Southwestern Desert Ecology of At-risk Species and their Habitats

Science Center Objects

The southwestern desert region is home to many sensitive species. Species are at-risk due to past, present, and future changes to the landscape. WERC’s Dr. Todd Esque, field researchers, and collaborators are using models, monitoring plans, and decision-support tools to provide land managers with the resources they need to answer questions about how environmental change influences plants, animals, and their habitats. Species and habitat modeling are powerful tools used by researchers to answer natural resource management questions. Dr. Todd Esque and WERC researchers use a variety of geospatial modeling approaches to understand the dynamics of arid ecosystems and how environmental changes affect our public lands. We use models to assist in identifying plant and animal priority sites, species and communities that are vulnerable to climate change, produce high quality habitat models for managing species of concern, and investigate ecosystem responses to land use change and climate change.

Illustrations of habitat map and the Mohave ground squirrel (Xerospermophilus mohavensis)

The Mohave ground squirrel (Xerospermophilus mohavensis) is small and brown brown with bristly hairs at the tip of it tail distinguishing them from their close relatives the round-railed ground squirrels (Xerospermophilus tereticaudus). These squirrels inhabit the west Mojave Desert of southern California. USGS-WERC researchers and collaborators developed habitat models for the squirrel that were used for conflict resolution in the development of the Desert Renewable Energy Conservation Plan. (Credit: Margaret Walden , University of Nevada, Reno. Public domain.)

Renewable Energy Development and Conservation of the Mohave Ground Squirrel

The Mohave ground squirrel (Xerospermophilus mohaviensis) is a rare mammal that lives in the western Mojave Desert of southern California and has the smallest distribution among ground squirrels in North America. Sunny, flat, desert valleys are preferred habitat for this species and the preferred siting locations for large scale renewable energy developments. The need to balance these national and state energy priorities with existing natural resource and land conservation policies has emerged as an expansive land use planning initiative known as the Desert Renewable Energy Conservation Plan (DRECP). With support from the California Energy Commission, Dr. Todd Esque and collaborators at USGS-WERC, US Bureau of Land Management, University of Nevada - Reno, St. Mary’s College, and Department of Defense - Ft. Irwin National Training Center conducted a synthesis of species habitat modeling, genetics, and Graph Theory to inform natural resource mangers about potential areas of conflict in land-use planning with the future conservation of the Mohave ground squirrel and future climate change. The work identified hypothetical species dispersal corridors and core habitat areas that were used toward the completion of BLM’s land use planning for the region. New work continues to seek resolution to questions about the value of land parcels as Mohave ground squirrel habitat that were previously unresolved by incorporating newly developed spatial layers of vegetation with data on the demography of the ground squirrel.

Desert landscape with yellow flowers

The Mohave ground squirrel (Xerospermophilus mohavensis) lives in harsh desert climates where food is available only during spring of each year. The squirrels take advantage of this abundance and remain dormant for large portions of the year in underground burrows.(Credit: Todd C. Esque, USGS WERC. Public domain.)


Desert sidewinder rattlesnakes (Crotalus cerastes)

Desert sidewinder rattlesnakes (Crotalus cerastes) occupy habitats of loose soil and windblown sands. They are a sit-and-wait predator that curl up in the sand and look like a Danich pastry until a rodent or lizard runs by, when they envenomate them with lightning speed. The name, sidewinder, stems from their mode of locomotion in which they throw their head to the side while using belly scales to propel themselves forward, and sideways, simultaneously. This species is among 24 different reptiles and amphibians for which habitat models are being constructed by various research groups for a comparison of methods and to consider how these species will do under projected climate scenarios.(Credit: Todd C. Esque, USGS WERC. Public domain.)

Desert Landscape Conservation Cooperative (DLCC) Reptile and Amphibian Research

The DLCC forms a network of public-private partnerships. Their mission is to provide scientific information and decision-support tools to inform resource managers for the southwestern desert region. Dr. Todd Esque and researchers at USGS WERC are identifying key reptile and amphibian species throughout the DLCC region that are at-risk of being exposed to substantial habitat loss due to potential climate change. WERC researchers are using the Species Distribution Modeling (SDM) to address questions of environmental sensitivity for approximately 25 species of reptiles and amphibians to changes in climatic and hydrologic conditions throughout the desert southwest in California, Nevada, Utah, Arizona, New Mexico, and Texas.


Colorado Desert Fringe-toed Lizards

The southwestern deserts is home to many sensitive species and is a high demand location for off-road vehicle recreation opportunities under BLM's multiple-use landscape management directives. The Imperial Sand Dunes Recreation Area (ISDRA) located in southeastern California is home to the Colorado Desert fringe-toed lizard (Uma notata). The fringe-toed lizard is an endemic species in the ISDRA that is specially adapted to the harsh temperature extremes, aridity, seasonal resource fluctuations, and constantly moving sands of the Algodones Dunes. Changes to the habitat of the fringe-toed lizard may result from the type of land management prescribed across the range of the lizard.

USGS WERC is assisting the BLM in designing a lizard and lizard habitat monitoring plan to meet BLM’s needs to understand how open versus closed recreational areas influence plant and animal resources. Our goal is to develop an effectiveness-monitoring plan for the Colorado Desert fringe-toed lizard, and the impacts to their habitats. USGS will collect baseline data for future comparisons of changes in plant and animal populations and to the conditions of their habitats.

Colorado Desert Fringe-toed lizards

Colorado fringe-toed lizards (Uma notata) occupy the vast windblown sands of the Algodones Dunes in Imperial County, California and crossing the border into Sonora, Mexico. The photo on left is a clear photograph of the lizard asleep on the sand in the open, while the second photo illustrates how the lizards wiggles out of site once it finds a place on the sand that it likes. Note the fringed scales on the trailing edge of their feet that aids in travel on loose sand.(Credit: Todd C. Esque, USGS WERC. Public domain.)


Searching for an Endangered Salamander in California’s Colorado Desert

In collaboration with US Bureau of Land Management – California, researchers at USGS-WERC continue the search for the Endangered desert slender salamander (Batrachoseps major aridus) that has not been seen in over 30 years. Dr. Todd Esque leads a team returning to one of two remote canyons where the salamander is thought to reside. Dr. Esque and Russell Duncan were the last to see and photograph the salamander alive in 1984. During their original studies, they visited the canyon and its 275 ft waterfall during one of the wettest periods on record. While surrounded by desert vegetation such as agaves, ocotillos, cactus, and thorny shrubs, the canyon walls supported lush maiden-hair ferns, tree frogs, and the rare salamander. Recent trips to find the tiny worm-like amphibian were unsuccessful but continue, and may be a result of the recent drought that was the driest period on record for southern California. 

Researchers rappel down the edge of a 275 dry waterfall

Researchers rappel down the edge of a 275 dry waterfall in search of the Endangered desert slender salamander that has not been seen in 30 years, since research ecologist Todd Esque studied their habitat requirements in 1984. The search continues for this rare amphibian that inhabits an oasis in a harsh desert climate. (Credit: Leigh Karp, BLM. Public domain.)


Dynamics of Prey and Their Predators in the Mojave Desert

Many species of Lagomorpha including jackrabbits (Lepus spp.) and cottontail rabbits (Sylvilagus spp.) are primary prey species for medium-sized to large predators in the western US, yet there is no general synthesis of rabbit ecology and population status from which to understand predator-prey fluctuations. The need for information on predator-prey relationships issue became particularly clear for natural resource managers during the recent review of golden eagle status carried out by the US Fish and Wildlife Service (USFWS), USGS, US Bureau of Land Management, State wildlife agencies, and private industry. USGS, USFWS, and cooperators at Arizona State University collected data sets from the literature and rabbit hunt data from 17 western states across 50 years to provide a current status-of-knowledge on the ecology and population dynamics of cottontail rabbits and jackrabbits in the western USA. The issue of predator-prey dynamics also became a central focus for conservation of desert tortoise when USGS-WERC research projects detected unsustainable numbers of desert tortoises being killed by predators during drought periods. Researchers determined that coyotes were switching to less desirable desert tortoise as prey when jackrabbit numbers were low. It was hypothesized that coyote populations in proximity to towns and cities maintain unusually high population densities due to subsidies of water and food that they glean by residing on the edges of towns across the desert. A new collaboration with USGS-WERC scientists Dr. Todd Esque, and Dr. Kathy Longshore, Clark County, Nevada, the US Fish and Wildlife Service, and the Nevada Department of Wildlife will track coyote, jackrabbit, and tortoise populations in relations to environmental fluctuations and at various distances from the edge of a town to determine how these populations fluctuate in response to their environments.


Desert At-Risk Species

Male silky flycatcher (Phainopepla nitens)

This male silky flycatcher (Phainopepla nitens) will build its nest near desert mistletoe plants as early as February each year. These flycatchers feed on insects found in the desert, but are particularly fond of eating the mistletoe berries. In return for the meal, the flycatchers deposit the seeds on Acacia trees which is the preferred host plant for the parasitic mistletoe.(Credit: Todd C. Esque, USGS WERC. Public domain.)

Male Costa’s hummingbird (Calypte costae)

This male Costa’s hummingbird (Calypte costae) is a summer resident in the Mojave Desert of Clark County, Nevada, and one of many species cover by the Clark County Multiple Species Habitat Conservation Plan. USGS-WERC researchers and their collaborators have provided species habitat models for decision-support in this process.(Credit: Todd C. Esque, USGS WERC. Public domain.)