The hawksbill is a small to medium sized sea turtle. The Caribbean population typically weighs 80 kg with a straight carapace length of 62 – 94 cm. Hatchlings weigh 13.5 – 19.5 g and measure 42 mm straight carapace length. The hawksbill turtle has two pairs of prefrontal scales; thick, overlapping scutes on the carapace; four pairs of costal scutes; and two claws on each flipper. The marginal scutes are distinctly serrated on all but the oldest turtles and the scutes of the carapace are patterned with amber and brown. The head is elongate with a sharply pointed, beak-like mouth. The plastron is yellow and plain. In juveniles, the shell is heart shaped.
Can be Confused With
Hawksbill turtles can be identified by their richly patterned, overlapping costal scutes and obvious serrations on their marginal scutes.
The hawksbill turtle is found throughout the world’s tropical oceans, although the species has in rare instances been found as far north as Massachusetts on the Atlantic coast of the United States. The United States National Marine Fisheries Service has designated Mona Island and Monito Island in Puerto Rico as critical habitat.
Ecology and Behavior
The hawksbill’s age at sexual maturity is estimated to be greater than 35 years. Females nest in low densities, with nesting in the United States concentrated in Puerto Rico, the Virgin Islands, Florida, and Hawaii. Females lay four to five nests of 130 eggs each during the breeding season, and are believed to breed every two or three years. Nests are often found under vegetation. Adult females are migratory, known to travel hundreds of kilometers between foraging grounds and nesting sites. Hatchlings are oceanic, found in floating vegetation at convergence points. They begin feeding in coastal areas at 20 – 25 cm in length, foraging in coral reefs, rocky outcroppings, or shoals; where these are absent hawksbill turtles may inhabit mangrove fringed bays, estuaries, or in rare circumstances, stone jetties.
Feeding and Prey
Hawksbills are grazers with a focused diet (specialists), dominated by invertebrates (sponges) for adults and algae for hatchlings. Tunicates, mollusks, algae, and marine plants are also occasionally found in adult hawksbill stomachs, but the proportion of these items to sponges is very low. Captive hatchlings have thrived on a diet of sargassum.
Prey species for juveniles include: Sargassum spp., Syringodium filiforme, Microdictyon sp.
Threats and Status
Threats to hawksbills include:
• Harvest of adults/eggs
• Habitat degradation in nesting sites and coral reefs
• Predators at nesting sites
• Entanglement in debris/fishing gear
• Fisheries bycatch
• Oil and plastic pollution
The hawksbill sea turtle is classified as critically endangered by the IUCN and is listed as endangered in the United States. Demand for the beautiful shell has resulted in the harvest of great numbers of this turtle. Demand for shells remains high despite the hawksbill turtle’s decline, as demonstrated by prices in excess of $225 per kg. Effective protection is difficult under these circumstances. The relatively late age of sexual maturity (35+ years) prevents the population from quickly recovering from the exploitation of hawksbills as well.
National Marine Fisheries Service Office of Protected Species. 2011. Hawksbill turtle (Eretmochelys imbricata). Available online here.
Lutz, P.L and J.A. Musick, eds. 1997. The biology of sea turtles. CRC Press LLC, New York, NY.
National Marine Fisheries Service. 1993. Recovery plan for the hawksbill turtles in the U.S. Caribbean Sea, Atlantic Ocean, and Gulf of Mexico. National Marine Fisheries Service, St. Petersburg, FL.
National Marine Fisheries Service and U.S. Fish and Wildlife Service. 1998. Recovery plan for the U.S. Pacific populations of the Hawksbill Turtle (Eretmochelys imbricata). National Marine Fisheries Service, Silver Spring, MD.