Hawksbill Sea Turtle – Why Are They Endangered?

Hawksbill Sea Turtle
Hawksbill Sea Turtle (Eritmochelys imbricata). Credit: Caroline S. Rogers, NOAA, CC-BY

The hawksbill sea turtle (Eretmochelys imbricata) is a critically endangered species. They are the smallest of all sea turtles and the only ones with a pointed beak.

Hawksbills are considered to be the most tropical of all sea turtles. They prefer to feed in areas near coral reefs and rocky outcroppings in shallow coastal areas.

The distribution of the Hawksbill turtle is circumtropical, occurring from 39oEN to 300ES latitude in the Atlantic, Pacific, and Indian Oceans and the surrounding bodies of water.

In the eastern Pacific Rim, 50 years ago, hawksbills found in near-shore waters from Mexico to Ecuador were common to abundant. Today, hawksbills are rare in most areas and there are no known nesting beaches remaining on the Pacific coast of Mexico.

In the Central Pacific, nesting is widely distributed and scattered. Foraging areas have been reported in almost all the island groups of Oceania from the Galapagos Islands in the eastern Pacific to the Republic of Palau in the western Pacific.

Hawksbills are also found to nest in the far western and southwestern Pacific islands, and mainland of Southeast Asia, from China, Japan, Philippines, Malaysia, Indonesia, Papua New Guinea, the Solomon Islands, and Australia.

What Does A Hawksbill Sea Turtle Look Like?

hawksbill sea turtle
A hawksbill sea turtle (Eretmochelys imbricata). Credit: prilfish CC-BY

The hawksbill’s appearance is similar to that of the other marine turtles. It has a flattened body shape, a protective carapace, and flipper-like limbs, adapted for swimming in the open ocean.

Characteristics of the hawksbill that distinguish it from other sea turtle species include:

  • two claws on each flipper
  • a beak-like mouth, with lower jaw that is V-shaped
  • hard carapace (shell) with large scutes (shell plates)
  • 4 costal (lateral) scutes. First costal scute does not touch nuchal
  • shell is imbricated, overlapping scutes, serrated along the posterior edge

The hawksbill is also biofluorescent, the first reptile recorded with this characteristic.

Why Is The Hawksbill Sea Turtle Endangered?

There are multiple threats to this sea turtle’s continued existence as a species.

Tortoiseshell objects such as combs, jewelry, furniture decoration, and collectibles are typically made from Hawksbill sea turtle shells. The shell has been described as the “world’s first plastic.” These products are still produced even though there is an international ban on trafficking them.

Turtle meat and eggs have provided food to many inhabitants and cultures that surround the Pacific. Turtle meat is considered a delicacy in some countries. Commercial and subsidence harvesting are both contributing to the depletion of the populations.

Sea turtles are prized for their ability to stay alive for long periods after they are captured. In areas where there is no refrigeration, sea turtles are highly sought after as a feast food.

Tools were made from turtle bones. Some parts of the turtle were used to make medicine. Turtles have been and still are on some islands the focus of important religious or ceremonial practices.

There is increased access to remote nesting beaches by indigenous fishermen equipped with spear guns and motorboats, SCUBA, and advanced fishing gear.

Add to that loss of nesting areas because of coastal development and erosion of beaches. Don’t forget ocean pollution including single-use plastics.

The International Union for the Conservation of Nature (IUCN) Red Data Book considers the hawksbill as endangered. The Convention on International Trade in Endangered Species of Wildlife Fauna and Flora (CITES) considers the hawksbill as most endangered.

Hawksbill sea turtles are protected under the U.S. Endangered Species Act (ESA) for Pacific territories (Guam, American Samoa) and commonwealths (CNMI) of the United States and for certain independent states.

Hawksbill Sea Turtle Diet and Life Cycle

Hawksbills eat sponges and other invertebrates found on coral reefs, which is likely why hawksbills are the most exclusively tropical of all sea turtles.

Females come ashore on nesting beaches every 2 to 5 years. After digging a nesting pit, they deposit up to 180 eggs.

The eggs hatch in about 60 days, then the tiny hatchlings make their way to the beach and swim for up to three days to the relative safety of deep water, where they drift for years. Upon reaching a size of 8 to 12 inches, they return to shallower water, where they spend many years foraging and growing.

At sexual maturity, both the male and the female return to the area where they were born to mate and begin the cycle again. Females lay from 2 to 4 clutches of eggs at two-week intervals before returning to their feeding grounds.

Foraging populations in the ocean do not always reflect the potential for nesting on adjacent beaches. Juveniles in their foraging habitat and adult females in their foraging home range may be from the same genetic stock but are likely to be geographically distant from each other and their natal beach.

Further research with tagging and genetic surveys is needed to determine the relatedness of proximal groups in the foraging and nesting sea turtles.

References:

  1. Gruber, David F.; Sparks, John S. (2015). First Observation of Fluorescence in Marine Turtles. American Museum Novitates (3845): 1–8.
  2. Kamel, Stephanie Jill; Delcroix, Eric (2009). Nesting Ecology of the Hawksbill Turtle, Eretmochelys imbricata, in Guadeloupe, French West Indies from 2000–07. Journal of Herpetology. 43 (3): 367–76.
  3. Incredible Journey: Hawksbill Sea turtles, 2007. The Nature Conservancy  (July 2007)
  4. Mortimer, J.A; Donnelly, M. (IUCN SSC Marine Turtle Specialist Group) (2008). Eretmochelys imbricata. IUCN Red List of Threatened Species. 2008: e.T8005A12881238.
  5. Spotila, Jim R. 2004. Seaturtles A Complete Guide to Their Biology, Behavior, and Conservation. The Johns Hopkins University Press, Baltimore, Maryland
  6. Witherington, B. (2006). Sea Turtles: An Extraordinary History of Some Uncommon Turtles. Minnesota: Voyager Press.