American Red Squirrel
Overview
 
The American Red Squirrel (Tamiasciurus hudsonicus) is one of three species of tree squirrel
Squirrel
Squirrels belong to a large family of small or medium-sized rodents called the Sciuridae. The family includes tree squirrels, ground squirrels, chipmunks, marmots , flying squirrels, and prairie dogs. Squirrels are indigenous to the Americas, Eurasia, and Africa and have been introduced to Australia...

 currently classified in the genus Tamiasciurus and known as pine squirrels (the other are the Douglas Squirrel
Douglas Squirrel
The Douglas Squirrel is a pine squirrel found in the Pacific coastal states and provinces of North America. It is sometimes known as the Chickaree or Pine Squirrel, but since Chickaree is also used for the American Red Squirrel and Pine Squirrel for the genus Tamiasciurus, these alternative names...

 T. douglasii and Mearns's Squirrel
Mearns's Squirrel
Mearns's Squirrel is a species of rodent in the family Sciuridae. It is endemic to pine and fir forests at altitudes of in central Baja California in Mexico. This endangered species occurs in low densities and is threatened by habitat loss...

 T. mearnsi). American Red Squirrels are also referred to as Pine Squirrels, North American Red Squirrels, and Chickarees. It is a medium sized (200–250 g) diurnal
Diurnal animal
Diurnality is a plant or animal behavior characterized by activity during the day and sleeping at night.-In animals:Animals that are not diurnal might be nocturnal or crepuscular . Many animal species are diurnal, including many mammals, insects, reptiles and birds...

 mammal that defends a year-round exclusive territory.
Encyclopedia
The American Red Squirrel (Tamiasciurus hudsonicus) is one of three species of tree squirrel
Squirrel
Squirrels belong to a large family of small or medium-sized rodents called the Sciuridae. The family includes tree squirrels, ground squirrels, chipmunks, marmots , flying squirrels, and prairie dogs. Squirrels are indigenous to the Americas, Eurasia, and Africa and have been introduced to Australia...

 currently classified in the genus Tamiasciurus and known as pine squirrels (the other are the Douglas Squirrel
Douglas Squirrel
The Douglas Squirrel is a pine squirrel found in the Pacific coastal states and provinces of North America. It is sometimes known as the Chickaree or Pine Squirrel, but since Chickaree is also used for the American Red Squirrel and Pine Squirrel for the genus Tamiasciurus, these alternative names...

 T. douglasii and Mearns's Squirrel
Mearns's Squirrel
Mearns's Squirrel is a species of rodent in the family Sciuridae. It is endemic to pine and fir forests at altitudes of in central Baja California in Mexico. This endangered species occurs in low densities and is threatened by habitat loss...

 T. mearnsi). American Red Squirrels are also referred to as Pine Squirrels, North American Red Squirrels, and Chickarees. It is a medium sized (200–250 g) diurnal
Diurnal animal
Diurnality is a plant or animal behavior characterized by activity during the day and sleeping at night.-In animals:Animals that are not diurnal might be nocturnal or crepuscular . Many animal species are diurnal, including many mammals, insects, reptiles and birds...

 mammal that defends a year-round exclusive territory. The diet of these tree squirrels is specialized on the seeds of conifer cones. As such, they are widely distributed across North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

 wherever conifers are common, except on the Pacific coasts where they are replaced by Douglas Squirrels. Recently, American Red Squirrels have been expanding their range to include primarily hardwood areas.

Taxonomy

American Red Squirrels should not be confused with Eurasian Red Squirrels (Sciurus vulgaris); since the ranges of these species do not overlap, they are both commonly referred to as "red squirrels" in the areas where they are native. The specific epithet hudsonicus refers to Hudson Bay
Hudson Bay
Hudson Bay , sometimes called Hudson's Bay, is a large body of saltwater in northeastern Canada. It drains a very large area, about , that includes parts of Ontario, Quebec, Saskatchewan, Alberta, most of Manitoba, southeastern Nunavut, as well as parts of North Dakota, South Dakota, Minnesota,...

, Canada, where the species was first catalogued by Erxleben in 1771. A recent phylogeny suggests that squirrels as a family can be divided into five major lineages. Two of these clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...

s are monotypic
Monotypic
In biology, a monotypic taxon is a taxonomic group with only one biological type. The term's usage differs slightly between botany and zoology. The term monotypic has a separate use in conservation biology, monotypic habitat, regarding species habitat conversion eliminating biodiversity and...

. Red squirrels (Tamiasciurus) fall within one of three remaining clades that includes flying squirrel
Flying squirrel
Flying squirrels, scientifically known as Pteromyini or Petauristini, are a tribe of 44 species of squirrels .- Description :...

s and other tree squirrels (e.g., Sciurus). This clade is thought to have diverged from ground squirrel
Ground squirrel
The ground squirrels are members of the squirrel family of rodents which generally live on or in the ground, rather than trees. The term is most often used for the medium-sized ground squirrels, as the larger ones are more commonly known as marmots or prairie dogs, while the smaller and less...

s, chipmunk
Chipmunk
Chipmunks are small striped squirrels native to North America and Asia. They are usually classed either as a single genus with three subgenera, or as three genera.-Etymology and taxonomy:...

s and marmot
Marmot
The marmots are a genus, Marmota, of squirrels. There are 14 species in this genus.Marmots are generally large ground squirrels. Those most often referred to as marmots tend to live in mountainous areas such as the Alps, northern Apennines, Eurasian steppes, Carpathians, Tatras, and Pyrenees in...

s. There are 25 recognized sub-species of red squirrels.

Description

Red squirrels can be easily identified from other North American tree squirrels by their smaller size, territorial behavior and reddish fur with a white venter (under-belly). Red squirrels are also somewhat larger than chipmunks. The Douglas Squirrel
Douglas Squirrel
The Douglas Squirrel is a pine squirrel found in the Pacific coastal states and provinces of North America. It is sometimes known as the Chickaree or Pine Squirrel, but since Chickaree is also used for the American Red Squirrel and Pine Squirrel for the genus Tamiasciurus, these alternative names...

 is morphologically similar to the American Red Squirrels but has a rust venter and is restricted to the southwestern coast of British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...

 and in the Pacific Northwest
Pacific Northwest
The Pacific Northwest is a region in northwestern North America, bounded by the Pacific Ocean to the west and, loosely, by the Rocky Mountains on the east. Definitions of the region vary and there is no commonly agreed upon boundary, even among Pacific Northwesterners. A common concept of the...

 of the United States. These two species do not co-occur.

The American Red Squirrel has been found in a black phase and recently, a white phase (not albino) in Alaska.

Distribution

American Red Squirrels are widely distributed across North America. Their range includes most of Canada, and extends into the United States in the Rocky Mountains, the North Central and North East. There are 25 recognized sub-species of red squirrels.

American Red Squirrels are abundant and not of conservation concern throughout much of their range. However, an isolated population of red squirrels in Arizona has experienced considerable declines in population size. In 1987, this portion of the population was listed as endangered
Endangered species
An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...

.

Feeding

American Red Squirrels are primarily granivores, but incorporate other food items into their diet opportunistically. In the Yukon, extensive behavioral observations suggest that white spruce
White Spruce
Picea glauca is a species of spruce native to boreal forests in the north of North America, from central Alaska east to Newfoundland, and south to northern Montana, Minnesota, Wisconsin, Michigan, upstate New York, Vermont, New Hampshire, and Maine; there is also an isolated population in the...

 seeds (Picea glauca) comprise over 50% of a red squirrel’s diet (McAdam & Boutin unpub. data), but squirrels have also been observed eating spruce buds and needles, mushrooms, willow
Willow
Willows, sallows, and osiers form the genus Salix, around 400 species of deciduous trees and shrubs, found primarily on moist soils in cold and temperate regions of the Northern Hemisphere...

 (Salix sp.) leaves, poplar
Poplar
Populus is a genus of 25–35 species of deciduous flowering plants in the family Salicaceae, native to most of the Northern Hemisphere. English names variously applied to different species include poplar , aspen, and cottonwood....

 (Populus sp.) buds and catkins, bearberry
Bearberry
Bearberries are three species of dwarf shrubs in the genus Arctostaphylos. Unlike the other species of Arctostaphylos , they are adapted to Arctic and sub-Arctic climates, and have a circumpolar distribution in northern North America, Asia and Europe, one with a small highly disjunctive population...

 (Arctostaphylos sp.) flowers and berries, and animal material such as bird eggs or even snowshoe hare leverets (baby snowshoe hares). White spruce cones mature in late July and are harvested by red squirrels in August and September. These harvested cones are stored in a central cache and provide energy and nutrients for survival over the winter and reproduction the following spring. The fallen scales from consumed seed cones can collect in piles, called middens, more than a meter across. White spruce exhibits 2–6 year masting cycles, where a year of superabundant cone production (mast year) is followed by several years in which few cones are produced. American Red Squirrel territories may contain only one or several middens.

Red squirrels clip and gather truffles/mushrooms and place them amongst the branches of trees to dry them in the sun.

Reproduction

American Red Squirrels are spontaneous ovulators
Ovulation
Ovulation is the process in a female's menstrual cycle by which a mature ovarian follicle ruptures and discharges an ovum . Ovulation also occurs in the estrous cycle of other female mammals, which differs in many fundamental ways from the menstrual cycle...

. Females enter estrus for only one day, but venture from their territory prior to ovulation
Ovulation
Ovulation is the process in a female's menstrual cycle by which a mature ovarian follicle ruptures and discharges an ovum . Ovulation also occurs in the estrous cycle of other female mammals, which differs in many fundamental ways from the menstrual cycle...

 and these exploratory forays may serve to advertise their upcoming estrus. On the day of estrus, females are chased by several males in an extended mating chase. Males compete with one another for the opportunity to mate with the estrous female. Estrous females will mate with 4–16 males. Gestation
Gestation
Gestation is the carrying of an embryo or fetus inside a female viviparous animal. Mammals during pregnancy can have one or more gestations at the same time ....

 has been reported to range from 31 to 35 days. Females can breed for the first time at one year of age but some females delay breeding until two years of age or older. Most females produce only one litter, but in some years reproduction is skipped while in other years some females attempted to breed twice. Litter sizes typically range from 1 to 5, but most litters contain 3 or 4 offspring. Offspring are pink and hairless at birth and weigh approximately 10 g. Offspring grow at approximately 1.8 g/day while nursing but do not reach adult body size until 125 days of age. Offspring first emerge from their natal nest at around 42 days of age but continue to nurse until approximately 70 days.

Nests are most commonly constructed of grass in the branches of spruce
Spruce
A spruce is a tree of the genus Picea , a genus of about 35 species of coniferous evergreen trees in the Family Pinaceae, found in the northern temperate and boreal regions of the earth. Spruces are large trees, from tall when mature, and can be distinguished by their whorled branches and conical...

 trees. Nests are also excavated from witches’ broom—abnormally dense vegetative growth resulting from a rust disease—or cavities in the trunks of spruce, poplar
Poplar
Populus is a genus of 25–35 species of deciduous flowering plants in the family Salicaceae, native to most of the Northern Hemisphere. English names variously applied to different species include poplar , aspen, and cottonwood....

 trees, and walnut
Walnut
Juglans is a plant genus of the family Juglandaceae, the seeds of which are known as walnuts. They are deciduous trees, 10–40 meters tall , with pinnate leaves 200–900 millimetres long , with 5–25 leaflets; the shoots have chambered pith, a character shared with the wingnuts , but not the hickories...

. Kluane
Kluane National Park and Reserve
Kluane National Park and Reserve are two units of Canada's national park system, located in the extreme southwestern corner of Yukon Territory. Kluane National Park Reserve was established in 1972, covering 22,016 square kilometres....

 red squirrels rarely nest below ground. Each individual squirrel has several nests within its territory and females with young move offspring between nests. Some behavior has been reported within human dwellings using insulation as nesting fodder.

In the June 2008 issue of Animal Behavior, researchers, studying a population of red squirrels over a period of three years in southwest Yukon
Yukon
Yukon is the westernmost and smallest of Canada's three federal territories. It was named after the Yukon River. The word Yukon means "Great River" in Gwich’in....

, reported that female red squirrels showed high levels of multi-male mating and would even mate with males that had similar genetic relatedness, basically mating with their relatives. While males mating with multiple females is quite common in the animal kingdom, females that multi-mate is much harder to explain. Through their observations, it was noted that when female red squirrels chose a mate to copulate with, genetic relatedness did not play a factor. The researchers also found that the relatedness of parents had no effect on the neonatal mass and growth rate of their offspring, nor did it affect the survival rate of offspring to one year of age.

Dispersal and survival

Juvenile American Red Squirrels must acquire a territory
Territory (animal)
In ethology the term territory refers to any sociographical area that an animal of a particular species consistently defends against conspecifics...

 and midden prior to their first winter. Juveniles without a midden do not survive their first winter. Offspring can acquire a territory by competing for a vacant territory, creating a new territory or by receiving all or part of a territory from their mother. This somewhat rare (15% of litters) female behavior is referred to as breeding dispersal or bequeathal and is a form of maternal investment in offspring. The prevalence of this behavior is related to the abundance of food resources and the age of the mother. In some cases females will acquire additional middens prior to reproduction, which they later bequeath to their offspring. Offspring that do not receive a midden from their mother typically settle within 150 m (3 territory diameters) from their natal territory.

American Red Squirrels experience severe early mortality (on average only 22% survive to one year of age). The survival probability, however, increases to age three at which point it begins to decrease again. Females that survive to one year of age have a life expectancy of 2.3 years and a maximum lifespan of eight years.

American Red Squirrels are preyed upon by Canadian Lynx (Lynx canadensis), Bobcat
Bobcat
The bobcat is a North American mammal of the cat family Felidae, appearing during the Irvingtonian stage of around 1.8 million years ago . With twelve recognized subspecies, it ranges from southern Canada to northern Mexico, including most of the continental United States...

 (Lynx rufus), Coyote
Coyote
The coyote , also known as the American jackal or the prairie wolf, is a species of canine found throughout North and Central America, ranging from Panama in the south, north through Mexico, the United States and Canada...

 (Canis latrans), Great Horned Owl
Great Horned Owl
The Great Horned Owl, , also known as the Tiger Owl, is a large owl native to the Americas. It is an adaptable bird with a vast range and is the most widely distributed true owl in the Americas.-Description:...

 (Bubo virginianus), Northern Goshawk (Accipiter gentilis), Red-tailed Hawk
Red-tailed Hawk
The Red-tailed Hawk is a bird of prey, one of three species colloquially known in the United States as the "chickenhawk," though it rarely preys on standard sized chickens. It breeds throughout most of North America, from western Alaska and northern Canada to as far south as Panama and the West...

 (Buteo jamaicensis), American Crow
American Crow
The American Crow is a large passerine bird species of the family Corvidae. It is a common bird found throughout much of North America...

 (Corvus brachyrynchos), American Marten
American Marten
The American marten is a North American member of the family Mustelidae, sometimes referred to as the pine marten. The name "pine marten" is derived from the common but distinct Eurasian species of Martes...

 (Martes americana), Red Fox
Red Fox
The red fox is the largest of the true foxes, as well as being the most geographically spread member of the Carnivora, being distributed across the entire northern hemisphere from the Arctic Circle to North Africa, Central America, and the steppes of Asia...

 (Vulpes vulpes), Gray Fox
Gray Fox
The gray fox is a mammal of the order Carnivora ranging throughout most of the southern half of North America from southern Canada to the northern part of South America...

 (Urocyon cinereoargenteus), Wolf (Canis lupus) and weasel
Weasel
Weasels are mammals forming the genus Mustela of the Mustelidae family. They are small, active predators, long and slender with short legs....

(Mustela sp.). However, predation on adult American Red Squirrels is thought to be relatively low compared to other mammals living in the North (e.g., snowshoe hares).

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
x
OK