Physical Appearance: Bottlenose dolphins are a dark gray color on their back, but have lighter gray or pinkish bellies. This pattern of light and dark coloration is common in aquatic animals so they match the light shining through the shallow waters when viewed from the bottom and blend in with the darker deeper waters when viewed from above. They range is size from 300 to 600 pounds and 6 to 12 feet in length, with males slightly larger than females (Bullard 2001). Males tend to have larger girths and presumably then larger axial muscles. Larger tail muscles might make them faster and better able to herd females. Bottlenose dolphins like all cetaceans lack secondary sexual characteristics (Tolley 1995).
Habitat: Dolphins have low locomotion costs and large memories so easily move over wide areas to locations they remember to be safe or plentiful based on environmental conditions. They can be found in all four oceans and cover most of the globe, excepting the waters within 45 degrees of either pole. Dolphins Dolphins seasonally utilize different areas of their year round home ranges. In the warmer months, dolphins can be found in the shallower regions. During the fall and winter they more toward deeper waters. Dolphins were also more concentrated near seagrass beds which provide them with food, shelter from predators, and nursery grounds (Barros 1998).
Food: The primary prey of the bottlenose dolphin are piscivores, especially pinfish, striped mullet, pigfish and spot. These fish tend to live in seagrass beds and are known sound producers, due to teeth grinding, splashing, or swim bladder contractions. It is possible that dolphins use passive listening because of their echolation abilities to track their noisy prey (Barros 1998).
Hunting: These fish are active both day and night, so it is likely that dolphins are diurnally active hunters. In the shallow water dolphins tend to hunt alone and go after individual fish. In more open waters, group foraging on schools of fish and individual hunting on solitary fish are common. Schooling dolphins benefit from decreased predation risks and enhanced foraging efficiency (Barros 1998).
Predation: Dolphins must always be alert even though the risk of predation from sharks is not too great. Dolphins will sometimes fight back against tiger shark attacks and often survive, but they more often flee from or avoid sharks (Diselvestro 1998). About 75% of adult dolphins have shark bits scars, especially from tiger sharks, and 11% of the dolphin population is attacked unsuccessfully every year. Humans are a major predation risk to dolphins. Coastal dolphins often follow fishing boats in scavenging attempts so are killed by many fisherman who view them as pests (Heithaus 2002).
