As an adaptation to their harsh desert environment, Gila monsters spend a large proportion of their time underground in burrows, hibernating during the winter and sheltering from the midday sun in the scorching summer months. The lizards emerge from hibernation in spring and the majority of their activity occurs in the following three-month period (3). Mating may takes place from April to June (9); males 'wrestle' to assert dominance (3). Females then lay their clutch of up to 12 eggs in late June or August (6). Eggs are laid in depressions dug into the soil and unusually remain incubating underground throughout the winter, hatching the following spring (4).
In springtime, Gila monsters are active during the day, although they are mainly above ground in the morning and late afternoon to avoid the midday heat (3). These lizards feed on eggs, young birds and rodents, as well as lizards; juveniles are able to consume over 50% of their body weight at one time (4). Gila monsters are able to survive for months without food as they store fat in their particularly large tail (3). The infamous venomous bite of the Gila monster is used as a defensive measure rather than to attack prey. If threatened, these lizards will back away hissing with their mouth open, and if provoked they attack surprisingly quickly with a bite that can be extremely painful to humans, although it is rarely life-threatening (6).