The U.S. Fish and Wildlife Service (Service) announced today that after an extensive status review of the Sonoran desert tortoise it has determined the population warrants protection under the Endangered Species Act (ESA) but is precluded by the need to address other higher priorities. The species will be added to the list of candidates for ESA protection, where its status will be reviewed annually.
“Much like the saguaro cactus, the Sonoran desert tortoise is symbolic of the rich Southwestern desert,” said Steve Spangle, the Service’s Arizona field supervisor. “A collection of various conservation partners have made great strides to better understand and protect the Sonoran desert tortoise, but our comprehensive analysis shows an increasing magnitude of threats is offsetting some conservation efforts. This candidate conservation status should increase opportunities for reversing this trend.”
The Service’s determination – also known as a 12-month finding – indicates sufficient scientific and commercial data exist to warrant protecting the Sonoran desert tortoise as a Distinct Population Segment (DPS) under the ESA. This follows a comprehensive review of the best available scientific information concerning the Sonoran desert tortoise and the threats it faces. A combination of habitat loss and threats resulting from increasing population growth in the Southwest and northern Mexico are threatening the Sonoran population of the desert tortoise.
A major threat to the species is the conversion of Sonoran desert scrub to fire-prone grasslands. In Mexico, grassland conversion programs continue to benefit livestock grazing. In the U.S., intentional conversion programs were discontinued by 1987, but the invasion of nonnative grasses continues, primarily along roadways and trails. Grassland wildfires also consume non-fire adapted Sonoran desert plants that provide cover and forage for desert tortoises and other wildlife. Climate change-caused shifts in rainfall patterns and continued drought are also affecting the availability of forage and habitat in the Southwest. Additional barriers to tortoise movement include roadways, urban development and anticipated large solar projects on desert floors. Sonoran desert tortoise populations can typically withstand any one of these impacts alone, but succumb to the combined effects of multiple threats.
The ESA provides a critical safety net for America’s native fish, wildlife and plants. The unprecedented challenge of climate change climate change
Climate change includes both global warming driven by human-induced emissions of greenhouse gases and the resulting large-scale shifts in weather patterns. Though there have been previous periods of climatic change, since the mid-20th century humans have had an unprecedented impact on Earth's climate system and caused change on a global scale.
Learn more about climate change and its broad, complex impacts on species and habitat make it even more imperative to have an effective, collaborative approach to conserving and recovering imperiled species.
The Sonoran desert tortoise differs from the Mojave desert tortoise, which has been listed under the ESA as threatened since 1989. The Sonoran desert tortoise occurs south and east of the Colorado River, and half of its range extends into northern Mexico where it is currently listed as threatened by the Mexican government. Unlike the Mojave population that generally occupies desert valley floors, the Sonoran desert tortoise generally prefers rocky, steep slopes and bajadas (lower mountain slopes including alluvial fans — fan-shaped deposits at the ends of canyons formed when fast flowing streams slow and widen) and, to a lesser extent, others may occupy flatter terrain.
The Service will add the Sonoran desert tortoise to its list of candidate species and review its status annually. Candidate species do not receive protection under the ESA, although the Service works to conserve them. The annual review and identification of candidate species provides landowners and resource managers with notice of species in need of conservation, allowing them to address threats and work to preclude the need to list the species. The Service is currently working with landowners and partners to implement voluntary conservation agreements covering 5 million acres of habitat for more than 130 candidate species.
Desert tortoises are recognized by their gray to orange-brown, high, domed shell. The desert tortoise may reach 8 to 15 inches in length and 4 to 6 inches in height, and may weigh 8 to 15 pounds as adults. The Sonoran desert tortoise occurs predominantly in desert scrub habitat. Primarily herbivores, Sonoran desert tortoises eat a variety of fresh, residual, and dried annuals, perennials, and plant litter. Sonoran desert tortoises are largely inactive from mid-October to late February or early March when they overwinter in constructed burrows or rocky cavities or crevices.
The Sonoran desert tortoise is a popular household pet for many Arizona families. At this stage, it is premature to speculate on federal rules regarding domestic tortoises if the Sonoran desert tortoise were listed. However, both federal and state wildlife agencies strongly encourage private citizens to never release captive tortoise back into the wild. Released captive tortoises pose a threat to wild populations through the spread of disease and genetic contamination. Breeding captive desert tortoises is also strongly discouraged, as this may hurt on-going conservation efforts and contributes to the over-abundance of unwanted tortoises.
A copy of the today’s finding, images, and other information about the desert tortoise is available at http://www.fws.gov/southwest/es/arizona/. Information regarding the status and conservation of, and any potential threat to, the Sonoran desert tortoise will be of value to the annual review of today’s finding and may be submitted by mail to Field Supervisor, Arizona Ecological Services Office, 2321 West Royal Palm Road, Suite 103, Phoenix, AZ 85021–4951 or email to SonoranDT@fws.gov
America’s fish, wildlife and plant resources belong to all of us, and ensuring the health of imperiled species is a shared responsibility. We’re working to actively engage conservation partners and the public in the search for improved and innovative ways to conserve and recover imperiled species. To learn more about the Endangered Species program, go to http://www.fws.gov/endangered/.
A photo slideshow is posted at: http://www.flickr.com/photos/usfws_southwest/sets/72157625590922502/show/with/5257642933/
