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.
Communication Channels: visual ; acoustic
Perception Channels: visual ; tactile ; acoustic ; chemical
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.
US Federal List: no special status
CITES: no special status
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.
Negative Impacts: injures humans (bites or stings, causes disease in humans , carries human disease); causes or carries domestic animal disease ; household pest
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.
Positive Impacts: food
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.
Species Used as Host:
Mutualist Species:
Commensal/Parasitic Species:
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.
Animal Foods: birds; eggs; insects; terrestrial non-insect arthropods; terrestrial worms
Plant Foods: leaves; roots and tubers; wood, bark, or stems; seeds, grains, and nuts; lichens
Other Foods: fungus
Primary Diet: herbivore (Granivore )
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.
Biogeographic Regions: neotropical (Native )
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.
Range elevation: 1560 to 2700 m.
Average elevation: 1650-1950 m.
Habitat Regions: temperate ; terrestrial
Terrestrial Biomes: forest
Other Habitat Features: riparian
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.
Average lifespan
Status: wild: Unknown years.
Average lifespan
Status: wild: Unknown years.
Average lifespan
Status: captivity: Unknown years.
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.
Average mass: 684 male, 707 female g.
Range length: 496 to 613 mm.
Average length: 554 mm.
Average basal metabolic rate: 0.003849 W/g cm3.O2/g/hr.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: female larger
Mexican fox squirrels have similar predators to other members of Family Sciuridae. Their known predators include raptors, snakes, small predatory mammals, and humans.
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.
Known Predators:
Anti-predator Adaptations: cryptic
Mating systems within family Sciuridae include polygynous, polyandrous, and polygynandrous, but no specific mating behavior has been observed in Sciurus nayaritensis.
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.
Breeding interval: Mexican fox squirrels breed 1 to 2 times a year.
Breeding season: Their breeding season is in April and early May.
Range number of offspring: 1 to 3.
Average gestation period: 43 days.
Average weaning age: 76 days.
Average time to independence: Unkown days.
Average age at sexual or reproductive maturity (female): 327 days.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; viviparous
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.
Parental Investment: female parental care ; pre-weaning/fledging (Provisioning: Female)
The Mexican fox squirrel (Sciurus nayaritensis) is a species of tree squirrel found throughout the Sierra Madre Occidental of Mexico as far south as Jalisco — and northward into the Chiricahua Mountains of southeastern Arizona, U.S.[3]
This species, or its subspecies, is sometimes called the Nayarit, Apache, or Chiricahua fox squirrel.[3] It has been evaluated as an IUCN Red List Least Concern species.
The Mexican fox squirrel has a grizzled brown back with a yellow to rufous underside, and a charcoal tail frosted with white. Two molts occur each year; the winter pelage is more rufous and the scrotum is often ringed with white.[4] Mass is approximately 700 grams (25 oz).[5]
Mexican fox squirrels are diurnal, non-territorial,[6] and do not hibernate during the winter months.[7]
The Mexican fox squirrel forages extensively on the ground and in the forest canopy for tree seeds, flowers, and fungi. Seeds from the cones from pine, Douglas fir, and true firs are extracted by removing individual cone scales. Acorns and walnuts are also eaten when available, along with a variety of other tree seeds, hypogeous and occasionally epigeous fungi, and insects.[8] Mexican fox squirrels occasionally cache large seeds by scatter-hoarding them in leaf litter and topsoil.[4]
The ecology of the Mexican fox squirrel has not been studied thoroughly, particularly outside the United States. Densities are often very low.[9] Large raptors, canids, felids, procyonids and snakes are likely the major predators.[10]
Mexican fox squirrels typically produce a single small litter of 1 or 2 young in late spring or summer.[9] Mexican fox squirrels nest in ball-shaped dreys composed of sticks and leaves in trees; cavities within large trees are occasionally used, especially by nursing females. They are known to communally nest at times. Mexican fox squirrels are notably silent and appear to prefer to seek cover and remain motionless. If startled, they may bark and chuck from safe locations in trees.[4]
Mexican fox squirrels are found in forests ranging from low elevation (~1,500 metres [ 4,900 ft ]) Madrean forests with a mixture of pine and oak to higher elevation mixed conifer forests < 2,700 metres [ 8,900 ft ].[11] Riparian areas with large cottonwoods and sycamores often harbor the highest densities. In the United States, the squirrel lives only in the Chiricahua Mountains of southeastern Arizona.[12]
The Mexican fox squirrel inhabits forests that were historically maintained by frequent, low-severity fire, and uses areas with open understory and large trees that are typical of such forests.[13]
There are three subspecies:[4]
The Mexican fox squirrel (Sciurus nayaritensis) is a species of tree squirrel found throughout the Sierra Madre Occidental of Mexico as far south as Jalisco — and northward into the Chiricahua Mountains of southeastern Arizona, U.S.
This species, or its subspecies, is sometimes called the Nayarit, Apache, or Chiricahua fox squirrel. It has been evaluated as an IUCN Red List Least Concern species.
