It is important that monitoring programs for endangered species provide valid scientific information to help in understanding species ecology, inform management, and provide feedback on the effectiveness of management actions. This is vital for helping to ensure long term persistence of the species. Spatial programs can be ideal for generating this information due to their power to model landscape and environmental covariates in relation to the presence of species across the landscape.
Stephens’ kangaroo rat (SKR) is a medium-sized nocturnal rodent of the family Heteromyidae. SKR are primarily known to eat seeds and are physiologically adapted to hot and arid environments. They travel using bipedal locomotion (hopping on hind feet) and, therefore, require open habitat on gentle slopes for efficient movement and foraging. Within the range of the species, SKR prefer open herb and grassland habitat with minimal shrub cover, area of open bare ground, and friable soils for digging and dust bathing.
The Stephens’ kangaroo rat was listed as a Threatened Species by the California Department of Fish and Game in 1971 and as an Endangered Species by the U.S. Fish and Wildlife Service in September 30, 1988. SKR are currently estimated to occupy 25,000 acres (10,117 ha) in Riverside and San Diego counties with approximately 50% of its historic habitat lost due to agriculture and residential development.
Since 2005, we have conducted an occupancy monitoring program for the threatened Stephens kangaroo rat (SKR) on Marine Corps Base Camp Pendleton (MCBCP), California. MCBCP harbors the southwestern-most population of SKR, a part of one of 11 populations units targeted for conservation by the U.S. Fish and Wildlife Service. This program has also been recently extended to a study area in Warner Springs, California.
Principal Investigator: Robert N. Fisher
Project Lead: Cheryl S. Brehme
In 2005, we implemented a new monitoring program for SKR on Marine Corps Base Camp Pendleton (MCBCP). It is a relatively simple, multi-tiered, habitat-based, adaptive monitoring program designed to track yearly trends in the total area occupied by SKR on base. There is a two-phased approach for sampling. The first phase involves a complete search for any potential kangaroo rat sign and measurement of habitat and environmental variables. If any potential sign is observed, two to four days of live-trapping are conducted for the second phase. Live-trapping is necessary to determine if plots are occupied by the Stephens’ kangaroo rat and/or the Dulzura kangaroo rat (D. simulans, DKR). We use the log-linear modeling program, PRESENCE, to calculate annual estimates of proportion area occupied (PAO), as well as the probabilities of detection, colonization, and extinction over time.
Multi-year models suggest that SKR are positively associated with the proportion of open ground and forbs, certain types of military disturbance, years since last fire, and greater fire frequency. SKR have long been associated with open forb-dominated areas. The results since 2005 for SKR on MCBCP support this and further show the direct positive effects of disturbance from certain types of military training and fires. In fact, since 2005, SKR have increased in disturbed training areas while they have decreased in undisturbed areas, where shrubs and other perennial vegetation have also increased. Current habitat management actions, such as implementation of regular prescribed burning of annual grasses and shrubs, should create habitat more suitable for the species. In Warner Springs, initial results indicate that some disturbance from cattle grazing may be beneficial to maintaining suitable habitat for SKR.
The objectives of these programs are 1) to better understand the spatial and temporal dynamics of SKR , 2) to detect and identify causes of positive or negative trends, and 3) to inform and maintain a feedback loop between monitoring and management of SKR.
USGS Contact For This Project
Brehme, C., Burnham, K., Kelt, D., Olsen, A., Montgomery, S., Hathaway, S., and R. Fisher. 2005. Stephens’ Kangaroo Rat (Dipodomys stephensi) Monitoring Protocol for MCB Camp Pendleton. Prepared for AC/S Environmental Security, Marine Corps Base, Camp Pendleton. 50 pp.