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This squirrel's name is derived from the Latin Sciurus meaning "squirrel" and oculus referring to the eye. It also goes by names black-backed, Toluca, and spectacled squirrel.

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Mowbray, W. 2008. "Sciurus oculatus" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Sciurus_oculatus.html
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Whitney Mowbray, Radford University
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Karen Francl, Radford University
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Tanya Dewey, Animal Diversity Web
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Behavior

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No information was found directly relating to Sciurus oculatus. However, tree squirrels rely heavily on vision to perceive their environment. Their retinas contain layers of both rod and cone cells. They can see yellow, red, and green, and can also distinguish blue from green. However, they lack a tapetum which allows some animals to see better in low light. They do have yellow tinted lenses to protect them from damaging ultraviolet rays in the daylight hours. Tree squirrels also process visual information quite rapidly; one study showed they process visual information at twice the speed of an average human. Like other mammals, they also use chemosensation and touch as important modes of perception. Squirrels have whiskers on their faces and wrists to help in navigating their complex environment.

Communication Channels: visual ; acoustic ; chemical

Other Communication Modes: scent marks

Perception Channels: visual ; tactile ; acoustic ; chemical

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Mowbray, W. 2008. "Sciurus oculatus" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Sciurus_oculatus.html
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Whitney Mowbray, Radford University
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Karen Francl, Radford University
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Tanya Dewey, Animal Diversity Web
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Conservation Status

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Sciurus oculatus has suffered severe habitat loss through logging, burning, and clearing of forest for agriculture in Mexico. As of 1991, it was considered a "fragile" species, though, as of 1996, IUCN listed it as "Lowest Risk/Least Concern." The IUCN web page recognizes that this listing is out of date.

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

IUCN Red List of Threatened Species: least concern

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Mowbray, W. 2008. "Sciurus oculatus" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Sciurus_oculatus.html
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Whitney Mowbray, Radford University
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Karen Francl, Radford University
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Tanya Dewey, Animal Diversity Web
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Benefits

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There are no known adverse effects of S. oculatus on humans.

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Mowbray, W. 2008. "Sciurus oculatus" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Sciurus_oculatus.html
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Whitney Mowbray, Radford University
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Karen Francl, Radford University
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Tanya Dewey, Animal Diversity Web
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Benefits

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No information was found directly related to the hunting of Sciurus oculatus, but is assumed that they are hunted for food and disperse seeds like other squirrel species.

Positive Impacts: food ; body parts are source of valuable material

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bibliographic citation
Mowbray, W. 2008. "Sciurus oculatus" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Sciurus_oculatus.html
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Whitney Mowbray, Radford University
editor
Karen Francl, Radford University
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Tanya Dewey, Animal Diversity Web
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Associations

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Tree squirrels (Sciurus) in general are host to a wide range of parasites such as botflies, fleas, ticks, mites, lice, roundworms, and tapeworms and are also vulnerable to rabies, pox, fibroma, monkeypox, and parapox viruses. The genus Enderleinellus is a parasite that is found on Sciurus oculatus and occurs exclusively on hosts of the family Sciuridae. Squirrels also disperse the seeds of plants through their seed caching behavior and via attachment to their fur.

Ecosystem Impact: disperses seeds

Commensal/Parasitic Species:

  • squirrel louse (Enderleinellus longiceps)
  • squirrel louse (Enderleinellus oculatus)
  • botflies (Oestridae)
  • fleas (Siphonaptera)
  • ticks and mites (Acari)
  • roundworms (Nematoda)
  • tapeworms (Cestoda)
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bibliographic citation
Mowbray, W. 2008. "Sciurus oculatus" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Sciurus_oculatus.html
author
Whitney Mowbray, Radford University
editor
Karen Francl, Radford University
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Tanya Dewey, Animal Diversity Web
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Trophic Strategy

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No specific studies were found that examined food habits of S. oculatus, however Best (1995) noted that some populations of S. oculatus consumed acorns and wild figs, while others rely primarily on pine nuts. Tree squirrels in general prefer foods that can be eaten quickly, are digestible, and provide high amounts of energy. Squirrels often eat animal foods as well as seeds and fruit. They drink surface water when it is available, however, in its absence they can extract enough moisture from their food with the exception of pregnant or nursing females.

Plant Foods: seeds, grains, and nuts; fruit

Foraging Behavior: stores or caches food

Primary Diet: herbivore (Frugivore , Granivore )

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Mowbray, W. 2008. "Sciurus oculatus" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Sciurus_oculatus.html
author
Whitney Mowbray, Radford University
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Karen Francl, Radford University
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Tanya Dewey, Animal Diversity Web
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Distribution

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Sciurus oculatus is a squirrel species endemic to Mexico. It ranges within the Trans-Mexican neovolcanic belt and the Mexican Plateau from Morelos, Distrito Federal, Mexico, Puebla and Veracruz northward into San Luis Potosi. In the summer months, Peter's squirrels are common in Alvarez, inhabiting the low oak forest of the mountainsides. As temperatures cool, they move to nearby valleys by late October. There are three recognized subspecies within this range: S. o. oculatus, S. o. shawi, and S. o. tolucae.

Biogeographic Regions: nearctic (Native )

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Mowbray, W. 2008. "Sciurus oculatus" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Sciurus_oculatus.html
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Whitney Mowbray, Radford University
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Karen Francl, Radford University
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Tanya Dewey, Animal Diversity Web
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Habitat

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Sciurus oculatus prefer habitats of oak (Quercus), pine (Pinus), and fir (Abies, Pseudotsuga) forest. Populations tend to occupy different tree species depending on their location and time of year. In the summer months, some populations live in low oak trees on mountainsides in Alvarez. By late October, however, this group migrates to Veracruz and usually occupies pine forests at higher elevations or on the timbered slopes of Cofre de Perote and Mount Orizaba.

Range elevation: 1500 to 3600 m.

Average elevation: 1800 m.

Habitat Regions: temperate ; tropical ; terrestrial

Terrestrial Biomes: forest ; mountains

Other Habitat Features: urban ; suburban

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Mowbray, W. 2008. "Sciurus oculatus" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Sciurus_oculatus.html
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Whitney Mowbray, Radford University
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Karen Francl, Radford University
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Tanya Dewey, Animal Diversity Web
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Life Expectancy

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No studies have determined the average lifespan for Sciurus oculatus.

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bibliographic citation
Mowbray, W. 2008. "Sciurus oculatus" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Sciurus_oculatus.html
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Whitney Mowbray, Radford University
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Karen Francl, Radford University
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Tanya Dewey, Animal Diversity Web
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Morphology

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Peter's squirrels are large tree squirrels with an average weight of 638 grams. They are mostly gray with white ears and a white underside. Peter’s squirrels have black tails and a 25 to 50 mm wide black stripe that extends from the back of the head to the tail. They have four pairs of mammae (one pectoral, one inguinal and two abdominal). Subspecies S. o. oculatus, S. o. tolucae, and S. o. shawi vary in total, tail, and hind foot lengths. The average total lengths for the subspecies are: S. o. oculatus 543mm, S. o. tolucae 531mm, and S. o. shawi 508mm. Average tail length of S. o. oculatus is 269 mm, S. o. tolucae is 263 mm, and S. o. shawi is 256 mm. Average hind foot length for S. o. oculatus is 73 mm, S. o. tolucae is 69 mm, and S. o. shawi is 68 mm.

Average mass: 638 g.

Range length: 530 to 560 mm.

Average length: 543 mm.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: sexes alike; male larger

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Mowbray, W. 2008. "Sciurus oculatus" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Sciurus_oculatus.html
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Whitney Mowbray, Radford University
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Karen Francl, Radford University
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Tanya Dewey, Animal Diversity Web
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Associations

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No other information was found directly relating to S. oculatus, but other tree squirrels (Sciurus) are preyed on by a number of predatory bird and mammal species. Large raptors and arboreal carnivores, such as Bassariscus species, are also likely predators of S. oculatus.

Known Predators:

  • humans (Homo sapiens)
  • diurnal raptors (Falconiformes)
  • Bassariscus species

Anti-predator Adaptations: cryptic

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bibliographic citation
Mowbray, W. 2008. "Sciurus oculatus" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Sciurus_oculatus.html
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Whitney Mowbray, Radford University
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Karen Francl, Radford University
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Tanya Dewey, Animal Diversity Web
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Reproduction

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No specific studies were found which examined the mating systems of Peter's squirrels. However, detailed information is available for a closely related species, eastern gray squirrels (Sciurus carolinensis). In this species, male and female squirrels communicate reproductive information through scent. Males leave their normal home range to pursue females when the females are near estrus. Males then follow females for about 5 days before she goes into estrus and attract her attention through a unique sneeze-like mating call. On the day of a female's estrus many males aggressively pursue her in a "mating chase." She then chooses a male with which to mate. After copulation, the male's semen forms a plug, in an attempt to prevent further mating. However, in as little as 20 seconds, females may remove the plug by eating or discarding it. Therefore, eastern gray squirrel females remain in estrus for about a day and may breed with several males. It is likely that the mating system of Sciurus oculatus is similar.

Mating System: polygynandrous (promiscuous)

Specific information on the reproductive behavior of Peter's squirrels is not available. However, their close relative, eastern gray squirrels (Sciurus carolinensis) are seasonal breeders; their mating activities are triggered by changes in day length and their productivity is linked strongly to food supply. A female squirrel usually produces her first litter at about a year old, unless food is scarce. In that case, they may wait until their second year to breed.

Breeding interval: Yearly, probably starting at age 2.

Breeding season: Female Sciurus oculatus have had enlarged mammae in July and August, indicating litters earlier in the season.

Average age at sexual or reproductive maturity (female): 2 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; viviparous

Information on parental investment in Peter's squirrels has not been documented. However, eastern grey squirrels (Sciurus carolinensis) depend on their mother's milk for 7 to 10 weeks and are born in strongly-built leaf nest held together by a woven framework of twigs or in tree cavities.

Parental Investment: altricial ; pre-fertilization (Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Male, Female); pre-independence (Protecting: Male, Female)

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Mowbray, W. 2008. "Sciurus oculatus" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Sciurus_oculatus.html
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Whitney Mowbray, Radford University
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Karen Francl, Radford University
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Tanya Dewey, Animal Diversity Web
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Peters's squirrel

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Peters's squirrel (Sciurus oculatus) is a tree squirrel in the genus Sciurus endemic to Mexico. It was first described by the German naturalist and explorer Wilhelm Peters in 1863. Three subspecies are recognised. It is a common species, and the IUCN has rated its conservation status as being of "least concern".

Description

Peters's squirrel is a large, mainly arboreal squirrel. The head-and-body length is 508 to 560 mm (20 to 22 in) with a tail of about 260 mm (10 in), and a weight of around 550 to 750 g (19 to 26 oz). The colouring varies somewhat between the subspecies but it is generally grey dorsally, the hairs having dark brown or black bases, and white or cream ventrally. The upper part of the tail is blackish while the underside is dark with white tips to the hairs. There is a pale ring of skin around the eyes, and an important identifying feature is the dentition, with one fewer upper premolars than other related species.[3]

Distribution and habitat

This squirrel is endemic to Mexico where it is found in the provinces of Guanajuato, Hidalgo, México State, Puebla, Querétaro, San Luis Potosí and Veracruz. It inhabits pine and oak forests, at altitudes between about 1,500 and 3,600 m (4,900 and 11,800 ft). It is also found on arid mountainsides and in valleys with arroyos.[1]

Ecology

The species is diurnal and usually lives a solitary life. During the summer these squirrels are frequently sighted, but not during the winter. The diet mainly consists of acorns and the seeds of pines, but other fruits and seeds are also eaten including wild figs and plums. The mating season seems to take place in summer and at this time, up to twenty individuals may accumulate in one tree, but little is known of their breeding behaviour. In parts of their range, they come into contact with the Mexican gray squirrel (Sciurus aureogaster) and the southern flying squirrel (Glaucomys volans).[3]

Status

Peters's squirrel has a wide range and is commonly seen in summer. No particular threats have been identified and it is present in a number of protected areas, so the International Union for Conservation of Nature has rated its conservation status as being of "least concern".[1]

References

  1. ^ a b c Álvarez-Castañeda, S.T.; Castro-Arellano, I.; Lacher, T.; Vázquez, E. (2016). "Sciurus oculatus". IUCN Red List of Threatened Species. 2016: e.T20017A22246721. doi:10.2305/IUCN.UK.2016-2.RLTS.T20017A22246721.en. Retrieved 12 November 2021.
  2. ^ Thorington, R.W., Jr.; Hoffman, R.S. (2005). "Sciurus (Sciurus) oculatus". In Wilson, D.E.; Reeder, D.M (eds.). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Johns Hopkins University Press. pp. 762–763. ISBN 978-0-8018-8221-0. OCLC 62265494.
  3. ^ a b Ceballos, Gerardo (2014). Mammals of Mexico. JHU Press. pp. 183–184. ISBN 978-1-4214-0843-9.
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Peters's squirrel: Brief Summary

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Peters's squirrel (Sciurus oculatus) is a tree squirrel in the genus Sciurus endemic to Mexico. It was first described by the German naturalist and explorer Wilhelm Peters in 1863. Three subspecies are recognised. It is a common species, and the IUCN has rated its conservation status as being of "least concern".

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