Helodermatidae, the Gila Monster family
IUCN Near Threatened.
Southwestern North America excepting most of the Californias.
Rocky areas in desert scrub and occasionally desert grassland and arid woodland.
They are the only venomous lizards in the U.S. and one of only 2 in the world. The other is a relative–the Mexican Beaded Lizard.
Large, heavy bodied lizards, black with pink or orange markings and bead-like scales. They have massive, flat heads with blunt snouts and short, stubby legs and tails. The bulges on the sides of their heads give a triangular shape like a rattlesnake, but these are powerful jaw muscles, not venom glands. They shelter in burrows, thickets, and under rocks in locations with ready access to moisture.
Their diet consists of the eggs of ground-nesting birds and reptiles, baby birds, squirrels, rabbits, rodents and small lizards. They store fat in their tails to provide energy when food is scarce and during hibernation, and they can go for long periods without drinking water.
Owls, hawks, coyotes, and foxes may take the young, but most animals stay away from adults. Their venom is probably more for defense than killing because it contains a strong pain producing substance–an effective lesson to predators. Venom glands are located along the lower jaw and venom is not injected but emitted through pores at the outside base of the teeth and chewed into the wound with sharp, grooved teeth.
They are believed to require a period of hibernation before successful breeding can take place in summer. On average, 5 eggs are laid in sand which will hatch after 9 months.