Mammals of the Kern River Valley

and Southern Sierran Nevada

More mammals live in this region than any other place in North America north of Mexico. The amazing diversity is a product of our geographical and climatic variation. The article below by Dr. John Harris, Mills College mammalogist, discusses mammal diversity highlighting the Kern River Valley as epicenter.  Our mammal checklist was compiled by our webmaster and local naturalist Alison Sheehey, after years of field and literature research. It covers Kern River Valley in Kern, Tulare, and Inyo Counties 

The following article is reprinted with permission from the Kern River Research Center. Please contact Bob Barnes if you would like to use this information. 

KERN RIVER RESEARCH CENTER

Fieldnotes

Winter 1996 Vol. 5, No. 1

Mammal Diversity and the Kern River Research Center

By John Harris

KRRC members are well aware that one of the Center's greatest attractions is its location at the junction of several major ecosystem types, providing Center biologists and visitors with the opportunity to study a wide array of species and ecological processes from a central location. The South Fork of the Kern River is famous for its riparian habitat and high diversity of birds, including many rare and endangered species. Yet within a few miles one can also visit Mojave desert, Great Basin desert, Sierra Nevada montane forests, oak woodland, chaparral, and Central Valley communities, as well as unique transitional communities that occur where these major bioregions come together.

Perhaps less well known is the very high diversity of mammals that occurs within reach of KRRC. In a classic 1964 paper entitled "Species diversity of North American recent mammals" (Systematic Zoology 13:57-73), George Gaylord Simpson analyzed patterns of mammalian diversity in North and Central America. Simpson divided the continent into a grid of squares 150 km on a side. He enumerated the mammal species in each square and produced the contour map of mammal species diversity shown here.

Several patterns are evident. The more dramatic topography of the western portion of the continent provides very high habitat diversity. In particular, the east side of the Sierra Nevada is a "front" of high mammal diversity. There is also a latitudinal gradient of mammal diversity: there are more species as one travels from north to south. The highest diversity of mammals in the United States (at least 115 species), is found in the portion of the continent that includes the southern Sierra Nevada (and KRRC!). In fact, this island of high diversity can only be exceeded by traveling to southern Mexico, where one reaches the tropical rainforest biome.

While preparing a presentation on mammals for a recent conference on Sierra Nevada Biodiversity (held at the California Academy of Sciences in 1995), I became interested in the extent to which the Sierra Nevada influences patterns of genetic diversity in mammal species. There are relatively few Sierran endemic species (Long-eared Chipmunk and Alpine Chipmunk are two examples), but there are many subspecies (about 45) that are restricted to the Sierra Nevada region. Some are montane, but there are also many recognized subspecies that occupy habitats in the foothill region or are restricted to the east side of the Sierra. The southern Sierra in particular is home to a large number of endemic subspecies of mammals, and thus it represents a critical reservoir of genetic diversity. Of the endemic species or subspecies of mammals in the Sierra, about 25 are restricted to the central and southern Sierra. This pattern results from the manner in which the Sierra Nevada creates a peninsula of cooler, moister, montane habitat projecting southward. Alpine habitats are especially island-like; as a consequence, about 43 % of the Sierran alpine mammal fauna are endemic species or subspecies. Kern River Research Center is ideally situated to take advantage of the high diversity of mammals resulting from high habitat diversity and to study the unique endemics of this high diversity region. For example, the rare Yellow-eared Pocket Mouse has only been found in the vicinity of Walker Pass, just a few miles from KRRC.

Research on mammals has been part of KRRC's objectives since its inception. In 1991 and 1992, Center biologists conducted surveys for furbearing mammals in the Sierra and Sequoia National Forests. Distribution and habitat relationships of mammals such as the rare Fisher and secretive Marten are poorly known, to the detriment of conservation efforts. KRRCs studies provided valuable information on a number of these species. For example, the occurrence of a Fisher population in the southern Sierra was carefully documented for the first time and populations of Black Bears were shown to be larger than had been thought.

Research on mammals will undoubtedly be an important part of the Center's future. How do mammals respond to the fluctuations in river channels and riparian vegetation that are part of a dynamic riparian system? Is the river's large population of woodrats an important factor in nest predation? How important is the South Fork Valley as a corridor for genetic interchange? These are just a few examples of the many interesting questions that could be studied at KRRC.

John Harris is a mammalogist, professor at Mills College in Oakland, California, and a member of KRRC Board of Directors.

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