Cactus mouse

Cactus mice are small cricetid rodents, with large eyes and ears, a pointed snout, and a long monocolor tail. Average dimensions for P. eremicus are as follows: total length, {{cvt|160|to|211|mm}}; length of body, {{cvt|72|to|100|mm}}; length of tail, {{cvt|84|to|120|mm}}; length of hind foot, {{cvt|18|to|22|mm}}; length of ear, {{cvt|13.4|to|20|mm}}; greatest length of skull, {{cvt|22.7|to|25.9|mm}} and zygomatic breadth, {{cvt|11.2|to|13.5|mm}}. Adults weigh between {{convert|18 and 40|g|oz}}. Females weigh slightly more than males and are significantly larger in body length, ear length, length of mandible, and bullar width of skull.

Cactus mice can be identified by having naked soles on their hind feet and almost naked flesh-colored tails (as opposed to the furry bicolored tail common in most Peromyscus species), which are usually the same length or longer than the animals' body length. Their ears are nearly hairless, large, and membranous.

Their fur is long and soft; coloration varies between subspecies and between different populations. Color of fur varies from ochre to cinnamon, with white ventral areas, and the sides and top of head slightly grayish.{{cite journal|last1=Veal|first1=Rita|last2=Caire|first2=William|year=1979|pages=1–6|journal=Mammalian Species|number=118|title=Peromyscus eremicus|publisher=American Society of Mammalogists|url=http://www.science.smith.edu/msi/pdf/i0076-3519-118-01-0001.pdf|doi=10.2307/3503858|jstor=3503858|s2cid=253931519 |access-date=2015-06-24|archive-url=https://web.archive.org/web/20120318014855/http://www.science.smith.edu/msi/pdf/i0076-3519-118-01-0001.pdf|archive-date=2012-03-18|url-status=dead}} Females tend to be slightly paler in color than males, while juveniles appear more gray than their parents.

Cactus mouse longevity is around one year in the wild, but in captivity can live up to 7.4 years.{{cite web|title=Cactus Mouse|last=Bales|first=Rebecca|website=a-z-animals.com|date=13 November 2021 |url=https://a-z-animals.com/animals/cactus-mouse/|access-date=22 August 2024}}

Cactus mice are found in dry desert habitats, steppe, and mountain foothills in arid regions of the southwestern United States and northern Mexico, as well as islands off the coast of the Baja California peninsula and in the Sea of Cortés.{{cite journal | last1 = Brand | first1 = Leonard R. | last2 = Ryckman | first2 = Raymond E. | year = 1968 | title = Laboratory Life Histories of Peromyscus eremicus and Peromyscus interparietalis | journal = Journal of Mammalogy | volume = 49 | issue = 3| pages = 495–501 | doi=10.2307/1378208 | jstor = 1378208 | pmid=5670808}}{{MSW3 |id=13000447 |access-date=2023-08-02}} Low average temperatures and lack of the mesquite species Prosopis juliflora might limit northern expansion.

The cactus mouse occurs sympatrically with five other deermouse species, including the California mouse, canyon mouse, Eva's desert mouse, mesquite mouse, and the western deermouse.

The cactus mouse feeds on seeds, mesquite beans, hackberry nutlets, insects, and green vegetation. In winter, they rely more on insects; on seeds and flowers in the spring; and seeds, leafy greens, and insects in the summer. In autumn, they transition to their winter diet.

Cactus mice, like most muroids, exhibit crepuscular behavior and may even appear in midday, but are mainly nocturnal. They may be less active during the full moon. They have been described as "shy and excitable, and seldom bites when handled". They vocalize a shrill, high-pitched squeak when frightened. In laboratory studies, cactus mice average a running speed of {{convert|8.14|mph}}.{{cite web |title=Peromyscus eremicus cactus mouse |url=https://animaldiversity.org/accounts/Peromyscus_eremicus/ |publisher=Animal Diversity Web |access-date=September 18, 2021}}

Compared to other Peromyscus species, cactus mice have a lower metabolism. This is thought to be an adaptation to arid environments, and maintained by lower activity of the thyroid gland. They may enter torpor when deprived of food in the winter, and food and/or water in the summer. Below {{convert|15|C|F}}, they enter torpor more slowly, which may partially explain their southern distribution. In the laboratory, onset of torpor was observed to occur within half an hour of food deprivation. When dehydrated, they reduce eating to conserve water that would be expended during digestion.{{cite journal |last1=Kay |first1=Jarren |title=Parched cactus mice save water by curbing their appetite |journal=Journal of Experimental Biology |date=December 1, 2023 |volume=226 |issue=23 |doi=10.1242/jeb.246924 |bibcode=2023JExpB.226B6924K |url=https://journals.biologists.com/jeb/article/226/23/jeb246924/335759/Parched-cactus-mice-save-water-by-curbing-their |access-date=September 16, 2024}}

They are important as seed predators and as prey items for other animals.

The mating habits of cactus mice are currently not well studied, but are inferred from other Peromyscus species to be promiscuous. They mate year around, but more so during warmer months. Unlike other muroids, male cactus mice have a simple penis, rather than a complex one, and females have two pairs of teats, rather than three. The number of teats in the female cactus mouse correlates with the number of offspring they can raise in their arid environment.

Females mate after about two months, however, male sexual maturity age is unknown.

File:P. eremicus.jpg]]

Cactus mice are ideal laboratory animals since they keep clean, live well in captivity, and have a high rate of productivity. They have been proposed for physiological and genetic studies.

There are no known negative effects on humans or human-related activities.

Specimens from Southern California have tested positive for hantavirus, however, infections in this species are likely incidental and localized, rather than a common reservoir.Journal of the Society Of Vector Ecologists, Volume 26, Issue 2, December 2001

{{Reflist}}

{{Neotominae}}

{{Taxonbar|from=Q1768203}}

Cactus mouse

Category:Rodents of Mexico

Category:Rodents of the United States

Category:Fauna of the Southwestern United States

Category:Fauna of the Baja California Peninsula

Category:Fauna of the California chaparral and woodlands

Category:Fauna of the Chihuahuan Desert

Category:Fauna of the Colorado Desert

Category:Fauna of the Sonoran Desert

Category:Fauna of Gulf of California islands

Category:Mammals described in 1858

Category:Taxa named by Spencer Fullerton Baird

Category:Taxonomy articles created by Polbot