Hawksbill Sea Turtle

Genus: Eretmochelys
Species: imbricata

Hawksbill Sea Turtle

The hawksbill is a small, agile turtle whose beautiful, translucent shell is unfortunately one of its greatest liabilities.
Even though listed as "endangered" under the Endangered Species Act since 1970, international trade in hawksbill products continues in much of the world - the shell is used to make jewelry, hair decorations and other ornaments.

Description:  The body is oval-shaped, and the toothless, powerful jaws accompany a raptor-like "beak" that gives the hawksbill its name.  This beak is perfectly suited for crushing, biting and tearing its favorite food – sponges.

The carapace (top shell) has a tortoiseshell coloring, ranging from dark to golden brown, with streaks of orange, red, and/or black. The shells of hatchlings are 1-2 inches (about 25 - 50 mm) long and are mostly brown and somewhat heart-shaped. The plastron (bottom shell) is clear yellow. The rear edge of the carapace is almost always serrated, except in older adults, and has overlapping horny plates called "scutes".

It is the only sea turtle species with a combination of two pairs of prefrontal scales on the head and four pairs of costal scutes on the carapace.

Size: Hawksbills weigh on average from 100 to 150 pounds (45 to 68 kg) as adults and have an average shell length of 30 inches (76 cm).

Diet:  Hawksbills are omnivorous, consuming sea grasses, sea urchins, barnacles, small animals and their favorite food, sponges. In the Caribbean, as hawksbills grow, they begin exclusively feeding on only a few types of sponges, and they can eat an average of 1200 lbs (544 kg) of sponges a year. Sponges — composed of tiny glasslike needles — apparently cause the turtle no harm. However, in the Indo-Pacific, hawksbills continue eating a varied diet that includes sponges, other invertebrates, and algae.

Interestingly, some of the sponges and small animals that hawksbills consume are toxic. The hawksbill's body fat absorbs the toxins without making the turtle ill, but their meat is potentially poisonous to humans. This discourages, but does not stop, the harvesting of hawksbills for meat.

Typical Lifespan: The normal lifespan of hawksbill turtles is thought to be about 30 to 50 years.

Habitat: Hawksbills are the most tropical of the sea turtles and use different habitats at different stages of their life cycle, but are rarely seen in water more than 65 feet (21 meters) deep. They are most commonly found in coral reefs, rocky areas, lagoons, and shallow coastal areas. They are also found in mangrove-fringed bays and estuaries, usually in areas where coral reefs are absent. Hawksbills are known to pick the same resting spot night after night.

Hatchlings are often found floating in masses of sea plants and algal mats where they find shelter.

Range and distribution: Hawksbill sea turtles are circumtropical, meaning they inhabit oceans, seas and associated waters across the globe, typically between 30° N and 30° S latitude but they are known to go as far south as the coast of Brazil. Hawksbills are not found in the Mediterranean Sea.

Sightings in U.S. waters are most common near Puerto Rico, the U.S. Virgin Islands, and off the coasts of Texas and southern Florida. 
 
Life History and Reproduction:  Like other sea turtles, hawksbill turtles are solitary for most of their lives; they meet only to mate. Every 2 to 3 years females return to nest on the very same beaches where they themselves were hatched. The nesting season in most locations occurs sometime between April and November. Hawksbills nest at night, laying 3 to 6 clutches per season at 2 week intervals. In Florida and the U.S. Caribbean, clutch size is approximately 140 eggs. The incubation period averages 60 days. Nesting occurs on undisturbed beaches, ranging from high energy beaches to very small pocket beaches, and a typical nesting site would be a sandy beach with woody vegetation near the water line. They lay their eggs under or in the beach/dune vegetation.

After the two-month incubation period, 2-inch hatchlings emerge as a group. Hatchlings use the bright, open view of the night sky over the water to find their way to the sea.

In contrast to all other sea turtle species, hawksbills nest in low densities on scattered small beaches. The Gulf and Caribbean coasts of the Yucatán Peninsula, Mexico, where hawksbills nest on long expanses of beach in densities of 20 to 30 nests/km, are exceptions. Several Yucatán beaches account for 25 to 30 percent of all hawksbill nesting in the Caribbean.

Hawksbills are recruited into the reef environment at about 14 inches (35 cm) in length and are believed to begin breeding about 30 years later. However, the time required to reach 35 cm in length is unknown and growth rates vary geographically. As a result, actual age at sexual maturity is not known.

 

Threats:

  • Direct and Indirect  Overexploitation — The hawksbill’s beautiful shell is its greatest liability. The shell is still used in some European and Asian countries to make jewelry, hair decorations and other ornaments, despite its endangered status and the fact that international trade in hawksbill products has been banned in much of the world.

  • Development — Degradation of nesting habitat from coastal development and beach armoring. Beachfront lighting causes hatchlings to mistake the artificial light for their true destination – the moonlit sea. Any distraction from their dash to the water is an opportunity for predators to pick up an easy meal.

  • Habitat Loss  — As coral reef communities continue to decline from degradation and destruction caused by human activities, and as research now suggests from global warming, the hawksbill’s primary source of food is reduced, putting the sea turtles at greater and greater risk.

  • Oil Spills — Swimming through oil, a turtle loses its ability to "cry" away extra salt, and respiration becomes difficult. Learn more about how the oil spill in the Gulf of Mexico has affected sea turtles.

  • Other — Marine pollution and debris, watercraft strikes, and incidental take from commercial fishing operations all contribute to human-related hawksbill sea turtle deaths

Conservation Efforts:

  • Hawksbill turtles are protected by various international treaties and agreements as well as national laws. They are listed in Appendix I of the Convention on International Trade in Endangered Species of Wild Flora and Fauna (CITES), which means that international trade of this species is prohibited. It is also classified by The World Conservation Union (IUCN) as critically endangered.

  • Bycatch of hawksbill turtles (accidental capture by commercial and sport fishermen) is being reduced by fishing gear modifications (i.e. use of TED’s or turtle exclusion devises), changes to fishing practices and closures of certain areas to fishing during nesting and hatching seasons.

  • Designation of critical habitat areas in coastal waters around parts of Puerto Rico.

  • Encourage use of low pressure sodium lighting along beach nesting areas.

  • Regular monitoring of hawksbill turtle populations by NOAA's National Marine Fisheries Service (NMFS).

Sources:

US Fish & Wildlife Service

Fish & Wildlife Research Institute - Florida Fish and Wildlife Conservation Commission

NOAA Fisheries Office of Protected Resources

The Humane Society of the United States

University of Michigan's Animal Diversity Web

NatureServe Explorer

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