Geology topics

Kevin Keith

Publications and source records attributed to Kevin Keith.

2 recordsLinked to original sources

USGS2008

When desert tortoises are rare: Testing a new protocol for assessing status

We developed and tested a new protocol for sampling populations of the desert tortoise, Gopherus agassizii, a state- and federally listed species, in areas where population densities are very low, historical data are sparse, and anthropogenic uses may threaten the well-being of tortoise populations and habitat. We conducted a 3-year (2002–2004) survey in Jawbone-Butterbredt Area of Critical Environmental Concern and Red Rock Canyon State Park in the western Mojave Desert of California where the status was previously unknown. We stratified the study area and used 751, 1-ha plots to evaluate 187.7 km2 of habitat, a 4% sample. Tortoise sign was found on 31 of the 751 plots (4.1%) in two limited areas: ~14 km2 on the Kiavah Apron and ~40 km2 in the Red Rock Canyon watershed.

California Fish and Game↗

USGS2008

Status of the desert tortoise in Red Rock Canyon State Park

We surveyed for desert tortoises, Gopherus agassizii, in the western part of Red Rock Canyon State Park and watershed in eastern Kern County, California, between 2002 and 2004. We used two techniques: a single demographic plot (~4 km2 ) and 37 landscape plots (1-ha each). We estimated population densities of tortoises to be between 2.7 and 3.57/km2 and the population in the Park to be 108 tortoises. We estimated the death rate at 67% for subadults and adults during the last 4 yrs. Mortality was high for several reasons: gunshot deaths, avian predation, mammalian predation, and probably disease. Historic and recent anthropogenic impacts from State Highway 14, secondary roads, trash, cross-country vehicle tracks, and livestock have contributed to elevated death rates and degradation of habitat. We propose conservation actions to reduce mortality.

California Fish and Game↗