Hawksbill turtle  (Eretmochelys imbricata)

The hawksbill turtle is classified as Critically Endangered (CR) on the IUCN Red List (1), and is listed on Appendix I of CITES (3), and Appendix I of the Convention on Migratory Species (CMS or Bonn Convention) (4).

The Critically Endangered hawksbill turtle (Eretmochelys imbricata) has been exploited for thousands of years as the sole source of commercial tortoiseshell. The beautiful carapace is generally streaked and marbled with amber, yellow or brown and often has a strongly serrated edge (5). The strongly hooked beak on the narrow head gives rise to the hawksbill turtle's common name (6). Unlike other marine turtles, the scales (scutes) of the hawksbill turtle’s carapace are imbricate, or overlapping, hence the scientific name 'imbricata' (7).

The hawksbill turtle is found throughout tropical waters worldwide, and is known to nest on beaches in at least 60 countries (8). Recent evidence indicates that it takes part in long distance migrations, with breeding and feeding grounds in very distant locations. However, the hawksbill turtle does tend to be more sedentary than other marine turtles species (5).

Hawksbill turtles are mainly associated with the clear, relatively shallow water of coastal reefs, bays, estuaries and lagoons, with nesting generally occurring on remote, isolated sandy beaches (6) (8). 

The hawksbill turtle may take decades to mature, first breeding at 20 to 40 years of age (9). Upon reaching sexual maturity, the female will typically lay up to five clutches of around 100 to 140 eggs in a single breeding season, and then wait a few years before nesting again (6). Nesting is much more dispersed than in other marine turtles, but individuals do tend to return to a particular beach season after season (9). Having survived the dash to the sea, hawksbill hatchlings are believed to spend their first few years in the open ocean before returning to more sheltered coastal waters. Recent studies indicate that the oceanic phase may be shorter for hawksbills, or even omitted in certain regions, as hatchlings swim less vigorously than those of other species (7). Probably less than one out of 1,000 eggs will survive and reach adulthood (9).

Adults are opportunistic predators, using their sharp beak to prize invertebrate prey from crevices within the reef. Unusually amongst marine animals (to whom they are often unpalatable), sponges make up the majority of the hawksbill's diet (6).

Global numbers are very difficult to estimate but it appears that the hawksbill turtle has suffered a drastic decline, probably by as much as 80 percent over the last century (1). 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 (10). 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 (11).

A further threat to the hawksbill turtle is global climate change. Average global temperatures are predicted to increase by at least 2 degrees Celsius in the next 40 years due to climate change. An increase in the temperature of the sand used for nesting could have serious consequences for the hawksbill turtle, as gender of the hatchlings is determined by incubation temperature. The outcome of this is likely to be a skewed sex ratio, which could threaten the stability of hawksbill turtle populations in the future (1) (12) (13).

Ocean levels are thought to have risen at an average rate of 1.8 millimetres per year since 1961. Ocean levels are predicted to rise even more rapidly in the future, while increases in storm frequency and severity are also expected. This is likely to lead to increased beach erosion and degradation, which could wash away hawksbill turtle nests and decrease nesting habitat (1) (12) (13).

Changes in ocean currents are also expected due to climate change. This may affect juvenile hawksbill turtles in their migrations following hatching, as well as adults’ navigation (1) (12) (13).

International trade in the hawksbill turtle is banned amongst signatory nations by its listing on Appendix I of the Convention on International Trade in Endangered Species (CITES) (3), but extensive illegal trafficking still occurs. Preventing this black market trade is the key to saving this species and TRAFFIC (the wildlife trade monitoring network) is involved in monitoring and highlighting this problem (14). In 1988, the government of the Seychelles took a very public stand against tortoiseshell trade by burning a stockpile of seized shells (4), in a manner reminiscent of burning ivory pyres in Kenya (10).

Action to save the world's marine turtles is being taken by many international bodies and recent increases in hawksbill nesting populations have been observed at a few well-protected sites (10). With successful monitoring of populations and a decrease in illegal trade, the hawksbill may respond well to long-term protection.

View information on this species at the UNEP World Conservation Monitoring Centre.

The UK Biodiversity Action Plan for this species is available at UK BAP.

Environment Agency - Abu Dhabi is a principal sponsor of ARKive. EAD is working to protect and conserve the environment as well as promoting sustainable development in the Emirate of Abu Dhabi.

To learn more about a Whitley Award-winning conservation project for this species, click here.

For more information on the hawksbill turtle see:

• CITES: Hawksbill Turtles in the Carribbean Region: Basic Biological Characteristics and Population Status:
  www.cites.org/common/prog/hbt/consolidated_paper.pdf
• WWF - Hawksbill Turtle:
  http://www.panda.org/what_we_do/endangered_species/marine_turtles/hawksbill_turtle/