The desert tortoise is an iconic species found across the deserts of the US southwest as well as northwestern Mexico. It is also the official State Reptile of both California and Nevada.
“Desert tortoise” actually refers to two different species—Gopherus agassizii and Gopherus morafkai—with Gopherus agassizii found entirely in the US and Gopherus morafkai found in Mexico as well as in parts of Arizona.
The desert tortoise was placed on the California Endangered Species List in 1989 and was listed as “threatened” on the Federal Endangered Species List in 1990.
Threats to Survival
Although they appear to be built like tanks covered with armor and can retract into their shells to protect themselves against predators, there are a number of factors that make desert tortoises a fragile species. They are slow moving, slow growing, and have low reproductive rates. Juvenile survival is low (with only about 2 or 3 tortoises out of 100 hatched eggs surviving to adulthood), and females do not breed until reaching the age of approximately 15-20 years old. They are impacted by some larger predators directly, but smaller predators such as roadrunners, ravens, and fire ants can also severally impact desert tortoise populations by targeting eggs and young. Ravens are particularly a problem, as the population of ravens increases as the population of humans in the desert increases (as does their production of trash, which the ravens feed off of).
For many decades, these animals were frequently removed from their habitat by humans and taken home to the suburbs and kept as pets, contributing to a decline in population. Later, as the public became more educated about the illegality of taking desert tortoises, some people thought they were doing the right thing by taking the animals back to the wild and releasing them. However, pet tortoises frequently carry infectious diseases which are easily transmitted to natural populations. In addition, captive-bred pet tortoises were also released into the wild, negatively impacting the natural population because of their different genetics and behaviors. Humans are even a direct threat, and the simple act of handling a tortoise in the wild can spread Upper Respiratory Tract Disease which has seen a marked increase in recent years.
Other threats to the desert tortoise include OHV use, grazing, military exercises, mining, agriculture, energy development, and invasive species.
Because of its iconic nature as well as its status as a threatened species, there are many things being done to help protect the desert tortoise and educate the community. A few examples include:
As we continue to expand our footprint across fragile desert ecosystems with more roads and more traffic on existing roads, desert tortoise mortality due to collisions with vehicles is increasing. One very simple yet highly effective solution is a type of low fencing technique called Desert Tortoise Exclusion Fencing. A ~36 inch tall piece of fencing is buried 12 inches below the ground, to prevent tortoises from digging underneath; and left to stand 24 inches above the ground—tall enough to prevent the low-slung desert tortoise from surmounting it, yet low enough to not impede the free movement of many other animals.
The Desert Tortoise Preserve Committee is a non-profit working to conserve desert tortoises and educate the public. Founded in 1974, they protect ~5,000 acres of desert tortoise habitat. The largest piece of land under their protection, the Desert Tortoise Natural Area, is a preserve in the western Mojave Desert encompassing 39.5 square miles. In 1980, the BLM designated the area as an Area of Critical Environmental Concern as well as a Research Natural Area.
Established in 1975, the Desert Tortoise Council is a non-profit organization that promotes desert tortoise conservation across the southwestern United States and Mexico. They offer several training courses covering topics for researchers and volunteers such as field techniques and health assessment procedures.
The Living Desert in Palm Desert, California, offers a Desert Tortoise Information and Youth Education Program which provides educators with a variety of resources to help teach about desert tortoises in their classrooms. They also offer a Desert Tortoise Adoption Program in partnership with the California Department of Fish and Game, allowing people to adopt captive-bred desert tortoises that are unsuitable for reintroduction into the wild.