Their hawk-like bill gives them their unique name. The hawksbill turtles are found in the sub-tropical and tropical waters of all the major oceans of the world. They can survive solely on a diet of sponges and are vital in maintaining a balance in the ecosystem of the marine world. Even as the hawksbill turtles continue to be hunted for their beautiful shell, climate change constitutes a fresh threat to the survival of the species.
The hawksbill turtle population has gone down about 84-87% of their population in the last three generations. And the downward spiral continues. Getting exact figures of the current population of the species is impossible as they spend long periods underwater. Estimates are based more often on the nesting females.
The Appearance Of The Hawksbill Turtles
The beautiful shells of the hawksbill turtles make it one of the most hunted species on earth. They are mottled and have an irregular combination of colors. The shell of the adult has around a dozen overlapping scales streaked with shades of gold, orange, brown, and red.
The head is tapered, and the lower jaw is V-shaped like a hawk, which given them their name. They grow between 2 and 3 feet in shell length and weigh between 100 and 150 pounds when fully grown.
The hatchlings are merely 2 to 3 inches long and are mostly brown. the hawksbill turtles have two pairs (four scales) between their eyes. They also have four scutes, made of keratin, going down the edge of both sides of their carapace, the outer convex bony part of the shell.
Their Diet And Behavior
The hawksbill turtles are omnivorous and feed on both animals and plants. But their favorite food in most areas is sea sponges. Other food includes corals, marine algae, mollusks, sea urchins, crustaceans, jellyfish, and small fish.
The limited availability of sponges in Hawaii has made the turtles turn to other forms of diet. Their hawk-like bill enables them to reach out into cracks and crevices in search of food.
The hawksbill turtle can easily migrate hundreds of miles between their nesting areas and their foraging grounds. A female hawksbill in the Atlantic traveled from its nesting ground in the Virgin Islands at Buck Island Reef Monument to Nicaragua’s Miskito Cays; a distance of 1,160 miles for foraging.
Hawksbill turtles in the Solomon Islands traverse a distance of 500-1000 miles between their nesting beaches in Arnavon to their foraging grounds in Australia.
Hawksbill turtles on the Hawaiian islands generally migrate shorter distances and stay within the islands.
Population Status Of The Hawksbill Turtles
The hawksbill turtles usually nest in minor numbers and often on isolated beaches. The biggest population of hawksbill turtles is present in the Indian, Indo-Pacific, and the Caribbean (West Atlantic) oceans.
The Great Barrier Reef is believed to be the biggest nesting spot for the hawksbill turtles. Between 6,000 and 8,000 female turtles nest there annually. The Northwest Australia coast is another place where they lay their eggs. Around 2,000 turtles turn up there during the season, while an equal number turn up in both Indonesia and the Solomon Islands. The Island of Seychelles has been another major nesting ground of the turtles.
The biggest rookery for the turtles is at the Arnavon Islands in the Solomon Islands in the South Pacific Ocean, but they have faced the greatest threat there. The Arnavon Hawksbill turtles have been exploited heavily for centuries for their shells. But recent conservation efforts have borne results and the population in these areas is recovering.
In the Atlantic region, the biggest nesting population of hawksbill turtles is found in Cuba, Barbados, and Mexico. But the nesting grounds are spread across the Insular Caribbean. In the US, the most important nesting grounds are in the Virgin Islands, and Puerto Rico. While 500-1000 hawksbill turtle nests are usually present in Mona island of Puerto Rico, 100-150 nests come up on Buck Island Reef off St. Croix.
Nesting grounds on the continental US are rare and the few found are restricted to the Florida Keys and the southeast coast of the southeastern US state.
Turtle nests are also found in Hawaii, but the numbers are far fewer. Only 10-25 turtles nest each year on the island’s south coast, and also on the east of the Molokai island. This is the biggest nesting ground in the north-central region of the Pacific Ocean. The eastern part of the Pacific sees around 700 turtles nest each year from Peru to Mexico.
The hawksbill turtles are different from other sea turtles in their nesting habits. They nest in smaller groups in isolated populations. They also nest higher on the beach, at times reaching close to the coastal vegetation line of grass or trees. This increases the threat of poachers.
Even though the hawksbill turtles are spread around the world, they tend to stick close to one single reef all their adult life instead of migrating over entire oceans.
This dependence on one coral reef proves a threat as climate changes are destroying reefs as seen in Australia. Ocean acidification has taken a toll on the native habitats of the turtles. Their growth rate declined in the Caribbean by 18% between 1997 and 2013. This decline has been directly found to be linked to the warming of the oceans.
Reproductive Pattern Of The Hawksbill Turtles
The hawksbill turtles reach maturity between 20 and 35 years. It depends on various factors, especially the availability of resources. The turtles are long-lived and can live up to the age of 50 to 60 years in the wild.
The female turtles return between 1 and 5 years to their nesting grounds on the beaches in the general area of the previous nesting. The turtles usually lay between 3 and 5 nests every season. Each nest has an average of 130 to 160 eggs.
The nesting season is generally between April and November, though it varies according to location. The turtles’ nest at night on tiny pocket beaches, that has very little sand and a rock-strewn approach. They prefer to nest higher up than other turtles close to the vegetation line.
The eggs hatch after 2 months of incubation and the hatchlings immediately make their way towards the ocean. The newborns orient their route by crawling towards the brighter horizon, away from the darker silhouette of the land.
Major Threats To The Population Of The Hawksbill Turtles
The hawksbill turtles are under multiple threats. Excessive hunting, loss of habitat, fishery bycatch, marine pollution, and coastal development are among a few of them.
The beautiful shells of the hawksbill turtles have attracted hunters for ages from the Roman period when it was used to make fashionable rings and combs. Even today, the shells of the hawksbill turtles are polished and carved into both functional and decorative objects. Trinkets, tortoise-shell jewelry, and even sunglasses.
The turtles are also hunted for their meat and eggs. The tortoiseshell imports by the Japanese had the most significant human impact on the population of the turtles and the effect is still being felt to this day. The trade continues to this day despite the hunting ban in place around the world and a couple of pounds of the shell is worth over $1,000 here.
A combined report in 2021 by TRAFFIC, WWF, and Japan Tiger and Elephant Fund revealed 71 seizures between 2000 and 2019 of around 1,240 pounds of hawksbill turtles. That represents 530 individual shells.
A study in 2019 in Science Advances discovered that over 9 million turtles were hunted down in 148 from 1842 to 1992. That is 6 times the previously estimated figures.
The killing of the hawksbill turtles was banned in 1977 and the endangered marine animal was assigned the highest grade of protection under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). This body regulates the cross-border trade in wildlife.
Change in habitats is not limited to coastal development. The increase in infrastructure near their habitat also leads to light pollution that disturbs their nesting habits.
This was discovered in North-Western Australia, home to one of the largest nesting populations of the hawksbill turtles. A study of 3 separate nesting areas revealed that almost 100% of the areas were affected by light pollution.
The presence of artificial light disorients the female turtles at the nesting sites. They affect both the mothers and the hatchlings as they start on their initial journey out to sea.
The turtles end up in the nets of commercial fishing boats by accident as they normally dwell near the coral reefs that are the hunting grounds of these fishing vessels. Though the hawksbill turtles live most of their life in the oceans, they still need to come above water to breathe. They drown if they cannot come up in time after getting caught or entangled in nets.
The most intense instance of exploitation of the turtles occurred in 1970-1985. This period constitutes 75% of the entire trade that took place since 1844. Exports from Malaysia, Indonesia, Belize, the Philippines, and Honduras were rampant before the CITES ban in 1977.
China was the major importer during this period and continues to flout international bans and continues in illegal trade with Malaysia, Indonesia, and the Philippines.
The black market in Japan also continues to be a major threat to the species survival. The shells are used as combs by Japanese women for over 3 centuries. They are also used in wedding attire throughout Japan.
The population of the hawksbill turtles has also been threatened by coastal encroachment into their nesting habitats. Commercial and residential developments are a major threat. There is also the threat from oil drilling, pollution, fishing.
The biggest threat will come in the form of climate change as rising water temperatures and acidification of the reefs have begun degrading the habitats of the turtles in the coral reefs. The Great Barrier Reef is one such victim and over half of the total corals have been destroyed due to rising temperatures.
The hawksbill turtles are vital grazers of the oceans and help in maintaining the health of the seagrass and the coral reefs. The decline in their pollution will affect the ecosystem of these fragile areas.
The hawksbill turtles continue to be hunted by small-time fisheries that are linked to international smuggling networks. And only integrated monitoring and prevention can help bring down this trafficking and poaching network.
Despite the international ban, the direct hunting of the turtles for their shells, meat, and eggs constitutes the biggest threat. The shells continue to be made into combs, hair clips, jewelry, and various trinkets. Stuffed turtles are a major part of the illegitimate wildlife trade.
The eggs of the hawksbill turtles are consumed by local communities in many countries. They are also sold in urban markets. The meat is considered a delicacy in many countries, though it is less in demand than other species of turtles. The meat of the hawksbill can be toxic as they feed on sponges. There have been cases of mass poising and death of both individuals and groups.
Rising seas, pollution, and coastal development constitute another major threat. Seawalls to protect the sea have resulted in the loss of beaches which are the nesting grounds of the turtles. Artificial lights deter females from nesting and can also disorient the hatchlings when they move out to sea.
Predators constitute another major threat. Rats, feral pigs, raccoons, mongoose, dogs, and cats are threats to the eggs and hatchlings of the turtles. Semi-domestic dogs live near the human population and are responsible for the large-scale destruction of their habitats and the death of the hatchlings.
The turtles are also threatened by vessel strikes as they come up to the surface. The increase in pollution here and onshore is affecting their population. The large-scale presence of debris, especially plastic, leads to ingestion by the turtles, mistaking them for food. They also get entangled in floating marine debris like discarded fishing nets and lines and are drowned, or starve to death.
Climate change will turn into the biggest threat to the turtles as it is a worldwide phenomenon and will affect its entire population. It will ring changes in the morphology of the beaches. Warmer sands could kill the eggs and hatchlings. It could also alter the male-female ratio of the hatchlings.
Rising seas will destroy beaches and wash away their nesting grounds. The hawksbill turtles will also face a shortage of food as it gets redistributed or decreased due to rising water temperatures. the destruction of the coral reefs will mean the end of their major hunting and foraging grounds.