The marine iguana is the only lizard in the world with the ability to live and forage at sea, and is endemic to the Galapagos Archipelago. There are eleven very similar subspecies, found on different islands, with those from Isabela and Fernandina being the largest. The adults are black for most of the year, however the males change colour during the mating season, with different subspecies adopting different colourations. Near Española and Floreana they are most colourful, turning bright green and red; on Santa Cruz they are red and black; and on Fernandina they become dull green and brick red. The juveniles are generally black, with a lighter dorsal stripe than the adults. During the mating season males fight for dominance over harems of females, which they will fiercely defend from rival males.