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Canadian Herpetological Society Société d'Herpétologie du Canada |
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Loggerhead Sea Turtle
Caretta caretta
Family: Cheloniidae
COSEWIC status:- Endangered
- Endangered
- Vulnerable
Description
The Loggerhead Sea Turtle has a proportionately larger head than other sea turtles. Individuals can attain a maximum carapace length of over 1.5 m, but most individuals are smaller than this. The elongated, heart-shaped carapace (top shell) is reddish-brown tinged with olive, often with yellow-bordered scutes (enlarged scales on the shell), and it has a keel down the centre and a serrated rear margin. The reddish brown to olive colouration on the top of the head grades into light yellow on the sides and below, and the jaws are yellowish brown. The flippers are reddish brown and fade to yellow and have claws. The plastron (bottom shell) is yellowish-white. Males have a longer tail and a claw on their front flippers that is much larger than the others. Hatchlings have an average carapace length of 4.3 cm, are yellowish brown, brown or greyish-black, and have three keels on the carapace.
Similar Species
The Loggerhead Sea Turtle can be differentiated from other sea turtles by its proportionately larger head and reddish-brown colouration.
Distribution
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In Canada, the Loggerhead Sea turtle occurs primarily in offshore waters in Atlantic Canada, although they also occur in shallower areas in the Bay of Fundy and around southwestern Nova Scotia. There are no records of this species occurring off the coast of B.C., but records in Washington and Alaska suggest that they may occasionally occur in Pacific Canada. Loggerhead Sea Turtles in the northwest Atlantic nest mainly along the coast of the United States from southern Virginia to Florida, with over 80% of all nesting occurring in Florida. This species’ global distribution includes tropical and temperate regions of the Atlantic, Pacific and Indian Oceans.
Habitat
Loggerhead Sea Turtles are aquatic and inhabit marine environments. In Canada, individuals forage in coastal areas as well as deep offshore waters. Females that forage in Canadian waters nest above the high tide line on sandy beaches along the coast of the southeastern United States.
Biology
Loggerhead Sea Turtles can migrate several thousand kilometres between foraging and nesting grounds, and females nest at the same beaches where they were hatched. Loggerhead Sea Turtles that forage in the Canadian Atlantic migrate south to nest during April to September, with the peak activity from May through July. Females typically reproduce every 2–3 years and lay between 3–4 clutches during the nesting season, usually spaced 10–18 days apart. Nesting typically occurs at night. Females excavate a nest cavity and deposit around 110–130 eggs. The eggs hatch after approximately 2 months, and the hatchlings emerge at night and use light cues to orient toward the ocean. The sex of the offspring is temperature-depend; incubation temperatures of 26°C and lower produce only males, temperatures of 32°C and higher produce only females, and intermediate temperatures produce both sexes. Individuals do not reach sexual maturity until they are 16–35 years of age. Maximum lifespan is unknown, but they can live for at least 60 years. Loggerhead Sea Turtles consume a wide variety of marine invertebrates, such as gastropods (e.g. snails), bivalves (e.g. clams and oysters), crustaceans and jellyfish, as well as other marine invertebrates, fish, plants and algae. Like other sea turtles, the Loggerhead cannot retract its head or flippers into its shell.
Threats
By-catch and entanglement in commercial fishing gear can result in high mortality rates and is the most significant threat to Loggerhead Sea Turtles in Canadian waters. Ingestion of garbage and plastic, particularly plastic bags that superficially resemble jellyfish, also causes the death of many sea turtles. Other threats in marine environments include oil spills and other environmental pollution, as well as propeller strikes from large ships that cause injury and mortality. Illegal poaching of eggs is also a widespread threat to this species. Climate change may also negatively affect sea turtles in several ways, including increased incidence of nesting beach erosion or shifts in sex ratio resulting from changes to nest incubation temperatures. Populations of Loggerhead Sea Turtles in the western Atlantic are undergoing significant decline.