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Marine Iguana (Amblyrhynchus Cristatus)

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Marine Iguana (Amblyrhynchus Cristatus) Carolyn Hollis ECOL 5960 Galapagos Marine Ecology June 10, 2008 Marine Iguana (Amblyrhynchus Cristatus) From their blunt nose and razor sharp 3-cusped teeth that allow them to scrape 1 cm high algae from rocks to their long sharp claws that grip rocks from the buffeting of waves, marine iguanas are exquisitely adapted for their environment. Their mostly black skin absorbs the sun’s rays helping to regain body temperature from dives in which they can drop as much as 10oC. The worlds only marine reptile, they are excellent swimmers. The flattened tail, combined with an undulating motion, sends the largest past the breakers to dive 1.5 to 5 meters deep to feed. While typical dives last 5 to 10 minutes they can slow metabolism and heart rate to stay underwater as long as an hour and dive as deep as 15 meters. They also shunt blood away from the body’s surface during a dive to conserve body temperature. Whereas the males wait for the intense noontime sun to feed, the juveniles and females, lacking a sufficient surface to volume ratio, feed in the intertidal areas and off exposed rock during the ebb tide. Feeding on a wide variety of algae, they take in copious amounts of salt water. A gland located near the eyes removes the salt and passes it through a duct to the nostrils. The salt is sneezed out, encrusting the iguana’s head with salt. This perhaps is one reason Darwin called it a “hideous looking creature”. When the warm ocean currents associated with El Nino make algae less abundant, the marine iguanas shrink. They become shorter as well as thinner. They absorb bone during times of famine and can alternate between growing and shrinking phases through out their lives. When warming up, they lie flat to maximize sun exposure. When the optimum body temperature of 35.5oC is reached, they face the sun and elevate the front part of the body. In this position air can pas under the body conducting heat away and the head shades the rest of the body. At 39oC they will pant to cool off. At night they mass together with as many as 50 in a pile to conserve body heat. Marine Iguana (Amblyrhynchus cristatus) is endemic to Galapagos and ubiquitous to the rocky southern shores with shallow reefs and extensive intertidal zones. 4,500 iguana may live along one mile of coastline. They are 3 to 4 feet long, the smallest on Genovesa and the largest on Fernando and Isabela. They are black or gray in color. The males have spots of color (green and red) that become blotches during mating season. The coloration varies from island to island. Red predominates on Espanola and green on Santiago. Mating season also varies from island to island, but sources do not agree on the times. Rothman says mating begins in January on Espanola but earlier on other islands. Jackson indicates that Santa Cruz is earliest, beginning in January. During mating season, the males that happily coexisted, become territorial. The favored territory is the dry region above the tidal zone near the sandy nesting area. Males position themselves on the high point of their turf and posture to make themselves big, bobbing their heads up and down. They engage is shoving matches that can last 5 hours, only pausing for more head bobbing. Territory established, the male waits for a female to saunter by. He woos her by circling her and nodding at her. If successful he mounts her, holding her by the neck and encircling with his tail. The male has two penis-like organs, one of which will be able to reach the female cloacae. Females migrate to sandy areas where five weeks later they bury 2 to 4 eggs. They become very aggressive toward other females who might dig up their eggs. When the hatchling emerge 3 to 4 months later they fall prey to snakes, lava lizards, heron and especially cats. By the time they reach maturity, they will only be prey to hawks. Galapagos Marine Iguana. Galapagos Conservation Trust, http://www.gct.org/iguana1.html Jackson, M. H., Galapagos: A natural history guide. The University of Calgary Press, 1985. Marine Iguanas. Department of Geological Sciences, Cornell University, http://www.geo.cornell.edu/geology/GalapagosWWW/marineIguanas.html Rothman, Robert H., Marine Iguana. Rochester Institute of Technology, http://people.rit.edu/rhrsbi/GalapagosPages/Marine Iguana.html .
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  • NAME: Land Iguana and Marine Iguana – Both in the Family Iguanidae CLASSIFICATION: Land: Ge- Nus Conolophus; Species (Two) Su
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