The reproductive cycle of the Green Iguana (Iguana iguana) is an annual event regulated by seasonal changes in their tropical and subtropical environments. This process is ritualized, beginning with male competition for territory and culminating in the construction of a nest for egg deposition. Mating and egg laying are synchronized so that hatchlings emerge when food resources are most plentiful. The sequence involves distinct behavioral displays and a unique physical mechanism for copulation.
Courtship Displays and Establishing Dominance
The beginning of the breeding season is marked by behavioral and physical changes in the male Green Iguana. Males often develop a vibrant, temporary orange or gold coloration, which contrasts with the females’ persistent green hue, signaling their readiness to compete. This visual transformation is accompanied by swelling in the jowls and the enlargement of the dorsal crests and spines, enhancing the male’s display of physical fitness.
Territorial defense becomes the male’s primary focus, as control over a breeding area is directly linked to reproductive success. Dominant males use physical displays to assert their status, most notably through rhythmic head-bobbing routines. These movements communicate threat and rank to rival males, often preventing physical confrontations.
The most successful males establish and actively patrol territories, which may contain several receptive females. They also secrete a waxy pheromone from their femoral pores, using this scent to mark their space and the females within it. If displays are insufficient, males engage in biting and physical combat, though injuries in the wild are rare.
Receptive females move within the territories of these dominant males, effectively choosing their mate based on the male’s displays and the quality of his territory. A male approaches a female with a specific display of head-bobbing and may gently nip or nuzzle her neck as part of the courtship ritual. Females may signal their rejection of a non-dominant male by turning away or becoming aggressive.
The Mechanism of Copulation
Once a female accepts a male’s advances, the physical act of mating proceeds quickly. The male climbs onto the female’s back, straddling her and securing his position by gripping the skin on her shoulders or neck with his teeth. This bite helps restrain the female and maintain stability during the process, sometimes resulting in minor wounds.
The male then brings his cloacal vent into alignment with the female’s cloaca. Male iguanas possess paired reproductive organs called hemipenes, which are stored within the base of the tail. During copulation, only one of the two hemipenes is everted and inserted into the female’s cloaca.
The hemipenis is equipped with species-specific ornamentation, such as spines or hooks, which help anchor the organ securely during the transfer of sperm. Copulation is brief, lasting for only a few minutes. After successful mating, the female has the ability to store sperm for an extended period, allowing her to fertilize eggs at a later date.
Nesting and Egg Laying
Following successful copulation, the female develops the eggs internally for approximately 65 days before seeking a suitable nesting site. During this gestation period, her appetite often diminishes as the egg mass takes up space. The site search requires soft, sandy soil or earth that provides the correct temperature and humidity for incubation.
Females often migrate considerable distances to reach traditional, sometimes communal, nesting grounds. Digging the nest burrow is performed primarily using her forelimbs to excavate the earth and her hind limbs to push the loosened soil out of the tunnel. The completed burrow can extend to a depth of 45 centimeters to over a meter.
The female excavates a small chamber at the end of the tunnel, where she deposits her clutch of eggs over a period of up to three days. Clutch size varies depending on the female’s size and age, but she may lay an average of 10 to 30 leathery, pale-colored eggs. After laying, the female backfills the chamber and tunnel, tamping down the soil to camouflage the nest opening.
The female departs immediately after sealing the burrow, marking her final parental investment. There is no subsequent maternal care or defense of the nest, which is abandoned to incubate naturally for 90 to 120 days. The female returns to her home territory.