The Rebound of the Eastern Collared Lizard

By Jeff Briggler | May 20, 2015
From Missouri Conservationist: Jun 2015

The eastern collared lizard (Crotaphytus collaris) is a large, conspicuous reptile that is considered one of the more charismatic and colorful species in Missouri. The two black collars circling its neck give the lizard its common name, though it’s also known by other names, including “mountain boomer.” This name originated with early settlers who mistakenly believed the mountain-dwelling lizard was making sounds. In reality, the collared lizard is voiceless.

Making a Home in Missouri

Collared lizards primarily live in arid portions of southwestern United States and northern Mexico, but their range extends east into the Ozark Highlands of Arkansas and Missouri. Although the arid conditions of the southwest don’t reach this far, the Ozark Highlands have a delicate, desert-like ecosystem called glades that support collared lizards and other interesting wildlife. Glades are dry, rocky openings on hills in forests, woodlands, and prairies. This lizard lives among the rocks and has adapted to the hot, dry, and sunny conditions of glades even with temperatures exceeding 90 degrees. The eastern collared lizard has also adapted to human-altered landscapes, using rock quarries, riprap along lake shorelines and levees, and large boulders that often adorn golf courses.

Surviving the Glade

Collared lizards have many interesting characteristics that help it survive on open, rocky glades. This lizard basically lives its life on a rock, preferring to view the world from a medium– to large–size rock during its active season from April through October. From atop a large rock, the lizard can bask in sunlight, observe its territory, and locate prey such as spiders, insects, small snakes, and other lizards. An eastern collared lizard sunning on a rock is wary and often difficult to approach. It will dart for cover under large rocks or in cracks and crevices along bedrock ledges, but it will slowly emerge and return to its preferred sunning and viewing location.

Although voiceless, collared lizards use body language as a form of communication. Males are highly territorial and use stereotypical posturing such as head bobbing, flattening of the body, and pushups to defend territories from other males or to court a female.

Considered one of the top predators on the glade, collared lizards eat anything that can fit into their mouths, but there are many species, such as snakes, small mammals, birds of prey, and roadrunners, that feed upon them. If forced to retreat from such predators in open habitats, they typically escape by running upright on their hind legs to a nearby rock. If captured, they are feisty and have powerful jaws that can deliver a substantial bite.

A Year in the Life

The majority of an adult collared lizard’s life is lived below ground. They are only active on the surface for about five months during the warmer spring and summer months. Courtship and mating occurs during this time, typically from mid-May into early June. The female will lay two to 21 white, leathery eggs, which are slightly over 1/2 inch, beneath a rock that she has excavated for their protection. Once the eggs are laid, the female plugs the nest’s entrance with dirt to further protect the eggs from predators and departs, allowing the eggs to develop and hatch on their own. The eggs hatch in approximately two to three months, depending upon temperature and weather conditions. The tiny hatchlings are only about an inch in size and dig their way out of the nests in late August or early September. They immediately begin feeding vigorously upon small insects to prepare for the upcoming winter. Young collared lizards grow remarkably fast and can double or even triple in size before cold weather arrives in October. During the winter months, collared lizards seek refuge beneath the ground, under large rocks, or within bedrock ledges only to emerge again in April. The lifespan of the lizard rarely exceeds five years.

Restoring and Reintroducing

Collared lizards were once known to be widespread on glades in Missouri, but due to reduced fire frequency, resulting in changes in vegetation on the glades, lizard populations became isolated. By the 1980s, lizards were rapidly disappearing from Missouri.

In response to these declines, the Department of Conservation began restoring the glades to their original open nature. Many cedar trees were removed, and periodic fires were set to maintain the open, rocky habitat on which the lizard depends.

Once the habitat was restored, a reintroduction plan was initiated to repopulate the glades that once housed collared lizards. Faculty and students at Washington University in St. Louis worked with Department biologists to relocate lizards to glades. With considerable research at these introduction sites, information was collected on animal growth, survival, reproduction, population size, and dispersal capability. It became clear that the restoration of glade habitats and opening the surrounding woodland understory led to the increased numbers and spread of collared lizards across many locations in the Ozarks.

With continued management of glades in the Ozarks by various agency staff and Missouri’s citizens, the eastern collared lizard is again thriving and will continue to be a part of Missouri’s biodiversity for many generations to come.

Be a Good Steward

The loss or degradation of habitat has been one of the leading causes of decline for many wild-life species, including the eastern collared lizard. This lizard, once common and widespread, was declining in Missouri due to fire suppression, resulting in woody encroachment (primarily by eastern red cedars) that overtook the open glade habitat that collared lizards require.

With habitat restoration and successful reintroductions, collared lizards are rebounding in Missouri. However, other threats to the species and their habitat have emerged. Glades are vulnerable habitats with many interesting plants and animals. Searching for amphibians and reptiles in their natural habitat can be an educational and rewarding pastime, but such activities can also be a real threat to these species. Plants are easily trampled or dug up, animals are collected and removed, or rocks that provide shelter for animals from heat and predation are removed, disturbed, or destroyed.

Rocks on glades are homes for a variety of animals from spiders to scorpions to many species of amphibians and reptiles, including the collared lizard. Repeatedly flipping and turning rocks on glades will ultimately destroy the microhabitat beneath the rock that is vital to the animal’s survival. In some cases, people believe it is okay to remove an animal like a collared lizard to keep as a pet. Not only are these actions illegal in some areas, but these animals do not make good pets and will quickly die in captivity. When searching for these animals, please be a good ambassador by knowing the laws, protecting the animals, and protecting the habitat they depend upon.

Capturing the Lizard in a Picture

Many of Missouri’s amphibians and reptiles are hard to spot due to their elusive nature. However, eastern collared lizards are large, conspicuous lizards that are active during the day and prefer to view their surroundings from atop a large rock. For avid wildlife watchers and photographers, these lizards are some of the most rewarding to photograph or observe. Even though collared lizards are wary of humans, with a little patience and time, you can easily get close to this colorful lizard to snap a few memories. You can even distinguish males from females and adults from juvenile lizards. Adults are typically 8 to 14 inches long, while juveniles are considerably smaller.

The males exhibit beautiful colors, especially during the breeding season, with shades of blue and green on their legs, belly, and tail, as well as a brightly colored orange throat. Females are not as brilliantly colored as males, but are typically more of a yellowish tan or light brown with vivid orange spots or bars on their sides and neck, an indication they are likely carrying eggs. Juveniles usually have a more reticulated pattern with dark bands or yellowish crossbands.

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This Issue's Staff

Editor - Angie Daly Morfeld
Art Director - Cliff White
Staff Writer/Editor - Bonnie Chasteen
Staff Writer - Heather Feeler
Photographer - Noppadol Paothong
Photographer - David Stonner
Designer - Stephanie Thurber
Circulation - Laura Scheuler