Scientific Name: Eretmochelys imbricata Fijian Name: ‘taku’
The hawksbill turtle is small to medium sized compared to other sea turtle species. Adults weigh 45 to 65kg on average, but can grow as large as 80kg. Hatchlings usually weigh about 14g.
The carapace or top shell of the hawksbill turtle makes it easy to distinguish from other turtle species. Adults have a carapace length ranging from 60 to 90cm in length and are coloured dark to golden brown, with streaks of orange, red, and/or black. The shells of hatchlings are about 2 inches (about 40mm) 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 “scutes.”
The hawksbill turtle’s head is elongated and tapers to a point, with a beak-like mouth that gives the species its name. The shape of the mouth allows the hawksbill turtle to reach into holes and crevices of coral reefs to find sponges, their primary food source as adults, and other invertebrates. Hawksbill turtles are unique among sea turtles in that they have two pairs of prefrontal scales on the top of the head and each of the flippers usually has two claws.
Male hawksbills mature when they are about 69cm long. Females mature at about 78cm. The ages at which turtles reach these lengths are unknown. Female hawksbills return to their nesting beaches (i.e. the same beaches they were born, otherwise also known as their natal beach) every 2 to 3 years to nest at night for approximately every 14 to16 days during the nesting season. A female hawksbill generally lays 3 to 5 nests per season, which contain an average of 130 eggs. Hawksbill turtles usually nest high up on the beach under or in the beach/dune vegetation on both calm and turbulent beaches. They commonly nest on pocket beaches, with little or no sand.
Habitat
Hawksbill turtles use different habitats at different stages of their life cycle, but are most commonly associated with healthy coral reefs. Post hatchlings habitat for hawksbill juveniles in the Pacific is unknown, however indications point to pelagic zones. After a few years in the pelagic zone, small juveniles retreat to coastal foraging grounds; their size at that time is 35 cm in carapace length. This shift in habitat also involves a shift in feeding strategies, from feeding primarily at the surface to feeding below the surface on animals associated with coral reef environments. Here, juveniles begin feeding on a varied diet that includes sponges, other invertebrates, and algae.
The ledges and caves of coral reefs provide shelter for resting hawksbills both during the day and at night. Hawksbills are known to inhabit the same resting spot night after night. Hawksbills are also found around rocky outcrops and high energy shoals, which are also optimum sites for sponge growth.
Distribution
Hawksbill turtles are circumtropical, usually in the Atlantic, Pacific, and Indian Oceans and associated bodies of water. Research indicates adult hawksbill turtles are capable of migrating long distances between nesting beaches and foraging areas, which are comparable to migrations of green and loggerhead turtles.
Population Trends
Hawksbills are solitary nesters, thus determining population trends or estimates on nesting beaches is difficult. The largest populations of hawksbills are found in the Caribbean, the Republic of Seychelles, Indonesia and Australia.
In Fiji, nesting sites for hawksbills are the Heemskerq and Ringgold Reefs, Namena Lala Island, Vatulele, Laucala, Leleuvia and the greater Mamanuca Group. Islands in the Mamanucas that are nesting grounds for hawksbill includes the islands of Namotu, Tavarua, Navini, Elevuka, Kadavu Lailai, Vunavadra, Tivua, Modriki, Mana, Malolo and Malolo Lailai.
Threats
Hawksbills face threats to their nesting beaches and in their marine environment generally. The primary global threat to hawksbills is habitat loss of coral reef communities. Coral reefs are vulnerable to destruction and degradation caused by human activities. Humans can alter coral reefs either gradually (i.e., pollution can degrade habitat quality) or catastrophically. Examples include toxic spills and vessel groundings. Recent evidence suggests that global climate change is negatively impacting coral reefs by causing higher incidences of coral diseases, which can ultimately kill entire coral reef communities. Hawksbill turtles rely on coral reefs for food resources and habitat. As these communities continue to decline in quantity and quality, hawksbills will have reduced foraging opportunities and limited habitat options.
Historically, commercial exploitation was the primary cause of the decline of hawksbill sea turtles. There remains a continuing demand for the hawksbill’s shell as well as other products, including leather, oil, perfume, and cosmetics. In the Pacific, widespread harvesting of nesting females and eggs on the beach and hawksbills in the water is still widespread. Incidental capture in fishing gear, primarily gillnets and vessel strikes also adversely affect this species’ recovery.
Conservation Efforts
The taku is a highly migratory species making it a shared resource among many nations. Conservation efforts for hawksbill populations in one country may be jeopardized by activities in another. 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.
