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The Life Cycle of Marine Iguanas

Marine iguanas are natives of the Galapagos Islands. In their native habitat, marine iguanas usually live for between five and 12 years. The marine iguana's herbivorous diet consists of algae and seaweed, and while males often venture into the water in search of food, females and young iguanas spend most of their time on the shore. The breeding season for marine iguanas begins in December of January each year, depending on the island. Although females can be mature enough to reproduce from 3 years of age, males do not reproduce until they are at least 6 years old.

Male Behavior in the Breeding Season
- Although marine iguanas live happily together for the majority of the year, they begin to show more aggressive behavior during the breeding season. During this time, male marine iguanas become territorial and eager to assert their dominance. Males defend the best nesting territories and groups of females through behavior known as head bobbing. The bobbing head is a warning which can lead to a fight between males if the intruder does not back away. When two male iguanas fight, they butt heads and each iguana attempts to assert his strength by pushing the other iguana away. Eventually, one of the male iguanas will back down and admit defeat without injury.
Color Change
- For most of the year, marine iguanas are gray to black. During the breeding season, male marine iguanas display much brighter hues of green and red. The exact color of an individual marine iguana varies from one island to another. According to Martin Wikelski, an assistant professor at the University of Illinois and member of the Charles Darwin Research Foundation, the bright colors do not influence the female iguana's choice of mate and do not indicate a male's health. Instead, the colors are probably the result of a pigment from certain types of algae available at the same time of year as breeding season.
Mating Habits
- Although male marine iguanas spend a lot of time in the water, they mate with females on land. Once a male marine iguana has asserted his dominance over a particular territory, he will mate with a female in this area. Once he has found a mate, the male climbs onto the female's back and holds onto her neck with his mouth and locks their tails together until they mate.
Nesting
- Around five weeks after mating, females create burrows between 12 and 31 inches deep in soft sand. The female marine iguana excavates the burrow using front and rear legs to remove the sand. A clutch may contain between one and six eggs, which the female will guard while they are incubated for around four months. During this time, females may become aggressive in protecting their eggs. The egg and infant stage of the marine iguana's life is the most perilous, as they are most at risk from becoming prey to animals such as rats, birds and cats. Young marine iguanas will leave the burrow and search for shelter elsewhere as soon as they have hatched.

Animals & Science