Caretta

Description of Caretta caretta
loggerhead sea turtle

Geographic Range Caretta caretta is found in nearly all the world's temperate and tropical oceans: the Atlantic Ocean from Newfoundland to Argentina, the Indian Ocean from southern Africa to the Arabian Gulf to western Australia, theMediterranean Sea, and the Pacific Ocean from Alaska to Chile and Australia to Japan. During winter months loggerhead sea turtles migrate to tropical and subtropical waters. ("NOAA Fisheries", 2006; Ernst, Barbour, and Lovich, 1994; Spotila, 2004)

Habitat

Preferred habitat of Caretta caretta individuals changes throughout the life cycle. Adult females go ashore to lay eggs and seem to prefersteeply sloped, high energy beaches. When hatchlings emerge from the nest, they head for the ocean. Young juveniles are typically found among driftingSargassum mats in warm ocean currents. Older juveniles and adults are most often found in coastal waters and tend to prefer a rocky or muddy substrate over a sandy one. They may also be found near coral reefs and venturing into salt marshes, brackishlagoons, and the mouths of rivers. ("MarineBio", 2006; "NOAA Fisheries", 2006; Ernst, Barbour, and Lovich, 1994; Spotila, 2004).

Physical Description

Named for their huge heads and powerful jaws, loggerhead turtles are the largest hard-shelled sea turtles alive today. They have a heart-shaped carapace, which is often covered with commensal organisms such as barnacles and algae. Generally, thecarapace is a reddish-brown hue with olive tones; there are five pairs of pleural scutes, the first pair touching the cervical (neck) scute. The plastron is cream to yellow, and has two longitudinal ridges that disappear with age. The skin is dull to reddish brown dorsally and medium to pale yellow around the edges and ventrally. The skin may have some orange coloration as well. The skin of males ismore brown and the head more yellow than those of females. Males also have wider carapaces and a long curved claw on each forelimb. Loggerhead sea turtle hatchlings tend to be dark brown to reddish brown on the carapace and cream to reddish brown or dark brown on the plastron. The average adult Caretta caretta in the Mediterranean Sea is smaller than the average adult in the Atlantic Ocean. Twosubspecies - C. caretta gigas in the Pacific and Indian Oceans and C. caretta caretta in the Atlantic - have been proposed but are not fully accepted. They differ in the number of neural bones in the carapace and marginal scutes on the edge of the carapace. Loggerhead sea turtles differ from other sea turtles in having relatively large heads and reddish coloration. Additionally, Ridley's sea turtles(Lepidochelys) have four inframarginal scutes on the bridge. Green sea turtles (Chelonia mydas) and hawksbill sea turtles (Eretmochelys imbricata) have only four pairs of pleural scutes on the carapace; the first pleurals do not touch the cervical scute. ("MarineBio", 2006; "NOAA Fisheries", 2006; Ernst, Barbour, and Lovich, 1994; Spotila, 2004).

DevelopmentLike many turtles, Caretta caretta has temperature-dependent sex determination (TSD). The sex of hatchlings is determined by egg temperature during the middle third of incubation. The pivotal temperature - the temperature at which an 50:50 ratio of males:females is produced - varies from location to location aroundthe world. For example, the pivotal temperature in South Africa is 29.7 ºC , but in Australia the pivotal temperature is 28.2 ºC. Generally, the pivotal temperature is between 28 and 30 ºC. Temperatures of 24 to 26 ºC tend to produce all males and temperatures of 32 to 34 ºC tend to produce all females. Eggs are not viable outside the extremes of these ranges. (Ernst, Barbour, and Lovich,...