Approximately 220 species of wild mammals occur in California and the surrounding waters (including introduced species, but not domestic species such as house cats). Amazingly, the state of California has about half of the total number of species that occur on the North American continent (about 440). In part, this diversity reflects the sheer number of different habitats available throughout the state, including alpine, desert, coniferous forest, grassland, oak woodland, and chaparral habitat types, among others102, 109, 100. About 17 mammal species are endemic to California; most of these are kangaroo rats, chipmunks, and squirrels.

Nearly 25% of California’s mammal species are either known or suspected to occur at Quail Ridge (See Mammal List). Species found at Quail Ridge are typical of both the Northwestern California and Great Central Valley mammalian faunas. Two California endemics, the Sonoma chipmunk (see Species Accounts for scientific names) and the San Joaquin pocket mouse, are known to occur at Quail Ridge. None of the mammals at Quail Ridge are listed as threatened or endangered by either the state or federal governments, although Townsend’s big-eared bat, which is suspected to occur at Quail Ridge, is a state-listed species of special concern.

Many mammal species are nocturnal, fossorial, fly, or are otherwise difficult to observe. However, it is still possible to detect the presence of mammals at Quail Ridge, both visually and by observation of their tracks, scat, and other sign. The mammals most often seen during the day are mule deer and western gray squirrels. Mice and rats are nocturnal and thus not often seen, although the large stick-houses of dusky-footed wood rats are apparent in oak woodland and riparian habitats. Carnivores such as mountain lions, foxes, and bobcats may be detected by the presence of scat and tracks left in mud or dust on the dirt roads. Black bear sign has even been observed, including claw marks on an abandoned truck on the west side of the peninsula, and bear tracks were found in the road leading into Decker Canyon in May 2003. Different species of mammals are found in the various plant communities at Quail Ridge. In chaparral, rodents such as brush mice, wood rats, and harvest mice are common. Ground squirrels, pocket gophers, harvest mice, and voles inhabit grassland habitats. Wood rats, gray squirrels, skunks, raccoons, and deer mice may be found in woodland habitats. Larger mammals such as mule deer, coyotes, bobcats, and mountain lions may be spotted across Quail Ridge. Some small mammals, such as deer mice and brush mice, can be found in more than one habitat type.

Potential Research Topics

Little research has been conducted on the mammals of Quail Ridge. Mammalogy students from the University of California, Davis have live-trapped small mammals in riparian areas of Decker Canyon, and in chaparral near the research station. Karen Mabry, a UC Davis animal behavior graduate student, is studying the dispersal and habitat selection behavior of brush mice from oak woodland and chaparral habitat types.

Hoary Bat; Photo courtesy of Dr. Lloyd Glenn Ingles © California Academy of SciencesMany questions about the mammals of Quail Ridge remain totally unanswered. As only 18 of the 58 species that may occur at Quail Ridge have actually been confirmed, a general survey of mammalian diversity would be extremely helpful. The bats are particularly understudied, in part because of the difficulty of observing flying, nocturnal animals, and the need for technology (e.g., ultrasonic bat detectors) to detect their calls, which can be undetectable to human ears. Quail Ridge is especially suited for a study of predator/prey dynamics; small mammals such as mice, rats, and voles are very abundant and form a prey base for a large number of mammalian and avian predators. At least two, and possibly three, species of Peromyscus mice coexist at Quail Ridge – what ecological factors allow such similar and closely related species to coexist? Large carnivores such as mountain lions may be particularly disturbed by human activities; human impacts at Quail Ridge are relatively minor compared to the surrounding areas. Does the presence of large tracts of protected land at Quail Ridge positively affect these animals? These are just a few of the many potential research projects that could be conducted with the mammals of Quail Ridge.

Species Accounts

Photo Credits: Title, Mule Deer (Mike Benard), Bear scratches (Shane Waddell), Hoary Bat (Dr. Lloyd Glenn Ingles). For more pictures see:

This page last updated: June 23, 2005  

Contact: Dr. Virginia Boucher
John Muir Institute of the Environment
109 The Barn, University of California, Davis, CA 95616
Phone: 530-752-6949; email:

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