Eretmochelys imbricata

Hawksbill Sea Turtle

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Hawksbill Sea Turtle



The hawksbill sea turtle (Eretmochelys imbricata) is a critically endangered sea turtle belonging to the family Cheloniidae. It is the only extant species in its genus. The species has a worldwide distribution, with Atlantic and Pacific subspecies. E. imbricata imbricata is the Atlantic subspecies, while E. imbricata bissa is found in the Indo-Pacific region.

This turtle has a unique characteristic that is strong homing instinct or strong memory and ability as bioindikator to know an area is polluted. With a strong memory, turtles will return to shore where they were first born to spawn and hawksbill turtle have a sharp beak and tapered with a large jaw like beak of eagle and overlapping scales. Adults travel hundereds or thousand of kilometers from foraging grounds to breeding areas and neonates are broadly dispersed by ocean currents.

Habitat: Frequent warm, shallow water habitats (less than 20 m) such as bays, shoals, coral reefs, and island (nesting), females lay several hundered eggs on exposed sand beach every 2 to 3 years.



Eretmochelys imbricata are found mainly in the tropical regions of the Atlantic and Pacific oceans. However, in the western hemisphere, they have been reported to have nests as far north as Woods Hole, Massachusetts. They are also present in the Long Island Sound. However, between the Carolinas and New Jersey, very few hawksbill turtles have been recorded.

Biogeographic Regions: australian ; oceanic islands ; indian ocean; atlantic ocean ; pacific ocean ; mediterranean sea



Hawksbills nest on insular and mainland sandy beaches throughout the tropics and subtropics. They are highly migratory and use a wide range of broadly separated localities and habitats during their lifetimes (for review see Witzell 1983). Available data indicate that newly emerged hatchlings enter the sea and are carried by offshore currents into major gyre systems where they remain until reaching a carapace length of some 20 to 30 cm. At that point they recruit into a neritic developmental foraging habitat that may comprise coral reefs or other hard bottom habitats, sea grass, algal beds, or mangrove bays and creeks (Musick and Limpus 1997) or mud flats (R. von Brandis unpubl. data). As they increase in size, immature Hawksbills typically inhabit a series of developmental habitats, with some tendency for larger turtles to inhabit deeper sites (van Dam and Diez 1997, Bowen et al. 2007). Once sexually mature, they undertake breeding migrations between foraging grounds and breeding areas at intervals of several years (Witzell 1983, Dobbs et al. 1999, Mortimer and Bresson 1999). Global population genetic studies have demonstrated the tendency of female sea turtles to return to breed at their natal rookery (Bowen and Karl 1997), even though as juveniles they may have foraged at developmental habitats located hundreds or thousands of kilometers from the natal beach. While Hawksbills undertake long migrations, some portion of immature animals may settle into foraging habitats near their beaches of origin (Bowen et al. 2007).


Roles in the Ecosystem

Like other species of sea turtles, Hawksbills contribute to marine and coastal food webs and transport nutrients within the oceans (Bouchard and Bjorndal 2000). Hawksbills are important components of healthy coral reef ecosystems and are primarily spongivorous in the Caribbean (Meylan 1988), but more omnivorous in the Indo-Pacific (review by Bjorndal 1997). They consume relatively large amounts of algae in northern Australia (Whiting 2000 cited in S. Whiting in litt. to J. Mortimer 4 Jun 2007), soft corals in the Great Barrier Reef region (C. Limpus unpublished data), and other combinations of forage depending on habitat (in Seychelles, J. Mortimer and R. von Brandis unpublished data; in Barbados, B. Krueger unpublished data). At sites where they are primarily spongivorous, Hawksbills have been found to support healthy reefs by controlling sponges which would otherwise out-compete reef-building corals for space (Hill 1998, León and Bjorndal 2002, Bjorndal and Jackson 2003).



Analysis of historic and recent published and unpublished accounts indicate extensive subpopulation declines in all major ocean basins over the last three Hawksbill generations as a result of over-exploitation of adult females and eggs at nesting beaches, degradation of nesting habitats, take of juveniles and adults in foraging areas, incidental mortality relating to marine fisheries, and degradation of marine habitats. Analyses of subpopulation changes at 25 Index Sites distributed globally (see W-Figure 1 in attached PDF) show an 84 to 87% decline in number of mature females nesting annually over the last 3 Hawksbill generations (see W-Table 1 in attached PDF). Numerous populations, especially some of the larger ones, have continued to decline since the last assessment of the species (Meylan and Donnelly 1999). Today, some protected populations are stable or increasing, but the overall decline of the species, when considered within the context of three generations, has been in excess of 80%.



Degree of Threat: A : Very threatened throughout its range communities directly exploited or their composition and structure irreversibly threatened by man-made forces, including exotic species

Global numbers are very difficult to estimate but it appears that this turtle has suffered drastic decline, probably by as much as 80 percent over the last century. Major threats to survival come from illegal trade in the turtle's prized shell, known as tortoiseshell, which has been sought for jewellery and ornaments for centuries. There is also a substantial market for eggs, meat and even stuffed juveniles as exotic gifts in some parts of the world. Additional pressure on the global population comes from harvests to support traditional customs, the loss of nesting sites, accidental entanglement in fishing lines and the deterioration of coral reef systems which act as feeding sites for these turtles.

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