Desert Tortoise

The desert tortoise is a slow, peaceful reptile that lives in the deserts of the southwestern United States and northern Mexico. It is one of the oldest desert survivors on Earth, with ancestors dating back over 50 million years. The tortoise can live for over 80 years in the wild and survive on the moisture in plants and dew, going without drinking for months at a time. It spends approx. 95% of its life underground in long burrows that it digs itself.

  • Lifespan50 to 80+ yearsIn the wild
  • Length25 to 38 cmAdult body length
  • Where it livesMojave and Sonoran desertsPlus parts of Mexico
  • BurrowsUp to 9 m deepStays cool 95% of its life inside
  • Water sourcePlants and dewCan go months without drinking
  • StatusEndangeredNumbers dropping fast

How long does the desert tortoise live?

Lifespan in the wild (years)
G.tort.150+
Tortoise80+
Crocodile70+
Dog12

The desert tortoise is one of the longest-lived land vertebrates in North America. Galapagos giant tortoises can live even longer, up to 150 or even 200 years.

What is the desert tortoise?

The desert tortoise is a medium-sized reptile in the family Testudinidae (true tortoises). There are actually two species: the Mojave desert tortoise (Gopherus agassizii) lives in the Mojave Desert in California, Nevada and Arizona, and the Sonoran desert tortoise (Gopherus morafkai) lives further south in the Sonoran Desert in Arizona and northwestern Mexico. The two species look almost identical but were classified as separate species in 2011 based on DNA differences.

Life in a burrow

The most remarkable thing about the desert tortoise is how much of its life it spends underground. The tortoise digs long burrows in the desert soil, sometimes up to 9 metres long. These burrows are essential survival features: they stay much cooler than the surface in summer (sometimes 20 °C cooler) and much warmer in winter. The tortoise spends about 95% of its life inside these burrows, only emerging to feed, drink and breed during cool parts of the year.

Each tortoise has several burrows that it uses at different times of year. A single tortoise may have a winter hibernation burrow, summer aestivation burrows (aestivation is summer hibernation), and short-term shelter burrows used during foraging trips. The burrows are also used by other desert species; over 200 different kinds of animal have been recorded sheltering in desert tortoise burrows.

Fact The desert tortoise stores up to 40% of its body weight in water in its bladder. After heavy spring rains it drinks vast amounts and stores the water for the dry months ahead. The downside: if a frightened tortoise empties its bladder when picked up, it can lose a vital water store and die.

How does it survive without drinking?

The desert tortoise has several ways to survive long periods without drinking:

  • Stores water in its bladder. The water can be reabsorbed slowly over months.
  • Eats lots of green grass and wildflowers in spring. The food provides moisture as well as nutrition.
  • Aestivates (sleeps deeply) in summer. Hides in cool burrows during the hottest months and barely moves.
  • Produces dry waste. Like the kangaroo rat, the desert tortoise has very efficient kidneys that release very little water in its droppings.
  • Drinks rainwater directly. When rare summer rains do come, the tortoise emerges and drinks from puddles. It can also catch raindrops in shallow basins it scrapes into the desert soil.

Threats and conservation

The desert tortoise is now endangered. The Mojave population has dropped by 80% to 90% since the 1980s. The main threats are:

  • Habitat loss from urban expansion (Las Vegas is built right in the middle of Mojave tortoise habitat), military training areas, and solar power facilities.
  • Invasive grasses that fuel wildfires the desert is not adapted to. Tortoise hibernation burrows offer no protection from intense brush fires.
  • Roads. Tortoises hit by cars die. Tortoise populations crash near busy roads even before direct kills add up.
  • Disease. An upper respiratory tract disease called URTD, possibly spread by pet tortoises released into the wild, has caused major die-offs.
  • Predation by ravens. Common ravens have increased dramatically as cities and rubbish dumps have expanded into the desert. Ravens prey on young tortoises whose shells are not yet hard enough to protect them.
Did you know? The desert tortoise is the state reptile of California and Nevada. Both states have made keeping captive-bred desert tortoises as pets relatively easy as a way to encourage public engagement with the species, but releasing pet tortoises into the wild is illegal because they can spread disease.
Deeper dive: tortoise biology, head-starting programmes and the Ivanpah controversy

Desert tortoises are slow-growing and extraordinarily slow to reach maturity. They take 15 to 20 years to be ready to breed, and a female lays only 4 to 6 eggs per year. Most eggs and hatchlings are eaten by predators (ravens, snakes, badgers, foxes, even ants), so each tortoise that survives to adulthood is the survivor of long odds. This long-slow-life-history is well-adapted to a stable desert environment where adults can live for decades, but it makes the species extremely vulnerable to any threat that increases adult mortality. A single year of bad fire or a sustained disease outbreak can wipe out decades of reproduction.

Several conservation organisations now run head-starting programmes for the desert tortoise. Eggs are collected from wild females (or from purpose-bred captive populations), incubated, and the hatchlings are raised in protected enclosures until their shells are large enough to resist most predators (typically approx. 5 years old). The young tortoises are then released into the wild. The technique has shown some promise but is expensive and time-consuming, and the released tortoises still face all the original threats. The most successful programmes combine head-starting with predator-control programmes that reduce raven populations and habitat-restoration projects that remove invasive grasses.

The conflict between desert tortoises and large-scale solar power development is one of the most difficult challenges in modern American conservation. The Mojave Desert, with its huge flat empty spaces and intense sunshine, is one of the best locations in North America for utility-scale solar power. But it is also the home of the endangered desert tortoise. The Ivanpah Solar Project, built between 2010 and 2014, displaced an estimated 700 tortoises during construction; tortoises were relocated to other areas, but several died in the process and the long-term survival of relocated populations is uncertain. The federal Bureau of Land Management has since designated specific "Solar Energy Zones" in the desert to focus solar development in areas where tortoise populations are smaller, but the trade-off between clean energy and desert biodiversity remains contentious.

For other desert animals, see desert animals. For the home deserts, see Mojave and Sonoran.