Scientific Name: Crotaphytus collaris
Common Name(s): Eastern Collard Lizard, Mountain Boomer

(Left – Male Collard Lizard; Right – Female Collard Lizard) | Peter Paplanus

Identification:

The eastern collared lizard is one of the largest species of lizard found in Arkansas, and it can run on its hind legs. It is listed as a “species of greatest conservation need” due to the decline in its preferred habitat of open, treeless habitats in forests, known as glades. Read more to understand how prescribed burns can help increase their populations by promoting glade habitats.

Collared lizards have large heads with teeth in the inner lower jaw. They also have two brown-black irregular lines that resemble a collar around their neck. Eastern collared lizards are between 8 and 14 inches, with males larger than females. Males are vibrant yellow, green, and teal-blue in color, while females are more muted green with some red or orange markings. Both have an overlain pattern of faint spots and banding.

Herps of Arkansas

Range:

Collard lizards are native to North American from Eastern Missouri to the West Coast, and south into Northern Mexico.

Ecology:

Eastern collared lizards have become a species of greatest conservation need because of a 70% to 80% decline in population numbers since the 1950s. This decline in population is linked to the collared lizard’s specialized need for open, rocky environments to thrive. Eastern collared lizards inhabit open, rocky glade habitats, characterized by treeless areas within the forest, featuring vegetation such as grasses, herbaceous plants, and wildflowers. However, with the advent of modern fire suppression, woody vegetation, such as trees and shrubs, has encroached on glade habitats, leading to population declines in species that thrive in those environments.

Eastern collared lizards are most active during the warm season, from April to September, and on warm sunny days. Rocky glades are termed heliothermic habitats because the openness allows sunlight to heat the rocks, which in turn enables amphibians and reptiles to warm their bodies. Since eastern collared lizards are cold-blooded, they rely on their interactions with the outside environment to support their body’s functions. In the mornings, eastern collared lizards bask on rocks, lying in the sun to enhance body metabolism to aid in bodily functions such as growth, reproduction, and digestion. Specifically, eastern collared lizards prefer the south and southwest-facing side of rocks such as limestone, sandstone, and granite.

Eastern collared lizards are an indicator species, which means their population numbers can help estimate the health of a habitat and help indicate the success of other species sharing their habitat. Eastern collared lizards are mainly predatory on insects, such as grasshoppers, beetles, and moths, but they are known to eat small lizards, snakes, or other small animals. They occasionally eat some plant material, but this is not their preferred food. Since collared lizards have eyes on either side of their head, they have reduced depth perception when not moving. Therefore, they detect their food through movement by performing push-ups with their body or moving their head up and down or side to side.  This up-and-down movement allows the lizard to better see and judge the distance of a prey item.  Eastern collared lizards are eaten by birds such as hawks and eagles.

Eastern collared lizards reach sexual maturity in their first or sometimes second year of life, depending on food availability and environmental conditions. They are most active during the breeding season, from May to July. During breeding season, males are highly territorial and use behavioral displays, such as head bobbing and body push-ups, as well as intimidation, and, as a last resort, fighting to ward off other males from their territory. Females breed once or sometimes twice in a season and produce a clutch of 4 to 24 eggs, depending on environmental conditions. Females dig and deposit eggs beneath large rocks. Eggs hatch in two to three months. Eastern collared lizards do not guard or care for their eggs, and young lizards are completely independent once hatched.

Glade habitats would increase with more prescribed and controlled burns. With a decrease in prescribed burns, increases in woody vegetation encroachment in glade habitats have resulted in more shade and thus cooler temperatures. This has been detrimental to collard lizards, who need the sunny environment in this habitat to function normally. Local researchers have found evidence that there is a connection between slower growth and lower reproductive rates of collard lizards found in habitats with more dense canopy cover.

Special Notes:

Efforts have been made to help increase eastern collared lizard populations through a collaboration between the Little Rock Zoo and local scientific research teams from the Arkansas Game and Fish Commission, the University of Arkansas, the University of Central Arkansas, and the Arkansas Game and Wildlife Research Unit. The Zoo has collaborated to provide unique collared lizards that are genetically unique from lizards in areas of introduction. Arkansas Game and Fish Commission habitat biologists have restored glade habitat with the use of safe prescribed burns. Additionally, local research biologists have collaborated to provide pockets of already established eastern collared lizard populations as a source to make more introductions or to restore or enhance other glade habitats. Cedars are the most widely known species that encroaches on glades and other habitats without adequate control burns. The increases in glade habitat also help other species that thrive in this habitat, such as bobwhite quail and wild turkey. The first release of collar lizards in this collaboration occurred in 2023, with more planned afterward.