San Estaban Island chuckwalla

February 14, 2017


On the islands of San Esteban, Roca Lobos, and Pelicanos in the Gulf of California, you will find the largest of the chuckwalla species.

Growing upwards of 30 inches long, this type of chuckwalla is endemic to the previously mentioned islands. Plants and animals that are endemic to an area are found in one location because there are physical barriers that prevent the animal from leaving -- in this case, the large body of water surrounding the island. Because of this, the San Esteban Island chuckwalla has developed a unique coloring and size.

All chuckwallas are found in the southwestern United States and Mexico. Thanks to the desert climates these lizards reside in, spending time sunning themselves helps these ectothermic, or cold-blooded, creatures keep their bodies at a healthy temperature.

Chuckwallas are mainly herbivores and receive most of the water they need to survive from the plant material they consume. On the islands in the Gulf of California, the vegetation may not seem appetizing to us, but the chuckwallas have developed a taste for shrubs, some fruits and even cactus flowers.

With few predators besides the passing bird of prey, the only opponents San Esteban Island chuckwallas have to contend with are humans. Thanks to policies like the Endangered Species Act, these chuckwallas are protected, and agencies like U.S. Fish and Wildlife and the Department of Interior work to ensure they are not being imported into the United States and becoming a part of the illegal pet trade industry.

If you look closely at the zoo's chuckwalla residents, you will notice they may have white deposits around their nostrils. Chuckwallas exhibit an interesting feature in the way they expel excess salt -- they sneeze it out!

Additionally, chuckwallas have the ability to inflate their lungs when they are feeling threatened and appear flatter when they are relaxed. There's a reason the scientific name for chuckwalla, sauromalus, translates to "flat lizard."

Jenny and Lt. Dan are the Pueblo Zoo's resident San Esteban Island chuckwallas. Jenny can be found in the Islands of Life Building and Lt. Dan can be found in the Discovery Room, when he isn't out in classrooms or helping the education department deliver animal and conservation messaging.

Just the Facts

Scientific name: Sauromalus varius

Common name: San Esteban Island chuckwalla, named for the island on which they reside.

Description: San Esteban Island chuckwallas are a medium-sized lizard which belong to the iguana family and can grow up to 30 inches in length. They come in a variety of colors, but normally have a splotchy pattern of yellow, black and grey all over their body. This provides them with camouflage in their rocky habitat. Chuckwallas are known for their unique defense strategy of inflating their lungs when they are feeling threatened. This has a few different effects: It can make the chuckwalla appear larger, which can intimidate predators; and chuckwalla can run into rock crevices when its lungs are deflated and then blow them up once inside, effectively preventing a predator from removing the lizard.

Diet: They are primarily herbivores, eating plant matter found in their habitat, including leaves, fruits, buds, seeds and blossoms. Occasionally, they will eat small invertebrates, such as bugs or insects.

Range: San Esteban Island chuckwallas are found on the islands of San Esteban, Pelicanos and Roca Lobos, located in the Sea of Cortez.

Habitat: The habitat on these islands is arid and desert like, with many rocks and boulders. The areas have dry canyons, open flats and rocky outcrops.

Reproduction and rearing: Chuckwallas have a social hierarchy in which a dominant male claims a territory and defends it from other males by head bobbing, mouth gaping and doing push-ups. Females move from territory to territory looking for a desirable mate. Clutches are up to 16 eggs in size, and the babies hatch after approximately 3 months. No parental care is provided to the young, who learn to defend themselves and find food on their own.

Lifespan: Early to mid-teens.

Threats: Wild threats are unknown because very little research has been done on the species. However, many chuckwallas were removed from these islands and put into the pet trade, which decreased the overall population.


-- Mo Walsh

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