Loggerhead Sea Turtle
Photo Credit: U. S. Fish and Wildlife Service
SCIENTIFIC NAME: Caretta caretta (Linnaeus)
OTHER NAMES: Loggerhead
DESCRIPTION: A large (United States adult ave. straight-line carapace length approx. 92 cm [36 in.]; ave. weight approx. 113 kg [250 lb.]) sea turtle with a brown to reddish-brown carapace and yellow to brown plastron (Dodd 1988b, Ernst et al. 1994). Has very large head with a massive jaw, and a short snout with two pairs of prefrontal scutes above the nostrils. Scutes on top of head normally brown to reddish brown, some with yellow borders; scutes on side of head can be brown to yellowish white. Jaw is normally yellow. Forelimbs and hindlimbs modified into long front flippers and short rear flippers, with two claws on each flipper. In adult males, one claw on each front flipper distinctly thickened and curved; also have long muscular tail extending well beyond carapace.
DISTRIBUTION: Wide ranging, including the Atlantic, Pacific, and Indian Oceans (Dodd 1988b, Magnuson et al. 1990, Ernst et al. 1994). Normally associated with waters along the continental shelf, and found in many coastal and estuarine areas. Most abundant sea turtle occurring along the Atlantic and Gulf coasts of the United States; a few occur off the coast of California. In the United States, they nest from North Carolina to the northern Gulf of Mexico (Magnuson et al. 1990, Turtle Expert Working Group 2000). Also, most abundant sea turtle occurring in the coastal waters and nesting on the beaches of Alabama.
HABITAT: Waters of the Continental Shelf, including many coastal and estuarine waters along the Atlantic and Gulf Coasts of the United States (Carr 1952, Magnuson et al. 1990, Ernst et al. 1994). Appears to be three genetically distinct nesting subpopulations along the Atlantic and Gulf Coasts: Florida Panhandle, southern Florida, and northern (occurs along the Atlantic Coast of the United States from northeastern Florida up through North Carolina) (Turtle Expert Working Group 2000). Highest density nesting in the United States occurs along the Atlantic Coast of Florida from approximately Cape Canaveral south to Broward County (Ehrhart 1999, Turtle Expert Working Group 2000). In Alabama, nest from Florida border to Dauphin Island, with majority nesting between Fort Morgan and Gulf Shores.
LIFE HISTORY AND ECOLOGY: During spring, adults migrate from foraging to breeding and nesting areas where mating often occurs. Females mate and then nest multiple times (one to seven times per season; average approximately four nests per season) at approximately 14-day intervals (Magnuson et al. 1990, Ernst et al. 1994). Typically, females will nest every other, or every third year. In the United States, nesting normally occurs early May through August, with the majority occurring during June and July. Nest during the night and normally lay approximately 110 eggs per nest. Eggs take approximately 50 to 65 days to hatch depending on the incubation temperature in the nest. Gender of hatchlings determined by the incubation temperature in the nest. Hatchlings emerge primarily during early morning hours and proceed down beach to the surf. Hatchlings assume a pelagic existence for approximately three to five years until they are large enough (approx. 45 cm [18 in.] carapace length) to begin foraging in coastal waters and estuaries, which serve as developmental habitats. During pelagic existence, often associated with floating sargassum rafts or debris, which collect in areas where surface waters converge (Magnuson et al. 1990). Growth rates of immatures vary widely, and age to maturity in the wild has been estimated to vary from 12 to 30 years. Juveniles and adults feed on a variety of benthic invertebrates, in particular molluscs and crustaceans (Carr 1952, Ernst et al. 1994).
BASIS FOR STATUS CLASSIFICATION: Stocks of females nesting in the southeastern U.S. were declining in the late 1980s, but nesting increased on certain beaches in the 1990s coincident with the requirement to use turtle excluder devices (TEDs) on shrimping vessels (Ehrhart 1999, Turtle Expert Working Group 2000). The National Research Council Committee on Sea Turtle Conservation estimated that prior to the use of TEDs, a minimum of 11,000 (and possibly 44,000 or more) sea turtles (primarily loggerheads and Kemp’s ridleys) died annually in the United States’ coastal waters of the Gulf of Mexico and Atlantic due to shrimping-related mortality (Magnuson et al. 1990). Further, if the number of nesting loggerheads continues to increase, one would predict an increased number of turtle/trawler interactions. Also, pelagic longline fishing can impact loggerheads during the pelagic phase of their lives. Many necropsies of stranded sea turtles indicate ingestion of marine debris also poses a hazard (Balazs 1985). Additionally, derelict fishing gear (e.g., nets, fishing line, etc.) has been implicated in the injury of marine turtles due to entanglement (Balazs 1985). Coastal development also has the potential of destroying or altering suitable nesting habitat. For example, beach lighting is well known for disorienting hatchlings during their movement from nest to surf, and in high population areas, nests may need to be moved or protected to ensure they are not disturbed and that hatchlings successfully orient down to the surf. When initially listed in 1978, this species was considered a single population, but genetic studies since indicate at least three distinct subpopulations nesting along the Atlantic and Gulf Coasts. The northern nesting subpopulation and Florida Panhandle nesting subpopulation are much smaller than the southern Florida subpopulation, and are therefore, of particular conservation interest. Although the number of nesting females has increased on some beaches in the southern Florida subpopulation over recent decades, there is no indication of such increases in the Florida Panhandle subpopulation and the northern subpopulation. In fact, there is some evidence of decline in the northern population (Turtle Expert Working Group 2000). Listed as a threatened by the U.S. Fish and Wildlife Service in 1978.
Author: Thane Wibbels