Cactus mouse

Peromyscus eremicus is found in the Southwestern United States, northern Mexico, Baja California and several nearby islands. The subspecies Peromyscus eremicus eremicus can be found farther north in Utah. Peromyscus eremicus often lives around cacti, hence its name cactus mouse. It lives in steppes and semi-arid deserts. Peromyscus eremicus may be found in the rocky foothills of desert mountain ranges, and the subspecies found in Utah (Peromyscus eremicus eremicus) can be semi-arboreal and inhabit shrubs. Cactus mice build nests in self-dug tunnels, lodges of other rodents, brickwork buildings, and piles of rock or brushwood.

Cactus mouse
The range of masses given includes both male and females, as little research has been conducted on sexual dimorphisms in size. Average body length (not including the tail) is 8.0 to 9.0 centimeters and the average tail length is 10.0 to 14.0 centimeters. This species is noted for its unusually long tail. A possible function for such a long tail is body temperature regulation. The color of Peromyscus eremicus' thick pelage appears to vary. Parker remarks that Peromyscus eremicus has a pale gray back. The Species Information Library, however, reports that species have been found in New Mexico with a spectrum of fur shades between pale yellowish and blackish. A possible explanation is that two subspecies, one with darker fur (Peromyscus eremicus anthonyi) and lighter fur (Peromyscus eremicus eremicus) have been interbreeding in New Mexico. Nowak describes the underparts of the cactus mouse as white or near-white. The tail is usually less haired than that of other mice in its genus. Cactus mice have naked soles on their hind feet, which distinguish them from other Southwestern Peromyscus species. Facial and skull characteristics are also important in distinguishing the cactus mouse from other Peromyscus mice. Peromyscus eremicus has small ears and one to two upper molars with usually one mesoloph. The zygomatic arches of the skull of the cactus mouse are weak and not flared out, and the auditory bulla are not greatly inflated. The nasal branches of the premaxilla extend posteriorly behind the nasals.

Reproduction
The gestation period for Peromyscus eremicus is twenty-one days. The average litter size is two to three offspring, and their average weight at birth is 2.1 to 2.9 grams. The female has two pairs of teats rather than three, which has been suggested to correlate with the number of offspring. The weaning period is unknown. Females reach sexual maturity after about two months, and the age of male sexual maturity is unknown. The average age for the female cactus mouse's first estrus is 39.2 days. Females have been observed to reproduce continuously and year round, and specifically during January, February, June, and September in central Arizona.

Behavior
Peromyscus eremicus is nocturnal. In Peromyscus species, males and females usually live together in pairs. There is a high degree of monogamy. The vocalizations of Peromyscus species have been described as thin squeaks and shrill buzzings. Most species, when excited, thump their forefeet rapidly upon the ground to produce a drumming noise. The cactus mouse has been described as shy and excitable, and seldom bites when handled. In a study of running speed, four males and three females averaged a speed of 13.1 kilometers per hour. Speed is important in more open habitats as a method of predator evasion.

Food Habits
The cactus mouse is an omnivore and is believed to be an opportunistic eater. It eats mainly fruits and blossoms of shrubs and annual seeds such as Hackberry (Ulmaceae) and Mesquite (Leguminoseae). Pinus and Juniperus seeds are eaten during the winter. In addition, the cactus mouse consumes insects, leaves, and green vegetation. In captivity they should be offered a complete diet of rodent lab blocks, and rat or mouse mix, with bits of fruit or veggies regularly. Cheerios or wheat bread are great treats, in small quantities. Do NOT feed chocolate, fried foods, salted foods, candy or junk food! They may enjoy crickets and mealworms if they are captive bred, never feed wild insects as they may carry parasites. Vitamins, like Nutri-Cal are a good addition to their diet, and added calcium during nursing and growth due to demands on their systems at those times, but take care not to overdo it. Water bottles should be used to proved constant, clean water. Ceramic or stoneware food dishes work well for keeping seeds or fresh foods off the floor, and a wire mesh hopper that allows them to eat the lab blocks through without extra waste.

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