Thursday, July 28, 2011

Life of Hawksbill Sea Turtle

Life of Sea | Hawksbill Sea Turtle (Eretmochelys imbricata) | Hawksbill sea turtles are one of critically endangered sea turtle.  They are most commonly found in coral reef habitats containing sponge. They also live in shoals, lagoons of oceanic islands and on continental shelves. They are most commonly found in water 18.3 m or shallower. The habitats of Hawksbill sea turtles change by following their life cycle. Young hawksbill ses turtles cannot dive into deep water. Therefore, they live on masses of floating sea plants, such as sargassum. Hawksbill sea turtles enter coastal waters when they reach approximately 20-25cm carapace length. The ledges and caves of the reef provide shelter for resting both during the day and night.  

Hawksbill sea turtles are also found around rocky outcrops and high energy shoals, which are also optimum sites for sponge growth. In areas where there are no coral reefs, Hawksbill sea turtles are found in mangrove-fringed bays and estuaries. In wild, Hawksbill sea turtles are found mainly in the tropical tropical reefs of the Indian, Pacific, and Atlantic oceans. In the western hemisphere, they have been reported to have nests as far north as Woods Hole, Massachusetts and are also present in the Long Island Sound. However, between the Carolinas and New Jersey, very few hawksbill turtles have been recorded. They  are also found around the Oceanic Islands and Indian Ocean.

Hawksbill sea turtles are beutiful sea turtle. They get their species name (imbricata) from the overlapping plates on their upper shell. They get their common name from the shape of its hooked jaw.  Hawksbill sea turtles have 5 features that distinguish them from other sea turtles. First, they have two pairs of prefrontal scales in the head. Second, they have two claws on each of their forelimbs. Third, they have thick and overlapping scutes on their carapaces. Fourth, they have four pairs of costal scutes in the carapaces. Last, they  have mouths that is like  a beak,which is going a sharp point at the end. Male turtles have brighter pigmentation, a concave plastron, long claws and a thicker tail.

Hawksbill sea turtles are omnivorous. Their diet primarily consists  of sponges. They are selective feeders choosing only certain species of sponges, some of which are toxic to other animals. Jellyfish and other coelenterates are also common prey for Hawksbill sea turtles. They also eat mollusks, fish, marine algae, crustaceans and other sea plants and animals. Hawksbill sea turtles have a hard shell that discourages predators from trying to eat them. Adult turtles are still consumed by humans, sharks, crocodiles, large fish, and octopi. Nests are commonly robbed by predators such as dogs, raccoons, rats, and humans.

Sea turtles live in almost every ocean of the world. Their smooth shells and paddlelike flippers help them speed through the water as fast as 24 kph. These long-distance travelers have been known to swim up to 4,828 km. Although sea turtles cannot withdraw their heads into their shells, the adults are protected from predators by their shells, large size and thick scaly skin on their heads and necks. Sea turtles can rest or sleep underwater for several hours at a time. But at emergency time, it can be much shorter while diving for food or to escape predators. Activity and stress affect  the breath-holding ability. That is the reason why turtles drown in shrimp trawls and other fishing gear within a relatively short time.

Sea turtles spend almost all their lives submerged but they must breathe air for the oxygen. With a single short fast exhalation, sea turtles can quickly replace the air in their lungs. The lungs are adapted to permit a rapid exchange of oxygen and to prevent gasses from being trapped during deep dives. The blood of sea turtles can deliver oxygen efficiently to body tissues even at the pressures encountered during diving. Green and loggerhead turtles can dive for about 4 to 5 minutes and surface to breathe for 1 to 3 seconds. A female loggerhead tracked at sea made up to 500 dives every 12 hours.

Hawksbill sea turtles females can travel up to 2400 kilometres between their feeding and breeding grounds. They only breed once every two to four years but during the breeding season they may nest up to six times, laying about 120 eggs in each clutch. The sex of the hatchlings depends on the temperature in the nest. After hatching, the baby turtles swim out to sea for several days. They then spend the next five to ten years drifting around in surface waters at the mercy of ocean currents, and they feed mainly on plankton. They are often found in huge rafts of drifting sargassum, a type of brown seaweed, where they are probably best able to hide from potential predators. Once they reach lengths of 30 or 40 centimetres they settle in one particular area around coral or rocky reef.

The eggs of Hawksbill sea turtles are once a popular food for humans as was the meat, however the sale and consumption of turtle eggs is now illegal. The meat is found to be  poisonous to humans. The skin of these turtles is also toxic to humans. The sale of hawksbill turtle shells is also illegal. Because of their sponge diet, their flesh is harmful to humans. Sponges contain toxic chemical compounds which accumulate in the animal’s tissues. The consumption of their meat by humans may cause serious illness and in extreme cases even death especially to children. The flesh has been found to contain chelonitoxin which may cause a number of symptoms including nausea, vomiting, diarrhea, burning sensation of lips, tongue and mouth, chest tightness, difficulty swallowing, hypersalivation, skin rash, coma and death. 

Hawksbill sea turtles are important inhabitants of coral reefs. By consuming sponges, they play an important role in the reef community, aiding corals in growth. It’s estimated that one turtle can consume over 1,000 pounds of sponges per year. Without them, sponges have the ability to overgrow corals and suffocate reefs.

It is illegal to trade, purchase or possess sea turtle products. When purchasing “tortoiseshell” products overseas, be sure you are buying synthetic materials. These turtles are solitary nesters, nesting in low densities on small scattered beaches. Adult females are well adapted for crawling over reefs and rocky areas to reach secluded nesting sites. On average, they nest roughly 4 times per season at 2 week intervals and lay around 140 eggs per nest. Nests however, may contain over 200 eggs. Hawksbill sea turtles are considered Critically Endangered around the world by the IUCN Red List and are listed as Endangered in the US. Some researchers believe the Eastern Pacific Hawksbill is likely the most endangered sea turtle population worldwide.

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