Sciurus oculatus
Peters's squirrel

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. (Best, 1995)

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. (Best, 1995; Burt, 1952; Kays and Wilson, 2002)

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. (Best, 1995; Davis, 1944)

No studies have determined the average lifespan for Sciurus oculatus.

Little information is available concerning the behavior of this squirrel. Sciurus oculatus is diurnal/crepuscular, most active around sunrise and before sunset. They are expert travelers in trees and can cross gaps greater than 2 m wide.

If this squirrel is similar in behavior to other tree squirrels, social hierarchy may be based on age and body size. Males usually dominate, but females will defend their nests against other females. (Best, 1995; Osborn, 1999; Thorington and Ferrell, 2006)

Home Range

No information was available for home range size of this species. However, in other tree squirrels ranges are larger during mating seasons and usually overlap with other individuals. Female home range sizes are usually smaller than those of males. (Osborn, 1999)

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. (Osborn, 1999; Thorington and Ferrell, 2006)

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. (Best, 1995; Osborn, 1999; Smith, 1998)

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. (Best, 1995; Kays and Wilson, 2002; Sanchez-Cordero et al., 2005)

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. (Best, 1995; Kim, 1966; Osborn, 1999; Thorington and Ferrell, 2006)

There are no known adverse effects of S. oculatus on humans. (Dagnall, Gurnell, and Pepper, 1998; Elbroch, 2003; Thorington and Ferrell, 2006)

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. (Osborn, 1999; Thorington and Ferrell, 2006)

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. (Sanchez-Cordero et al., 2005)

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. (Best, 1995; Osborn, 1999)