Gila Monsters

‘Flower’ Gila Monster
Click for larger view
Copyright Daniel D. Beck
Central Washington University

Hi, I’m Holly Strand from Stokes Nature Center in beautiful Logan Canyon.

Turn up your radio and see if you can imagine the Utah creature who makes this sound.

[Sound: Jeff Rice, Gila Monster recorded at Arizona-Sonora Desert Museum]

That was the gasping breathing of a gila monster. It was recorded by Jeff Rice of the University of Utah’s Western Soundscape Archive.

Gila Monsters occur in pockets across the desert southwest. In Utah they are found only in Mojave habitat in the southwest corner of Washington County.

Once you get to know them, gilas are not at all monstrous. They are the largest of all lizards native to the U.S. An average gila might be 14-16 in. in length and would weigh about a pound and a half. They have thick sausage-like tails and large heads. The scales on the backs of these lizards resemble a beadwork pattern of black, orange, pink, and yellow.

Of the nearly4000 lizard species in the entire world only two are venomous. And one of them is the gila monster. But only a small amount of venom is introduced during a bite—not enough to kill a healthy human. Nevertheless, the bites are notoriously painful.

Gila Monster
Click map for larger view
Copyright Daniel D. Beck
Central Washington University

But gilas are reluctant to strike. Victims of bites have usually provoked the lizard in some way. Before biting, the lizard will hiss, and then back away from its would-be attacker. But if these warning efforts fail, it will latch on with frightening speed and tenacity. For gilas are the pitbulls of the lizard world.

A long-held belief has been that the breath of a gila monster is nauseating and toxic. In fact, it was even thought that gilas killed their prey with halitosis. The truth is that like many other animals, a frightened gila may regurgitate a recent meal when molested. Because gilas have such a slow metabolism, that last meal might be pretty old and smelly. Also, excited or reproductively active monsters can transmit a detectable body odor which some people find offensive.

These days, you’d be very lucky to see a gila monster in the wild. For in many areas their numbers are decreasing though collection and habitat loss. Another reason is that gila monsters are homebodies. They spend up to 97% of their lifetime tucked away in burrows or rock crevices.

For sources and pictures of gila monsters, see

Thanks to the Rocky Mountain Power Foundation for support of this Wild About Utah topic.

For Wild About Utah and Stokes Nature Center, I’m Holly Strand.

Images: Courtesy & Copyright Daniel D. Beck, Central Washington University

Text:     Holly Strand, Stokes Nature Center

Sources & Additional Reading

Beck, Daniel D. 2005. Biology of Gila monsters and beaded lizards

Beck, Daniel D.,1990. Ecology and behavior of the Gila Monster in southwestern Utah. Journal of Herpetology 24, pp. 54–68.

Brown, David. E. Carmony, Neil. B. 1999. Gila Monster : Facts and Folklore of America’s Aztec Lizard. Salt Lake City: University of Utah Press.

Rice. Jeff. Western Soundscape Archive. J. Willard Marriott Library at the University of Utah,

State of Utah Natural Resources. Division of Wildlife Resources Species Database. Gila Monster. [Accessed Feb 2, 2010]

For More Information:

National Geographic . Wild Detectives: Gila Monster [Accessed Feb 2, 2010]

Arizona-Sonora Desert Museum [Accessed Feb 2, 2010]

Don’t Tread on Me!

Don't tread on me! Great Basin Rattlesnake Courtesy & Copyright © 2009 Holly Strand
Great Basin Rattlesnake
Courtesy & Copyright © 2009 Holly Strand
Holly: Hi, I’m Holly Strand from Stokes Nature Center in beautiful Logan Canyon. Don’t Tread on Me!

Rattlesnakes are pit vipers with heavy bodies and broad heads. There are about 30 species and 40 more subspecies found in North and South America. They aren’t found anywhere else. All possess rattles and all are venomous.

Here in Utah we have 5 species plus 2 subspecies. The Great basin rattlesnake is the most widespread, living all across Western Utah at elevations up to 9000 feet. Another subspecies of western rattler–the midget faded rattlesnake –is dominant in the eastern part of the state. The Hopi rattlesnake and the greenish colored prairie rattlesnake are found in southeastern Utah. And the Mojave rattlesnake, speckled rattlesnake, and sidewinder are found only in the extreme southwest corner of Utah.

The rattle itself is a unique biological feature. It’s a loose, but interlocking series of nested segments—actually modified scales– at the end of the tail. When vibrated, the rattle produces a hissing sound. Kevin Colver– an expert in natural sound recordings –provided this clip of a Mojave rattlesnake.

A snake gets a new rattle segment every time it sheds—and it sheds from one to four times a year. 15 or 16 rattles are common in captive snakes, but in wild snakes six to eight are more common. In wild snakes, rattles are subject to a lot of wear and tear. So they break off before they get very long.
The rattle sound is the reaction of a startled or threatened snake. You’ll often see the rattling snake in a defensive S-shaped coil—but not always!

Aggression and venom in rattlesnakes vary by both species type and by individual. The western diamondback rattlesnake is the archetypal large, aggressive and very dangerous species, responsible for the majority of human fatalities in America. But it’s northern range limit is south of the Utah border. However, the Mojave rattler found in southeastern Utah is extremely toxic, excitable and its venom attacks both the nervous system and circulatory system.

But rattlesnakes aren’t out to get us—mainly they just want to be left alone. You’ll generally be fine if you stay aware of what might be in or around rocks, and don’t walk barefoot or in open-toed shoes in their habitat. Also, use a flashlight after dark –most rattlesnakes are active at night too!

Thanks to the Rocky Mountain Power Foundation for supporting the development of this Wild About Utah topic.
And to Kevin Colver for the sound of the rattlesnake. Additional nature sound recordings can be found at

For Wild About Utah and Stokes Nature Center, I’m Holly Strand.


Sound: Courtesy and Copyright 2006 Kevin Colver
Image: Courtesy and Copyright 2009 Holly Strand
Text: Holly Strand, Stokes Nature Center

Sources & Additional Reading

Klauber, Laurence M. 1982. Rattlesnakes. Their Habits, Life Histories, and Influence on Mankind. Berkeley: University of California Press, (1997 Version)

Utah Division of Wildlife Resources. Utah Conservation Data Center. (Accessed July 17, 2009)

The Lizard and His Tail

Collared Lizard
Copyright © 2005 & Courtesy of Jerry Shue
Canyonlands Natural History Association

Hi, I’m Holly Strand of Stokes Nature Center in beautiful Logan Canyon.

One of the most beautiful lizards I’ve ever seen lives right here in Utah. The collared lizard has a gold head, a green body and 2 black collar stripes. I stumbled upon one last week during a hike in Professor Valley north of Moab. It was just shy of a foot long from tip to tail, with most of that length in the tail. It bravely stood its ground as I crept closer to admire it. Instinctively, I wanted to reach down and catch it!

The urge to catch lizards seems to be innate. Maybe our ancient ancestors used to eat them and the desire to catch them is a relict evolutionary trait.

When you catch a lizard, you might just cause him to drop his tail. Tail dropping is a defense mechanism. In many species of lizard the tail has weak fracture planes between the vertebra, allowing the tail to detach easily. After breaking off, the thrashing tail attracts the would-be predator, enabling the lizard to escape. Some lizard tails are brightly colored, which enhances the decoy effect.

Unfortunately, there are serious consequences to losing one’s tail. A long tail acts as a counterbalance, enabling a lizard to lift its forelegs when running. This is important because a lizard can move more quickly on two legs than on four. A large lizard running on two legs can sprint up to 12 miles an hour!

Male lizards need their long tails for social status. Low status males have much more difficulty mating. Tail loss also might mean that a juvenile will have trouble acquiring a home range due to low social standing.
Finally, fat stored in a tail provides a food source during periods of starvation and reproduction.
With this in mind, I hope you can join me in my effort not to catch lizards. Let’s admire these wonderful creatures from a distance.

For Wild About Utah and Stokes Nature Center I’m Holly Strand

This Wild About Utah topic was adapted from A Naturalist’s Guide to Canyon Country by David B. Williams, courtesy of the Canyonlands Natural History Association.

Thanks to the Sorrel River Ranch Resort and Spa for supporting the development of this Wild About Utah topic. The Ranch offers deluxe lodging and services on a scenic bend of the Colorado River, 20 minutes from Moab in the spectacular Professor Valley.


Images: Photo Copyright © 2005 & courtesy of Jerry Shue, Canyonlands Natural History Association

Text: Stokes Nature Center: Holly Strand

Sources & Additional Reading

Williams, David B. 2000. A Naturalist’s Guide to Canyon Country., Published jointly by the Globe Pequot Press and the Canyonlands Natural History Association.

Canyonlands Natural History Association