Iguanas are large, cold-blooded reptiles that spend their days as active, grazing herbivores in tropical and subtropical climates. As diurnal creatures, their existence is centered around the sun, which dictates their body temperature and activity level. Once the sun sets, the iguana’s behavior changes as it seeks a safe location to spend the dark, cooler hours. Their nighttime habits are a survival strategy driven by the need to manage body heat and avoid being eaten.
The Vertical Retreat: Primary Sleeping Locations
As the evening twilight deepens, iguanas transition from active foraging to nocturnal immobility known as roosting. These reptiles are naturally arboreal, meaning their primary sleeping spots are typically high off the ground in the dense canopy of trees and bushes. They seek the highest, most stable point they can reach near their daytime feeding areas.
A preferred location is often a thick, horizontal branch or a sturdy vertical trunk that provides reliable support. Iguanas use their sharp claws to firmly secure themselves to the substrate, preventing them from falling during the night. In urban environments, this arboreal preference translates to them utilizing man-made vertical structures, such as roofs, fences, and elevated ledges.
A branch that hangs directly over a body of water is highly advantageous for many green iguanas. This placement allows for a quick escape route if they are disturbed by a predator during the night. They lay on their stomach, tucking their limbs close to their body, and remain still for the duration of the night.
Thermoregulation: The Necessity of Elevation
The selection of an elevated roosting spot is not merely for comfort; it is a thermal imperative for these ectothermic animals. Iguanas depend on external heat sources to regulate their body temperature, and as the ambient temperature drops at night, their internal metabolism slows significantly.
Sleeping high in a tree or on a structure helps them avoid the lowest, coldest air pockets that accumulate near the ground. Low-lying vegetation loses heat rapidly after sunset and is often damp with dew, which would further chill the reptile through evaporative cooling. By maintaining a higher elevation, the iguana conserves body heat and prevents its core temperature from dropping too low.
This strategic positioning also prepares the iguana for the following morning. The elevated perch ensures the reptile is in an optimal location to intercept the first rays of sunlight. This allows the iguana to begin basking and raise its body temperature to a functional range much faster than if it were on the shaded, cold ground. A quicker warm-up means an earlier start to the day for foraging and digestion.
Nocturnal Security: Avoiding Predators
The second motive for the vertical retreat is the increased security it offers from nocturnal threats. Climbing high reduces the risk of encountering most terrestrial predators, such as raccoons, opossums, and certain types of snakes, which cannot easily access the slender upper branches.
Once settled, the iguana’s defense relies on extreme immobility and camouflage. The combination of its natural coloration and stillness in the dense foliage makes it difficult for visually oriented predators to detect. While less susceptible to ground threats, they must still contend with nocturnal avian predators, most notably owls, which hunt from above.
If a threat is detected, the iguana has options for defense, depending on its location. An iguana roosting over water can instantly release its grip and drop below, using its swimming ability to escape a land-based attacker. For those in the canopy, their strong grip and low heart rate allow them to remain motionless, relying on invisibility until the danger passes.