From a taxonomy perspective, sea turtles belong to the overall class of reptilia. The order is testudines. The suborder cryptodira also includes fresh water turtles. There are two families of sea turtles. Based on their carapaces, sea turtles are divided into two families: bony -- covered with horny scutes -- turtles and leatherback turtles. There are eight species of sea turtles: green Chelonia mydas, black Chelonia agassizii, loggerhead Caretta, Kemp's ridley Lepidochelys kempii, olive ridley Lepidochelys olivacea, hawksbill Eretmochelys imbricate and. flatback Natator depressus. The first turtle records are from the Triassic era.
The habitat of sea turtles is mostly relatively temperate waters. They are often found in the shallower waters of lagoons, costal waters and bays. The migration process however often involves thousands of miles. Females often make this migratory trip to lay eggs on certain beaches. When these eggs hatch, the hatchlings make the journey out to open oceans. Migratory habits differ from different species and even among the same species, depending on locations. Population studies of sea turtles are often difficult because they can only be counted based on females nesting and hatchlings moving to oceans. Confounders are that females either make regular trips to the same beaches, or they go to different beaches, or they nest more than once a season.
Sea turtle species sizes are measured across the edges of the carapace and the weight. The larges are green turtles -- the largest measured had a carapace diameter of five feet and weighed more than eight hundred and fifty pounds. The ridleys are the smallest less than a foot across and about fifty kilograms in weight. The species are identified and classified based on color. Their heads and flippers are not retractable (unlike land turtles). The fore flippers are used for paddling. The hind limbs serve for balance and change in direction in the water. Locomotion on land for sea turtles is clumsy and unwieldy.
Sea turtles are do not have teeth. Their jaws are hardened to an extent. This explains their eating choices -- mostly jellyfish.
Until maturity, it is difficult to separate males from females. Males have longer and thicker tails, which house the male reproductive organs. The fore flippers of males also have better developed claws to help grasp the females. Sea turtles hearing ranges are typically at lower frequencies. They can also see well in water and are partial to ultra violet electromagnetic radiation. Their sense of smell is also acute and better in water. Shrimp is one of the favorite foods, which sea turtles have to be ferreted out from the mud.
Sea turtles are adapted to swimming. They swim at approximately one mile per hour. Leatherback turtles are known to swim up to four miles per hour faster. Sea turtles are good divers, diving up to 1000 feet. The slow metabolisms enable them to swim without breathing for longer periods of time. Green sea turtles can remain under water for several hours and slow down their heart rates for up to nine minutes per beat. Sea turtles are generally non-sociable. They remain isolated. Though some males also help in the nesting process. Hatchlings once out of the egg (they use a temporary tooth to break through the papery or leathery shell) are on their own. Between two and nine eggs are laid. The incubation time ranges from forty-five to seventy days.
Sea turtles are susceptible to shark attacks. On land, they are more vulnerable to land predators such as monitor lizards and foxes. Use of beaches also has reduced nesting areas. Turtle eggs have been removed for food or as an aphrodisiac. On the open seas, turtles are often caught in the nets of shrimp trawlers. Water pollution often causes sea turtles to eat plastic mistaken for jellyfish. Newly hatched sea turtles are attracted to the open horizon and the light. Artificial lights from human inhabited streets often disorient the hatchlings.
Very few people have not seen dolphins. These oceanic mammals are the "special feature" in most marine shows. The bottlenose dolphin is the most popular. It is also the most studied cetaceans because it is often found in costal waters. They also fares relatively well in captivity. A second type of bottlenose dolphin ventures farther out into oceans. Bottlenose dolphins avoid waters that are more than 30 meters deep. Though, they have been able to dive to depths of up to 300 feet.
Bottlenose dolphins are fairly sociable. They interact freely with other cetaceans. These include other dolphins and even humpbacked whales. There has been a reported instant of dolphins cavorting with fish and seals. Bottlenose dolphins have been given different names: Grey, Black, Atlantic and Pacific bottlenose dolphins. They are also called cowfish and bottlenose porpoises. (SeaWorld, 2002)
Bottlenose dolphins are classified in the suborder of Odontoceti (toothed). They have between 20-26 teeth on the side of either jaw. Their binomial classification is Tursiops truncatus. The have a distinctive bottle-shaped beak, which gives them a their English name. Bottlenose dolphins live for twenty-five years. Some as old as fifty years have been reported. They grow to between eight and twelve feet in length. They're color with a few subtle variations is mostly slate gray with a lighter underside. This beak is white in color. The fins and tail flukes are darker. Their dorsal fin is relatively tall and curved backwards. The vertebrae in the neck region for bottlenose dolphins are not fused. They have greater flexibility in the neck region. In this characteristic, they are similar to beluga whales. They can weigh up to 1500 pounds or higher. In terms of sexual dimorphism, males are much larger than females. Males reach sexual maturity between 10 and 13 years of age. Females reach sexual maturity between five and twelve years. Gestation takes about one year. The calf remains with the mother between three and six years. Some times a mother will use a surrogate to take care of her calf. Tossing a calf in the air is often observed and is ascribed to a disciplinary measure. Bottlenose dolphins live in social pods of twenty. Sometimes larger groups of up to 100 animals have been observed.
Bottlenose dolphins have been found in both hemispheres. They're temperature-based habitat ranges from tropical to temperate waters. They are rarely if ever found in polar waters. They are ubiquitous in most tropical waters. They are supposed to be abundant in the waters of the North Pacific. Male bottlenose dolphins often bear scars. These are from encounters with killer whales, other dolphins and even sharks. In studying populations, short terms migrations are often observed if the habitat is endangered due to excess fishing or the presence of sharks and killer whales. These dolphins do not have specific food habits. They eat most small fish such as herring and cod. They also go after shrimp, crabs and shellfish. Their beak like snouts help them feed on burrowed marine animals. During feeding, animals will even surf onto sand to strand a fish, which they will eat. They use their tail fins to create shock waves to immobilize fish. Occasionally a pod of dolphins will herd a whole shoal of several million fish into ever tightening balls. Deprived of oxygen the fish become sluggish and are then easy prey for the dolphins. Such a feeding technique is typical of smaller cetaceans.
Bottlenose dolphins are known to swim at a relatively leisurely pace of about five to seven miles per hour. In danger however, they can accelerate to speeds of 30 miles per hour. Human encroachment is probably the biggest dangers faced by bottlenose dolphins. Whalers often accidentally hunt them. In some cases, they are deliberately harpooned. They get caught in shrimp and shark nets too. Chemicals in the water have resulted in pollution related problems for bottlenose dolphins. In 1987, these animals died en masse on the East Coast of the U.S. due to a viral infection.
Speckled Dolphins are also called Indo-Pacific Humpbacked dolphins. The former have the binomial name Sousa chinensis. The latter are called Sousa plumbea. Both species are the same; the name difference depends on location. Smaller than the bottlenose dolphins they are typically about seven to nine feet in length and weight just over 280 kilograms. They have a well-developed long beak. Their color is brown-gray, pale-gray and pink-white. They have a lighter underside and the skin has a mottled or speckled appearance, hence the name. The name is given because the dorsal fin is less pronounced and is situated on a hump. The dorsal fin is triangular. The flippers are well rounded. Another reason for the pronounced hump is the way these animals surface. The snout appears first and then the rest of the body curves accentuating the hump before the dolphin submerges. (Amador, 1999)
Like bottlenoses, speckled dolphins prefer coastal waters of depths of less than 20 meters. They are also found in rivers basins and muddied waters. Their food…