bottlenose dolphin

Description:

They are grey, varying from dark grey at the top near the dorsal fin to very light grey and almost white at the underside. This countershading makes it hard to see, both from above and below, when swimming. Adults range in length between 2 and 4 metres (6.6 and 13 ft), and in weight between 150 and 650 kilograms (330 and 1,400 lb). Males are on average slightly longer and considerably heavier than females. In most parts of the world, the adult's length is about 2.5 m (8.2 ft), with weight ranges between 200 and 300 kilograms (440 and 660 lb).Their size varies considerably with habitat. Except in the eastern Pacific, dolphins in warmer, shallower waters tend to be smaller than those in cooler pelagic waters. The bottlenose dolphin can behave aggressively. Males fight for rank and access to females. During mating season, males compete vigorously with each other through displays of toughness and size, with a series of acts such as head-butting. They display aggression towards sharks and smaller dolphin species.The bottlenose dolphin sometimes forms mixed species groups with other species from the dolphin family, particularly larger species such as the short-finned pilot whale, the false killer whale and Risso's dolphin.They also interact with smaller species, such as the Atlantic spotted dolphin and the rough-toothed dolphin.While interactions with smaller species are sometimes affiliative, they can also be hostile. Some large shark species, such as the tiger shark, the dusky shark, the great white shark and the bull shark, prey on the bottlenose dolphin, especially calves. This is an example of parasitism.The bottlenose dolphin is capable of defending itself by charging the predator; dolphin 'mobbing' behavior of sharks can occasionally prove fatal for the shark.Targeting a single adult dolphin can be dangerous for a shark of similar size. Certain (but not all) killer whale (orca) populations may also prey on dolphins, but this seems rare,] and other orcas may swim with dolphins. Swimming in pods allows dolphins to better defend themselves against predators. Bottlenose dolphins either use complex evasive strategies to outswim their predators, or mobbing techniques to batter the predator to death or force it to flee. The dolphins blow hole allows it to stay under water for longer peirods of time. They breach in waves or rest at the surfaceto get oxygen. Both genders have genital slits on the underside of their bodies. The male can retract and conceal its penis through its slit. The female's slit houses its vagina and anus. Females have two mammary slits, each housing one nipple, one on each side of the genital slit.The ability to stow their reproductive organs (especially in males) allows for maximum hydrodynamics. The breeding season produces significant physiological changes in males. At that time, testes enlarge, enabling it to hold more sperm. Large amounts of sperm allow a male to wash away the previous suitor's sperm, while leaving some of his own for fertilization. Also, sperm concentration markedly increases. Having less sperm for out-of-season social mating means it wastes less. This suggests sperm production is energetically expensive. Males have large testes in relation to their body size. Bottlenose dolphins have been known to hybridize with other dolphin species.

Habitat:

Its diet consists mainly of small fish, crustaceans, and squid. Although this varies by location, many populations share an appetite for fish from the mullet family, the tuna and mackerel family, and the drum and croaker family. Its cone-like teeth serve to grasp, but do not chew food. When they encounter a shoal of fish, they work as a team to herd them towards the shore to maximize the harvest. They also hunt alone, often targeting bottom-dwelling species. The bottlenose dolphin sometimes hits a fish with its fluke, sometimes knocking it out of the water, using a strategy called "fish whacking"."Strand feeding", is an inherited feeding technique used by bottlenose dolphins near and around coastal regions of Georgia and South Carolina. When a pod finds a school of fish, they will circle the school and trap the fish in a mini whirlpool. Then, the dolphins will charge at the school and push their bodies up onto a mud-flat, forcing the fish on the mud-flat as well. The dolphins then crawl around on their sides, consuming the fish they washed up on shore. Some foraging behaviors are found only in certain habitats or regions. Mud plume feeding is an example. This behavior is performed by a small community of bottlenose dolphins over shallow seagrass beds (<1m) in the Florida Keys. The behavior involves creation of a U-shaped plume of mud in the water column and then rushing through the plume to capture fish. Bottlenose dolphins conflict with small-scale coastal commercial fisheries in some Mediterranean areas. Common bottlenose dolphins are probably attracted to fishing nets because they offer a concentrated food source.They inhabit warm and temperate seas worldwide. Adult males live mostly alone or in groups of two to three, and join pods for short periods of time. Adult female and young dolphins normally live in groups of up to 15 animals. However, they live in fission-fusion societies of varying group size, within which individuals change associations, often on a daily or hourly basis. Group compositions are usually determined by sex, age, reproductive condition, familial relations and affiliation histories.