Iguanas are large, herbivorous lizards whose life cycle is tightly regulated by seasonal environmental changes. These reptiles exhibit a strictly annual reproductive pattern. The seasonal cycle ensures that the vulnerable hatchlings emerge when food resources are most plentiful. Their reproductive drive is a distinct period triggered by shifts in daylight, temperature, and precipitation patterns.
Timing of the Breeding Cycle
The onset of the iguana breeding season is a direct response to climatic shifts in their tropical and subtropical habitats. Mating generally occurs toward the end of the wet season, which, for iguanas in the Northern Hemisphere, typically falls between late fall and early winter, from November through January. The environmental factors that cue this cycle are a decrease in temperature and daylight hours, alongside the transition into the dry season. Iguanas breed during the dry season so that the eggs can incubate in the ground. This strategic timing ensures that the hatchlings emerge several months later, coinciding with the return of the rainy season and the resulting explosion of vegetation.
Behavioral Changes During Mating Season
The mating window precipitates a surge in hormonal activity, particularly in males. Male iguanas become highly territorial, actively defending a breeding area from rival males. They engage in intense dominance displays, including rapid, exaggerated head bobbing and the aggressive inflation of the large dewlap beneath their chin. Males often darken their skin color, sometimes developing deep orange or rusty red pigmentation, which visually signals their reproductive condition and dominance status.
Courtship involves securing a mate within the male’s territory, which can appear aggressive. A male will physically mount the female, restraining her by gripping the skin on her shoulder with his jaws, a behavior that may result in minor wounds. Females generally aggregate in the territories of the largest, most dominant males. While the male’s aggressive behavior can last for several months, females are typically only receptive to mating for about one to two weeks.
The Nesting and Egg Laying Process
Following successful mating, the female focuses on the development and deposition of her eggs. The pre-ovipositional period lasts approximately 65 days after copulation, during which time she becomes gravid and often reduces or ceases eating. Once ready, the female migrates to a suitable nesting site, often in sandy or well-drained soil, sometimes congregating in communal nesting grounds. She meticulously excavates a deep burrow, creating a tunnel that can extend 45 centimeters to over a meter into the ground, culminating in a subterranean egg chamber.
The number of eggs laid, known as the clutch size, averages 10 to 30 eggs, though larger females can produce up to 65. The female carefully covers the nest chamber, using her snout to pack the soil tightly. This conceals and protects the eggs from predators and environmental changes. The female provides no further parental care, leaving the eggs to incubate for about 90 to 120 days until the juveniles hatch.