Ecology: As their name suggests, marine iguanas spend a significant portion of their life in the water. There, they feed largely on algae, with a fondness for green and red algae, stripping them from the rocks with their sharp teeth. Despite a mostly vegetarian diet, marine iguanas will sometimes feed on small crustaceans and terrestrial insects to supplement the protein in their diet. Larger marine iguanas tend to forage in the subtidal zone, able to stay warmer for longer due to their body size with increased insulation. In contrast, smaller individuals tend to stay closer to shore in the intertidal zone. Despite being on the equator, the water surrounding the Galapagos is cooled from the Humboldt Current and many marine iguanas have to bask after foraging to regain their energy and digest. In order to warm up, they will bask on the cooled lava fields that make up much of the shoreline. When basking, marine iguanas stay between 35°C and 37°C, any warmer and they risk overheating and potentially dying. To avoid this, marine iguanas will regularly change position to minimize the amount of direct sunlight. The majority of their time is spend basking, and during this time they also excrete salts from their body as large amounts building up can be harmful. Many animals have adapted different ways to excrete salt, some through tears, others sweat it out, the marine iguana however sneezes it. Salt glands excrete salts into the nasal cavity of the iguana, from there it mixes with mucus and is excreted through puffs of air. Salts are also excreted from the cloaca but to a lesser extent.
Sources:
Bartholomew, George A. "A Field Study of the Temperature Relations in the Galápagos Marine Iguana." Jstor, Copeia, 21 June 1966, www.jstor.org/stable/1441131. Accessed 4 Sept. 2022. Dunson, William A. "Electrolyte Excretion by the Salt Gland of a Galápagos Marine Iguana." American Journal of Physiology, 1 Apr. 1969, journals.physiology.org/doi/abs/10.1152/ajplegacy.1969.216.4.995?journalCode=ajplegacy. Accessed 4 Sept. 2022. Trillmich, Krisztina G., and Fritz Trillmich. "Foraging Strategies of the Marine Iguana, Amblyrhynchus cristatus." Springer Link, Behavioral Ecology and Sociobiology, Feb. 1986, link.springer.com/article/10.1007/BF00300002. Accessed 4 Sept. 2022. |