PPM 6/15/10- A Mighty Mouse

A Mighty Mouse: The Pacific Pocket Mouse

(Perognathus longimembris pacificus)

While surveying on Camp Pendleton, we sometimes run into people who want to know what we are researching. When we tell people that our dogs are trained to find the Pacific pocket mouse, we often get the same response: 

“A mouse?!? I’ve got a few of those in my garage that I would like to get rid of.”

In truth, these mice are not just any old rodent. The Pacific pocket mouse is special because of its rarity and its unique role in the environment.

The Pacific pocket mouse (PPM) is one of 18 subspecies of the little pocket mouse of the Heteromyidae rodent family. Not only one of the smallest mammals, the Pacific pocket mouse is also one of the most endangered species in the United States. Thought to be extinct for over twenty years, a small population of less than fifty mice was discovered in California coast in 1994. Today, there are only four known populations to exist in southern California; three of them reside on the Camp Pendleton Marine Corps base. Tiny in size, an adult PPM only weighs that of a silver quarter and is only a couple of inches in length. This mouse is named not for its size, but for external cheek pouches that allows temporary storage of seed while foraging.

Small but mighty, pocket mice are considered a keystone species because they influence environmental characteristics in the desert, shrub, and grassland ecosystems in which they live. Specifically, pocket mice disperse native grass seeds, create healthy soil disturbance and serve as a food source for native predators.

As shown in the photos below, these avid burrowers can change the landscape of southern California’s coastal sage scrub environment. Sandy patches mark the habitat of the PPM. This soil disturbance acts as a natural soil tiller, ensuring that the sandy terrain is a fertile, healthy environment for the next generation of native plants and animals.

Expert burrowers and seed gatherers, PPM are an important member of the coastal community.  So next time you see a mouse, don’t assume it’s just any old mouse…it just may be a mighty mouse.