Mexican fox squirrels (Sciurus nayaritensis), have a limited distribution in pine oak forests of the Chiricahua Mountains in Arizona and the Sierra Madre Occidental Mountains of Mexico, as far south as Jalisco. (Best, 1995; Lee and Hoffmeister, 1963)
Mexican fox squirrels are primarily found in riparian habitats where sycamores, ashes, walnuts, and large evergreen oaks grow. The greatest abundance of S. nayaritensis is found in the upper Sonoran zone, located in canyon bottoms that have dense concentrations of trees and shrubs. They tend to avoid oak-cover slopes near the canyons, except when oak mast is plentiful. In the Chiricahua Mountains, S. nayaritensis occur in elevations that range from 1,560 to 2,700 m. In this location, they prefer open apache pine-oak, rather than dense stands of trees. In the San Luis Mountains, S. nayaritensis inhabits areas 1,700 to 2,100 m in elevation. Sciurus nayaritensis are common in the Durango, in oak-pine forests above 2,100 m in elevation. The San Luis Mountains harbor S. nayatirensis at elevations of 1,700 to 1,800 m, where they feed and take shelter in silverleaf oaks. ("Sciurus nayaritensis", 1890; Lee and Hoffmeister, 1963; Linzey, et al., 2008; Pasch and Koprowski, 2005)
Sciurus nayaritensis have bushy tails that are tan to yellow. They have side colorations that are reddish or ochraceous. Their pelage is thick and soft, with long underfur. Legs and feet are reddish or ochraceous in color, with naked soles that are dark purplish. Their coat coloration varies between ranges, seasons, and subspecies. There are three subspecies of Sciurus nayaritensis, Sciurus nayaritensis chiricahuae, Sciurus nayaritensis apache, and Sciurus nayaritensis nayaritensis. The subspecies differ mostly in coloration. Sciurus nayaritensis chiricahuae differs from S. n. apache, primarily in the darkness of the ochraceous underparts, orbital ring and post auricular areas. Sciurus nayaritensis chiricahuae differs from S. n. nayaritensis in color dorsally and ventrally, and also their dark-ochraceous underparts, orbital rings, and post auricular areas. Another feature differentiating S. n. chiricahuae and S. n. nayaritensis is the skull of S. n. chiricahuae, which is shorter and broader, with a rostrum laterally expanded at the distal ends of the nasal. Metabolic rate is unknown for Sciurus nayaritensis, but a closely related species, Sciurus aberti, has a basal metabolic rate of 0.003849 W/g. (Best, 1995; Lee and Hoffmeister, 1963)
Sciurus nayaritensis have a low reproductive potential, which leaves the species with a limited ability to recover quickly from disturbance events. Due to the lack of research on the reproductive process for S. nayaritensis, it may be assumed that they are similar to the closely related sympatric species, Albert's squirrels (Sciurus aberti), Mexican gray squirrels (Sciurus aureogaster), and Collie's squirrels (Sciurus colliaei). Albert's squirrels are able to mate before they are a year old and reproduce 1 to 2 times a year, April through May. After approximately a 43-day gestation period, they have a litter of 1 to 3 young, each weighing approximately 12 grams. Young are weaned in approximately 76 days. ("An Age entry for Sciurus aberti", 2012; Pasch and Koprowski, 2005)
Females are responsible for all of the care of their young, males have no parental investment. There is no information about Mexican fox squirrels, but it is likely that their close relative, Albert's squirrels, are very similar. Female Albert's squirrels wean their young after approximately 76 days; after which, young eat other foods, including tree seeds. ("An Age entry for Sciurus aberti", 2012)
The lifespan of Mexican fox squirrels has not been recorded; however, a close relative, Sciurus aureogaster, was born in the wild and survived to be 11.5 years old in captivity. Due to the lack of information on either species, the lifespan data is far from conclusive. ("An Age entry for Sciurus aberti", 2012)
Mexican fox squirrels live and rest in trees and are diurnal animals that leave their nests after dawn and return before dusk. Mexican fox squirrels spend most of their time on the ground and are not agile in trees. They are not totally built for arboreal life and are clumsy and awkward when climbing up and down tree trunks and along branches. The young routinely fall out of trees and even the adults are not adept climbers. They are secretive in nature and can be difficult to find, especially in the early summer, when females are pregnant or nursing their young. They are also difficult to find in the winter when forests are bare and open. (Best, 1995; "Sciurus nayaritensis", 2012)
Home ranges of Mexican fox squirrels vary between males and females. Males have larger home ranges expanding 30 to 40 hectares. Females, on the other hand, have home ranges of 10 to 20 hectares. During the mating season, home ranges shrink slightly. (Pasch and Koprowski, 2006)
Mexican fox squirrels do not usually vocalize. When they do, it is generally due to disturbance. Their vocalization is usually accompanied by a visual warning, such as flicking their tail. In some subspecies, tail flicking is not accompanied by vocalizations. (Best, 1995)
Mexican fox squirrels are foragers that do not cache food or bury nuts like other members of Family Sciuridae. In the Chiricahua Mountains, Mexican fox squirrels eat pine and Douglas fir seeds, along with acorns and walnuts. When oak mast and other tree seeds are unavailable, they eat roots, bulbs, and buds. In the Durango, Mexican fox squirrels mainly survive by eating pine seeds. Berries, hypogeous fungi, and a few small insects and larvae are occasionally a part of Mexican fox squirrels diet. Rarely, Mexican fox squirrels also eat bark, leaves, and lichens, representing a proportion of less than 0.003 of their total diet. They may also occasionally rob eggs and nestlings from bird nests and eat invertebrates when rummaging on the forest floor. Sciurus nayaritensis chiricahuae may avoid camping sites and other areas that contain human food. They seem to only be attracted to native foods. (Best, 1995; Goldman, 2011; Koprowski and Corse, 2001; "Sciurus nayaritensis", 2012)
Mexican fox squirrels have similar predators to other members of Family Sciuridae. Their known predators include raptors, snakes, small predatory mammals, and humans. (Best, 1995; Kneeland, et al., 1995)
If caught by surprise, Mexican fox squirrels remain motionless to stay undetected by potential predators. If startled or caught in the open, they will retreat to the nearest or tallest tree, where they will hide and remain motionless for more than 45 minutes, or as long as the danger is perceived. Mexican fox squirrels are usually quiet, but will vocalize a warning once they are safely in a tree. Their alarm barks are raspy and gruff and sometimes followed by a whirring screech or scream. A subspecies of S. nayaritensis, S. n. apache are more vocal than S. n. chiricahuae and routinely screams in response to human or hawk activity. Whereas, when S. n. chiricahuae faces disturbance, it flicks its tail but does not vocalize. (Best, 1995; Goldman, 2011; Kneeland, et al., 1995; "Sciurus nayaritensis", 2012)
Mexican fox squirrels do not have a big impact on the ecosystem, but are seed predators and reduce the fitness of the trees on which they feed. They do not cache food, so seed dispersal is limited. They have a commensalistic interaction with oaks and pines, where they make their nests. (Pasch and Koprowski, 2005; "Sciurus nayaritensis", 2012)
Mexican fox squirrels have been exploited by humans in the past for food. They are not a popular game species, but are still hunted in some areas, while in other areas, such as the Chiricahuas, hunting is prohibited. (Goldman, 2011; Pasch and Koprowski, 2005)
Besides carrying parasites such as ticks, lice, and fleas that can be transmitted to humans, Mexican fox squirrels do not have a negative impact on humans. However, they are carriers of the rabies virus, and could transmit the virus to humans or household pets. Toxoplasma gondii can be transmitted to humans from eating undercooked Sciurus nayaritensis meat. Toxoplasma gondii is usually present, but provides no symptoms. It can cause toxoplasmosis, which can be a serious illness in humans when symptoms are shown. (Alvarado-Esquivel, et al., 2008; "Toxoplasmosis", 2005)
Sciurus nayaritensis is listed as a category-two species by the United States Department of the Interior, Fish and Wildlife Service. Category-two species are candidates for official listing as endangered or threatened. (Best, 1995; "Chiricahua Nayarit squirrel (Sciurus nayaritensis chiricahuae)", 2012)
James Stribrny (author), University of Alaska Fairbanks, Laura Prugh (editor), University of Alaska Fairbanks, Leila Siciliano (editor), Michigan State University.
living in the southern part of the New World. In other words, Central and South America.
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.
an animal which directly causes disease in humans. For example, diseases caused by infection of filarial nematodes (elephantiasis and river blindness).
either directly causes, or indirectly transmits, a disease to a domestic animal
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
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.
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).
having the capacity to move from one place to another.
the area in which the animal is naturally found, the region in which it is endemic.
Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).
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
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.
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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Alvarado-Esquivel, C., H. Cruz-Magallanes, R. Esquivel-Cruz, S. Estrada-Martinez, M. Rivas-Gonza ́lez, O. Liesenfeld, S. Martinez-Garcia, E. E. Ramirez, A. Torres-Castorena, A. Castaneda, J. Dubey. 2008. Seroepidemiology of Toxoplasm gondii Infection in Human Adults From Three Rural Communities in Durango State, Mexico. The Journal of Parasitology, Vol. 94 No. 4: 811-816. Accessed November 16, 2012 at http://naldc.nal.usda.gov/download/20549/PDF.
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Lee, R., D. Hoffmeister. 1963. Status of Certain Fox Squirrels in Mexico and Arizona. Proceedings of the Biological Society of Washington, Vol. 76: 181-190. Accessed November 16, 2012 at http://biostor.org/reference/82603.
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