The average life expectancy of North America's largest and rarest tortoise species is unknown. But scientists say the animals could live more than 100 years.
The Bolson tortoise is an endangered species. Saving it from extinction is a long-term project. But a conservation effort took a step toward that goal last week.
United States wildlife officials reached an agreement with the Turner Endangered Species Fund. The deal permits the release of Bolson tortoises on land owned by Ted Turner, a media industry leader.
The release of captive tortoises on the Armendaris Ranch is designed to create a free-roaming population. Last week, 20 adult tortoises were released on the property, which is already home to 23 of them. There are also many younger tortoises.
The tortoises usually spend about 85 percent of the time in their underground burrows, which in some cases can be about 20 meters long. The animals live long lives and are slow to reproduce.
Shawn Sartorius is with the Fish and Wildlife Service. He said the results of the breeding and restoration project will not be seen in his lifetime.
“What we’re doing here is establishing a population here that can be handed off to the next generation,” Sartorius said.
It is a step toward one day releasing the tortoises in more places in the Southwest. Conservationists are also pushing the federal government to consider creating a recovery plan for the species. The tortoise is part of a growing effort to find new homes for endangered species as they flee climate change and other threats to their natural habitats.
Wild Bolson tortoises are found only in the grasslands of north-central Mexico. The animal once lived in a much greater area that included the southwestern United States. Fossil records also show it was once present it the southern Great Plains, including parts of Texas and Oklahoma.
Scientists estimate the wild population of Bolson tortoises in Mexico is under 2,500. Experts say the animals are hunted as food and as pets. Their habitat is shrinking, as more desert grasslands become farmland.
The 1,450 square kilometer Armendaris Ranch appears to be a great area for the tortoises. In all, the Turner Endangered Species Fund and its partners have been able to grow the population from 30 tortoises to about 800, said Chris Wiese. She leads the project at the Armendaris Ranch.
“The releases are the essential step to getting them back on the ground and letting them be wild tortoises,” she said.
The tortoises released last week will be able to live freely in the 6.6-hectare pen. They are given electronic trackers, and wildlife workers will check on them once a year.
Depending on weather and other factors, it can take a few years or more for a hatchling to reach just over 110 millimeters long. They can eventually grow to about 370 millimeters.
The species was unknown to science until the late 1950s and has not been studied closely.
The goal is to build a strong captive population that can be used as research for future releases into the wild — both in the U.S. and Mexico. That work will include getting state and federal permits to release tortoises outside Turner lands.
Those recently released hit the ground crawling. They wandered through grass and around desert plants as the Fra Cristobal mountain range appeared in the distance.
It was a moment that Wiese and her team have been working toward for years.
“We are not in the business of making pets,” she said. “We're in the business of making wild animals and that means you have to let them go.”
I’m Dan Novak.
