Gila monster

The Gila monster (Heloderma suspectum, /ˈhiːlə/ HEE-lə) is a species of venomous lizard native to the southwestern United States and northwestern Mexican state of Sonora. A heavy, typically slow-moving lizard, up to 60 cm (2.0 ft) long, the Gila monster is the only venomous lizard native to the United States and one of only two known species of venomous lizards in North America, the other being its close relative, the Mexican beaded lizard (H. horridum). Although the Gila monster is venomous, its sluggish nature means it represents little threat to humans. However, it has acquired a fearsome reputation, and is sometimes killed despite being protected by state law in Arizona. In 2019, the state of Utah made the Gila monster its official state reptile. Gila monster is the largest extant lizard native to North America north of the Mexican border (non-natives like green iguanas are larger). Its snout-to-vent length is 26 to 36 cm (10 to 14 in). The tail is about 20% of the body size and the largest specimens may reach 51 to 56 cm (20 to 22 in) in total length. Body mass is typically in the range of 350 to 700 g (0.77 to 1.54 lb), with 11 males having been found to average 468 g (1.032 lb). Reportedly the very largest specimens can weigh as much as 2,300 g (5.1 lb). The Gila monster has one close living relative, the beaded lizard (H. horridum), as well as many extinct relatives in the Helodermatidae, the evolutionary history of which may be traced back to the Cretaceous period. The genus Heloderma has existed since the Miocene, when H. texana lived, and fragments of osteoderms from the Gila monster have been found in late Pleistocene (10,000–8,000 years ago) deposits near Las Vegas, Nevada. Because the helodermatids have remained relatively unchanged morphologically, they are occasionally regarded as living fossils. Although the Gila monster appears closely related to the monitor lizards (varanids) of Africa, Asia and Australia, their wide geographical separation and the unique features not found in the varanids indicate the Gila monster is better placed in a separate family. The name 'Gila' refers to the Gila River Basin in the U.S. states of New Mexico and Arizona, where the Gila monster was once plentiful. Heloderma means 'studded skin', from the Ancient Greek words helos (ἧλος), 'the head of a nail or stud', and derma (δέρμα), 'skin'. Suspectum comes from the describer, paleontologist Edward Drinker Cope, who suspected the lizard might be venomous due to the grooves in the teeth. The Gila monster is found in the Southwestern United States and Mexico, a range including Sonora, Arizona, parts of California, Nevada, Utah, and New Mexico (potentially including Baja California). They inhabit scrubland, succulent desert, and oak woodland, seeking shelter in burrows, thickets, and under rocks in locations with ready access to moisture. In fact, Gila monsters seem to like water and can be observed immersing themselves in puddles of water after a summer rain. They avoid living in open areas such as flats and farmland. Gila monsters spend 90% of their time underground in burrows or rocky shelters. They are active in the morning during the dry season (spring and early summer); later in the summer, they may be active on warm nights or after a thunderstorm. They maintain a surface body temperature of about 30 °C (86 °F). Gila monsters are slow in sprinting ability, but they have relatively high endurance and maximal aerobic capacity (VO2 max) for a lizard. They are preyed upon by coyotes and raptors. The Gila monster eats small birds, small mammals, frogs, smaller lizards, insects, and carrion. The Gila monster feeds primarily on bird and reptile eggs, and eats infrequently (only five to ten times a year in the wild), but when it does feed, it may eat up to one-third of its body mass. It uses its extremely acute sense of smell to locate prey, especially eggs. Its sense of smell is so keen, it can locate and dig up chicken eggs buried 15 cm (6 in) deep and accurately follow a trail made by a rolling egg. Prey may be crushed to death if large or eaten alive if small, swallowed head-first, and helped down by muscular contractions and neck flexing. Unusually, after food has been swallowed, the Gila monster immediately resumes tongue flicking and search behavior, probably as a result of a history of finding clumped prey such as eggs and young in nests. Gila monsters are able to climb trees and cacti in search of eggs.