As members of Heteromyidae—which consists of animals surviving on seeds and grain—Pacific pocket mice have fur-lined cheek pouches externally.

There are typically two patches of hair that are lighter at the base of the ear, a distinguishing mark of the Pacific pocket mouse.

The soles of the hind feet are hairy, which are also the distinguishing marks on the Pacific pocket mouse (along with the two patches of hair that are lighter at the base of the ear).

[citation needed] The Pacific pocket mouse is endemic to the immediate coast of southern California from Marina del Rey and El Segundo in Los Angeles County, south to the vicinity of the U.S.-Mexican border in San Diego County.

Predators such as a gray fox and feral or domestic cats threaten the survival of the Pacific pocket mouse.

These ants invade the coastal sage scrub areas of the Pacific pocket mouse's habitat.

[5] Like other heteromyids, the Perognathus longimembris pacificus (Pacific pocket mouse) is generally asocial and solitary.

[6] Generally, the breeding season for the Pacific pocket mouse is the months April through July, peaking in the spring.

The temperature, amount of food available, and the quantity of plant growth around the Pacific pocket mouse's habitat can all affect its breeding season.

The Pacific pocket mouse's diet consists of seeds, nuts, and green vegetation, when available.

[8] These granivores will leave the burrow at night to gather the seeds, in order to avoid direct contact with the desert sun.

When seeds are not easily accessible, the mouse will use its forelimbs to dig holes in order to find resources.

Due to the harsh climate, many pocket mice are susceptible to droughts, heat, and extreme temperature changes that can happen within the day.

Density of food supply: This aspect can determine if a pocket mouse will have enough resources available within a certain distance of its burrow.

When a pocket mouse has found sufficient seeds, it will begin to store these resources in its fur-lined cheeks.

Also, during the spring and autumn months, pocket mice will forage more often in order to prepare for the coming of summer and winter when it will be harder to find food.

Perognathus longimembris pacificus (Pacific pocket mouse) was believed to be extinct for nearly 20 years until it was rediscovered in 1993.

Fish and Wildlife Service published a recovery plan for the Pacific pocket mouse with the intent of down listing its status to threatened by the year 2023.

Marine Corps Base Camp Pendleton in San Diego and the city of Dana Point have expressed deep concern for the protection of the Pacific pocket mouse.

The United States Marine Corps has authorized the relocation of the Pacific pocket mouse to off-base sites in order to create new populations.

[9] They also decided that the Dana Point Headlands Pacific pocket mouse property would be privately owned.

project at Camp Pendleton, scat detection dogs from Conservation Canines were used to locate Pacific pocket mice.

[10] The principal threats to the species and the cause of its present reduced state are habitat destruction, degradation, and fragmentation.

Other threats include ground disturbances or vegetation removal from grading, ripping, or off-road driving.