Most, if not all, herpetologists can attribute their involvement with reptiles and amphibians with a fascination of dinosaurs when they were young. It was definitely the case with me, and I can remember the summer days of my childhood observing a modern-day dinosaur, the Eastern Collared Lizard, often coined the name “Mountain Boomer” by those who encounter this species frequently.
The Eastern Collared Lizard (Crotaphytus collaris) is one of two species of “Mountain Boomers” that live in Texas, and by far it has the largest area of distribution. It can be observed throughout the western ¾ of the state, including the entirety of the Panhandle, Trans-Pecos, and Edwards Plateau eco-regions. It also occurs to the north to southern Nebraska, westward to northern Arizona, and then southward into central Mexico.
The habitats that this conspicuous lizard prefers are arid to semi-arid rocky arroyos, rocky hillsides, and mesas. They prefer open areas with large rocks for basking and hunting and the large rocks strewn along caliche county roads are frequently utilized.
The Eastern Collared Lizard is among the most brilliantly colored and impressive lacertilian species in the United States. The scales on the back are small and granular in appearance and texture, and the background coloration varies from a light tan to gray to greenish-gray, and many small light spots and reticulate lines are often present. There is a very prominent double black collar on the neck on all specimens, giving this animal its common namesake. The head is large and almost disproportionate in size to the body. The front legs are smaller than the back legs, and the tail, which is colored like the back, is extremely long.
During breeding season, however, the animals take on a completely different appearance, particularly sexually mature males. While attempting to attract a mate, the head of the male becomes a bright yellow while the background coloration changes from a light dull color to a brilliant blue, green or turquoise. This double black neck collar and light spots are set off even more by this extraordinary display.
Males are the larger sex, achieving total lengths of up to fourteen inches, although most are just under one foot. Females are slightly smaller than the males, topping out at approximately ten inches.
“Mountain Boomers”, like other lizard species, are “cold-blooded”, or ectothermic. This means that they do not generate heat from the inside of their body, as mammals and birds do, but rather are dependent on outside sources for heating and cooling. They are active throughout the day from early April to October, and unlike many other reptile species, the high metabolism of this lizard enables it to be observed during the hottest part of the summer afternoons.
This species of lizard is an opportunistic carnivore, feeding on almost any smaller animal that it can fit into its gigantic mouth. It prefers to feed on large insects such as lubber grasshoppers, although studies of this species stomach contents show that it will feed upon any invertebrate animal that wanders close enough to its basking site. Studies have also shown that it will also occasionally feed on smaller lizards, even ones of its own kind, although apparently this is not a common occurrence.
The Eastern Collared Lizard is oviparous, which is a fancy way of saying that it lays eggs. After emerging from the winter-long brumation period (reptiles do not hibernate in the true sense of the word), males will search out females to mate. After mating, the female will lay a medium-sized clutch of eggs (between one and fourteen, average six) in moisture retaining soil. Older, larger females can lay multiple clutches of eggs per summer. After approximately two months of incubation, the three inch long young emerge prepared to fend for and care for themselves.
These lizards are gregarious baskers and the higher basking areas are utilized by the larger alpha male. When threatened, it has a habit of lifting its front legs and tail off of the ground in a bipedal motion, running much like a miniature Tyrannosaurus Rex.