Along with the many snake species we study at Stone Canyon, we also catch and take data from Gila monsters. Heloderma suspectum is the largest native lizard in the United states, and also a member of the only dangerously venomous lizard in the world. This summer, our crew caught 27 individuals of this species, with ages ranging from adult to neonate. Below, you can see a neonate at the end of data collection, awaiting recording of body weight, to then be released back to his capture point.
Gila monsters are found in two body morphs. The Banded, and the Reticulate. At our study site, we predominantly find the Reticulate form (photo below), as they are usually seen in central and southeastern Arizona. The banded form is more commonly seen in northwestern and western Arizona. However, their pattern may vary geographically, and each morph has been known to be seen outside their respective ranges. The Banded form differs from the Reticulate in that the tail stripes are more uniformly pink and black, and the black blotches across its body fill in less space.
Male Heloderma suspectum are known to aggressively fight each other for access to females. This often results in bodily injury, and scars. Matches between males may last up to several hours. Often when our lab is determining sex of this species, the amount of scars coupled with poor body condition is a strong signal that we are dealing with a male. Below, find a photo of a male Gila missing portions of his hind left toes, most likely lost to skirmishes with rival males.
Gila monsters are usually found on rocky hillsides, bajadas, and mountainous terrain. They are fossorial, meaning they spend most of their lives underground. They do this by living in burrows, abandoned pack-rat middens, or rock crevices. Typically, this species spends winters in its chosen underground home, however they can be seen active at any point in the year, with a peak in late spring and after monsoons. A photo of our study sight can be seen below, exemplifying the type of habitat these animals prefer.