I met this Gila Monster out and about on a spring day in 2023. At the time, there were a lot of quail eggs and baby cottontails to find out there, which gets these animals active and observable.
These animals are the only venomous lizard in the United States, and one of five species of the Heloderma genus found across Central America.
A Lesser Earless Lizard (Holbrookia maculata) from the western edge of Arizona. These lizards, as the name suggests, lack external ear openings to help live in the sandy, debris-filled environment. They still have ears, however, just hidden by skin. This one took a break from skittering away from me for a photo.
Sonoran Collared Lizards (Crotaphytus nebrius) are generally less brilliantly colored than their bright green relatives north of the Gila River. They can be standing tall on top of rocks on hillsides and outcrops, even in the heat of an Arizona summer day. When they are startled (which can happen from a disappointingly long distance) they can escape quickly by running on their hind legs. They have powerful jaws and consider about anything small enough to fit in that big head as food, which often includes other lizards. Personally, the image of large, fast, bipedal lizards that hunt other lizards fills that “I wish dinosaurs were still here” void just a little.
We found this one in a desert mountain range near Yuma a couple of years ago. It let us get some photos, then disappeared into the crevice above.
Arizona has some amazing, large lizards. This brightly colored one is an Eastern Collared Lizard. Based on a number of factors, they may be any variation of bright greens, blues, yellows, and oranges. This one was seen at a Prairie Rattlesnake den, carefully considering if we were something it needed to run away from.
This skinny young Gila Monster wasn’t doing great when we spotted it out and about in the mountains west of Phoenix. The skinny tail and narrow head show that it’s not been successful in finding food. Hopefully, it managed to do so since this photo was taken back in 2021.
Collared Treerunners (Plica plica) are one of the larger arboreal lizards seen occasionally hiking in Peru. At night they sleep in trees, mostly high and out of sight. But sometimes they are in the understory and can be photographed.
The least likely thing we could have seen in Guatemala – The Torre de Guatel Arboreal Alligator Lizard. Spotted by the laser eyes of Jake Scott, moments after a discussion about how impossible this search was going to be.
A Gila Monster out and about on a warm Spring day that I found a while back.
At that time, more than a decade ago, I knew relatively little about the day-to-day habits of these animals. Finding one was more a matter of luck than anything else. But, I’ve since learned a lot, and these are now often a higher observation count in a day than I’d had seen in an entire year.
Recommended reading, if you can find it:
Biology of Gila Monsters and Beaded Lizards — Daniel D. Beck (UC Press)
Switak’s Banded Gecko that we found in Baja California Sur, Mexico. These are closely related to the Western Banded Geckos we’re all familiar with here in Arizona, with some notable differences. The most obvious being its larger size, this one about the size of a small mouse. When seen in this boulder field, they hop from rock to rock and disappear (or try to, anyway) or wag their tails in a defensive display.
1. Murray, S. S., Dugan, E. A., Clause, A. G., & Mills, A. M. (2024). Maximum size and mass of Switak’s Banded Gecko, Coleonyx switaki (Murphy, 1974). Herpetology Notes.
2. Lovich, R. E., Grismer, L. L., & Danemann, G. (2009). Conservation status of the herpetofauna of Baja California, México and associated islands in the Sea of Cortez and Pacific Ocean. Herpetological Conservation and Biology, 4(3), 386–405.
3. Lemm, J. (2023). Field guide to amphibians and reptiles of the San Diego region. University of California Press.
