Members of the genus Sciuridae with 28 species currently recognized throughout the old and new world. This genus was originally described by Linnaeus in 1758 and are colloquially referred to as the tree squirrels. These species vary across elevations and temperature but are all arboreal, spending a large portion of their lives in trees, making use of large tails to aid in balance and thermoregulation. The squirrels descend from trees mainly to scavenge. They are diurnal and typically solitary where territories between members are not guarded and are prone to overlapping (Armstrong, Fitzgerald, and Meaney, 2011; Diggins, 2021; Magris, 2005; Thorington Jr. et al., 2012). (Armstrong, et al., 2011; Diggins, 2021; Magris, 2005; Thorington Jr., et al., 2012)comprise the largest genus in the family
Family Sciuridae that the genus is part of likely first appeared in the late Eocene period in North America roughly 36 million years ago. This family expanded into Asia and South America roughly 3.4 million years ago and diverged into five different subfamilies across every continent except Antarctica and Australia (though they were introduced to Australia by humans). The subfamilies Xerinae and Sciurinae further diversified into five tribes, falls under the tribe Sciurini, the Holarctic tree squirrels which is sister taxa to tribe Pteromyini, the flying squirrels (Mendes, Koprowski and Galleti, 2019; Thorington Jr. et al., 2012).
The family Sciuridae is divided into three main types of squirrels; ground squirrels, tree squirrels, and flying squirrels. There are currently 58 genera comprised of 285 species in the family Sciuridae. (Mendes, et al., 2019; Thorington Jr., et al., 2012)is the most speciose genus with 28 recognized species. The genus was originally described by Karl Linnaeus in 1758 (Mendes, Koprowski and Galleti, 2019; Thorington Jr. et al., 2012).
Tree squirrels in the genus Sciurus aestuans) to the largest species averaging 764.3g (Sciurus niger). The males range from 176.0g (Sciurus lis) to 767.5g (Sciurus niger). Body length, excluding the tail, in females ranges from 160.1mm (Sciurus pucheranii) to 289.8mm (Sciurus griseus) and 165.1mm (Sciurus pucheranii) to 308.3mm in males. Tail length also differs among the species, frequently longer than their body length with the longest average in females at 313.3mm (Sciurus flammifer) and shortest at 148.8mm (Sciurus anomalus). In males the longest average tail length is in Sciurus nayaritensis at 280.0mm, the shortest is in Sciurus lis species averaging 152.3mm (Hayssen, 2008; Koprowski, 1998; Thorington Jr. et al., 2012). (Hayssen, 2008; Koprowski, 1998; Thorington Jr., et al., 2012)are small rodents that have long and bushy tails with long legs that have physiological adaptations in their ankles that allow 180 degree rotation. These traits work in tandem to aid their arboreal lifestyles. There is little sexual dimorphism across , most averages in mass and length are close. Females range in size across this genus in the smallest species averaging 200.0g (
Female tree squirrels have a preference for mating in low risk areas that are secluded and hidden from potential predators and other threats. They rarely pursue the males for this reason, maintaining their own safety. While generally accepted to be polygynous, there are records of females trying to maximize their own success, limiting the success of individual males by mating with multiple males and removing copulatory plugs created by semen of the males (Cudworth and Koprowski, 2013; Koprowski, 1998; Wood, Koprowski, and Lurz, 2007). (Cudworth and Koprowski, 2013; Koprowski, 1998; Wood, et al., 2007)
Vocal communication in these tree squirrels serves a multitude of functions in reproduction, predator defense, recognition, and general group unity. Tree squirrels in general are lacking in research regarding vocalization, but several species of (Diggins, 2021; McRae and Green, 2014; McRae and Green, 2017)are known to produce alarm calls, neonatal calls, and agonistic deterrent calls. Different sequences of tail twitches have also been documented as signals and there is some range of specificity in the types of tail twitches given to signal types of predators and whether they are approaching aerially versus terrestrially. Some species have been seen to perceive these vocalizations and tail twitches in tandem to make decisions about retreat and they tend to respond quicker to aerial threats than terrestrial and, when foraging, tend to retreat to and climb trees on the side opposite of the threat. There is also evidence to suggest some of these tree squirrels may not be able to differentiate between types of alarm calls (Diggins, 2021; McRae and Green, 2014; McRae and Green, 2017).
Tree squirrels play an important role in seed dispersal and predation, making their role as mutualists versus antagonists difficult to define. Oak species of trees show evidence of mutualism with (Randler, 2006; Steele, 2008; Steele and Yi, 2020)species through adaptations in seeds to encourage their dispersal, some oak are preferentially cached by these tree squirrels in response to the evolutionary relationship they evolved. These tree squirrel species move seeds into micro caches for later retrieval, burying them. This storage of the seeds also serves to allow germination of the seeds and growth of new trees. Their role as a food source for many species of animals also gives them an important role in maintaining healthy populations of birds and meat eating mammals (Randler, 2006; Steele, 2008; Steele and Yi, 2020).
These tree squirrels benefit humans as use for food and their pelts, as well as the pet trade. (Mendes, et al., 2019)are also desirable inhabitants of parks to humans due to their human tolerance and diurnal activity (Mendes, Koprowski and Galleti, 2019).
Brennen Troyer (author), Colorado State University, Audrey Bowman (editor), Colorado State University.
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.
living in the southern part of the New World. In other words, Central and South America.
living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.
uses sound to communicate
Referring to an animal that lives in trees; tree-climbing.
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. Synapomorphy of the Bilateria.
uses smells or other chemicals to communicate
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
parental care is carried out by females
union of egg and spermatozoan
A substance that provides both nutrients and energy to a living thing.
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
an animal that mainly eats seeds
An animal that eats mainly plants or parts of plants.
a distribution that more or less circles the Arctic, so occurring in both the Nearctic and Palearctic biogeographic regions.
Found in northern North America and northern Europe or Asia.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
a species whose presence or absence strongly affects populations of other species in that area such that the extirpation of the keystone species in an area will result in the ultimate extirpation of many more species in that area (Example: sea otter).
having the capacity to move from one place to another.
This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.
the area in which the animal is naturally found, the region in which it is endemic.
the business of buying and selling animals for people to keep in their homes as pets.
having more than one female as a mate at one time
rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.
breeding is confined to a particular season
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
places a food item in a special place to be eaten later. Also called "hoarding"
living in residential areas on the outskirts of large cities or towns.
a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.
uses touch to communicate
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).
Living on the ground.
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
living in cities and large towns, landscapes dominated by human structures and activity.
uses sight to communicate
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
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