Normally a dolphin will stay in a long-lasting group of 2-40animals called pods, but larger groups of hundreds of dolphins have been reported and those are called herds. Dolphins are carnivores that feed on fish, squid, octopus, cuttlefish, crabs, shrimps, and lobsters. Dolphins are food for sharks, killer whales, humans. Man is the most dangerous predator for the dolphin. Humans will kill dolphins for their meat, their fat, even for being in the area they are fishing. Additionally, studies are currently being done to evaluate the effect of pollution in the water on dolphins.
Dolphins bear live young, and the mother nurses the calf with her milk and provides care. The calf is nursed one and one half to three years and a mother will stay with her young three to eight years. Dolphins are believed to live about 30 years. Dolphins vary based on their ecosystem and what is required for them to survive in their niche. In the Gulf of Alaska there are few dolphin species, one of which is the pacific white-sided dolphin. This dolphin has a short, rounded beak with about 30 curved teeth in each side of the jaw.
Very energetic and is seen frequently leaping, belly flopping and summersaulting. It is attractively marked with black back, gray sides and white stripes from its eyes to its tail. Its dorsal fin is tall and sharply hooked, its flippers are small and rounded at the tips, and its flukes have a notch in the center. They are seven to eight feet in length and weigh up to 300 pounds. Beginnings (EO. Reddit. com, 2011) Dolphins, porpoises, and whales are related in some way. Fossil has been found that indicates early dolphins were aquatic 40 – 50 million years ago.
It is believed that animals that spent a great deal of time looking for food around water areas went through a stage before becoming committed to the water. Once in the water records show that by changes in their teeth it took millions of years for true cetaceans to develop. Adaptations (Animalfiles. com, 2011) The dolphin has come a long way from the once amphibious animal it is believed to have evolved from. Fossil evidence shows that once dolphins long ago decided to be aquatic, it it wasn’t long for bones of the hind limbs to disappear.
Anatomically, dolphins’ bodies have become more streamlined to move in the water. Their front limbs evolved into flippers and their powerful tail is their main propulsion mechanism. They have a thickened body with a raised head that caused the vertebrae neck to fuse together. Instead of a major blood supply to the brain on the outside of the neck, the dolphins blood flows through an artery in the vertebrae that provides a constant supply of blood, which is most essential when diving into the depths of the ocean. The dolphins’ skin is extremely smooth, hairless, is thick, and lacks glands.
This skin is kept smooth by constantly sloughing off and being replaced. On average their skin is replaced at a rate nine times faster than a human, and in the case of the bottlenose dolphin, the outer most layer of skin is replaced every two hours. Dolphins tent to rely on their sense of hearing to survive. They are said to have good eyesight, but in the blackness of the ocean, other senses have had to develop for survival. The shape of the dolphins melon (the fatty tissue in front of the blowhole) acts as a lens to focus sound when the dolphin produces high pitched clicks for echolocation.
The dolphin has adapted well to its watery world, and evolved in shape and skill to breed successfully and thrive. The fascinating skill of echolocation gives the dolphin a huge advantage when feeding in the darkness of the ocean. Dolphins are very energetic, kind, and smart animals. For the most part they are left alone in their ecosystems and traditionally only humans to fear. References American Cetacean Society (2011). Pacific White-Sided Dolphin. Retrieved on April 21, 2013 from http://www. csonline. org/factpack/PacWhiteSided. htm. Animal Files. com (2011) Anatomy of a Dolphin. Retrieved on April 21, 2013 from http://www. theanimalfiles. com/anatomy/dolphin_anatomy. html EO. Reddit. com (2013) Evolution Timeline of a While and Dolphin. Retrieved on April 21, 2013 from eo. reddit. com/r/todayilearned/comments/dq4v7/til_the_evolution_ timeline_of_whales_and_dolphins/ Looney, Z. (1996) Dolphin Evolution. Retrieved on April 21, 2013 from http://tursiops. org/dolfin/guide/dolphinevo. html