Seeing Double: Desert Tortoises Are Really Two

Just like Lindsay Lohan, the desert tortoise can’t seem to stay out of the news these days.

Proving that the only thing better than one desert tortoise is two desert tortoises, the Zoology journal ZooKeys has announced the recent discovery that the charming tortoise found roaming the Mojave and Sonoran deserts is not one but two distinct species of helmeted reptiles.

In a quirk of geography that would make Charles Darwin smile, the dividing line appears to be the Colorado River. The originally named species – Gopherus agassizii – is found west and north of the river, predominately in California. The new species of desert tortoise – Gopherus  morafkai – makes its home east and south of the Colorado, mostly in Arizona and Mexico.

The Desert Dispatch reports:

Along with the genetic differences between the tortoises, there are also some physical and behavioral differences, said Mickey Quillman, chief of resources for the Barstow Bureau of Land Management office. Sonoran tortoises normally have taller shells, often live in rockier climates and have different reproductive patterns. Mojave tortoises sometimes lay more than one clutch of eggs a year while Sonoran tortoises usually only lay one clutch of eggs each year, said Quillman.

According to the study, the designation of a new species would result in the loss of 70 percent of the home range for the Mojave tortoise, because much of the current desert tortoise habitat is in Arizona and Mexico.

This revelation could mean some interesting maneuverings for companies that want to build massive solar power plants on terrapin territories. Instead of one endangered species, they will have to contend with the possibility of two.

According to EE News

…the Mojave Desert tortoise is listed by the Fish and Wildlife Service as threatened under the Endangered Species Act. FWS last year evaluated the Sonoran tortoise population independently and placed it on a “candidate” list of species that warrant federal protection but cannot be listed due to a backlog of other deserving species.

But environmentalists say the new study highlights the need to list the Sonoran tortoises as threatened or endangered to protect its dwindling habitat.

When the Mojave and Sonoran tortoises were considered a single species, their combined habitat extended for millions of acres, and mitigating the impacts of large-scale renewable-energy projects was simple because there was still plenty of land for displaced tortoises to relocate. But if the tortoises are two distinct populations occupying two distinct — and thus significantly smaller — regions, that could complicate renewables development.

Some in high places aren’t putting too much stock into the findings, tho. According to Forbes:

The United States Fish and Wildlife Service already manages the Mojave and Sonoran populations separately and a spokeswoman said the new species designations will not change the way the agency analyzes the impact of solar power plants on the Agassiz’s desert tortoise.

“We independently evaluated the Mojave population of desert tortoise and there is no evidence to suggest the species is expected to go extinct, which is the threshold for uplisting to endangered status,” Jeannie Stafford, a public affairs officer in the agency’s Nevada office, said in an email. “We do not anticipate any changes in the way development projects will be evaluated for the Agassiz’s desert tortoise in the future.”

 Others, including the researchers of the paper, beg to differ:

“This reduction has important implications for the conservation and protection of Gopherus agassizii, which may deserve a higher level of protection…Whereas species with broad distributions may survive population declines, those that have small distributions are far more likely to become extinct.”

“Given drastic population declines of G. agassizii during the past few decades, it might be endangered.”

In 1990, the feds listed the (Mojave) Desert tortoise as a threatened species with its critical habitat designated in 1994. It’s been a rough ride for the reptiles even with protections in place – their numbers decline for many reasons: they get squished by vehicles, their habitat is shrinking because of development and they catch diseases, to name a few.

Maybe being a “double” will increase their chance of survival as a whole?