American red squirrel (Tamiasciurus hudsonicus)

Description

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American red squirrel fact file

• Description
• Biology
• Range
• Habitat
• Status
• Threats
• Conservation
• Find out more
• Glossary
• References
• Print factsheet

American red squirrel description

Distinguished from other tree squirrels by its smaller size ^{(3) (5)}, the American red squirrel is, as its common name suggests, a deep reddish brown in colour, with white underparts and a white ring around the eye. The ears may be slightly tufted during winter, while in summer there is usually a blackish line along the side of the body, separating the red of the upperparts from the white of the underparts ^{(2) (3) (5) (6)}. The tail is shorter and less bushy than in other tree squirrels, and varies from yellowish-grey to reddish brown in colour, often with yellowish to white tips to the hairs ^{(3) (5) (6)}. The male and female American red squirrel are similar in appearance, and the species can be distinguished from the closely related Douglas’s squirrel (Tamiasciurus douglasii) mainly by the white rather than reddish underparts ^{(3) (6)}. Around 25 subspecies are recognised ^{(3) (5) (7)}. The American red squirrel is quite vocal, using calls which include a rattle, chirp, screech, growl and buzz ^{(2) (3) (5) (6)}.

Also known as

chickaree, Mount Graham red squirrel, North American red squirrel, pine squirrel, red squirrel.

Size

Head-body length: 16.5 - 23 cm ⁽²⁾

Tail length: 9 - 16 cm ^{(2) (3)}

Weight

197 - 282 g ⁽³⁾

American red squirrel biology

Most active during the day, the American red squirrel feeds mainly on seeds, conifer cones and nuts, but will also take a variety of other items including fruits, buds, bark, flowers, fungi, and even insects, birds’ eggs and small vertebrates, such as nestling birds and mice ^{(2) (3) (5) (6) (8)}. It has also been recorded biting into maple trees to feed on the sugary sap, and at some times of year will strip bark to feed on the underlying tissues ^{(2) (3) (6)}. In some areas, the American red squirrel gathers cones into a few large ‘middens’, usually located in hollow stumps or under logs, which serve as central larders during poor conditions. Each midden may contain 2,000 to 4,000, or even up to an incredible 18,000 cones, and may be used by several generations. The American red squirrel is more territorial than most other North American squirrels, vigorously defending an area around the middens. Contrary to the popular misconception, the species does not hibernate, instead becoming inactive for short periods during bad weather, and taking shelter in a nest located in a tree hole, an underground cavity, or in a loosely constructed ball of sticks and vegetation in a tree ^{(2) (3) (5) (6) (8)}.

The American red squirrel usually breeds from February to April, sometimes with a second litter from June to August ^{(1) (2) (3) (5)}. The female may mate with several males, the potential suitors actively pursuing oestrus females in a conspicuous ‘mating chase’ that may last several hours ^{(3) (5) (6) (8)}. The female gives birth to an average of 3 to 5 young, after a gestation period of 31 to 35 days. Born naked and helpless, the young squirrels are weaned by 7 to 8 weeks, and become independent by around 18 weeks, reaching sexual maturity by about a year old ^{(2) (3) (5) (6)}. The female will sometimes relinquish all or part of the territory to one or more juveniles, and move away to establish a new one, giving the young squirrels a greater chance at becoming territory holders ^{(3) (5)}. The American red squirrel may live for up to ten years in the wild, although average lifespan rarely exceeds around three to seven years ^{(2) (3) (5) (6)}.

American red squirrel range

The American red squirrel has a widespread but patchy distribution across North America, from Alaska, east across Canada, and south through the Rocky and Appalachian mountain ranges, to Arizona and New Mexico in the west, and northern Georgia in the east ^{(1) (2) (3) (6) (7)}. It has also been introduced to the island of Newfoundland, eastern Canada ⁽¹⁾. Subspecies T. h. grahamensis is restricted to the Pinaleño (Graham) Mountains of southeastern Arizona, where it isolated from all other subspecies ^{(2) (4) (5) (7)}.

American red squirrel habitat

The American red squirrel mainly inhabits boreal coniferous forests, but also occurs in mixed or deciduous forests, plantations, second-growth areas and hedgerows ^{(1) (2) (3) (6)}. At the southern limits of its range, the species may be restricted to isolated areas of coniferous forest on mountaintops ^{(3) (7)}.

American red squirrel status

Classified as Least Concern (LC) on the IUCN Red List ⁽¹⁾. Subspecies Tamiasciurus hudsonicus grahamensis (Mount Graham red squirrel) was previously classified as Critically Endangered (CR) on the IUCN Red List ⁽⁴⁾.

American red squirrel threats

The American red squirrel is a widespread and common species that is not thought to face any major threats ⁽¹⁾. In some areas, the species may cause damage to conifer plantations by stripping bark and feeding on buds and seeds, although it may also play a role in reforestation by spreading and burying seeds. In Canada, it is one of the most commonly harvested species for its fur ^{(2) (3) (6)}.

However, although the species as a whole is not currently threatened, the Mount Graham subspecies consists of a tiny population, estimated at around 250 in 2009 ⁽⁹⁾, restricted to just one small and isolated area ^{(4) (6) (7)}. Believed to be extinct in the 1950s, the Mount Graham red squirrel was rediscovered in the 1970s ⁽⁵⁾, but has been declining in both range and numbers during recent decades ⁽¹⁰⁾. The main threat to this subspecies is the loss and fragmentation of its habitat due to timber harvesting, development of roads and recreational facilities, and the construction of a controversial observatory complex ^{(4) (5) (6) (7) (10)}, while drought, wildfires and insect outbreaks have caused further damage ^{(11) (12)}. Habitat loss may also potentially increase competition with the introduced Abert’s squirrel, Sciurus aberti ^{(7) (11)}, and it is feared that climate change may further reduce available habitat ⁽¹¹⁾.

American red squirrel conservation

The American red squirrel occurs in a number of protected areas throughout its range ⁽¹⁾, but no specific conservation measures are known to be in place for the species. The Mount Graham subspecies is listed as Endangered by the U.S. Fish and Wildlife Service ⁽¹³⁾, and is subject to a range of conservation measures, including annual surveys and ongoing research ^{(5) (7)}. A recovery plan has been in place for the subspecies since 1993, with the aim of stabilising or increasing the population by protecting and restoring its habitat, and a refuge has been established in part of its range ^{(7) (10)}. Further recommended conservation measures include improved habitat protection, reforestation, more research into the subspecies’ life history, reducing the probability of catastrophic wildfires, controlling insect outbreaks, and creating a captive population ^{(7) (11) (12)}. As with many other small mammals, it is thought that, given the right conditions, this tiny, unique population should have a good chance of recovery ⁽⁹⁾.

Find out more

To find out more about the American red squirrel, and about the conservation of the Mount Graham subspecies, see:

• Steele, M.A. (1998) Tamiasciurus hudsonicus. Mammalian Species, 586: 1-9. Available at:
  http://www.science.smith.edu/departments/Biology/VHAYSSEN/msi/pdf/i0076-3519-586-01-0001.pdf
• Hafner, D.J., Yensen, E. and Kirkland Jr, G.L. (1998) North American Rodents: Status Survey and Conservation Action Plan. IUCN/SSC Rodent Specialist Group, IUCN, Gland, Switzerland and Cambridge, UK. Available at:
  http://data.iucn.org/dbtw-wpd/edocs/1998-039.pdf
• University of Arizona - Mount Graham Biology Program: Mount Graham Red Squirrel (Tamiasciurus hudsonicus grahamensis):
  http://ag.arizona.edu/research/redsquirrel/

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Glossary

Boreal forest

The sub-arctic forest of the high northern latitudes that surrounds the pole and is mainly composed of coniferous trees.

Deciduous forest

Forest consisting mainly of deciduous trees, which shed their leaves at the end of the growing season.

Gestation

The state of being pregnant; the period from conception to birth.

Oestrus

The time of ovulation (release of an egg from the ovary) in female mammals, when the female becomes receptive to males, also known as ‘heat’.

Second-growth

Vegetation that has re-grown after a major disturbance, such as fire or clearance.

Subspecies

A population usually restricted to a geographical area that differs from other populations of the same species, but not to the extent of being classified as a separate species.

Territorial

Describes an animal, a pair of animals or a colony that occupies and defends an area.

Territory

An area occupied and defended by an animal, a pair of animals or a colony.

Vertebrates

Animals with a backbone, including mammals, birds, reptiles, amphibians and fish.

References

1. IUCN Red List (December, 2009)
   http://www.iucnredlist.org/
2. Nowak, R.M. (1991) Walker's Mammals of the World. The Johns Hopkins University Press, Baltimore and London.
3. Steele, M.A. (1998) Tamiasciurus hudsonicus. Mammalian Species, 586: 1-9. Available at:
   http://www.science.smith.edu/departments/Biology/VHAYSSEN/msi/pdf/i0076-3519-586-01-0001.pdf
4. IUCN Red List (July, 2008)
   http://www.iucnredlist.org
5. University of Arizona - Mount Graham Biology Program: Mount Graham Red Squirrel (Tamiasciurus hudsonicus grahamensis) (December, 2009)
   http://ag.arizona.edu/research/redsquirrel/
6. Feldhamer, G.A., Thompson, B.C. and Chapman, J.A. (2003) Wild Mammals of North America: Biology, Management, and Conservation. Second Edition. The Johns Hopkins University Press, Baltimore.
7. Hafner, D.J., Yensen, E. and Kirkland Jr, G.L. (1998) North American Rodents: Status Survey and Conservation Action Plan. IUCN/SSC Rodent Specialist Group, IUCN, Gland, Switzerland and Cambridge, UK. Available at:
   http://data.iucn.org/dbtw-wpd/edocs/1998-039.pdf
8. Macdonald, D.W. (2006) The Encyclopedia of Mammals. Oxford University Press, Oxford.
9. Arizona Game and Fish Department - Wildlife Blog: Wildlife News, November 9th, 2009 - Mount Graham red squirrel fall 2009 count announced (December, 2009)
   http://www.azgfd.net/wildlife/conservation-news/
10. U.S. Fish and Wildlife Service. (1992) Mount Graham Red Squirrel Recovery Plan. U.S. Fish and Wildlife Service, Albuquerque, New Mexico. Available at:
    http://ecos.fws.gov/docs/recovery_plan/930503.pdf
11. U.S. Fish and Wildlife Service. (2008) Mount Graham Red Squirrel (Tamiasciurus hudsonicus grahamensis). 5-Year Review: Summary and Evaluation. U.S. Fish and Wildlife Service, Phoenix, Arizona. Available at:
    http://ecos.fws.gov/docs/five_year_review/doc1617.pdf
12. Koprowski, J.L., Alanen, M.I. and Lynch, A.M. (2005) Nowhere to run and nowhere to hide: response of endemic Mt. Graham red squirrels to catastrophic forest damage. Biological Conservation, 126: 491-498.
13. U.S. Fish and Wildlife Service: Species Profile - Mount Graham Red Squirrel (Tamiasciurus hudsonicus grahamensis) (December, 2009)
    http://ecos.fws.gov/speciesProfile/profile/speciesProfile.action?spcode=A09O