Chaetodipus pernix
| Sinaloan pocket mouse | |
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| Pictured: Desert pocket mouse, closest sister species to Sinaloan pocket mouse | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Rodentia |
| Family: | Heteromyidae |
| Genus: | Chaetodipus |
| Species: | C. pernix |
| Binomial name | |
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Chaetodipus pernix (J. A. Allen, 1898) |
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The Sinaloan pocket mouse (Chaetodipus pernix) is one of 17 species of pocket mice in the genus Chaetodipus. Two subspecies of C. pernix are recognized, C. p. pernix and C. p. rostratus, all are endemic to Mexico.
This small mouse lives among shrubs and has a wide range of coat colors.
C. pernix mostly lives in the coastal plain of Sinaloa state within Mexico, which extends from Southern Sonora to Northern Nayarit. Their habitat consists mostly of small trees, shrubs, and cacti. Sinaloan pocket mice are found on sandy soil, living under low bushes or dense networks of vines and grasses. Their habitat does not contain any rock material, unlike in its sister species, the rock pocket mouse.
The Sinaloan pocket mouse is one of the smallest in the genus Chaetodipus with a total length of less than 200mm. Their skull is narrow with an elongated nose and medium-sized ears. C. pernix has a thinly haired tail that is longer than the body length. Their coat color is variable (usually yellowish-brown), but always darker on the back and lighter on the sides and belly. Their diet consists of grains and seeds. The average litter size is seven.
Color Polymorphism
Coat color is a genetic polymorphism. Many different coat colors are seen between species of pocket mice and even within the same population because of differences in their genotype. Multiple aspects of the environment put selective pressures on pocket mice to adapt their coat colors. Variation in coat color between pocket mice can be a selective advantage for two main reasons: concealment and regulation of physiological processes.
Concealment offers a large selective advantage for pocket mice that are able to successfully hide from potential predators, also known as Crypsis. Pocket mice generally show two forms of crypsis: camouflage and countershading. Camouflage is seen when an organism's coloring helps it blend into its background or environment. Evidence of camouflage is seen between different populations of pocket mice that live in two different environments. The Sinaloan pocket mouse usually has a yellow-brown coat with black hairs because they live in a sandy environment under shrubs, while the Rock pocket mouse usually has a grey or black coat color and lives among rocks. Mice who show a very different coat color than their environment are more susceptible to predation because they can be seen easier than mice that blend in with their environment. Countershading is another type of camouflage and is seen when an organism's pigmentation is darker on the upper side of the body and lighter on the underside of the body. Sinaloan pocket mice almost always have a lighter belly and sides compared to the darker color of their back. The selective advantage of this color patterning is again, concealment from predators, mostly owls in this case. Countershading helps the pocket mouse to reduce the appearance of their shadow in sunny environments. Living in the sunny desert, this color pattern has a large selective advantage. Mice whose shadows were easily seen by owls flying overhead would more likely become prey, than mice whose shadows weren't as obvious.
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Wikipedia