The hawksbill turtle (Eretmochelys imbricata) gets its name from its narrow, elongated head that tapers sharply to a V-shaped lower jaw. Its other prominent feature is the saw-like appearance of its shell margins. The hawksbill is one of the smallest species of marine turtles, with adults measuring about 75-90 cm in length and weighing around 70 kg. Indian Ocean turtles tend to be smaller than their Pacific and Atlantic counterparts, with females measuring 70 cm and weighing 44 kg, on average. Males and females tend to be around the same size, but males may have longer claws and brighter colouring. The carapace of the hawksbill is unique amongst the sea turtles as the scutes overlap. It has five central and four pairs of lateral scutes on its carapace. These scutes are streaked and marbled with amber, yellow, black, or brown and the turtle has a yellowish plastron.
Hawksbill Turtle Biology and Behaviour
Hawksbills reach sexual maturity at around 30 years of age. They mate approximately every 2 years in secluded lagoons off their nesting beaches. Females may nest 2 to 5 times per season. The female lays an average of 160 eggs in each nest that take about 60 days to incubate. Female hawksbills seem to prefer nesting in vegetation at the back of beaches. Track marks are about 70 to 85 cm wide, shallow, and have asymmetrical (alternating) forelimb marks. Tail marks may be present or absent. Hatchlings weigh around 25 g and are 40 mm long at birth. The hatchlings have a light-brown, heart-shaped shell, which elongates with age. Their life span remains unknown. Hawksbills often rest in caves or under ledges around reefs during the day and prefer to return to the same spot night after night to rest.
Hawksbill Turtle Diet
The hawksbill’s narrow head and beak-like jaw shape allows them to forage in crevices in coral reefs. They feed mainly on sponges, but anemones, soft corals, urchins, jellyfish, squid, and shrimp are also in their diet. Both sessile and mobile animals are eaten and hawksbills appear to be opportunistic predators. Juvenile hawksbills eat Sargassum seaweed as well as prey that can be found within the floating algae mats such as fish eggs, crabs, and other invertebrates.
Hawksbill Turtle Habitat and Distribution
This species can be found throughout the central Atlantic and Indo-Pacific regions; in fact, these two populations are sufficiently different to be considered subspecies. Post-hatchling hawksbills occupy the pelagic environment, taking shelter under algal mats accumulating at convergence points.
Hawksbills recruit to coastal foraging areas when they reach approximately 20-25 cm in length (around 1-4 years of age). This shift in habitat also involves a shift in feeding strategies: from feeding primarily at the surface to feeding on animals associated with coral reef environments below the surface.
Adults forage almost exclusively on coral reefs and are seldom seen foraging in waters deeper than 20 metres. Once a convenient feeding area is located, hawksbills remain loyal to that site, moving only when there is increased competition, decreased food availability, or to make their nesting migrations. Marine biologists and divers stationed around the country report seeing the same turtles on their house reefs year after year.
Like other marine turtles, the hawksbill makes long nesting migrations and nests on both low- and high-energy beaches. Thanks to their small body size and great agility, they can traverse fringing reefs inaccessible to other species. They often nest on small, isolated islands and sometimes on mainland coasts.
Although generally not found in large concentrations, hawksbills are widely distributed across the Indian Ocean. Nesting density is low throughout their global range and many populations are now severely depleted, though new, previously unknown, nesting populations were recently discovered in the central Pacific. In the Indian Ocean, large nesting populations occur in the Seychelles, Indonesia, and Australia. Smaller nesting populations can be found in the Lakshadweep Islands, the Andaman and Nico-
bar Islands, Chagos Islands, Oman, Saudi Arabia, the Maldives, and Madagascar.
Hawksbill Turtles in the Maldives
Hawksbill turtles are known in the Maldives as “kahan’bu” and forage throughout the archipelago year-round. The Maldives is probably one of the most important feeding areas for hawksbill turtles in the Indian Ocean; marine biologists and citizen scientists have photographed over 1,000 individuals throughout the archipelago. Many of the photographed turtles were juveniles, with a carapace less than 60 cm long, whereas few males and adult females have been photographed. Adult turtles may be foraging in the Maldives and nesting in other Indian Ocean locations such as the Chagos Islands to the south, the Lakshadweeps to the north, or further afield.
Based on reports from marine biologists and professional divers stationed around the country, the number of confirmed hawksbill sightings is around ten times higher than that of green turtles. However, the number of hawksbill turtles nesting in the Maldives appears to be lower than the number of nesting green turtles. Nesting likely occurs in most atolls on uninhabited islands and sandbanks. In the Indian Ocean, the peak of the nesting season is October to January, which marks the onset of the North-west Monsoon. The population of nesting hawksbills in the Maldives is currently unknown, though recent nesting activity has been reported in Kaafu, Baa, Thaa, and Laamu atolls.
Hawksbill Turtle Conservation Status
IUCN Red List Status: Critically Endangered (2008) – the last category before “Extinct”.
Current global population estimate: Approximately 8,000 adult nesting female hawksbill turtles.
Sources: Hudgins, Ali, and Mancini (2017) “Marine Turtles of the Maldives: A field identification and conduct guide”. An IUCN Publication funded by USAID.