Mexican Bolson Tortoise
(Gopherus flavomarginatus)

La Tortuga de Mapimí en Español This page is also available in Spanish.

by Alida Madero Enkerlin

The Mexican Bolson Tortoise (Gopherus flavomarginatus) is one of four North American tortoise species. Although it is the largest, its carapace (upper shell) may reach 18 in. in length, the remoteness of its habitat and its secretive nature kept it unknown to the scientific world until 1958. That year, some researchers from Illinois on a field trip to Mexico discovered a bolson carapace being used as a chicken feeder by people, and found it to be of an undescribed species. Later, in 1973, David Morafka from California State University, conducted a survey to determine the animal's status, and found that the population was in big trouble. The tortoise's habitat (a small desert area in north-central Mexico, known as Bolsón de Mapimí) was shrinking, and it was hunted by local people for food.

In 1976 the Mexican Government declared the area as a Biosphere Reserve, and the Instituto de Ecologia established a biological station there. Gustavo Aguirre, a Mexican biologist, was sent to the biological station to start the tortoise research, and develop a plan for its conservation.

Aguirre, together with Morafka and Gary Adest, from the University of California at San Diego, started to define the natural history of the Bolson Tortoise. They found that the tortoise's range extended from the Great Plains west of Arizona to southern Mexico over 10,000 years ago. Changes in conditions brought by the end of the last ice age reduced its range to the desert basin where they are now found. Tortoises live in colonies of up to 100 individuals, where they forage during the early and late daylight hours. During the rest of the day, the tortoises hide from the sun inside their burrows, which they excavate using their forelimbs. In winter, they remain dormant inside their burrows. Their lifespan has been estimated at up to 80 to 100 years, and they start breeding at 12 to 15 years of age.

Mexican Bolson tortoises feed from the wiry Tobosa bunch grass, which has been replaced by irrigated pastures for cattle in many areas. During the rainy season, the tortoises come out of their burrows and drink up to one pint of water. This is enough to keep them alive another year in the desert. Following that, they mate, establish their nests, and lay eggs. Unlike marine turtles that lay hundreds of eggs, the Mexican Bolson tortoise lay only 12 to 15 eggs. The eggs and young are easy prey for ravens, coyotes, badgers, skunks, roadrunners and hawks, and only about 3% of hatchlings survive.

Gustavo Aguirre also focused his research on the local human population. He started to educate them of the problems, uniqueness, and value of their tortoise neighbor. Education has paid off. Over the past years, attitudes have shifted, and local people have agreed not to consume the tortoise anymore. They now have a sense of pride for their reserve and its wildlife.

bolson hatcling Additionally, an artificial incubation program was started, and ex-tortoise hunters, now help to find gravid (egg laden) females. The females are taken to the research center, where their eggs are collected and incubated. Furthermore, local people were also hired and trained to maintain the research center, feed the young hatchlings, and monitor their progress for the 3 to 5 years that the young tortoises are kept there. The results have been very successful, with survival at about 80%.

Although in 1973 David Morafka feared the extinction of the tortoise by the year 2000, things seem more optimistic today. High hopes are being set on the reintroduction of captive reared Tortoises to gradually increase their population and have this wonderful animal come back from the edge.

*NOTE: Special thanks to Gustavo Aguirre from the Instituto de Ecologia A.C. for all his help in providing the materials to write this animal profile.

Mexican Bolson Tortoise (Gopherus flavomarginatus)

Mexican Bolson Tortoise
(Gopherus flavomarginatus)