HAWKSBILL SEA TURTLES
Hawksbill sea turtles (Scientific name: Eretmochelys imbricata) are frequently seen by divers and snorkelers. They cruise around reefs, grazing on sponges and other plant life, but stay close to the reef in case they need to make a quick escape from a predator such as a shark.
Hawksbill sea turtles inhabit tropical and sub-tropical waters in all of the world’s major oceans. They get their name from their unique beak-like mouth, which resembles that of a hawk and is perfect for finding food sources in hard-to-reach cracks and crevices. They are the only species of sea turtle that can survive on a diet consisting mainly of sponges. Hawksbill turtles play a key role in the function of marine ecosystems. Hawksbills are estimated to reach maturity between 20 to 35 years of age, depending upon a variety of factors, especially resource availability. Although life expectancy remains unconfirmed, they are long-lived and estimated to live 50 to 60 years. [Source: NOAA]
Warm water and sand during the middle third of the incubation period of hawksbill sea turtle eggs causes the eggs to yield more females. These days more females are being produced. Global warming is blamed for causing warmer temperatures and producing storms that clear away trees that normally provide beach cover to keep the eggs cool.
Websites and Resources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Fishbase fishbase.se; Encyclopedia of Life eol.org; Smithsonian Oceans Portal ocean.si.edu/ocean-life-ecosystems ; Monterey Bay Aquarium montereybayaquarium.org ; MarineBio marinebio.org/oceans/creatures
Hawksbill Sea Turtle Nesting Sites, Migrations and Where They Are Found
Hawksbills can be found living in nearshore habitats in all of the world’s major oceans. The largest nesting populations of hawksbill turtles occur in Australia and Solomon Islands. Approximately 2,000 hawksbills nest annually on the northwest coast of Australia and 6,000 to 8,000 nest annually in the vicinity of the Great Barrier Reef. The largest rookery for hawksbill turtles in the South Pacific Ocean is in the Arnavon Islands of the Solomon Islands, where approximately 2,000 hawksbill nest each year. Arnavon hawksbills have been heavily exploited for their shell for centuries, but two decades of conservation and monitoring efforts are showing encouraging signs of recovery. Around 2,000 hawksbills nest each year in Indonesia and 1,000 in the Republic of Seychelles. [Source: NOAA]
In the Atlantic, the greatest number of hawksbill nests are laid in Mexico, Cuba, and Barbados, but nesting occurs throughout the Insular Caribbean. The most significant nesting within the United States occurs in Puerto Rico and the U.S. Virgin Islands. Each year, about 500 to 1,000 hawksbill nests are laid on Mona Island, Puerto Rico and another 100 to 150 nests on Buck Island Reef National Monument off St. Croix. In the continental United States, nesting is rare and is restricted primarily to the southeast coast of Florida and the Florida Keys.
In the U.S. Pacific, hawksbills nest primarily in Hawaii where 10 to 25 females nest annually on beaches along the south coast of the island of Hawaii and the east coast of the island of Molokai. This population may constitute one of the smallest hawksbill nesting populations in the world, but is the largest in the Central North Pacific Ocean. In the Eastern Pacific, approximately 700 females nest annually from Mexico to Peru. The 2013 Endangered Species Act (ESA, U.S. Fish and Wildlife) 5-year review of the hawksbill sea turtle provides additional information for this species. The occurrence of hawksbills across many countries makes it critical for citizens and governments to work together for the protection and recovery of the species.
Like other sea turtle species, hawksbills can migrate long distances between foraging areas and nesting beaches. In the Atlantic, a female hawksbill that nested at Buck Island Reef National Monument in the U.S. Virgin Islands was tracked 1,867 kilometers (1,160 miles) to foraging habitat in the Miskito Cays in Nicaragua. Solomon Island hawksbills can travel 500 to 1000 miles (800 to 1,650 kilometers) between Arnavon nesting beaches and foraging areas off Australia. However, some hawksbill populations, such as Hawaiian hawksbills, migrate shorter distances and stay within the island chain.
Hawksbill Sea Turtle Habitats
Hawksbill sea turtle Hawksbill sea turtles live in saltwater or marine environments and are usually found in reefs and coastal areas at depths of zero to 20 meters (66 feet) usually close to the surface. Hawksbill turtles often nest in small numbers, and usually on remote beaches. The largest populations of hawksbills are found in the west Atlantic (Caribbean), Indian, and Indo-Pacific Oceans. [Source: NOAA **]
Hawksbill turtles are most commonly found in hard-bottomed and reef habitats containing sponges. They also reside in shoals, lagoons of oceanic islands, and continental shelves. When hawksbill turtles are young, the are unable to dive into deep water, and therefore are forced to live in masses of floating sea plants, such as sargassum. [Source: Michael Edelman, Animal Diversity Web (ADW)]
Hawksbill turtles use a variety of habitats during different stages of their life cycle, but largely inhabit nearshore foraging grounds, especially healthy coral reef habitats. In the Eastern Pacific, large hawksbill populations have been found in mangrove estuaries. Upon leaving their nesting beaches, most hawksbill hatchlings enter pelagic (open sea) habitat, where they take shelter in floating algal mats and drift lines of flotsam and jetsam for approximately 1 to 5 years. Eventually, juveniles migrate to shallower coastal feeding grounds, including their preferred coral reef habitats, where they mature to adulthood and spend the remainder of their lives. The ledges and caves of coral reefs provide shelter for resting hawksbills during the day and at night. Hawksbills are also found around rock formations, high energy shoals (sand bars in shallow water), and estuaries that provide good habitat for sponge growth. **
Hawksbill Sea Turtle Physical Characteristics
Hawksbill sea turtles are relatively small sea turtles. They range in weight from 38 to 127 kilograms (79 to 280 pounds), with their average weight being 80 kilograms (176 pounds). They range in length from 62.5 to 114 centimeters (25 to 45 inches), with their average length being 87 centimeters (34 inches). A typical adult weighs between 45 and 68 kilograms (100 to 150 pounds) and is 60 to 120 centimeters (2 to 3.5 feet) in length. The average a length of nesting females is 87 centimeters in curved carapace length; their weight is around 80 kilograms. In regard to sexual dimorphism (differences between males and females), males are more colorful than females and males and females have different shapes. Males have brighter pigmentation, a concave plastron, long claws, and a thicker tail. [Source: Michael Edelman, Animal Diversity Web (ADW) /=]
Hawksbill turtles have mottled shells consisting of an irregular combination of shades of amber, orange, red, yellow, black and brown. The shells typically have serrated edges, with overlapping scutes. Their head comes to a tapered point and their lower jaw is V-shaped, giving them a hawk-like appearance. Hatchlings are only 5 to 7.5 centimeters (2 to 3 inches) long and mostly brown in color. Hawksbills have four scales (two pairs) between their eyes and four scutes along the edge of each side of their carapace. [Source: NOAA]
Hawksbill sea turtles have four features that distinguish them from other sea turtles. 1) Their heads have two pairs of prefrontal scales. 2) They also have two claws on each of their forelimbs. 3) There are thick, overlapping scutes on their carapaces, which also have four pairs of costal scutes. 4) Their elongate mouths resemble a beak, that taper off to a sharp point at the end. /=\
Hawksbill Sea Turtle Behavior and Senses
Hawksbill turtles are diurnal (active mainly during the daytime), motile (move around as opposed to being stationary), migratory (make seasonal movements between regions, such as between breeding and wintering grounds) and solitary. [Source: Michael Edelman, Animal Diversity Web (ADW) /=]
Usually diurnal (except during mating season), solitary hawksbill turtles comb the reefs and continental shelves searching for food. They were once thought to have remained in one local area for the duration of their lives. However, recent studies have proven that they migrate very long distances during their lifetimes. /=\
Hawksbill turtles sense using vision, touch, sound, magnetism and chemicals usually detected with smelling or smelling-like senses and communicate with vision and touch. The mechanisms that aid hawksbill turtles in returning to their nesting beaches are still unknown. It has been thought that these turtles are guided inland by magnetic fields and lunar phases. Ritual mating behaviors is one way they communicate.
Hawksbill Sea Turtle Food, Eating Behavior and Predators
hawksbill turtle Hawksbill sea turtles are omnivorous (feeding on both plants and other animals), but their preferred food in many areas is sea sponges. They will also eat marine algae, corals, mollusks, tunicates, crustaceans, sea urchins, small fish, jellyfish, other coelenterates, fish, marine algae, crustaceans, and other sea plants and animals. [Source: NOAA]
Hawksbill sea turtles show a large level of feeding selectivity in the way that they only eat certain species of sponges, some of which are toxic to other animals. In Hawaii, they tend to be opportunistic given the limited availability of sponges. The shape of their mouth and their sharp beaks enable them to reach into small holes and crevices in the reefs to find food. A preferred feeding ground of the turtles is in shallow shoals abundant with brown algae. By feeding on sponges, the turtles free up space on reefs for other organisms. [Source: Michael Edelman, Animal Diversity Web (ADW)]
The main known predators of adult hawksbill sea turtles are humans, tiger sharks, requiem sharks and estuarine crocodiles. These creatures and groupers and common octopus feed on juveniles. Domestic dogs, raccoons, rats, gulls and ghost crabs are among the animals that feed on hawksbill eggs and hatchlings. Like all turtles, hawksbill turtles have a hard shell to deter predators Nests are commonly dug up and robbed by land predators mentioned above. Right after hatching is the most dangerous time for these turtles. Numerous hatchlings are preyed on by gulls and large crabs during the few minutes it takes them to scramble from their nest to the ocean.
Hawksbill Sea Turtle Mating, Reproduction and Offspring
Hawksbill sea turtles are oviparous (young are hatched from eggs) and engage in seasonal breeding. On average females reach sexual maturity at age three years. Nesting generally occurs in the spring, summer and fall. Females lay three to five clutches a year at an interval of roughly thirteen to fifteen days, with an average of 130 to 160 eggs in each clutch. The average gestation period is 60 days. Females come ashore to lay eggs on the beach and then return to the water. After the eggs hatch, newborn turtles make a mad dash for the water where they will mature.. There is no parental involvement in the raising of offspring. [Source: Michael Edelman, Animal Diversity Web (ADW) /=]
Every one to five years, female hawksbill turtles return to nest on beaches in the general areas where they hatched decades earlier. The nesting season varies by location, but in most places occurs between April and November of each year. Hawksbills typically nest at night on small and isolated “pocket” beaches, with little or no sand and a rocky approach. They usually nest high up on the beach under or in vegetation. After about two months incubating in the warm sand, the eggs hatch, and the hatchlings make their way to the water. Hatchlings orient seaward by moving away from the darkest silhouette of the landward dune or vegetation to crawl towards the brightest horizon. On undeveloped beaches, this is toward the open horizon over the ocean. [Source: NOAA]
Mating occurs mainly in shallow waters near the shore. Males lie and wait in the shallow water for the females to return from nesting. At times, males have been seen following the females on shore but this behavior is rare. The entire nesting process takes roughly one to three hours and involves activities similar to those of other species of sea turtles. The turtles come out of the sea and select a site in which to lay their eggs. They then clear the area and dig a pit in the sand. Next they lay their eggs and then proceed to fill in the pit in with their hind limbs. After the site is disguised, the turtles return to the sea. /=\
Before they are born sex is determined by temperature. Warm water and sand during the middle third of the incubation period of hawksbill sea turtle eggs causes the eggs to yield more females. These days more females are being produced. Global warming is blamed for causing warmer temperatures and producing storms that clear away trees that normally provide beach cover to keep the eggs cool./=\
Hatchlings are only 5 to 7.5 centimeters (2 to 3 inches) long and mostly brown in color. They have a heart-shaped carapace. As they turtles mature, their carapaces becomes more elongated. The average shell length of hatchling hawksbill sea turtles in the U.S. Caribbean is about 4.2 centimeters. They weigh 13.5 to 19.5 grams. /=\
Hawksbill Sea Turtles and Humans
Humans have utilize hawksbill sea turtles for food. Their body parts are sources of valuable materials. For years, humans have hunted the hawksbill turtles in order to sell their scutes (the thickened horny or bony plate on a turtle's shell). Also, humans have eat their meat and eggs. [Source: Michael Edelman, Animal Diversity Web (ADW) /=]
Hawksbill sea turtles have traditionally been hunted for their shells: a source of some of the most beautiful tortoise shell. The shells of many hawksbill sea turtles ended up in Japan, where the shells are carved into hair decorations traditionally worn by Japanese brides on their wedding day. At one point Japan reportedly imported 31,000 shells a year, paying an average of $375 a shell. Under U.S. pressure Japan agreed to stop importing the shells in 1992. [Source: National Geographic]
Japanese are not the only ones that have sought hawksbills for their beautiful shell. Remember tortoise shell glasses. “Tortoise shell” is carved into hair clips and combs and used by craftspeople to create many types of jewelry and accessories. The historical hunting and killing of hawksbills for their shell nearly drove the species to extinction.
Whole turtles are still harvested and stuffed and sold in the illegal wildlife trade. Hawksbill eggs are dug up and consumed by coastal community members, or sold for consumption in nearby urban centers. Hawksbill meat is still consumed in many countries, although it is often considered less of a delicacy than the meat of other sea turtle species. Due to the sponges hawksbills eat, their meat can become toxic, which has led to the mass poisoning, illness and death of groups of individuals. [Source: NOAA]
Endangered Hawksbill Sea Turtles
Hawksbill sea turtles are listed as Critically Endangered on the International Union for Conservation of Nature (IUCN) Red List. On the U.S. Endangered Species Act (ESA, U.S. Fish and Wildlife) they are designated “Endangered throughout its range.”. The Convention on International Trade in Endangered Species (CITES) lists them in Appendix I, which lists species that are the most endangered among CITES-listed animals and plants. Specially Protected Areas and Wildlife (SPAW) list them in Annex II throughout the Wider Caribbean Region:
It is very difficult to classify how Endangered hawksbill turtles are because they are found throughout the world and are migratory. In some places, they may be very scarce, and in others they may thrive. Also, since there is little knowledge of their early population levels, it is very hard to know how much the populations have declined.
The Convention on International Trade of Endangered Species (CITES) forbids the trade of any turtle products on the international market, including hawksbill tortoise shell, but illegal hunting continues to represent a threat to the species in many parts of the world. In order to protect hawksbill turtles there needs to be international coordination and cooperation involving all nations that have hawksbill populations in their waters. [Source: NOAA]
Threats include bycatch in fishing gear, climate change, direct harvest of turtles and eggs, loss and degradation of nesting and foraging habitat, ocean pollution/marine debris, predation of eggs and hatchlings, vessel strikes
Threats to Hawksbill Sea Turtles
Bycatch in Fishing Gear: A primary threat to sea turtles is their unintended capture in fishing gear which can result in drowning or cause injuries that lead to death or debilitation (for example, swallowing hooks or flipper entanglement). The term for this unintended capture is bycatch. Sea turtle bycatch is a worldwide problem. The primary types of gear that result in bycatch of hawksbill turtles include gillnets and hook and line fisheries operating in coastal habitats. [Source: NOAA]
Direct Harvest of Turtles and Eggs: Despite their protection under various national and international frameworks, the intentional killing of hawksbills for the wildlife trade and the harvest of their eggs, meat and shells is still widespread.
Predation of Eggs and Hatchlings: The destruction and consumption of eggs and hatchlings by non-native and native predators (particularly feral pigs, rats, racoons, mongoose, feral cats and dogs) is a major threat to sea turtles around the world. In particular, burgeoning populations of feral and semi-domesticated dogs have accompanied the development of human coastal communities, resulting in the rampant consumption of hawksbill eggs and hatchlings around the globe.
Ocean Pollution/Marine Debris: Increasing pollution of nearshore and offshore marine habitats threatens all sea turtles and degrades their habitats. Hawksbill turtles may ingest marine debris such as fishing line, balloons, plastic bags, floating tar or oil, and other materials discarded by humans which they can mistake for food. They may also become entangled in marine debris, including lost or discarded fishing gear, and can be killed or seriously injured.
Hawksbill Sea Turtles and Tortoiseshell Accessories
Hawksbill sea turtles have traditionally been hunted for their shells: a source of some of the most beautiful tortoise shell. The shells of many hawksbill sea turtles ended up in Japan, where the shells are carved into hair decorations traditionally worn by Japanese brides on their wedding day. At one point Japan reportedly imported 31,000 shells a year, paying an average of $375 a shell in the 1980s. Under U.S. pressure Japan agreed to stop importing the shells in 1992.
Tortoiseshell has traditionally been used to make brooches, hairpieces and other accessories in Japan. The yellow-colored plastron and back-and-brown-spotted carapace from shell from endangered hawksbill turtles is highly prized and has been dubbed the “jewel of the sea.” Tortoise shell craftsmen use a heated iron to bend and shape the shell and stick pieces together. If too much heat is applied the shell will char. If not enough is applies the pieces will come apart easily.
Tortoiseshell art is believed to have originated in China more than 2,000 year and was used in making the crown of Chinese Emperor Qin Shi Huangdi. In Japan , the industry has been centered in Nagasaki where hawksbill turtles were brought in by foreign traders. A craftsman at a tortoiseshell workshop that was established in 1709, told the Daily Yomiuri,, “People are attracted to tortoiseshell products because of their luster and their colors, which are peculiar to natural materials. Since each pattern is different, people can feel satisfaction by possessing something that is truly unique.”
Craig Welch wrote in National Geographic: “New research suggests that nine million hawksbills were slaughtered in the past 150 years, mostly for their fiery red and gold carapaces, which were fashioned into hair clips, eyeglasses, jewelry boxes, and furniture. “The Convention on International Trade in Endangered Species (CITES) began banning the sale of turtle goods in the 1970s, but that hasn’t always worked. In 2012, researchers found thousands of hawksbill pieces for sale in Japan and China. Solid numbers are unavailable, but scientists estimate that only 60,000 to 80,000 nesting female hawksbills remain worldwide. [Source: Craig Welch, National Geographic, October 2019]
Alternatives to Luxury Tortoiseshell Eyewear
Audrey Hepburn, Maria Callas, French presidents François Mitterrand and Jacques Chirac, did Yves Saint Laurent, Jackie Kennedy and the architect Le Corbusier all wore eyewear made by the luxury French tortoiseshell artisan, Bonnet. AFP reported: Decades after the trade in tortoiseshell was banned under the 1973 Convention on International Trade in Endangered Species (CITES) convention, the fourth-generation family firm sees itself as custodian of a rare craft, fashioning made-to-measure spectacles from stocks amassed before the ban. [Source: AFP, Published: 6 December 2012]
Maison Bonnet describes its customers as "aesthetes" more concerned about style, the timeless kind, than fashion. Christian Bonnet, who learned the trade from his father and grandfather, holds the rank of "maitre d'art", an honorific title granted by France's culture ministry and currently held by just over 100 craftsmen nationwide.
Today, jointly headed by Christian and his sons Franck and Steven, Bonnet turns out around 100 pairs of hand-made tortoiseshell glasses per year for prices ranging from 3,500 to 30,000 euros. "My father didn't want me to go into the trade, because of the problem with tortoiseshell supply," produced mainly from the shell of the endangered hawksbill turtle, Franck Bonnet told AFP. With 12 grammes of tortoiseshell needed for one pair of glasses, the firm says it uses around two to three kilos of the stuff per year.
AFP reported: Declared part of French national heritage in 2007, Bonnet will not say how much stock it holds, but the supply is finite. "It is inconceivable that we would ever fish another turtle out of the ocean," says the 41-year-old, himself a staunch environmentalist. So he decided a few years ago it was time to look to the future — and to a wider market. "For my father, my grandfather and great-grandfather before them, it was tortoiseshell, tortoiseshell, tortoiseshell only. "I said to my father, 'You are the last tortoiseshell craftsman, but you are also the last hand-made eyewear maker. If we could only use more readily available materials, maybe I can keep our craft alive?'" [Source: AFP, Published: 6 December 2012]
“That is how in 2008 he introduced buffalo horn — lowering the average frame price to between 1,200 and 1,500 euros, and acetate, for budgets between 850 and 1,150 euros. Tortoiseshell aside, the dozen workers at its Paris boutique and workshop in Sens, a few hours southeast of the capital, now produce some 700 pairs using new materials. The next step towards broadening what they offer is to come from customization — allowing people to change the size and colour on standard models.
Image Sources: Wikimedia Commons, NOAA
Text Sources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.
Last Updated May 2023