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New Jersey Endangered and Threatened Species Field Guide


Image of Hawksbill sea turtle.Zoom+ Hawksbill sea turtle. © Tim Sheerman-Chase

Atlantic hawksbill turtle

Eretmochelys imbricata

Species Group: Reptile

Conservation Status

State: Endangered

Federal: Endangered

 


Identification

The most colorful sea turtle, the medium-sized hawksbill turtle has an elongated, oval shell with overlapping scutes on the carapace. The overlapping is most pronounced at maturity, but often disappears in older individuals. Barnacles are often found on the carapace and plastron. Its medium-sized head is narrow, with a pointed beak. There are two claws on each fore and rear flipper. As is true of other sea turtles, males have stronger, more curved claws and longer tails than the females.

Color varies widely, from very bright colors to heavy dark brown (in the eastern Pacific). The scales of the head have creamy or yellow margins, while the carapace has an amber "ground" color overlaid with spots or stripes of brown, red black and yellow usually arranged in a radiant, fan-shaped pattern. Underneath, the plastron is amber colored. The dorsal, or upper, part of the head and flippers are darker, with less variation in color.

The carapace of hatchlings and juveniles is wider than the shell of adults, with three keels of spines along the carapace which disappear with age. Hatchlings are mostly brown, with paler blotches on the rear part of the carapace, with small pale spots on the top of each scute along the plastron's two keels. Juveniles, though, are the most vibrantly colored, with bold amber/brown/greenish/gold variegation. Adults are 30.4 to 35.6 inches and typically weigh between 94.6 and 165 pounds, but may weigh as much as 200 pounds.

Image of This species does not normally occur off the coast of New Jersey.Zoom+ This species does not normally occur off the coast of New Jersey.

Distribution and Habitat

Unlike land turtles from which they evolved more than 150 million years ago, sea turtles spend almost their entire lives in the sea. When active, they often come to the surface to breathe, but can remain underwater for several hours at a time while resting.

Though most sea turtles inhabit warm tropical and subtropical waters, they migrate northward as water temperatures increase in the late spring and summer and remain in northern waters until late fall. From late May until November, New Jersey coastal waters provide important seasonal foraging habitat to several species of sea turtles.

Hawksbill turtles are circumpolar, inhabiting tropical and subtropical oceans in the Atlantic, Indian, and Pacific Oceans. Within the Atlantic Ocean, they can be found from Brazil in the south to Massachusetts in the north, including the Gulf of Mexico and Caribbean Sea. Within the U.S., they are common in the waters near Puerto Rico and the Virgin Islands. They can also be found from Texas to Florida. Sightings are rare north of Florida. According to the New Jersey Endangered and Nongame Species Program, there are no sightings currently documented within New Jersey waters for this species.

Hawksbill turtles nest in Puerto Rico, the Virgin Islands, Mexico, Costa Rica, Cuba, and several other tropical areas. Their largest nesting location is in Australia.

Hawksbill turtles occupy several different habitats depending on their age, but they are most commonly found near coral reefs. Nesting occurs on sandy beaches. Hatchlings move directly to sea after hatching, often floating in masses of sea plants for several years and feeding at the surface. Once the juveniles are approximately 8-10 inches long, they move to coral reefs where they’ll feed within the coral reef.

Diet

The hawksbill’s diet consists primarily of sponges. They will also eat other invertebrates and algae found within coral reefs. Juveniles have a more varied diet than adults, some of which may feed almost exclusively on sponges.

Life Cycle

Female hawksbill turtles are sexually mature when they are about 31 inches long and males when they are about 27 inches long. Female hawksbill turtles return to the beaches where they were born in order to lay their eggs every 2-3 years. They lay an average of 3-5 clutches of about 130 eggs at intervals of about 2 weeks. Nesting occurs at night.

Egg mortality may result from predation, beach erosion, invasion of clutches by plant roots, crushing by off-road vehicles, or flooding by sea water or excessive rainfall. The gender of hatchlings is affected by incubation temperature, with warmer temperatures resulting in a higher number of females and cooler temperatures producing mainly males. Hatchlings emerge from the nest typically during darkness, each weighing about half an ounce and measuring 1-2 inches. Of every thousand hatchlings, only a few are believed to survive to adulthood. Once they reach water, male hatchlings will never return to land while females will only do so to nest.

Hawksbill turtles are not typically found in New Jersey waters. However, if they do appear, it would be between summer and fall, when water temperatures are warmer. When water temperatures begin to drop, they must migrate south or risk dying or becoming “cold-stunned”. “Cold-stunning” occurs when sea turtles become immobile due to the dramatic decrease in water temperature (usually below 50°F) making it impossible for them to escape the cold water and migrate to warmer water. A cold-stunned sea turtle may appear to be dead, but may actually be alive. Without proper intervention a cold-stunned sea turtle will inevitably die.

Aside from humans, the only predator of adult green turtles is large sharks. Hatchlings may be preyed upon as soon as they leave their nest by raccoons, crabs, and birds. Once in the ocean, hatchlings may also be preyed upon by large fish and seabirds.

Current Threats, Status, and Conservation

Hawksbill turtle populations have been decimated by overharvesting of adults and eggs, loss of nesting habitat, interactions with fisheries, and entanglement or ingestion of marine debris. Commercial exploitation, for their meat and shell, has been the primarily cause for the decline of this species. Their populations are currently a small fraction of their historical size. As a result of such declines, the hawksbill was listed as federally endangered in 1970 and was listed as endangered by the state of New Jersey in 1979. The number of adult hawksbill turtles within the Caribbean was estimated to be 27,000 in 2003.

Hawksbill turtles are currently faced with many threats such as the direct exploitation for food (including eggs), entanglement in fishing gear, oil spills, habitat degradation (such as beach development), beachfront lighting, ocean pollution (including marine debris, which may be ingested), and dredging (direct kills and injuries). Beach cleaning operations can destroy nests or produce tire ruts that inhibit movement of hatchlings to sea. Additional threats include predation and trampling of eggs and young by raccoons and feral mammals, crushing of eggs or young by vehicles or humans, collisions with boats and intentional attacks by fishermen. Long-term threats include sea level rise which, coupled with inland urbanization, may reduce available nesting beaches. Since sexual differentiation depends on incubation temperature, there is concern that global warming may result in an imbalance in the sex ratio.

The primarily threat to hawksbill turtles, in addition to direct killing of adults and eggs, is the loss of healthy coral reef habitat. Coral reefs are vulnerable to human disturbances such as pollution and direct damage, such as dropping of anchors on reefs or fishing with the use of explosives. Global climate change also damages and destroys reefs by causing the coral animals which create the reefs to become diseased or die as water temperatures increase. Hawksbill turtles need healthy coral reefs to survive and are therefore negatively impacted by anything which harms the reef itself.


Scientific Classification

Kingdom: Animalia
    Phylum: Chordata
       Class: Reptilia
          Order: Testudines
             Family: Cheloniidae
                Genus: Eretmochelys
                   Species: E. imbricata

Find Related Info: Endangered, Reptiles

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