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