A Carrizo Plain National Monument sign stands in a large valley with mountains in the background.
Rafting the Kern River Three Pump Jacks, Midway-Sunset Oilfield Painted Rock. Carrizo Plain National Monument. Poppy Piedras Blancas Lightstation, San Simeon
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Bakersfield Field Office

Effects of Livestock Grazing on a Community of Species at Risk of Extinction in the San Joaquin Valley, California


Download a fact sheet (56kb pdf format) for this project.

Principal Investigators: Dr. David Germano, Dr. Ellen Cypher, Dr. Galen Rathbun, Larry Saslaw, Sam Fitton

large areas of desert, dominated by salt bushes (Atriplex spp.).
large areas of desert, dominated
by salt bushes (Atriplex spp.).
What used to be relatively bare ground between the salt bushes has become choked with a dense growth of grass and accumulated thatch.
What used to be relatively bare ground between the salt bushes has become choked with a dense growth of grass and accumulated thatch.
The southern San Joaquin Valley historically included large areas of desert, dominated by salt bush scrub (Atriplex spp.). Agricultural, oil, and urban development have displaced most of this habitat. What remains is being changed by the invasion of numerous species of annual grasses, most notably the genus Bromus, that have been introduced from the Mediterranean area of Europe over the last 200 years. What used to be relatively bare ground between the salt bushes has become choked with a dense growth of grass and accumulated thatch.
   Some of the native annual forbs (wildflowers) in the southwestern San Joaquin Valley.    
Some of the native annual forbs (wildflowers) in the southwestern San Joaquin Valley are disappearing because they can not effectively compete with the exotic grasses. The Kern mallow (Eremalche parryi ssp. kernensis), which is endemic to the region, has been listed by the US Fish and Wildlife Service as endangered.---->>
Blunt nose leopard lizard.
Blunt-nosed leopard lizard.

Giant Kangaroo rat.
Giant kangaroo rat.

San Joaquin antelope squirrel. San Joaquin antelope squirrel.
Some of the terrestrial vertebrates endemic to the southwestern San Joaquin Valley are also declining, and have been declared threatened or endangered. These include the blunt-nosed leopard lizard (Gambelia sila), giant kangaroo rat (Dipodomys ingens), and San Joaquin antelope squirrel (Ammospermophilus nelsoni). These animals, which rely on rapid locomotion across relatively bare ground to catch food and escape predators, are being adversely affected by the disappearance of open ground as exotic grasses invade the desert.

More information on Endangered Animals at:
Cow grazing in study area.
Cow grazing in study area.

Aerial of Lokern study area. Aerial of the Lokern study area.
We are carrying out an experiment to see if well-managed herds of cattle can be used to reduce the amount of accumulated grass, and thus benefit the declining plants and animals. Our experiment includes four pastures that are about a square mile each where cattle are grazed (treatments), and four pastures about 60 acres each, where no grazing occurs (controls).
Our experiment is located on the Lokern Natural Area in western Kern County, California. In February 1998 we started grazing the pastures. By August, after the cattle were removed for the year, we had achieved a significant grazing effect on the treatment pastures. This aerial photograph, shows the control and treatment plots within the four square-mile pastures. The diagonal straight lines running through the plots are pipeline roads.
View looking down the fence line.
View looking down the fence line.

In conjunction with plot studies, we started gathering home range and habitat use information on Blunt-nosed leopard lizards andSan Joaquin antelope squirrels in 2002. Adult lizards are followed from May through early August, and squirrels are tracked from August through early October.

Image of the San Joaquin antelope squirrelwith a transmitter. image of Blunt-nosed lepoard lizard with a transmitter.

The San Joaquin antelope squirrel and Blunt-nosed leopard lizard with transmitters.

image of home ranges of blunt-nosed leopard lizards in sec. 27 and 33 in 2003.
Home ranges of blunt-nosed leopard lizards in sec. 27 and 33 in 2003.


This report contains a summary of results from the seventh year of plant and animal censuses on the Lokern Natural Area study site. In 2003, we again had below average rainfall, the fourth year in a row of dry conditions. Summer vegetation structure and biomass (residual dry matter) were low and virtually the same in control and treatment plots. Because there was little new grass growth this year, cattle again were not placed on the study site in 2003. Plant studies continue with no significant effect of treatment visible yet. The total number of nocturnal rodents caught was about the same as in the past 2 years, but more were caught on control than treatment plots. Short-nosed kangaroo rats decreased in abundance overall, but increased on control plots. Heermann's kangaroo rat numbers decreased on both control and treatment plots. San Joaquin pocket mice increased on all plots compared to last year. Although only 7 giant kangaroo rats were caught in 2003, this is the most captured since the study began. San Joaquin antelope squirrel numbers continued to increase and like last year, they were caught in greater numbers on control plots. In 2003 the number of sage sparrows declined on control plots but a few individuals were seen on treatment plots for the first time since 1999. Western meadowlarks were not found in 2003, but numbers of horned larks increased on both control and treatment plots. Side-blotched lizards and western whiptails continue to be found throughout the study area abundantly with little difference between treatment and control plots. Blunt-nosed leopard lizards also have become relatively abundant and were found in 3 of 4 sections, and virtually all were from treatment areas. Numbers of grasshoppers were much greater than last year, but ground invertebrates captured in pitfall traps remained low. In 2003 we continued radio-tagging studies of blunt-nosed leopard lizards. Because of insignificant differences in vegetation between control and treatment plots, San Joaquin antelope squirrels were not radio-tracked this year.

We will continue to gather information on the year-to-year variation in rainfall, plot condition, and relative abundance of plants and animals. We will also continue the radio tagging studies next year. Numbers of most of the focus species are at relatively high levels now and we just need several years of adequate rainfall to return the control plots to a grassy state. We can only hope that this unusually long stretch of dry years is broken this coming rain year. As we have indicated in the past, the success of this study depends on time, patience, and resources. The continuation of the field research on the Lokern requires about $72,000 per year, and this does not include the considerable in-kind support from cooperating agencies and organizations. We hope that all our cooperators and supporters will continue their devotion to the research.



The main supporters and participants in the research include:
Aera Energy
Bureau of Land Management
Bureau of Reclamation
California Cattlemen's Association
California Department of Fish and Game
California State University, Bakersfield
Center for Natural Lands Management
Chevron/Texaco Exploration & Production Company
Endangered Species Recovery Program
Eureka Livestock Company
Great Valley Center
National Fish and Wildlife Foundation
Occidental Oil, Elk Hills
US Fish and Wildlife Service
Western Ecological Research Center, U.S. Geological Survey


The following scientists have been responsible for implementing the different aspects of the Lokern research:

  • Dr. Ellen Cypher
    Research Ecologist, Endangered Species Recovery Program, PO Box 9622, Bakersfield, CA 93389-9622. ECypher@esrp.org. Vegetation and rare plant studies.
  • Mr. Sam Fitton
    Wildlife Biologist, Bureau of Land Management, 20 Hamilton Court, Hollister, CA 95023. SFitton@ca.blm.gov. Bird studies.
  • Dr. David Germano
    Associate Professor, Department of Biology, California State University, Bakersfield, CA 93311. DGermano@csub.edu. Lizard, mammal, and invertebrate studies. Report coordination and preparation.
  • Dr. Galen Rathbun
    Research Biologist, Piedras Blancas Field Station, Western Ecological Research Center, US Geological Survey, San Simeon, CA 93452-0070. grathbun@CalAcademy.org. Mammal and invertebrate studies.
  • Mr. Larry Saslaw
    Wildlife Biologist, Bureau of Land Management, 3801 Pegasus Drive, Bakersfield, CA 93308. Lawrence_Saslaw@ca.blm.gov. Plot and cattle studies.

2003 Annual Report, 828kb pdf
2002 Annual Report , 1200kb pdf
2001 Annual Report , 612kb pdf
2000 Annual Report , 720kb pdf
1999 Annual Report , 689kb pdf
1998 Annual Report , 513kb pdf
1997 Annual Report , 569kb pdf

Germano, D. J, G. B. Rathbun, and L. R. Saslaw. 2001. Managing exotic grasses and conserving declining species. Wildlife Society Bulletin 29:551-559.

Germano, D. J. 2001. Salvadora hexalepis (western patchnose snake). Herpetological Review 32:61.

Andreasen, K., E.A. Cypher, and B.G. Baldwin. 2002. Sympatry between desert mallow, Eremalche exilis, and Kern mallow, E. kernensis (Malvaceae): molecular and morphological perspectives. Madrono 49(1):22-24.

Germano, D. J., and J. Brown. 2003. Gambelia sila (Blunt-nosed leopard lizard) Predation. Herpetological Review 34:143-14