Pleistocene Rewilding: Endangered Tortoises Land In New Mexico

From New Mexico Wilderness Alliance

Thirty-seven endangered bolson tortoises, the largest tortoises found in North America at up to 18 inches long, came to New Mexico this year from a ranch in Arizona.

Most are at Ted Turner’s Armendaris Ranch near Truth or Consequences.

Turner’s ranches in New Mexico also are home to endangered Mexican gray wolves, black-footed ferrets and aplomado falcons.

The bolson tortoises are believed to have been in the Southwest for thousands of years but were discovered by scientists only in the late 1950s in Mexico.

There are 26 adult tortoises in a pair of 8-acre pens at the Armendaris and four tortoises at the Living Desert Zoo and Gardens State Park in Carlsbad. Seven additional young tortoises that hatched this summer are at Turner’s Ladder Ranch, also near T or C.
Bolson tortoises once were found in New Mexico, Arizona, Texas and Oklahoma, as well as in Mexico. The only ones left in the wild now are a small population in the Chihuahuan Desert in Mexico.

In the summer, research will focus on nutrition, reproduction and growth of the young, said Joe Truett, senior biologist for the Turner Endangered Species Fund and overseer of the bolson program.

“The first priority next year is to figure out how to capture the eggs— so we can hatch even more young,” Truett said.

The bolson tortoises don’t start breeding until they are 15 or 16 years old. Females lay 12 to 15 eggs at a time, then bury them and leave them to fend for themselves.

Only about 3 percent survive in the wild. This year, seven of 10 eggs placed in an incubator hatched.

The good news is that the captive population is large enough to seed a wild population.

“The long-term plan is to release them into the wild (on the Turner ranches) on an experimental basis,” Truett said, but he added that the effort would be undertaken very cautiously and wouldn’t start for several years.

Like all tortoises, the bolsons don’t do anything quickly. They don’t mature until their teenage years and can live to be more than 100 years old.

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