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Cheryl Brehme

Cheryl has been a biologist with the USGS, Western Ecological Research Center since 2003.

She specializes in long-term monitoring programs, conservation ecology and road ecology. She uses current ecological concepts and principles to design, implement, improve, and interpret complex research and monitoring projects for reptiles, amphibians and mammals.  In addition to conducting fieldwork for her projects, she models a variety of spatial and demographic population processes and community dynamics in response to habitat change.

Long-Term monitoring

Cheryl has been integral in the design, fieldwork and dynamic occupancy analysis of data for long-term monitoring of endangered species on MCB Camp Pendleton to inform species status and trends and effective habitat and species management actions.  These include the arroyo toad (since 2003), Stephens kangaroo rat (since 2005) and Pacific pocket mouse (since 2011). 

Road Ecology

Cheryl leads a wide array of research on road ecology, particularly with respect to reptiles and amphibians for the Department of Transportation and other partners. Projects range from assessing risk of road impacts across multiple species, testing the effectiveness of individual components of crossing systems, designing new passages, to conducting wide scale landscape connectivity projects.

American Badger Research

Since 2011, Cheryl has led research studying badger distribution and activity in San Diego County using canine scent detection, badger sign surveys, infrared cameras, facial recognition, hair snags, outreach efforts, and road mortality to document their distribution and core use areas.  Future goals include distribution mapping, designing a long-term monitoring program, and employing the use of radiotelemetry to better understand their space use patterns and conservation needs.

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Pacific pocket mouse

Pacific Pocket Mouse Monitoring and Research Program

Once thought to be extinct, the Pacific pocket mouse (Perognathus longimembris pacificus) was rediscovered in 1993 and is currently found at three population sites along the southern California coast. USGS researchers and their partners developed a comprehensive long-term monitoring plan to assess the status and trends of Pacific pocket mouse and identify important drivers of population dynamics...
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Western Ecological Research Center (WERC)
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Pacific Pocket Mouse Monitoring and Research Program

Once thought to be extinct, the Pacific pocket mouse (Perognathus longimembris pacificus) was rediscovered in 1993 and is currently found at three population sites along the southern California coast. USGS researchers and their partners developed a comprehensive long-term monitoring plan to assess the status and trends of Pacific pocket mouse and identify important drivers of population dynamics...
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A Yosemite toad looks through a mesh fence, holding itself up on its back legs

Reptile and Amphibian Road Ecology

USGS is working with many partners to help reptiles, amphibians and other animals cross roads safely, improving access to essential habitat.
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Western Ecological Research Center (WERC)
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Reptile and Amphibian Road Ecology

USGS is working with many partners to help reptiles, amphibians and other animals cross roads safely, improving access to essential habitat.
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Species observations from pitfall trap arrays, species pool matrices, and patch locations in southern California from 1995-2015

Observations (reduced to detected/not detected) of 45 vertebrate species (seven mammals, seven amphibians, and 31 reptiles) across Southern California pitfall sampling projects conducted between 1995 through 2015. Habitat patch locations of every pitfall sampling project presented in a shapefile. Habitat patches were measured based on the size when pitfall sampling began within each. Sampling proj
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Western Ecological Research Center (WERC)

Masticophis occupancy in southern California, 1995-2000

These data are CSV files comprised of a heading and tables from Appendix 1 and Appendix 2 in the accompanying paper. The tables show the sampling dates and locations for the coachwhip (Masticophis flagellum) and striped racer (Masticophis lateralis) in pit-fall arrays (Fisher et al. 2008) monitored in southern California from 1995-2000. GPS data are shown in decimal degrees and were collected in t
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Western Ecological Research Center (WERC)
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Responses of migratory amphibians to barrier fencing inform the spacing of road underpasses: A case study with California tiger salamanders (Ambystoma californiense) in Stanford, CA, USA

Migratory amphibians are at high risk of negative impacts when roads intersect their upland and breeding habitats. Road mortality can reduce population abundance, survivorship, breeding, recruitment, and probability of long-term persistence. Increasingly, environmental planners recommend installation of under-road tunnels with barrier fencing to reduce mortality and direct amphibians towards the p
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Ecosystems, Western Ecological Research Center (WERC)

Research to inform Caltrans best management practices for reptile and amphibian road crossings

In October of 2014, the U.S. Geological Survey (USGS) began a 5-year project to conduct research to inform Best Management Practices (BMPs) for amphibian and reptile crossing and barrier systems in California. To inform future conservation and transportation planning, this project involved identification of species at highest risk of negative road impacts, creation of geodatabase and spatial mapp
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Ecosystems, Western Ecological Research Center (WERC)

Track tube construction and field protocol for small mammal surveys with emphasis on the endangered Pacific pocket mouse (Perognathus longimembris pacificus)

Track tubes are used to identify small animals by their tracks. Animals that are small enough to fit into the tubes walk over ink pads and onto cardstock paper to obtain bait within the tube, leaving their footprints. The tracking tubes described in this document are designed to be set on the ground with free access and exit at either end with additional design components for stability, durability
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Ecosystems, Western Ecological Research Center (WERC)

Quantifying climate sensitivity and climate-driven change in North American amphibian communities

Changing climate will impact species’ ranges only when environmental variability directly impacts the demography of local populations. However, measurement of demographic responses to climate change has largely been limited to single species and locations. Here we show that amphibian communities are responsive to climatic variability, using >500,000 time-series observations for 81 species across 8
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Ecosystems, Water Resources, Wildlife Program, Eastern Ecological Science Center, Forest and Rangeland Ecosystem Science Center, Fort Collins Science Center, Northern Rocky Mountain Science Center, Patuxent Wildlife Research Center, South Atlantic Water Science Center (SAWSC), Southwest Biological Science Center, Upper Midwest Environmental Sciences Center, Western Ecological Research Center (WERC), Wetland and Aquatic Research Center , John Wesley Powell Center for Analysis and Synthesis

Effects of urbanization, and habitat composition on site occupancy of two snake species using regional monitoring data from southern California

Detection data from a regional, reptile-monitoring program conducted by the U.S. Geological Survey were analyzed to understand the effects of urbanization and habitat composition on site occupancy of the coachwhip (Masticophis flagellum) and striped racer (M. lateralis) in coastal southern California. Likelihood-based occupancy models indicated striped racers responded to habitat composition, favo
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Ecosystems, Western Ecological Research Center (WERC)

An objective road risk assessment method for multiple species: ranking 166 reptiles and amphibians in California

ContextTransportation and wildlife agencies may consider the need for barrier structures and safe wildlife road-crossings to maintain the long-term viability of wildlife populations. In order to prioritize these efforts, it is important to identify species that are most at risk of extirpation from road-related impacts.PurposeOur goal was to identify reptiles and amphibians in California most susce
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Ecosystems, Western Ecological Research Center (WERC)

Longevity and population age structure of the arroyo southwestern toad (Anaxyrus californicus) with drought implications

The arroyo southwestern toad is a specialized and federally endangered amphibian endemic to the coastal plains and mountains of central and southern California and northwestern Baja California. It is largely unknown how long these toads live in natural systems, how their population demographics vary across occupied drainages, and how hydrology affects age structure. We used skeletochronology to es
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Ecosystems, Western Ecological Research Center (WERC)

An improved camera trap for amphibians, reptiles, small mammals, and large invertebrates

Camera traps are valuable sampling tools commonly used to inventory and monitor wildlife communities but are challenged to reliably sample small animals. We introduce a novel active camera trap system enabling the reliable and efficient use of wildlife cameras for sampling small animals, particularly reptiles, amphibians, small mammals and large invertebrates. It surpasses the detection ability of
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Ecosystems, Western Ecological Research Center (WERC)

Metabarcoding of fecal samples to determine herbivore diets: A case study of the endangered Pacific pocket mouse

Understanding the diet of an endangered species illuminates the animal’s ecology, habitat requirements, and conservation needs. However, direct observation of diet can be difficult, particularly for small, nocturnal animals such as the Pacific pocket mouse (Heteromyidae: Perognathus longimembris pacificus). Very little is known of the dietary habits of this federally endangered rodent, hindering m
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Ecosystems, Eastern Ecological Science Center

Permeability of roads to movement of scrubland lizards and small mammals

A primary objective of road ecology is to understand and predict how roads affect connectivity of wildlife populations. Road avoidance behavior can fragment populations, whereas lack of road avoidance can result in high mortality due to wildlife-vehicle collisions. Many small animal species focus their activities to particular microhabitats within their larger habitat. We sought to assess how diff
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Ecosystems, Western Ecological Research Center (WERC)

Joint estimation of habitat dynamics and species interactions: Disturbance reduces co-occurrence of non-native predators with an endangered toad

1. Ecologists have long been interested in the processes that determine patterns of species occurrence and co-occurrence. Potential short-comings of many existing empirical approaches that address these questions include a reliance on patterns of occurrence at a single time point, failure to account properly for imperfect detection and treating the environment as a static variable.2. We fit detect
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Ecosystems, Eastern Ecological Science Center, Patuxent Wildlife Research Center, Western Ecological Research Center (WERC)

Wildfires alter rodent community structure across four vegetation types in southern California, USA

We surveyed burned and unburned plots across four habitat reserves in San Diego County, California, USA, in 2005 and 2006, to assess the effects of the 2003 wildfires on the community structure and relative abundance of rodent species. The reserves each contained multiple vegetation types (coastal sage scrub, chaparral, woodland, and grassland) and spanned from 250 m to 1078 m in elevation. Multiv
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Ecosystems, Western Ecological Research Center (WERC)
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Animal Crossing: New Research Guides Efforts to Protect California’s Amphibians and Reptiles from Road Danger

Roads can be dangerous for California’s reptiles and amphibians, but a five-year study and new video show that there are effective strategies to help...

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Caught on Camera: Sierra Martens and Flying Squirrels Using Wildlife Passage

The adorable Sierra Marten pictured below was caught on wildlife camera in October. The camera was set up to study animal movement under a new road...

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Large-scale Review of Amphibian Species and Community Response to Climate Change

Amphibian species and community richness has been declining in North America and climate change may play a role in these declines. Global climate...

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Toad Crossing Ahead: New Study Tests Elevated Roads as Underpasses for Rare Toad

Many amphibians are either too small or too slow to avoid an oncoming car. For some populations of the Federally threatened Yosemite toad (Anaxyrus...

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New USGS Study Paves a Path Forward for Reptiles, Amphibians, and Roadways

In a new study, U.S. Geological Survey (USGS) scientists ranked more than 160 species and sub-species of reptiles and amphibians in terms of their...

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