Animal Spotlight: Hawksbill Turtle

Taxonomy:

2004675535
@William Goodwin
  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Reptilia
  • Order: Testudines
  • Family: Cheloniidae
  • Genus: Eretmochelys
  • Species: Imbricata
  • Estimated Average Life Span: 30 to 50 years
  • Average Weight: 100 to 150 pounds (45 to 68 kg)
  • Average Shell Length: 30-40 inches (76-102 cm)

Hawksbill turtles are the smallest species of sea turtles and are named for their narrow, pointed beak. They have a distinctive pattern of overlapping scales on their shells that form a serrated-look on the edges. However, these colored and patterned shells make them highly-valuable and commonly sold as “tortoiseshell” in markets.

They are a fundamental link in marine ecosystems, helping to maintain the health of coral reefs and seagrass beds. As they remove prey such as sponges from the reef’s surface, they provide better access for reef fish to feed.

The turtles also have cultural significance and tourism value. For example, for local residents in the Coral Triangle, the flow of visitors who come to admire turtles is a vital source of income.

Hawksbills are found in tropical and subtropical regions of the Atlantic, Pacific, and Indian Oceans. They are seldom seen in waters deeper than 65 feet. Instead, the turtles prefer coastlines, rocky areas, coral reefs, shallow coastal areas, lagoons, or oceanic islands where sponges are abundant and sandy nesting sites are within reach.

Physical characteristics:

The hawksbill is a small to medium-sized marine turtle that has an elongated oval shell, a relatively small head with a distinctive hawk-like beak, and flippers with two claws. Its raptor-like beak, though toothless, is powerful, perfectly suited for crushing, biting, and tearing sponges. The turtle also has two pairs of prefrontal scales, scales in front of its eyes.

While young, hawksbill turtle’s carapace, or upper shell, is heart-shaped and as they mature, it elongates. The shells of hatchings are only 1-2 inches (about 25-50 mm) long and mostly brown or black.

mid_225023-circle-hawksbill-turtle
@Nils Aukan

As they age, the carapace gains a tortoiseshell coloring, ranging from dark to golden brown, with streaks of orange, red, and/or black. Its strikingly colored carapace is serrated with overlapping scutes, or thick bony plates, except in older adults.

The plastron, or bottom shell, is yellowish with black spots on the intergular and postanal scutes.

Diet:

Hawksbills are omnivorous, consuming sea grasses, sea urchins, barnacles, jellyfish, and other small animals. However, their preferred diet is sponges. They are known to eat an average of 1200 pounds (554 kg) of sponges per year.

In the Caribbean, as hawksbills mature, they begin to exclusively feed on only a few species of sponges. But in the Indo-Pacific, hawksbills will continue to eat a varied diet that includes sponges, other invertebrates, and algae.

Interestingly, some of the sponges and small animals that these sea turtles consume are toxic. Its body fat absorbed the toxins without making the turtle ill, but their meat is potentially poisonous to humans. This discourages, but does not stop, the harvesting of hawksbills for meat.

Behavior:

Like many other sea turtles, hawksbills migrate between feeding sites to nesting grounds. Mating usually occurs every two to three years, taking place in shallow waters close to the shore. Females will then leave the water to choose an area to lay their eggs after digging a pit. Once the eggs are buried, the females retreat back to the sea. After 60 days, the eggs hatch and the hatchlings head towards the water.

hawksbill turtle.PNG
Photo By: Casper Douma

 

In contrast to all other sea turtle species, hawksbills nest in low densities on scattered small beaches. In 2007, it was estimated about 21,212 to 28,138 hawksbills nest each year at 83 nesting sites distributed among the ten ocean regions around the world.

The Caribbean accounts for 20-30% of the world’s hawksbills population. Once supporting the single most important population in the Caribbean, Panama is now only a remnant population. Instead, Mexico and Cuba support the largest nesting populations in the region with 534 to 891 nesting females recorded in the Yucatan Peninsula, Mexico, each year during 2001-2006 and 400-833 nesting females in Cuba in 2002. Other significant nesting sites recorded are Mona Island, Puerto Rico and Buck Island Reef National Monument, U.S. Virgin Islands.

Out of the remaining ocean regions, nesting populations are doing much better in the Atlantic than in the Indo-Pacific, although it has been greatly depleted from historical levels. The situation in the Pacific Ocean is particularly dire, despite the fact that it still has more nesting hawksbills than in either the Atlantic or Indian Oceans. Only four regional populations remain, one in Indonesia and three in Australia. In the U.S. Pacific, hawksbills nest only on main island beaches in Hawaii, primarily along the east coast of the island of Hawaii.

Conservation and Threats:

Since 1996, the International Union for the Conservation of Nature (IUCN) has listed the hawksbill turtle as critically endangered with an estimate of 20,000 to 23,000 nesting females. While global numbers are very difficult to estimate, studies show that the species has suffered a drastic decline, probably by as much as 80% over the last century. Like many sea turtles, hawksbills are threatened many due to human impact: the loss of nesting and feeding habitats, excessive egg collection for consumption, fishery-related mortality (bycatch and entanglement), pollution, and coastal development.

However, they are most threatened by wildlife trade. Despite their current protections under the Convention on International Trade in Endangered Species (CITES) and many national laws, there is still a large amount of illegal trade in hawksbill shells and products. They are much sought after for their beautiful shells that are manufactured into tortoiseshell items for jewelry and ornaments. In recent decades, eastern Asia has provided an eager market for tortoiseshell.

Hawksbill TurtleThe demand for its shell has been prized since ancient times. Surrounded by legend, the tortoiseshell has been described as “one of the romantic articles of commerce, not only because of where it comes from, but because of the creatures from which it is obtained and the people engaged in the trade” (quoted in Parsons 1972).Jewlery and other tortoiseshell objects have been unearthed from predynastic graves of the Nubian rulers of Egypt and excavated from the ruins of the Han Empire of China. Over 2,000 years ago, Julius Caesar considered the warehouses of Alexandria brimming with the material to be the chief spoil of his triumph. By the 9th century, caravans of Arab traders carried rhino horn, ivory, and tortoiseshell throughout the Indian Ocean. For the next 1,000 years, the tortoiseshell trade flourished. It has been closely linked to European discovery, conquest, and commerce around the world. The East Indies was a major source of the shell of antiquity and has been called the world’s most productive seas for tortoiseshell. It wasn’t until the mid 19th century for the Pacific trade to be established, but once it was, it took a tremendous toll on the region’s population.

During the 20th century, Japan was the world’s largest importer of tortoiseshell. Japanese statistics document the import of shell equivalent to more than 1.3 million large Hawksbills from around the world between 1950-1992 and more than 575,000 stuffed juveniles from Asia between 1970-1986. At the end of 1992, Japanese imports ceased, but the industry continued to operate with stockpiled material.

When Japanese, European, American, and other Asian imports are considered along with the large quantities of tortoiseshell used locally in places like Sri Lanka and Madagascar, it is apparent that some millions of turtles were killed for the tortoiseshell trade in the last 100 years.

hawksbill turtle 2
© yaman ibrahim

Significant domestic trade in Hawksbill products continues to be a major problem in many countries. Despite international and domestic prohibitions and lessening of the volume in the last decade, the trade remains to be an ongoing and pervasive threat in the Americas and southeast Asia.

Another critical threat to the hawksbill turtle’s survival 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. The increase in the temperature of the sand could have serious consequences for the creature, as gender of the hatchlings is determined by incubation temperature. A skewed sex ratio could threaten the stability of hawksbill turtle populations in the future.

Changes in ocean currents are also to be expected and may affect juvenile turtles in their migrations following hatching,  as well as adults’ navigation. Raised ocean levels and increases in storm frequency and severity are also likely to lead to increased beach erosion and degradation, which could wash away nests and decreasing available habitat.

There has been several conservation efforts taking place to preserve the hawksbill turtle’s population and habitat.

Around parts of Puerto Rico, critical habitat areas in coastal habitat areas are designated for the turtle during mating seasons. Fishing gear modifications such as the use of TED’s (turtle exclusion devices), changes to fishing practices, and closure of certain areas to fishing during nesting and hatching seasons are being implemented to reduce the risk of bycatch. NOAA’s National Marine Fisheries Service will regularly monitor hawksbill turtle populations. Low pressure sodium lighting along beach nesting areas are highly encouraged. The number of protected areas and biologists and conservationists focusing on sea turtles are increasing.

While hawksbills benefit globally from being listed in CITES’ Appendix I and CMS, the Convention on Migratory Species (Appendix I and II), regional agreements also help to conserve the sea turtle and its habitat.

Public awareness is also critical. Interest in hawksbills and other marine turtle species is at an all-time high globally with ecotourism is growing. With public awareness on the rise, legislation that will temporarily or permanently ban all exploitation of sea turtles and their eggs will also be further implemented and enforced.

377440-tropical-fish-underwater-sea-life-hawksbill-sea-turtle

Interesting Facts:

  • The most dangerous time of a hawksbill’s life is when a hatchling makes the journey from their nests to the sea. Crabs and gulls prey on the young turtles during this short scamper.
  • Young hawksbill turtles are unable to dive deep and spend their early years floating amongst sea plants near the water’s surface.
  • Unlike many other marine turtles, the scutes (scales) of the hawksbill turtle’s carapace are imbricate, or overlapping, hence the scientific name ‘imbricata’.
  • It is the only sea turtle with a combination of two pairs of prefrontal scales on the head and four pairs of costal scutes on the carapace.
  • Though their hard shells protect them from many predators, they still fall prey to large fish, sharks, crocodiles, octopuses, and humans.

References:

IUCN: Eretmochelys imbricata

Hawksbill turtle (Eretmochelys imbricata)

Information About Sea Turtles: Hawksbill Sea Turtle

National Wildlife Federation: Hawksbill Sea Turtle

U.S. Fish and Wildlife Service: Hawksbill Sea Turtle (Eretmochelys imbricata)

WWF: Hawksbill Turtles

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