The critically endangered Bolson tortoise is the largest North American land reptile. Its closest living relative is the gopher tortoise of the southeastern US, while the desert tortoises of the desert southwest are more distant cousins. Bolson tortoises occupied much of the Chihuahuan Desert during the Pleistocene, before humans greatly reduced their numbers and range. Today, only about 2,500 bolson tortoises still exist in the wild. They live in the “Bolson de Mapimi” region of north-central Mexico where the provinces of Chihuahua, Durango, and Coahila meet.

The Turner Endangered Species Fund spearheads a unique bolson tortoise breeding program on two of Ted Turner’s southern New Mexico ranches that lie in prehistoric bolson tortoise range at the northern edge of the Chihuahuan desert. The female bolson tortoise shown here is one of 24 semi-captive adult tortoises that live in large outdoor enclosures encompassing ranch grassland. She weighs about 12 kg (26 lbs) and her shell measures ~390 mm (16.2 in). We don’t know for sure how old she is, but we know that she is at least 60.

Bolson tortoises live in underground burrows (some of which were started for them by humans, but all of which were further excavated and lengthened by the tortoises themselves and many now measure more than 20 m in length) and forage on native vegetation consisting mostly of grasses. Robust reproductive output by the tortoises has resulted in over 600 new bolson tortoises to date. (Watch this space for pictures of bolson tortoise hatchlings in the future). We hope to allow these tortoises to contribute to establishing new wild bolson tortoise populations on protected lands in the near future.