American Red Squirrel (Tamiasciurus hudsonicus) - Wiki
American Red Squirrel
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[Photo] TAMIASCIURUS HUDSONICUS http://www.scarysquirrel.org/current/redsbyjohn/ Photos ?? Patriot Plaistow John - distribute freely with credit.
The North American red squirrel (Tamiasciurus hudsonicus) is a medium sized (200???250g) diurnal 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 throughout North America wherever conifers are common. Recently red squirrels have been expanding their range to include primarily hardwood areas (Goheen et al. 2003)
Nomenclature and Identification
North American red squirrels are also referred to as pine squirrels, American red squirrels and chickarees. North American red squirrels should not be confused with Eurasian red squirrels (Sciurus vulgaris), which are of special concern in the UK. Tamiasciurus is Latin for “hoarder squirrel” or "the steward who sits in the shadow of his tail", while hudsonicus refers to Hudson Bay, Canada, where the species was first catalogued by Erxleben in 1771 (Woods 1980). 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; Steele 1998). Red squirrels are also much bigger than chipmunks. The similar Douglas squirrel (T. douglasii) is morphologically similar to red squirrels but has a rust venter and is restricted to the southwestern coast of British Columbia and in the Pacific Northwest of the United States. These two species do not co-occur.
Red squirrels are in the Order Rodentia, Suborder Sciurognathi, Family Sciuridae. Red squirrels are widely distributed throughout North America. There are 25 recognized sub-species of red squirrels (Steele 1998). The sub-species of red squirrel found in the southwest Yukon is T. hudsonicus petulans (Osgood, 1900) (see Steele 1998). A recent phylogeny (Mercer and Roth, 2003) suggests that squirrels as a family can be divided into five major lineages. Two of these clades are monotypic. Red squirrels (Tamiasciurus) fall within one of three remaining clades that includes flying squirrels and other new world tree squirrels (e.g. Sciurus). This clade is thought to have diverged from ground squirrels, chipmunks and marmots approximately 23 million years ago. See Mercer and Roth (2003) for details and interesting discussion of the climatic and tectonic events associated with these diversifications.
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 population was listed as Endangered.
Red squirrels are primarily granivores, but incorporate other food items into their diet opportunistically (Steele 1998). In the Yukon, extensive behavioral observations suggest that white spruce seeds (Picea glauca) comprise over 50% of a red squirrel’s diet (McAdam & Boutin unpub. data), but squirrels have also been observed eating the following: spruce buds and needles, mushrooms,willow (Salix sp.) leaves, poplar(Populus sp.) buds and catkins, bearberry (Arctostaphylos sp.) flowers and berries, and animal material. 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 called a midden and provide energy and nutrients for survival over the winter and reproduction the following spring. White spruce exhibits 2-6 year masting cycles, where a year of superabundant cone production (mast year; Kelly 1994) is followed by several years in which few cones are produced (Nienstaedt & Zasada 1990). Red squirrel territories may contain only one or several middens.
Nests are most commonly constructed of grass in the branches of spruce trees. Nests are also excavated from witches’ broom ??? abnormally dense vegetative growth resulting from a rust disease ??? or cavities in the trunks of spruce or poplar trees. Kluane red squirrels rarely nest below ground. Each individual red squirrel has several nests within its territory and females with young move offspring between nests.
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.
Red squirrels are spontaneous ovulators (Layne 1954, Millar 1970). Females enter estrus for only one day, but venture from their territory prior to ovulation 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 time has been reported to range from 31 to 35 days (Lair 1985). 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 10g. 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 of age.
Juvenile red squirrels must acquire a territory 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 (Berteaux and Boutin 2000). 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 (Boutin et al 2000). Offspring that do not receive a midden from their mother typically settle within 150m (3 territory diameters) from their natal territory (Berteaux and Boutin 2000).
Red squirrels are preyed upon by Canada Lynx (Lynx canadensis), coyote (Canis latrans), great horned owl (Bubo virginianus), northern goshawk (Accipiter gentiles), red-tailed hawk (Buteo jamaicensis), American Marten (Martes americana), fox (Vulpes vulpes), wolf (Canis lupus) and weasel (Mustela sp.).
The red squirrel has been found in a black phase and recently, a white phase (not albino) in Alaska.
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