The Return: Great news for the Bolson Tortoise

The Turner Endangered Species Fund with the help from partners including the El Paso Zoo and Botanical Gardens recently made conservation history by releasing captive-born Bolson Tortoises in the Chihuahuan Desert grasslands of New Mexico.

Thirty years ago, I was very fortunate to join a team of scientists and National Park managers on a trip to the land of the bolson tortoise.   Up until earlier this year there was only one wild population of this  species at the Bolson Mapimi Biosphere Reserve in northern Mexico.  According to the IUCN Red List assessment bolson tortoises are critically endangered and only about 2,500 individuals remain in the wild at the intersection of the states of Chihuahua, Durango and Coahuila.  Ever since the species was first discovered in 1959 the fate of the largest tortoise in North America has hung in the balance.  

Fossil evidence documents a distribution throughout the Chihuahuan Desert, from Arizona to western Texas, as recently as the late Pleistocene. The likely cause of the current restricted range was predation by humans after the last Ice Age.

Adult bolson tortoise at the El Paso Zoo

When we met at the Bolson Mapimi everyone agreed that saving this relict species would involve restoring the species to its former habitat in the Chihuahuan Desert.  Such an effort would also have the added benefit of helping to restore desert habitat via a native, burrowing herbivore.   The El Paso Zoo and Botanical Gardens has been supporting this effort for over 20 years and most recently our medical staff worked with the Turner Endangered Species Fund and the Living Desert Zoo and Gardens State Park in 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.

This project is very noteworthy for our Zoo.  The successful restoration of the bolson tortoise represents the first extinct Pleistocene species to be rewilded in the United States. Pleistocene rewilding is the advocacy of the reintroduction of extant Pleistocene megafauna, or the close ecological equivalents of extinct megafauna. Other species that have been proposed to be rewilded include tapirs, jaguars, camels and cheetahs.

Rick LoBello, Chair, Chihuahuan Desert Education Coalition

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