BioKIDS home

Kids' Inquiry of Diverse Species

red squirrel

Tamiasciurus hudsonicus

What do they look like?

Red squirrels look different from other squirrels that live in trees because they are small and have deep reddish fur. They are much smaller than grey squirrels. They have a reddish back and white underside with dark colored lines which are easiest to see in summer. Their back is reddish brown or olive gray, but usually has a reddish or brownish band along the middle. Their tails are smaller and flatter than other tree squirrels and can be yellowish-gray or rusty red, with a band black band along it. Their underside is all white or cream, instead of Douglas squirrels, which are rust-colored or dark on their bellies. Male and female red squirrels are very difficult to tell apart. (Flyger and Gates, 1982; Hall, 1981; Lane, et al., 2010; Steele, 1998)

Red squirrels might be a little bit bigger or smaller in some place, but they weigh 200 to 250 g on average. They are 270 to 385 mm long. This includes their tail, which is 92 to 158 mm long by itself. Their back feet are 35 to 57 mm long and their ears are 19 to 31 mm long. (Hall, 1981; Kramm, et al., 1975; Lindsay, 1982)

Red squirrels get all new fur on their bodies twice a year, and once a year on their tail. These change helps scientists figure out how old they are. So does studying their teeth for permanent teeth and signs of wear. Red squirrels have 20 or 22 teeth. (Lane, et al., 2010; Steele, 1998)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    197.3 to 282.2 g
    6.95 to 9.95 oz
  • Average mass
    212.97 g
    7.51 oz
  • Range length
    270 to 385 mm
    10.63 to 15.16 in
  • Average basal metabolic rate
    166 cm3.O2/g/hr
  • Average basal metabolic rate
    1.615 W
    AnAge

Where do they live?

Red squirrels are native to the Neartic region and have a very broad distribution covering almost all of the northern half of North America. Their range extends south along the Rocky Mountains to Arizona and New Mexico and east all the way to Quebec, Canada. This species is restricted to forest habitat, so in the southern extent of its range where the forested environment is sparse, their distribution is patchy. Red squirrels can be found on both coasts of North America and are widespread throughout Canada and Alaska. (McAdam, et al., 2007; Steele, 1998)

Red squirrels live in a very large area in the northern half of North America. They can be found in the Rocky Mountains down to Arizona and New Mexico and east all the way up to Quebec, Canada. They live only in forest habitats, so in the southern parts of this area, there are not quite as many of them. Red squirrels are found on both coasts of North America and are common throughout Canada and Alaska. (McAdam, et al., 2007; Steele, 1998)

What kind of habitat do they need?

Red squirrels prefer to live in shady northern forests with lots of tall pine trees and mushrooms. These are called boreal forests. This means that in the southern and eastern parts of their range, they live only around mountains. In the Rocky Mountains, they can live at elevations as high as 2,500 ft (762 m). The habitat of red squirrels changes depending on their location. They live in areas with seasons as well as places that are cold all year round. They can also live in other kinds of forests as well as around human homes if there are cool pine forests nearby. (Ruff and Wilson, 1999; Steele, 1998)

  • Range elevation
    0 to 762 m
    0.00 to 2500.00 ft

How do they reproduce?

Red squirrels breed either once or twice a year for 105 days. They mate in early spring from March to May and again in August to early September. In the warmer parts of their range, they breed twice. Males and females have multiple mates. Males invade the territory of females and chase them. They drive off other males by calling or chasing them. (Gurnell, 1984; Lane, et al., 2010; Layne, 1952; Smith, 1968; Steele, 1998; Wirsing, et al., 2002)

Red squirrels breed once or twice a year, depending on where they live. In the south and east, they breed once in spring and once in late summer. Where it is colder, they usually breeding once a year. Red squirrels usually build nests within 30 m of where they have stored food. Their nests are in holes in trees, in the leaves, or can even be underground. They make nests out of grass, moss, parts of plants, shredded bark, feathers, or fur. If food is hard to come by, adult females choose not to reproduce but females older than 6 do anyway. This is because they are closer to the end of their life. (Lane, et al., 2010; Steele, 1998)

Baby red squirrels grow inside their mothers' bodies for 35 days, and then the mother gives birth to 1 to 8 young, and 3.97 on average. They weigh 7.08 g at birth and have no hair except for whiskers and some soft hairs on their chins. Their eyes open after 26 to 35 days, and they have all of their fur after 40 days. The young drink milk from their mother for the first 70 days, and then leave the nest to find their own territory. If the mother is not healthy, she might give part of her territory to one of the young. Mothers feed milk to their young for the first 70 days. After 7 weeks, they can go outside the nest, but the leave permanently after day 70. Young red squirrels are full size and have all of their teeth by the time they are 125 days old. (Descamps, et al., 2009; Hayssen, 2008; Lane, et al., 2010; Layne, 1952; Nice, et al., 1954; Ruff and Wilson, 1999; Steele, 1998)

  • How often does reproduction occur?
    Red squirrels breed once or twice a year, depending on their geographic location.
  • Breeding season
    The time of breeding depends on their geographic location.
  • Range number of offspring
    1 to 8
  • Average number of offspring
    3.97
  • Average number of offspring
    4.2
    AnAge
  • Average gestation period
    35 days
  • Average gestation period
    37 days
    AnAge
  • Average weaning age
    70 days
  • Average time to independence
    7 weeks
  • Average age at sexual or reproductive maturity (female)
    1 years
  • Average age at sexual or reproductive maturity (female)
    Sex: female
    342 days
    AnAge
  • Average age at sexual or reproductive maturity (male)
    1 years

Females raise the young without any help from males. They carry the young in their bodies for 35 days and then feed them milk after they are born for 70 days. When the young become independent, mothers sometimes give their territory or part of it away to their young. (Boutin and Larsen, 1993; Humphries and Boutin, 2000; Steele, 1998)

  • Parental Investment
  • altricial
  • female parental care
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • provisioning
      • female
    • protecting
      • female

How long do they live?

Red squirrels live long lives compared to their size. The oldest squirrel in the wild was 10 years old, and the oldest in captivity was 9 years old. Their average lifespan is 5 years. However, red squirrels have difficulty surviving past 1 year old. In fact, only 25% of red squirrels survive past 1 year. (Lane, et al., 2010; Ruff and Wilson, 1999; Steele, 1998)

  • Range lifespan
    Status: wild
    10 (high) years
  • Range lifespan
    Status: captivity
    9 (high) years
  • Average lifespan
    Status: wild
    5 years
  • Average lifespan
    Status: captivity
    9.8 years
    AnAge

How do they behave?

Red squirrels are mostly active during the day, but sometimes at night too. In the spring and summer they are most active in the morning and afternoon. In the fall, they are gathering food for the winter so they are active all day. In the winter, they move around more in the middle of the day when it is warmest outside. They rarely stay in the nest for more than 1 day without looking for food. When it is less than -31.6 degrees Celsius, red squirrels living in warmer areas are not active at all. (Clarkson and Ferguson, 1969; Pauls, 1978; Pruitt and Lucier, 1958; Steele, 1998)

In most places they live and especially in pine forests, red squirrels claim and defend territories. They stockpile cones in their territories and don't allow others in. Their territories can be anywhere from 2400 to 48000 square meters in size. In forests without pine trees, they usually defend only their nests and food stores instead of a whole territory. (Kemp and Keith, 1970; Layne, 1952; Steele, 1998)

  • Range territory size
    2400 to 48000 m^2

Home Range

Red squirrels usually move around in an area that is 1 to 2.4 hectares in size. (Ruff and Wilson, 1999)

How do they communicate with each other?

Red squirrels have excellent senses of smell, sight, and hearing. They often call to each other, making noises like rattles, screeches, growls, buzzes and chirps. These noises are very important for defending their territory. They are also used to drive away other males competing for mates. Red squirrels may even be able to recognize each other by their calls. Often they make a different call for predators in the air compared to predators on the ground, but scientists aren't sure about this. Red squirrels also recognize each other through scent marks, which is important because its less noticeable to predators and can avoid unneeded fights between neighbors. (Digweed and Rendall, 2010; Greene and Meagher, 1998; Price, et al., 1986; Ruff and Wilson, 1999; Vache, et al., 2001)

What do they eat?

Red squirrels eat mostly seeds of pine trees. The amount of pine tree seeds available changes a lot during the year, so their diet is flexible. In the mountains of Oregon and Washington, they also eat at least 45 different kinds of mushrooms. Red squirrels eat tree buds and flowers, fleshy fruits, tree sap, bark, insects, and even bird eggs or young snowshoe hares. In the winter, spring, and early summer, they strip bark of trees and eat the parts of the tree that transport nutrients. Red squirrels are energy efficient when foraging. This means they start by eating the cones with the most energy, and then the cones with a little bit less energy, and son on. (Boutin, et al., 2006; McAdam and Boutin, 2003; Steele, 1998; Wilson, et al., 2003)

Red squirrels hoard food, so they take pine tree cones and store them somewhere moist and cool. They store up enough food to last one or two seasons. The same storage spots are often used by several generations of squirrels. In the eastern United States and Canada, they often have multiple small hoards instead of one big one. Their great sense of smell helps them find their hoards, which they can find even under 4 meters of snow. Sometimes red squirrels steal food from other squirrels, which is very common in Arizona and also happens in Vermont. (Dempsey and Keppie, 1993; Donald and Boutin, 2011; Gurnell, 1984; Hurly and Robertson, 1986; Ruff and Wilson, 1999; Smith and Reichman, 1984; Smith, 1968)

  • Animal Foods
  • birds
  • mammals
  • eggs
  • insects
  • Plant Foods
  • wood, bark, or stems
  • seeds, grains, and nuts
  • fruit
  • flowers
  • sap or other plant fluids
  • Other Foods
  • fungus

What eats them and how do they avoid being eaten?

Red squirrels are eaten by a wide variety of animals from snakes and birds of prey to mammals. Birds of prey that eat them are Cooper's hawks, northern goshawks, bald eagles, great gray owls, great horned owls, American kestrels, red-shouldered hawks, northern harriers, red-tailed hawks, sharp-shinned hawks. Mammals that eat them are American martens and fishers, weasels, mink, red foxes and their relatives, and also lynx and their relatives . They are preyed upon by timber rattlesnakes. Humans hunt red squirrels for both their fur and meat. (Gurnell, 1984; Steele, 1998)

Red squirrels make alarm calls when there are predators nearby. They make a call with a high frequency when they notice flying predators and a barking call when they notice land predators. They are difficult for predators to catch because they are quick on their feet and can escape into tree cover. They are fairly aggressive and defend themselves if needed. (Digweed and Rendall, 2010; Greene and Meagher, 1998; Ruff and Wilson, 1999; Stuart-Smith and Boutin, 1995; Wirsing, et al., 2002)

What roles do they have in the ecosystem?

Red squirrels spread seeds and mushrooms through the forest when they store food somewhere and never end up eating it. The fungi in their food storage spots help small trees get nutrients and grow. Other times, red squirrels damage trees by eating their seeds and tissues. However, peeling away the bark on lodgepole pines in winter allows porcupines to eat. They also cause pine trees to grow more than one top. This makes selling the wood from the trees worth less, but creates places to nest for rodents that live in trees as well as songbirds. (Aubry, et al., 2003; Ruff and Wilson, 1999; Sullivan, et al., 1993)

Red squirrels have many parasites that live both inside them and on their skin. There are 9 species of roundworms and 9 species of tapeworms including (Hymenolepis). Other parasites inside their bodies are tularemia bacteria called Francisella tularensis and Emmonsia crescens, and some kinds of protists like sarocysts, and Haplosporanigium. Their lungs can get infected by a fungus, giving them adiaspiromycosis. On the outside of their bodies there can be 31 species of mites, ticks, and chiggers (Glycyphagidae and Acarina), 25 species of fleas including Siphonaptera, Opisodasys robustus, Orchopeas caedens, Orchopeas neotomae, Orchopeas leucopus, Oropsylla idahoensis, Ceratophyllus vison. They may also carry botfly larvae. Viruses that infect them are silverwater virus, California encephalitis virus, and Powassan virus. (Edwards, et al., 2003)

  • Ecosystem Impact
  • disperses seeds
Commensal or parasitic species (or larger taxonomic groups) that use this species as a host

Do they cause problems?

Red squirrels have a negative impact on planting pine trees because they eat 60 to 100% of the cones, eat the buds, and strip the bark. They also nest in homes and gnaw on human property. If provoked, they sometimes bite people. (Ruff and Wilson, 1999; Steele, 1998)

  • Ways that these animals might be a problem for humans
  • injures humans
    • bites or stings
  • household pest

How do they interact with us?

Red squirrels are caught for their fur. Selling it in Canada is worth a total of about $1 million a year. In Minnesota, they are hunted for food. They are also eaten by important species like lynx and martens. (Kemp and Keith, 1970; Ruff and Wilson, 1999)

  • Ways that people benefit from these animals:
  • food
  • body parts are source of valuable material

Are they endangered?

As of 2008, red squirrels are classified as Least Concern on the ICUN Red List and by the United States government. They are widespread and common, have suitable habitat throughout their range, and face no major threats. One subspecies, Mt. Graham red squirrels (Tamiasciurus hudsonicus grahamensis), is endangered according to the ICUN Red List. This subspecies is only found in southeast Arizona and its population is about 150 individuals. (Ruff and Wilson, 1999)

Red squirrels live in a large area and are common, so they are not endangered or close to becoming endangered. They are listed as "Least Concern" on the ICUN Red List and by the United States government. A subspecies called Mt. Graham red squirrels that lives in southeast Arizona is as endangered on the ICUN Red List. There are only about 150 of them. (Ruff and Wilson, 1999)

Some more information...

Pine squirrels like red squirrels probably separated from bushy-tailed squirrels in the late Pliocene time period. Red squirrels are first reported in the Irvingtonian age (1,800,000 to 240,000 years ago). They are found in many fossils in the central and eastern United States that are from 240,000 to 11,000 years ago. (Hafner, 1984; Steele, 1998)

Contributors

Catherine Rubin (author), University of Alaska Fairbanks, Link Olson (editor), University of Alaska Fairbanks, Catherine Kent (editor), Special Projects.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

acoustic

uses sound to communicate

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

arboreal

Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends.

chemical

uses smells or other chemicals to communicate

diurnal
  1. active during the day, 2. lasting for one day.
endothermic

animals that generate their own body heat through metabolic processes.

female parental care

parental care is carried out by females

food

A substance that provides both nutrients and energy to a living thing.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

granivore

an animal that mainly eats seeds

herbivore

An animal that eats mainly plants or parts of plants.

motile

having the capacity to move from one place to another.

mountains

This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

native range

the area in which the animal is naturally found, the region in which it is endemic.

pheromones

chemicals released into air or water that are detected by and responded to by other animals of the same species

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

scent marks

communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

stores or caches food

places a food item in a special place to be eaten later. Also called "hoarding"

suburban

living in residential areas on the outskirts of large cities or towns.

tactile

uses touch to communicate

taiga

this biome is characterized by large expanses of coniferous forest, there is an extended cold season and heavy snowfall.

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

urban

living in cities and large towns, landscapes dominated by human structures and activity.

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

References

Aubry, K., J. Hayes, B. Biswell, B. Marcot. 2003. Community and ecosystem relations. Ch. 12 The ecological role of tree-dwelling mammals in coniferous forests. University Publishing Online: Cambridge University Press. Accessed October 07, 2012 at http://ebooks.cambridge.org/chapter.jsf?bid=CBO9780511615757&cid=CBO9780511615757A019.

Boutin, S., K. Larsen. 1993. Does food availability affect growth and survival of males and females differently in a promiscuous small mammal, Tamiasciurus hudsonicus?. Journal of Animal Ecology, 62: 364-370.

Boutin, S., L. Wauters, A. McAdam, M. Humphries. 2006. Anticipatory reproduction and population growth in seed predators. Science, 314: 1928-1930.

Clarkson, D., H. Ferguson. 1969. Effect of temperature upon activity in the red squirrel. American Zoologist, 9: 1110.

Dempsey, J., D. Keppie. 1993. Foraging patterns of eastern red squirrels. Journal of Mammalogy, 74: 1007-1013.

Descamps, S., S. Boutin, A. McAdam, D. Berteaux, J. Gaillard. 2009. Survival costs of reproduction vary with age in North American red squirrels. Proceedings of the Royal Society of London. Series B: Biological Sciences, 276: 1129-1135.

Digweed, S., D. Rendall. 2010. Are the alarm calls of North American red squirrels (Tamiasciurus hudsonicus) functionally referential?. Behaviour, 147: 1201-1218. Accessed January 03, 2012 at http://classes.uleth.ca/201003/biol4850a/Ch14C%20Low%20Priority%20Digweed.pdf.

Donald, J., S. Boutin. 2011. Intraspecific cache pilferage by larder-hoarding red squirrels (Tamiasciurus hudsonicus). Journal of Mammalogy, 92/5: 1013-1020. Accessed October 22, 2011 at http://www.bioone.org/doi/full/10.1644/10-MAMM-A_340.1.

Edwards, J., M. Ford, D. Guynn. 2003. Wild Mammals of North America: Biology, Management, and Conservation. Baltimore, MD: John Hopkins University Press.

Flyger, V., J. Gates. 1982. Pine Squirrels: Tamiasciurus hudsonicus, T. douglasii. Pp. 230-237 in J Chapman, G Feldhamer, eds. Wild mammals of North America. Baltimore: John Hopkins University Press.

Greene, E., T. Meagher. 1998. Red squirrels, Tamiasciurus hudsonicus, produce predator-class specific alarm calls. Animal Behavior, 55/3: 511-518. Accessed January 03, 2012 at http://www.ncbi.nlm.nih.gov/pubmed/9514668.

Gurnell, J. 1984. Home range, territoriality, caching behavior and food supply of the red squirrel (Tamiasciurus hudsonicus) in a subalpine forest. Animal Behavior, 32: 1119-1131.

Hafner, D. 1984. Evolutionary relationship of the near arctic Sciuridae. Pp. 459 in J Murie, G Michener, eds. The biology of ground dwelling squirrels. Lincoln: University of Nebraska Press.

Hall, E. 1981. Red Squirrel, Tamiasciurus hudsonicus. The Mammals of North America. Ronald Press.

Halvorson, C., R. Engeman. 1983. Survival analysis for a red squirrel population. Journal of Mammalogy, 64: 332-336.

Hayssen, V. 2008. Patterns of body and tail length and body mass in Sciuridae. Journal of Mammalogy, 89/4: 852-873.

Humphries, M., S. Boutin. 2000. The determinants of optimal litter size in free-ranging red squirrels. Ecology, 81: 2867-2877.

Hurly, T., R. Robertson. 1986. Scatter-hoarding by territorial red squirrels: a test of the optimal density model. Canadian Journal of Zoology, 65: 1247-1252.

Kemp, G., L. Keith. 1970. Dynamic and Regulation of Red Squirrel (Tamiasciurus hudsonicus) Populations. Ecology, 51/5: 763-779. Accessed October 13, 2011 at http://www.jstor.org/stable/1933969.

Klugh, A. 1927. Ecology of the red squirrel. Journal of Mammalogy, 8: 1-32.

Kramm, K., D. Maki, J. Glime. 1975. Variation within and among populations of red squirrel in the Lake Superior Region. Journal of Mammalogy, 56/1: 258-262. Accessed October 14, 2011 at http://www.jstor.org/stable/1379633.

Lane, J., S. Boutin, J. Speakman, M. Humphries. 2010. Energetic costs of male reproduction in a scramble competition mating system. Journal of Animal Ecology, 79: 27-34.

Layne, J. 1952. The Os Genitale of the red squirrel, Tamiasciurus. Journal of Mammalogy, 33/4: 457-459.

Lindsay, S. 1982. Systematic relationship of parapatric tree squirrel species (Tamiasciurus) in the Pacific Northwest. Canadian Journal of Zoology, 60/9: 2149-2156.

Linzey, A., D. Linzey. 1971. Mammals of Great Smoky Mountains National Park. Knoxville: The University of Tennessee Press, 114 p.

McAdam, A., S. Boutin, A. Sykes, M. Humphries. 2007. Life histories of red squirrels and their contributions to population growth and lifetime fitness. Ecoscience, 14: 362-369.

McAdam, A., S. Boutin. 2003. Variation in viability selection among cohorts of juvenile red squirrels (Tamiasciurus hudsonicus). Evolution, 57: 1689-1697.

Mercer, J., V. Roth. 2003. The Effects of Cenozoic Global Change on Squirrel Phylogeny. Science, 299/5612: 1568-1572. Accessed January 03, 2012 at http://www.sciencemag.org/content/299/5612/1568.abstract.

Millar, J. 1970. The breeding season and reproductive cycle of the western red squirrel. Canadian Journal of Zoology, 48: 471-473.

Nellis, C. 1969. Sex and age variation in red squirrel skulls from Missoula County, Montana. The Canadian Field Naturalist, 83: 324-330.

Nice, M., C. Nice, D. Ewers. 1954. Comparison of behavioral development in snowshoe hares and red squirrels. Journal of Mammalogy, 37: 64-74.

Pauls, R. 1978. Behavioral strategies relevant to the energy economy of the red squirrel (Tamiasciurus hudsonicus). Canadian Journal of Zoology, 56: 1519-1525.

Price, K., K. Broughton, S. Boutin, A. Sinclair. 1986. Territory size and ownership in red squirrels: response to removals. Canadian Journal of Zoology, 64: 1144-1147.

Pruitt, W., C. Lucier. 1958. Winter activity of red squirrels in interior Alaska. Journal of Mammalogy, 39: 443-444.

Ruff, S., D. Wilson. 1999. The Smithsonian Book of North American Mammals. Washington (D.C.): Smithsonian Institution Press in association with the American Society of Mammalogists.

Smith, C. 1968. The adaptive nature of social organization in the genus of tree squirrels Tamiasciurus. Ecology Monographs, 38: 31-63.

Smith, C., O. Reichman. 1984. The evolution of food caching by birds and mammals. Annual Review of Ecology and Systematics, 15: 329-351.

Steele, M. 1998. Mammalian Species. Pp. 1-9 in Tamiasciurus hudsonicus, Vol. 586. American Society of Mammalogists.

Stuart-Smith, A., S. Boutin. 1995. Behavioral differences between surviving and depredated juvenile red squirrels. Ecoscience, 2: 34-40.

Sullivan, T., H. Coates, L. Jozsa, P. Diggle. 1993. Influence of feeding damage by small mammals on tree growth and wood quality in young lodgepole pine. Canadian Journal of Forest Research, 23: 799-809.

Vache, M., J. Ferron, P. Gouat. 2001. The ability of red squirrels (Tamiasciurus hudsonicus) to discriminate conspecific olfactory signatures. Canadian Journal of Zoology, 79/7: 1296-1300. Accessed January 03, 2012 at http://www.nrcresearchpress.com/doi/abs/10.1139/z01-085?journalCode=cjz.

Walton, M. 1903. A hermit's wild friends. Boston, Massachusetts: D. Estes, 304 p..

Wilson, M., T. De Santo, K. Sieving. 2003. Red squirrels and predation risk to bird nests in northern forests. Canadian Journal of Zoology, 81/7: 1202-1208.

Wirsing, A., T. Steury, D. Murray. 2002. Relationship between body condition and vulnerability to predation in red squirrels and snowshoe hares. Journal of Mammalogy, 83/3: 707-715. Accessed November 03, 2011 at http://www.asmjournals.org/doi/abs/10.1644/1545-1542(2002)083%3C0707%3ARBBCAV%3E2.0.CO%3B2.

Wrigley, R. 1969. Ecological notes on the mammals of southern Quebec. Canadian Field-Naturalist, 83: 201-211.

 
University of Michigan Museum of ZoologyNational Science Foundation

BioKIDS home  |  Questions?  |  Animal Diversity Web  |  Cybertracker Tools

Rubin, C. 2012. "Tamiasciurus hudsonicus" (On-line), Animal Diversity Web. Accessed April 16, 2014 at http://www.biokids.umich.edu/accounts/Tamiasciurus_hudsonicus/

BioKIDS is sponsored in part by the Interagency Education Research Initiative. It is a partnership of the University of Michigan School of Education, University of Michigan Museum of Zoology, and the Detroit Public Schools. This material is based upon work supported by the National Science Foundation under Grant DRL-0628151.
Copyright © 2002-2014, The Regents of the University of Michigan. All rights reserved.

University of Michigan