Threatened and Endangered Species

USGS Southwest Biological Science Center's Grand Canyon Monitoring and Research Center leadership and PIs prepared a cooperator publication and a presentation that report on modeling results to evaluate potential effects of reservoir management on various resources in Lake Powell and Grand Canyon.

Grand Canyon National Park is a hotspot for bat diversity. Twenty-two bat species have been documented in the Park, more than any other national park unit.

The saguaro cactus ( Carnegiea gigantea ) is a keystone species that grows only in the Sonoran Desert of northern Mexico and the southwestern United States. The USGS’ Southwest Biological Science Center is working to better understand the species’ biological features, its role as a keystone species that supports greater than 100 other plant and animal species, and its responses to climate change...

Did you know that moths can be pollinators? Even more amazing is that Joshua trees, the scraggly icons of the Mojave Desert, require a single moth species to ensure fertile seed production. The association between the Joshua tree and its pollinating moth is a rare example of an obligate mutualism, which means that the species are entirely dependent upon each other. Joshua trees depend on the moth...

The federally-listed threatened humpback chub is a native fish of the Colorado River. Despite the environmental changes to the river following the construction of Glen Canyon Dam, humpback chub persists alongside nonnative species, including rainbow trout. The pre-dam Colorado River experienced seasonal variation in temperature and discharge. Seasonal flooding resulted in sediments carried...

In the western United States (U.S.), there are many regionally restricted, rare species resulting from complex demographic and ecological processes through time. In addition to the inherent risks associated with being rare (i.e., having few individuals spread over a limited area that could be disproportionately affected by chance events), anthropogenic disturbances are increasing in magnitude...

Glen Canyon Dam has altered ecological processes of the Colorado River in Grand Canyon. Before the dam was built, the Colorado River experienced seasonable variable flow rates, including springtime flooding events. These spring floods scoured the river bottom and enhanced natural processes that sustained the Colorado River ecosystem. Since the dam’s construction in 1963, springtime floods have...

Just below Glen Canyon Dam on the Colorado River is a very popular Blue Ribbon trout fishery known for its rainbow trout. However, approximately 78 miles downstream, near were the Little Colorado River flows into the Colorado River, is a population of endangered humpback chub. The introduced rainbow trout can negatively affect native humpback chub by competing with them for food (immature black...

Introductions of bio-control beetles (genus Diorhabda) are causing defoliation and dieback of exotic Tamarix spp. in riparian zones across the western U.S., yet the factors that determine the plant communities that follow Tamarix decline are poorly understood. In particular, Tamarix-dominated soils are often higher in nutrients, organic matter, and salts than nearby soils, and these soil...

Rainbow trout is a desirable sport fish that has been introduced in many locations around the world. Although introductions of rainbow trout and other nonnative fishes provide recreational fishing opportunities, they also pose threats to native fish populations. The Glen Canyon Dam Adaptive Management Program has tasked scientists and managers with identifying management options that allow rainbow...

Introduced rainbow trout and brown trout are considered a threat to the endangered humpback chub in the Colorado River in Grand Canyon. These introduced species eat native fish, but impacts are difficult to assess because predation vulnerability depends on the physical conditions under which predation takes place. We studied how predation vulnerability of juvenile humpback chub changes in response...

Although it is not listed on the Federal Endangered Species list, there is considerable concern over northern leopard frog declines in western North America. It is listed as a “special concern” species by some state wildlife agencies (e.g., Arizona Game and Fish Department 1996) and declines have been reported in Arizona, Colorado, New Mexico, and other areas across the west. Leopard frogs have...