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OCH BLOG

Native Rodents of Orange County: Part 1

Updated: Mar 18, 2022

Orange County (OC) is home to many native rodents. These animals play an important role in the natural ecosystem. However, we consider rodents as pests. In fact, native rodents live in wildlands, generally away from human homes. But, the rodents (mostly rats) that we see in and around human homes are non-natives that were introduced here from Europe about one hundred years ago. It is important to know about our native rodents that have played a key role in balancing our natural ecosystem of OC. Before diving into the details of the OC rodents, it is essential to know about rodents themselves.


Rodents are mammals characterized by a single pair of continuously growing incisors (front teeth) in the upper and lower jaw. They vary in their ecology and lifestyles and are found in almost every terrestrial habitat. They can be arboreal, fossorial (burrowing), saltatorial/ricochetal (leaping on their hind legs), or semi-aquatic. In general, they have well-developed senses of smell, hearing, and vision. Rodents include mice, rats, squirrels, prairie dogs, porcupines, beavers, guinea pigs, gophers, and hamsters. They play an essential role in the ecosystem and are important in seed and spore dispersal, pollination, seed predation, energy and nutrient cycle, modification of plant succession, and species composition. Furthermore, they play an important role in the health of grassland and woodland systems and are a significant source of food for many predators and scavengers such as hawks, foxes, bobcats, and even wolves.


Although there are many species of rodents in OC, in the next couple of weeks, we will be highlighting native species from the following groups:

  • Rat/Mouse: Dusky-footed woodrat, Cactus mouse, California mouse, Harvest mouse, Deer mouse, Desert woodrat, San Diego pocket mouse, Pacific pocket mouse

  • Gopher: Botta’s pocket gopher

  • Squirrel: Western gray squirrel, California ground squirrel

  • Beaver: North American beaver or Golden beaver

The link below has more information about the above-listed species of OC.



The smallest mouse species in North America, the Pacific pocket mouse. Photo from San Diego Zoo Wildlife Alliance

Pacific pocket mouse, Perognathus longimembris pacific, is a federally listed endangered animal species. It is endemic to coastal southwest California, and it is a member of the Heteromyidae family. This mouse is a nocturnal granivore (feeding on seeds) ranging in size from 4.3 to 5.2 inches from nose to tip of the tail.


This mouse lives on fine-grain, sandy substrate and historically inhabited coastal dunes, river alluvium, and sage scrub habitats growing on marine terraces within approximately 2.5 miles of the ocean. The breeding season generally peaks in spring but varies with temperatures, food supply, and plant growth. The breeding season is in the months of April through July in which most females typically produce one litter per year, about two to eight pups.


Pacific pocket mouse foraging for food. Photo by Cheryl S Brehme | USGS

The pocket mouse feeds primarily on seeds, grasses, forbs, green vegetation in spring, and sometimes on insects. It lives about three to five years, but the lifespan of this mouse is sporadic because of its vulnerability in its habitat.


This species was believed to be extinct for nearly 20 years until it was rediscovered in 1993. It was immediately placed on the emergency listings by the U.S. Fish and Wildlife Service and received full protection status in 1994. In September 1997, the U.S. Fish and Wildlife Service published a recovery plan for the Pacific pocket mouse to downlist its status to threatened by the year 2023. According to Iwanowicz et. al., 2016, Dana Point Headlands is the only site located in OC where the Pacific Pocket Mouse can only be found.


Current Range of Pacific Pocket Mouse in Orange County, CA. Photo by Amy G Vandergast

The principal threats to the species and the cause of its present reduced state are habitat destruction, degradation, and fragmentation. These threats are due to different kinds of area development such as urban, agricultural, residential, and recreational. Other threats include ground disturbances or vegetation removal from grading, ripping, or off-road driving.


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