Grand Cayman rock iguanas are solitary except during the mating season. Mating is generally polygamous, but some individuals may also be promiscuous or monogamous. During the breeding season, the home range of a dominant male frequently overlaps that of one or more females.
Throughout the breeding season, Grand Cayman rock iguanas take on an intense blue coloration. In the spring, hormones surge and males begin to reassert dominance. Males lose weight during this time, as they devote their energy to breeding and dominating other males. Males expand their territory range, attempting to monopolize as many female territories as possible. Males in overlapping territories challenge each other, and, in most cases, smaller iguanas flee from larger individuals. Physical contact and fighting is rare and is usually restricted to individuals of similiar size. Fights can be vicious and bloody. Toes, tail tips, crest spines, and chunks of skin may be torn off in combat.
By March, the abdomen of female Grand Cayman rock iguanas is swollen, as their eggs have formed inside them. They do not become receptive to breeding until late April. Females generally avoid males until they begin to mate in May, retreating into their rock holes whenever males are nearby. Gravid females reduce food intake about 2 weeks before oviposition, because their digestive tract is squeezed by the expanding mass of eggs. They also increase activity levels during this time.
Copulation is preceded by a mating ritual. A male bobs its head then circles around behind a female. He grasps the nape of her neck and attempts to restrain her. The male maneuvers his tail under that of the female and positions himself for intromission. Copulation rarely lasts longer than 30 to 90 seconds, and a pair rarely mates more than once or twice per day. Mature pregnant females display a distended abdomen, and the outline of individual eggs may be seen.
At the end of the receptive period, female Grand Cayman rock iguanas become intolerant of males and chase them out of their territories. Females become so aggressive, in fact, that a female can successfully scare off males much larger than herself.
Mating System: polygynous
The breeding season of Grand Cayman rock iguanas lasts 2 to 3 weeks between late May and mid June. Oviposition occurs approximately 40 days after fertilization, generally during the months of June and July. Females lay 1 to 22 eggs each year. Clutch size varies with age and size of females. Older, larger females are able to produce more eggs. Eggs are then incubated in the nest chamber that is dug about a foot below the surface of the soil. Incubation period ranges from 65 to 90 days. Temperature within the nest remains relatively constant at 30 to 33 degrees Celsius throughout this period. Grand Cayman rock iguanas usually begin breeding around 4 years of age in captivity. In the wild, they reach sexual maturity between 2 and 9 years of age.
Breeding interval: Female Grand Cayman rock iguanas breed once yearly.
Breeding season: Copulation occurs from late May until mid June. Egg-laying occurs approximately 40 days later in the months of June and July.
Range number of offspring: 1 to 22.
Average gestation period: 40 days.
Average time to independence: 0 minutes.
Range age at sexual or reproductive maturity (female): 2 to 9 years.
Range age at sexual or reproductive maturity (male): 2 to 9 years.
Key Reproductive Features: seasonal breeding ; sexual ; fertilization ; oviparous
Female Grand Cayman rock iguanas often travel outside of their normal range to locate suitable nesting areas. Nest burrows are dug in sand or soil exposed to the sun. Several days before laying their eggs, females begin to dig in preparation for building their nests. It may take an entire afternoon to excavate a complete nest burrow. Female ground iguanas remain in nest burrows overnight to lay their eggs. While most emerge the following morning, some females remain underground for up to 2 days while laying their eggs. A female iguana fills the nest burrow with sand until a large mound is formed over the nesting site. She then scatters leaves over the area until the nest is completely disguised. When the nest is secure, she allows herself to feed again but remains close to the next. Females guard their next site for several weeks to prevent other iguanas from using the area for nesting and to protect from predators. Hatchlings are vulnerable to native snakes, such as Alsophis cantherigeruscaymanus, and suffer an extremely high mortality rate.
There is no direct parental investment of Grand Cayman rock iguanas after hatching.
Parental Investment: no parental involvement; female parental care ; pre-fertilization (Protecting: Female); pre-hatching/birth (Protecting: Female)