Bolson Tortoises of the Chihuahuan Desert by Rick LoBello
Bolson tortoises live in two locations at the Zoo, on the north side of the Americas Land exhibit where they live with our peninsular pronghorns and javelinas and across from the entrance to the El Paso Water Utilities Discovery Education Center.
The bolson tortoise is an endemic species of the Chihuahuan Desert that was only recently discovered in 1959. Biologists use the term “endemic” to describe any plant or animal species living in one particular place or region. Of the 156 reptile species living in the Chihuahuan Desert, 24 species are endemics. This tortoise is also known as the Mexican giant tortoise or yellow-bordered tortoise. In Mexico it is called tortuga grande, tortuga llanero or tortuga topo.
Long before the coming of the first European explorers to North America, bolson tortoises are believed to have lived in the El Paso region during the Pleistocene Epoch that lasted from 1.65 million to 10,000 years ago. It was during this period about 14-30,000 years ago that humans migrated to North America. More than likely some early humans might have eaten tortoises as a source of protein.
Bolsons are the largest tortoises in North America reaching 18" in length and weighing up to 30 pounds. The species was discovered by accident in 1959 when scientists working in an area where the boundaries of the Mexican states of Chihuahua, Coahuila and Durango come together, came across the species by chance. The story goes that they found a tortoise shell being used as a dish to hold chicken feed. When they asked the rancher where the shell came from he pointed into the desert describing the “la tortuga grande del desierto,” the big turtle of the desert. Not long after, a new species of tortoise was described and given the Latin name Gopherus flavomarginatus.
Bolsons are the largest tortoises in North America reaching 18" in length and weighing up to 30 pounds. The species was discovered by accident in 1959 when scientists working in an area where the boundaries of the Mexican states of Chihuahua, Coahuila and Durango come together, came across the species by chance. The story goes that they found a tortoise shell being used as a dish to hold chicken feed. When they asked the rancher where the shell came from he pointed into the desert describing the “la tortuga grande del desierto,” the big turtle of the desert. Not long after, a new species of tortoise was described and given the Latin name Gopherus flavomarginatus.
Today bolson tortoises survive mainly in one small area of northern Mexico near Torreón, Coahuila called the Bolsón de Mapimí. I first came to know this species during the spring of 1990 when I was working for the Big Bend Natural History Association. Big Bend National Park Superintendent Jim Carrico, Chief Ranger Phil Koepp and I joined officials from Texas Parks and Wildlife Department on a trip to visit critical bolson tortoise habitat in Mexico. We were joined by scientists from California who were studying the bolson tortoise at the Bolsón de Mapimí Man and the Biosphere Reserve and Research Station in Durango. Soon after we returned the Los Angeles Times published a story about a proposed reintroduction effort that would return bolson tortoises to their former Pleistocene range in Big Bend National Park. Twenty-four years later there are no plans to return this species to the park, but the effort remains on the radar screen of Big Bend park officials.
Bolson tortoises live in two locations at the Zoo, on the north side of the Americas Land exhibit where they live with our peninsular pronghorns and javelinas and across from the entrance to the El Paso Water Utilities Discovery Education Center. The Zoo Education Team also has some bolson tortoises in our education animal collection. These tortoises are shown to Zoo guests during special animal encounter programs and as part of Zoo Adventure classes for school children.
During the winter months from about November to February bolson tortoises hibernate in underground burrows and as are result are not visible. The bolson is the only animal at the Zoo that hibernates in its exhibit.
During the winter months from about November to February bolson tortoises hibernate in underground burrows and as are result are not visible. The bolson is the only animal at the Zoo that hibernates in its exhibit.
The El Paso Zoo is working with the Turner Endangered Species Fund and the Living Desert Zoo and Gardens State Park in helping with a reintroduction project near Truth or Consequences, New Mexico at the Ladder and Armendaris Ranches. Zoo staff is assisting research scientists in determining the gender of baby tortoises, as part of a larger effort to breed bolson tortoises for eventual release into portions of their former range.
According to the IUCN Red List “this species is listed as Vulnerable because it has experienced a population decline of up to 50% over the past 3 generations. It faced catastrophic levels of exploitation during the middle of the 20th century, with subsequent lower levels of exploitation. At present the species is protected from direct exploitation and part of its extent of occurrence is protected, but some subsistence collection and habitat degradation impacts likely still occur. With the worst impacts over, it is rated Vulnerable (under A1) rather than Endangered (under A2). About six separate subpopulations exist, comprising some 7,000 to 10,000 adults, collectively occurring over about 7,000 sq. km."
You can help support El Paso Zoo conservation efforts my making a tax deductible contribution to the El Paso Zoological Society.
Tortoises, like these Galapagos tortoises, are one of several dozen species of animals at the Zoo that get to enjoy pumpkins during Boo at the Zoo. This year’s Boo at the Zoo is planned for October 25-26.
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