In 1997, high ocean temperatures during a severe El Niño season caused failure of the seaweed beds around the Galapagos Islands and about half the marine iguanas starved to death.

[1] A unique set of circumstances on South Plaza Island helps explain why the hybrid iguanas have been observed only there.

[2] Elsewhere in the Galápagos, reproductive isolation between the two species is maintained by separation of breeding in both place and time: there is little overlap between the inland habitat favored by the land iguanas and the coastal habitat of the marine iguana, and the short breeding seasons of the two species normally do not overlap.

[3][4] Despite the long evolutionary separation between the two parent species, which are assigned to different genera, the offspring are viable, although likely sterile.

They also have sharp claws like their marine fathers, which enable them to climb for food rather than waiting for it to drop from a cactus as the land iguanas do.