Beaded Lizard

Adult beaded lizards range from 57 to 91 cm (22 to 36 in) in length. They are substantially larger than the Gila monster, which only reaches lengths of 30 to 56 cm (12 to 22 in). The snout-to-vent length of a beaded lizard averages 33 to 48 cm (13 to 19 in). The average body mass of an adult beaded lizard is 800 g (1.8 lb), about 45% heavier than the average mass of a Gila monster, with large specimens exceeding 2,000 g (4.4 lb). Maximum weight known is 4,000 g (8.8 lb) Although males are slightly larger than females, the beaded lizards are not sexually dimorphic. Both males and females are stocky with broad heads, although the males' heads tend to be broader. The beaded lizards' scales are small, beadlike, and not overlapping. Except for the underside, the majority of its scales are underlaid with bony osteoderms.

Their base color is black and marked with varying amounts of yellow spots or bands. The beaded lizards have short tails, which are used to store fat so they can survive during months of estivation. Unlike many other lizards, this tail does not regenerate if broken. Beaded lizards have forked, pink tongues that they use to smell, with the help of a Jacobson's organ; they stick their tongues out to gather scents and touch them to the opening of the organ when the tongue is retracted.

Beaded lizards are found in the Pacific drainages from southern Sonora to southwestern Guatemala and two Atlantic drainages, from central Chiapas to southeastern Guatemala. Their habitats are primarily in the desert, tropical deciduous forests, and thorn scrub forests, but are found in pine-oak forests, with elevations from sea level to 1500 m. In the wild, the lizards are only active from April to mid-November, spending about an hour per day above the ground.

The Mexican beaded lizard H. horridum is found in Mexico, from Sonora to Oaxaca. The Rio Fuerte beaded lizard (H. exasperatum) is found from southern Sonora to northern Sinaloa. The Chiapan beaded lizard (H. alvarezi) is found in northern Chiapas and the depression of the Río Lagartero in Huehuetenango to northwestern Guatemala. The ranges of these three species overlap, making them sympatric. The Guatemalan beaded lizard (H. charlesbogerti) is the only allopatric one, separated from the nearest population (H. alvarezi) by 250 km of unsuitable habitat. The Guatemalan beaded lizard is the most endangered of the species, if not of all lizards; it is found only in the dry valley of the Río Motagua in northeastern Guatemala; fewer than 200 are believed to exist in the wild.

The beaded lizard is a specialized vertebrate nest predator, feeding primarily on bird and reptile eggs. A semiarboreal species, it is found climbing deciduous trees in search of prey when encountered above ground. It occasionally preys upon small birds, mammals, frogs, lizards, and insects. Steve Angeli and Robert Applegate, noted captive breeders of the beaded lizard, have remarked that captive specimens do best on a diet of small vertebrates such as mice and rats. Confiscated wild-caught specimens can be made to feed by using egg on the prey item.