishing near roads.

Some species of domesticated mammals and birds, imported from Europe and Asia, are an important source of food and have been introduced in the NWT as part of our small but growing agriculture industry or as part of tourism operations. This indicator does not track the number of animals and birds that are kept in captivity for these purposes. This indicator tracks only introduced or alien species that are not captive, and that can survive in NWT's ecosystems without continuous care by humans.

Past introduction of species that are not still present in the NWT are noted, but are not part the indicator. The indicator helps track mammals and birds that are not native to the NWT using three categories.

Grey fieldslug in Hay River. © Robert Forsyth, 2013.

Alien - Introduced from outside NA = species that have been introduced into North America as a result of human activities:

Alien - Introduced from NA = species that have been introduced into the NWT from other parts of North America as a result of human activities. These species are native to the continent, but not to the NWT.

Introduced from another watershed (fish only) = fish species that have been introduced into any watershed in the NWT other than their original one as a result of human activities. These species are native to the NWT but not to the watershed where they were introduced1.

This indicator uses information collated from NWT residents and visitors, including information posted on the Facebook group 'NWT Species'2. This information is also used to track the status of mammals, birds, and fish in the NWT General Status Ranking Program.

NWT Focus

Changes in the number of alien mammals and birds are monitored as their presence and abundance may affect the status of wild species native to the NWT. Official species lists have been compiled for the NWT General Status Ranking Program3 since 2000. Species lists include all mammals and birds. Updates on introduced alien species in the NWT are only possible with to the contribution of many NWT residents and tourists interested in NWT biodiversity.

Current view: status and trend

One mammal and three bird species have been introduced in the NWT and are still present today.

Horses have been introduced to the NWT, but they are not included in the list of introduced species as all six were geldings. They were surviving with bison north of Fort Providence in late 1980s and early 1990s. Only one was still alive in 2007. These animals apparently escaped from captivity3. In addition to horses, wild boar (Sus scrofa) was released as part of a sport hunting venture in 1996-2000. By 2000, these animals were captured and rapidly moved outside the NWT. In 2010, one animal was seen near Enterprise. It is unknown if this animal is a recent escape, and if it is part of a large group.

In 1935, after a five-year trek from Nome, Alaska, 2,370 reindeer arrived in the Mackenzie Delta4. Reindeer can still be found on the Tuktoyaktuk Peninsula today. Reindeer are the same species as caribou (Rangifer tanrandus), so they are not included in the list of introduced mammals, but these particular animals (i.e., subspecies) are not native to the NWT.

Alien bird species were introduced to North America and are not part of NWT’s list of native bird species. They probably spread to NWT towns on their own.

All fish introductions were carried out as part of stocking initiatives Other than rainbow trout and introduced arctic char, attempts to stock other species of freshwater fish in lakes in the NWT have failed. There were attempts to introduce brook trout (Salvelinus fontinalis) from Alberta into Seven Mile Lake (1949) and Little Buffalo River (1960-61)1. Cutthroat trout (Oncorhynchus clarki) and splake (Salvelinus namaycush x Salvelinus fontinalis), a hybrid between Lake trout and Brook trout, were introduced into Seven Mile Lake (1964), but were also unsuccessful1. Brook trout (or splake) was also introduced into Polar Lake (1971), but is not present there today1. These introductions are noted here for completeness, but are excluded from the indicator (see table below) as they did not result in viable populations. Fish stocking has not occurred in NWT since 1990.

Common Name Scientific species name Definition
Code
Comments
Birds  
Rock Pigeon Columba livia Alien - introduced from outside NA Species present only in Fort Smith, Taiga Plains (south). Introduced to North America from in early 1600s5. It is not known when they were first introduced into the NWT. Appear to survive only if fed and provided some shelter so may not be truly feral.
House Sparrow Passer domesticus Alien - introduced from outside NA Species present in all NWT towns. Does not seem to be able to survive outside habitats modified by humans. Population numbers in Yellowknife fluctuate greatly7. Introduced to North America from England in late 1800s6. Quickly expanded its range. It is not known when they were first introduced into the NWT. Known to destroy nests of other cavity-nesting species. The effects of the species on NWT native birds are not known.
European Starling Sturnus vulgaris Alien - introduced from outside NA Species present in towns south of Great Slave Lake (Taiga Plains south), very rarely seen in Yellowknife. Is not able to survive outside habitats modified by humans. Introduced to North America in 1890 in New York8. Quickly expanded its range. It is not known when they were first introduced into the NWT. Known to destroy nests of other cavity-nesting species. The effects of the species on NWT native birds are not known.
Fish  
Introduced Arctic Char Salvefinus alpinus Introduced from another watershed Introduced in 1989 from Tree River, Nunavut into several lakes (and streams?) in the Yellowknife (Taiga Shield) and Hay River areas (Taiga Plains south), including Polar Lake, where it is still fished today1.
Rainbow Trout Oncorhynchus mykiss Alien – introduced from NA Introduced in Seven Mile Lake (Taiga Plains) in 19591. Unsuccessfully stocked into Lake Nine, near Polar Lake (year uncertain) and in a borrow pit south of Hay River (Taiga Plains). Many introductions in Polar Lake, near Hay River, starting in 19771. Also introduced into Upper Cabin Lake, on the Ingraham Trail (Taiga Shield) in 1982, 1985, 1990. No sign of reproduction. The year of the most recent stocking is unknown3. It is uncertain but it is possible that some of the introduced Rainbow trout populations are still present. Polar Lake was stocked with 10,000 rainbow trout (triploids) in summer 2011 for use by an angling group in Hay River. This is the first time in many years.
Mollusc      
Grey Fieldslug Deroceras reticulatum Alien - introduced from Europe Introduced by accident to garders in North America.  First record for NWT was in Hay River in 20132.
Source: Information from the NWT General Status Ranking Program and as referenced.

Looking forward

Some wildlife species thrive near humans. The number of introduced or alien mammals and birds is expected to increase as human population increases in the NWT and as habitats become fragmented and disturbed because many species introduced by humans survive better near communities or in habitats created by humans. The number of alien or introduced mammals, birds, and fish in the NWT is very small compared to other jurisdictions in southern Canada and the U.S. Our climate makes survival in NWT’s ecosystem a challenge unless species are adapted to the North or humans provide some help in the form of shelter and food. As NWT's winter climate becomes milder, all residents have a role to play in preventing unintentional releases of mammals, birds, and fish that may become naturalized and negatively affect NWT's ecosystems.

Find out more

  • For more information on the NWT General Status Ranking Program visit the NWT Species at Risk website. 

Other focal points

  • See CLIMATE AND WEATHER for other indicators on climate in the NWT.
  • See VEGETATION for indicators related to alien vascular plants in the NWT.
  • See HUMAN ACTIVITES and LANDSCAPE CHANGES for indicators on short-term and long-term changes to ecosystems that result in increased number of alien or introduced mammals, birds and fish.

References:

Ref. 1. Crossman E.J. 1991. Introduced freshwater fishes: a review of the North American perspective with emphasis on Canada. Can. J. Fish Aquat. Sci. 48 (Suppl. 1): 46-57

Ref. 2. Facebook group: NWT Species

Ref. 3. Working Group on General Status of NWT Species.  2011. NWT Species Infobase 2011-2015.  Yellowknife, GNWT. 

Ref. 4. Prince of Wales Northern Heritage Centre. 1999. 1935 Reindeer Herding in the Northwest Territories. Historical timeline of the Northwest Territories.

Ref. 5. Johnston R.F. 1992. Rock Pigeon (Columba livia). in The Birds of North America Online, Ed. (A.Poole, Ed. Cornell Lab of Ornithology, Ithaca.

Ref. 6. Lowther P.E., and C.L.Cink. 2006. House Sparrow (Passer domesticus). in The Birds of North America Online, Ed. (A.Poole, Ed. Cornell Lab of Ornithology, Ithaca.

Ref. 7. Audubon. Current. Christmas Bird Count.

Ref. 8. Cabe P.R. 1993. European Starling (Sturnus vulgaris). in The Birds of North America Online, Ed. (A.Poole, Ed. Cornell Lab of Ornithology;  Ithaca.