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US Fish & Wildlife Service FieldNotes

NEVADA FWO: Desert Tortoise Taxonomic Change

Region 8, July 27, 2011

The U. S. Geological Survey announced recently announced a new study that shows that the desert tortoise, thought to be one species for the past 150 years, now includes two separate and distinct species. The study, which validates previous suspicions that tortoises west and east of the Colorado River were separate species, is based on DNA evidence and biological and geographical distinctions.

The newly recognized species (Gopherus morafkai) represents populations of desert tortoise naturally occurring east and south of the Colorado River, from Arizona extending into Mexico. These tortoises have been managed as the Sonoran population of desert tortoise.

In December 2010, the Service determined the Sonoran population of desert tortoise warranted protection under the ESA, but that listing was precluded by higher priority listing needs, placing them on the candidate list.

The originally recognized species (Gopherus agassizii) will now only represent desert tortoise populations occurring west and north of the Colorado River in Arizona, California, Nevada, and Utah. These tortoises, managed as the Mojave population of desert tortoise were listed as endangered in 1989 and reclassified as threatened in 1990.

The recognition of Morafka’s desert tortoise as a new species will not change the way the Mojave and Sonoran desert tortoises are managed. The range of both the Mojave and Sonoran desert tortoises remains the same. Status evaluations of each species was conducted independently of each other. Likewise, conservation actions for both species (populations) have been, and will continue to be, managed separately.

 

Contact Info: Scott Flaherty, , Scott_Flaherty@fws.gov