Hawksbill turtles are named for their prominent bird-like beak. They feed mainly on sponges and play a caretaker role on coral reefs: by eating sponges they make room for more corals to settle and stop corals from being overgrown. As such hawksbills may play a significant role in coral reef growth, a role that is under threat as numbers of hawksbills decline. In part this decline is due to souvenir and jewellery makers targeting them for their distinctively patterned and coloured shells. However the full monetary value of a hawksbill turtle is realised by keeping them alive. It is estimated that a live hawksbill is worth US$30,000 in tourism revenue to resort communities.

Scientific Name
Eretmochelys imbricata

Conservation status
Hawksbill turtles are classified as Critically Endangered by the International Union for Conservation of Nature (IUCN)

Description
Adults have a brown carapace (top of shell) with brown and black patterns. They have overlapping scutes (bony external plate) on the carapace. Their plastron (under part of shell) is cream coloured with occasional black spots. They have a distinctive beak-like mouth and narrow head. Average carapace length of adults is 0.8 metres.

Hatchlings have a dark brown carapace and plastron.

Distribution
The current global hawksbill population size is less than 10% of the population a century ago, and the figure from a century ago is less than 5% of the population centuries before that. Hawksbills live in the waters of 82 countries and nest in 60 of those countries. Genetic tests show that typically hawksbills travel over state borders between nesting and feeding grounds, meaning no one country can call a hawksbill population their own. The largest populations are found in the Caribbean, Seychelles, Indonesia and Australia.

Habitat
Found in tidal and subtidal coral and rocky reefs in tropical and subtropical waters of all oceans of the world. In Australia the main feeding areas are the east coast, including northern NSW, the Great Barrier Reef, and the Torres Strait; the Northern Territory; and Western Australia down to Shark Bay.

Lifecycle
After leaving the nest and entering the water, hawksbill turtle hatchlings enter an oceanic phase. Not much is known of this period of their lives, though it is thought they drift with oceanic currents taking shelter in floating rafts of sargassum seaweed. When they reach approximately 20 cm in carapace length they move towards the coast and settle on a feeding ground where they stay for 20 to 30 years depending on their location (longer in the Pacific, shorter in the Atlantic).

Adults migrate great distances, sometimes thousands of kilometres, to nest close to their natal beach (the beach on which they hatched), even though there may be suitable nesting sites near their feeding grounds.

Diet
Hawksbills mainly eat sponges. Despite the benign name, sponges are full of sharp shards and toxic chemicals and hawksbills have had to adjust their physiology to avoid being injured. However by doing so, they have almost exclusive use of sponges as a food source. A diet very high in sponges has made hawksbill flesh toxic to humans. Unfortunately this has not saved them from hunting as their shells have been highly sought after for centuries for making jewellery and souvenirs.

Hawksbills also eat seagrass, algae, sea cucumbers, soft corals and shellfish. Adult females will eat coral prior to nesting, presumably seeking the calcium for egg formation. Hatchlings are omnivores (feeds on plants and animals).

Nesting
The largest areas for nesting are in Australia, especially the Great Barrier Reef where 6000-8000 nest per annum. Other significant sites are in Mexico, Indonesia and the Seychelles. Once hawksbills nested in large aggregations, now it is not unusual for only 1 turtle to nest on a beach. Tag returns from hawksbills nesting and foraging in the Great Barrier Reef indicate that migration occurs to Indonesia, Papua New Guinea, the Solomon Islands, and Vanuatu.