C. pernix mostly lives in the coastal plain of Sinaloa state within Mexico, which extends from southern Sonora to northern Nayarit.

Sinaloan pocket mice are found on sandy soil, living under low bushes or dense networks of vines and grasses.

[5] Multiple aspects of the environment put selective pressures on pocket mice to adapt their coat colors.

[5] Variation in coat color between pocket mice can be a selective advantage for two main reasons: concealment and regulation of physiological processes.

[5] Concealment offers a large selective advantage for pocket mice that are able to successfully hide from potential predators, also known as Crypsis.

Light coat colors have a selective advantage in hot, sunny environments because they can help regulate body temperature.

Geographic variation between environments is another selective pressure that helped color polymorphism evolve between pocket mice.

Pocket mice that live in sunny environments with an abundance of sand will have a selective advantage with light colored yellow or brown coats.

In contrast, pocket mice that live on rocks in environments with less sun are more likely to have a selective advantage with darker colored grey or black coats.