Reptiles
Chuckwalla
Sauromalus ater · also called common chuckwalla, chuckwalla
The chuckwalla is a fat, loose-skinned, slow-moving lizard of the American Southwest deserts, and it has one very effective trick: when something wants to eat it, it runs into a rock crack and blows itself up like a balloon until it is impossible to remove.
Overview
Chuckwallas live in rocky desert, lava flows, and boulder hillsides of the southwestern US and northwestern Mexico, including many Gulf of California islands. They are strictly diurnal and closely tied to rock crevices, always foraging within a short sprint of one. They are herbivores — leaves, flowers, buds, and fruit of desert plants — and they hibernate through winter, active only a few hours a day in the warm season.
Wedge and inflate
A chuckwalla is slow and unarmed. Its whole defence is to reach a narrow crack before a predator reaches it, then gulp air to over-inflate its lungs and puff out the loose skin folds along its body until it is jammed tight against the rock. A coyote, snake, or hawk cannot pull it out. It deflates only once the threat is gone.
No drinking, a vegetarian, and salty sneezes
The chuckwalla never drinks — all its water comes from succulent desert plants. Eating that much plant matter loads it with salt, which it excretes as a crust from nasal glands and clears with forceful, sneeze-like exhalations — the same salt-gland system its relative the marine iguana uses on seawater. Being a strict herbivore is rare among lizards; it works because the chuckwalla has a large fermenting gut, stays hot while digesting, and lives slowly.
Status
The chuckwalla is Least Concern, common across suitable rocky desert. Some island and local populations are protected, and collection for the pet trade presses on a few.
Chuckwalla: common questions
How does the chuckwalla's inflation defence work?
The chuckwalla is a slow, ground-dwelling lizard with no venom, no sharp claws or teeth to speak of, and no ability to outrun a coyote, snake, or bird of prey. Its defence is to never be caught in the open. It always forages within a short dash of a rock crevice, and when threatened it bolts into the crack and then inflates — gulping air to over-expand its lungs and puffing out the loose folds of skin along its sides — until its body is wedged so firmly against the rock walls that it cannot be dragged out. A predator would have to break the rock, and even a person trying to extract one risks tearing the lizard. It can hold this state for a long time and deflates only when the danger has passed. (The old idea that Native Americans hunted them by puncturing the inflated lizard with a sharp stick is described in some accounts.)
Does a chuckwalla ever drink water?
Essentially never. It is fully adapted to a desert with long rainless periods and gets all the water it needs from the plants it eats — leaves, flowers, and fruit that are much more succulent than they look, especially in spring. Eating that much plant matter brings in a lot of mineral salt, more than the kidneys can handle, so the chuckwalla has salt glands in its nasal passages that concentrate the excess and expel it as a dry, whitish crust, which the lizard clears by forceful exhalations that look and sound like sneezing. Marine iguanas, its relatives, use the same nasal salt-gland system to deal with the salt in seawater.
Why is the chuckwalla a vegetarian when most lizards eat insects?
Herbivory is genuinely rare among lizards — most are insectivores or general carnivores, because a diet of leaves is hard to digest and low in energy, and it requires a large gut, a slow lifestyle, and often a large body size to make it work. The chuckwalla, like the iguanas it is related to and the marine iguana, is one of the exceptions. It has a capacious hindgut with fermenting microbes that break down plant fibre, it keeps its body temperature high while digesting to speed the process, and it moves and metabolises slowly to match its low-energy food. This lets it exploit the abundant desert vegetation that insect-eating lizards cannot use.
Can you keep a chuckwalla as a pet?
They are kept, and captive-bred chuckwallas are available, but they are considered a specialist reptile rather than a beginner's animal. They need a large enclosure with a hot basking area (up to around 40°C), strong UVB lighting, low humidity, rock structures to climb and hide in, and a herbivore diet of dark leafy greens, flowers, and some vegetables and fruit — an insect-based diet will make them ill. They are generally calm and can become tame, and they are long-lived, so they are a 20-year-plus commitment. Wild-caught chuckwallas are still traded in places, and collection is a pressure on some local populations, so captive-bred animals should be sought.