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| Bottle-Nosed Dolphin Tursiops truncatus [tur sE' ops trun' kah tuhs] Description The bottle-nosed dolphin is 10-14 feet long and weighs up to 1,100 pounds, with males being slightly larger than females. Its flippers taper to a point, and its dorsal fin has a harply-pointed apex that is directed backwards. The body is light gray to black in color, with the belly always being lighter than the rest of the body. The most distinguishing feature of the bottle-nosed dolphin is its short, thick beak with 20-28 sharp conical teeth on each side of the jaw. These teeth are what makes the bottle-nosed dolphin's lower jaw seem to protrude beyond the upper jaw, which in turn creates the bottle-nosed dolphin's characteristic "smiling face." Distribution and Habitat Bottle-nosed dolphins live in temperate and warm waters around the globe, including all oceans except the Arctic and the Mediterranean Sea. They do not migrate, but will sometimes travel long distances in search of food. Diet Fish make up the majority of the bottle-nosed dolphin's diet, but squid and shrimp are also taken. Prey is tracked by echolocation. Although the bottle-nosed dolphin will dive as deep as 70 feet or more to take prey underwater, it usually prefers to strike prey with its flukes, knocking it clear out of the water and then catching it in its mouth. Groups of dolphins will also hunt in packs, herding schools of small fish into an increasingly smaller area and picking off stragglers. Bottle-nosed dolphins are also known to follow fishing boats and feast on leftover bait and castoffs. Reproduction Breeding activity peaks in March and April, during which period males compete viciously for females. Once a male has spotted a potential mate and fought off any competition he will posture and gesture to the female until she either allows him to mate with her or swims away. One calf is born after a gestation period of twelve months. The mother will help her newborn calf to the surface so it can breathe, but it can swim on its own soon after birth. The calf will stay as close to its mother as possible for the first couple of weeks, but will start taking off on its own for short "hunting trips" as it grows. It will be weaned at 18-20 months, but will stay with its mother until 4-5 years of age. The mother will not mate until her calf is independent. The age of sexual maturity varies greatly by geographic population, ranging from 5 to 12 years for females and 9 to 13 for males, and females as old as 45 years have given birth to healthy calves. Average life span in the wild is 40-50 years. Other Habits and Behaviors Bottle-nosed dolphins live and travel in pods containing about a dozen or so individuals of both sexes and all ages. There are no leaders in a pod, but there is a hierarchy based on size. The process by which individual dolphins come together into various pods is not known, nor is it known whether individual dolphins stay with one pod for life or move from one pod to another. As social animals, bottle-nosed dolphins have developed a very complex communications system of squeaks and whistles, with each individual dolphin having its own distinctive whistle. While individual animals of many species are known to show distress when another of their kind is injured or sick, and there are many examples of one animal putting itself at risk to protect another, the bottle-nosed dolphin is one of the few animals known to actually "come to the rescue" of a sick or injured "colleague." It is not at all uncommon for one, two, or more individual dolphins to help an injured "comrade" to the surface so it can breathe, and for them to stay with him/her until it can either stay at the surface on its own or dies. The swimming motion of the bottle-nosed dolphin is an up-and-down movement of the fluke, and it can swim at speeds of over 18 miles per hour. Although it can dive to depths of 70 feet or more and stay submerged for up to 15 minutes, the bottle-nosed dolphin typically surfaces to breathe two or three times a minute. It is also very fond of leaping clear out of the water and can get as high as 16 feet above the surface before landing with a splash on its back or side. Other Information Because bottle-nosed dolphins are among the most intelligent animals in the sea, and because they are very active and playful, they are star attractions at marine parks around the world. A bottle-nosed dolphin was the star of "Flipper," a television series that aired from 1964 to 1967. Although many people use the terms "dolphin" and "porpoise" interchangeably, dolphins are actually a subgroup with porpoises, a group that also includes the orca (killer whale) and beluga whale. Conservation Status Bottle-nosed dolphins are threatened by commercial fishing, especially tuna fishing, but their population appears fairly consistent. Although they are not listed as an endangered species, they are protected by law in the U.S. and other nations. Scientific Classification phylum Chordata |
| SKC Films Library >> Science >> Zoology >> Mammals >> Order Cetacea This page was last updated on May 19, 2017. |