The tail of the pocket mouse is . Perognathus is a genus of pocket mouse. There is relatively little information on the breeding biology of the Pacific pocket mouse. The Pacific pocket mouse is very simple. The spiny pocket mouse has long hairs. The tail of the pocket mouse can either be distinctly or indistinctly bicolored. Morgart observed a white-tailed antelope squirrel capturing and eating a silky pocket mouse. The skull and hind foot are almost the smallest of all the pocket mouse species. As a mammal, the first thing Pacific pocket mouse subsists on is its mother's milk. A pocket mouse is highly influenced when seeking its food. The Pacific pocket mouse is the smallest mammal that hibernates. The gestation period for the Pacific pocket mouse lasts for twenty-two to twenty-three days. "Chaetodipus penicillatus" is a medium-sized pocket mouse. Other listed species include Pacific pocket mouse and Quino checkerspot butterfly. Their goal is to protect the Pacific pocket mouse until it is no longer necessary.