The U.S. Fish and Wildlife Service acknowledges threats to the Sonoran desert tortoise posed by housing developments and off-road vehicles, saying these may increase over time. But it says the tortoise isn’t at risk of extinction in the foreseeable future.

 Kelly Presnell, Arizona Daily Star

Leer en espaΓ±ol

After years of pressure and litigation from environmental groups, the U.S. Fish and Wildlife Service is sticking with a previous stance that the Sonoran desert tortoise doesn't need federal protection from development, wildfires, drought or other environmental threats.

The service announced this week that a comprehensive scientific review determined the tortoise isn't at risk of extinction in the foreseeable future, despite a wide range of threats to the animals and their habitat. So it won’t list the tortoise as endangered or threatened, the service said.

An activist from one of two environmental groups that’s pushed for federal protection of the tortoise accused the service of ignoring threats to the armored-shell animal from livestock grazing. The agency's Federal Register notice announcing its decision made no mention of grazing as a threat to the tortoise's existence, while listing other threats, noted Cyndi Tuell of the Western Watersheds Project.

"They're painting this rosy picture. They're not looking at all the risks to tortoise in their (computerized) prediction models. They are underestimating how quickly the tortoise populations will decline in the future," said Tuell, the group's Arizona-New Mexico director.

The service's decision, announced Monday, said the tortoise numbers in the hundreds of thousands. Computer modeling indicates an estimated 49,222 square miles of suitable Sonoran desert tortoise habitat occurs in Arizona and Sonora. The service has widely varying estimates of total tortoise population, from 148,358 to 2.5 million adults with an average estimate of about 549,000.

The Arizona Cattle Growers Association is gratified by the service’s decision, said Jeff Eisenberg, an association lobbyist.

β€œWe always want the Fish and Wildlife Service to make decisions based on the facts and science and too often in our view that is not the case. So we are gratified that the evaluation of the information led to this conclusion and we just hope it will be supported by the facts and science and it will be sustainable in court,” Eisenberg said Tuesday.

Environmentalists said the tortoise's habitat also is degraded by invasive species, increased fire risk, housing developments, off-road vehicles, habitat fragmentation, and increased predation facilitated by human activities.

The wildlife service acknowledged many of these threats and said several, mainly development and drought, may increase over time. But the species and its associated habitat are projected to remain at levels that don't threaten the tortoise's survival, the service said.

"The service has found the Sonoran desert tortoise currently occupies much of its historical range where populations remain stable. ... Available survey data have not indicated systematic declines or extirpations," the service said.

The decision comes more than 13 years since Western Watersheds Project and Wild Earth Guardians petitioned the federal wildlife agency to list the tortoise as endangered or threatened.

The service found in 2010 that its listing was warranted but precluded by higher priority species, then found in 2015 that a listing wasn't warranted.

The two groups sued the service in 2019 seeking to overturn the latter finding. In 2020, the service agreed in an out-of-court settlement to reconsider it, but Monday's decision reaffirmed it.

"It’s hopeful news that the Service thinks the future is rosy for the Sonoran desert tortoise based on the agency’s modeling scenarios, and we certainly hope they are right,” said Tuell in a written statement.

But the tortoise's habitat remains "gravely threatened," said Tuell, who is based in Tucson.

The tortoises live in the Sonoran Desert of Arizona and Sonora in Mexico. Adult tortoises range from 8 to 15 inches long, with a relatively high domed shell, usually brownish with a pattern and prominent growth lines. They can live to be 35 to 40.

Sonoran desert tortoises spend most of their time in below-ground shelter areas, and their emergence into the open air is timed to availability of resources such as precipitation or forage, the service said.

Their habitat typically consists of rocky slopes and washes that support shelter sites, the service said.

The service estimated the Sonoran desert tortoise not only occupies much of its historic range, but is "abundant" in Arizona and Sonora.

The agency's computer modeling projects future drought is expected to result in a negative growth rate for tortoise populations by the end of this century and likely declines in its overall abundance, the service said.

But the modeling found less than a 1% risk that by the end of the century, the tortoise will reach a state of quasi-extinction, in which a species population may be doomed to extinction even if individuals are still alive, the service said.

Last year, the watersheds project sent the service a detailed report, outlining what its staffers believe are grazing impacts on the tortoise. It cited peer-reviewed studies the watersheds project said identified risks to tortoises or to their habitat from grazing.

β€œIn brief, livestock compete with tortoises for the same food, especially in late winter/early spring or monsoon rainy seasons. They crush plants tortoises rely on for food. They crush burrows and actual tortoises.”

Livestock infrastructure also harms tortoise habitat, the group said. First, fences and roads can create barriers to movement, it said. Fences provide perches for ravens and other tortoise predators, and increases in watering tanks for livestock provide increased predator populations in tortoise habitat, the group said.

Tuell noted that more than 8,500 square miles of tortoise habitat is managed by the Bureau of Land Management for livestock grazing. Over 77% of the bureau’s grazing allotments have 10-year permits that have been renewed at least once without analysis of impacts on the tortoise, she said.

That’s possible due to a 2014 congressional legislative rider that allows BLM to continue authorizing grazing on federal lands without requiring collection or analysis of grazing’s impacts, she said.

Last September, a wildlife service report on the tortoise said livestock grazing management is an example of how β€œmulti-use” lands can bring at least indirect wildlife benefits and moderate conservation value to the tortoise. On those lands, β€œbest management practices” are designed and implemented to reduce potential negative effects in some cases and provide direct benefits in others, the wildlife service said.

That report listed grazing as one of a variety of β€œstressors” that may affect individual tortoises but don’t have measurable effects on population levels, the wildlife service wrote.

Arizona cattle growers recognize that the Endangered Species Act is an established law in this country, their lobbyist Eisenberg said.

β€œWithin the implementation of that act, to extent the agency has discretion, we also strongly believe it’s important to take into consideration the impacts of their decisions on people,” Eisenberg said. β€œOur concern always is it’s not taken into consideration enough.”

Become a #ThisIsTucson member! Your contribution helps our team bring you stories that keep you connected to the community. Become a member today.