Bottlenose Dolphin

Bottlenose Dolphins are small cetaceans that have a long, beaklike snout, a falcate (sickle-shaped) dorsal fin, one blowhole, and 20-28 sharp conical teeth on each side of each jaw. They are light to dark gray over their dorsal surface and white or cream along their ventral region. The Bottlenose dolphin is the largest of the beaked dolphins weighing in at 150-200 kg, with males being much larger than females. Two distinct ecotypes of Bottlenose dolphins are recognized: the coastal, which have a smaller average body size and larger flippers and the offshore, which have a larger body size and darker coloration. They are a very social species, usually traveling in groups of as many as a dozen (called pods), but they have been seen in aggregations of several hundred. Most populations do not migrate, but travel fairly widely to find food or locate waters of preferred temperature. They regularly swim at speeds of approximately 5-11kph, and sometimes up to 35 kph. They can dive down to depths of more than 30 meters (under experimental conditions, a trained dolphin dove 547 meters!) and jump 6 meters out of the water. They usually breathe air at the surface every 2 minutes through their blowhole, but can make dives for up to 8-10 minutes. A typical life span for these creatures is 25 years however about 1-2% may reach the maximum life span of 50 years.

They have a larger brain than those of humans, and show a high degree of intelligence. Cognitive abilities investigated in the dolphin include concept formation, sensory skills, and the use of mental representation of dolphins. They communicate with a wide variety of vocalizations and it is hypothesized they have a complex language and perhaps one day people may eventually be able to communicate meaningfully with dolphins. Each dolphin appears to have its own distinctive whistle by which it communicates a limited amount of information on its identity, location, and condition to other dolphins. Dolphins also use click-like pulses produced by nasal sacs in the forehead for echolocation.

Sharks such as Bulls and Tigers prey on dolphins, as well as Orcas. However, the dolphin definitely puts up a fight!

Scientific Name :  Tursiops truncatu

 

Encounters

The Bottlenose dolphin is fond of warm, shallow inshore waters. They are commonly seen in bays and lagoons, and sometimes ascend large rivers. They are found primarily in temperate and tropical waters of the Atlantic Ocean and adjoining seas, as well as Nearctic, Neotropical, and Pacific Oceans. In USA waters, the Bottlenose dolphin ranges as far north as Cape Hatteras, NC in the summer and in the west to Point Conception, CA. Year-round it can be found off the coasts of Hawaii and Florida.

Diet
In the wild, dolphins feed on squid, shrimp, eels, crustaceans and a wide variety of fishes. In some waters, Bottlenoses habitually follow shrimp boats to consume what the shrimpers discard or miss. They often hunt as a team, herding small fishes such as menhaden ahead of them and picking off the stragglers. They have been observed chasing fish onto mudflats, then sliding out of the water to seize their prey. They generally consume approximately 6-15 kg of seafood per day.

Reproduction

Males fight viciously over females during the breeding season, which is between March and April. A hierarchy based on size is generally established in a group of males. Courtship can sometimes be rather violent, with males and females bumping heads forcefully. Intromission is rapid (10 seconds, but may be repeated) and takes place underwater belly to belly when the female rolls over on her side, presenting her ventral surface to the male. The normal interval between calves is 2-3 years, but another offspring may be produced a year later if the first calf dies at birth. Gestation is 12 months. Newborn calves are 98-126 cm long and weigh 9-11 kg. Lactation lasts from 12-18 months, but young begin to eat solid food when they are less than 6 months old. Mother and calf often remain closely associated until the young is 4 or 5 years old. In fact, the mother-offspring bond is so strong that females have often been observed holding stillborn or otherwise dead babies at the surface of the water. Females become sexually mature at 5-12 years of age, while males are mature at 9-13 years.

Captivity

Since 1949, Bottlenose dolphins have been used in shows in oceanariums that feature dolphins doing tricks to entertain the audience. They are easily trained to perform acrobatics, locate hidden objects and play with balls. They are also used widely in research work involving cetacean physiology, psychology and sociology. The United States Navy has a trained team of dolphins who are used on underwater missions.

Conservation
The Bottlenose dolphin is Protected under the Marine Mammal act of 1972, which prohibits the taking of dolphins without a special permit. Because of commercial fishing operations operating in the late 1800's, bottlenose dolphin numbers were drastically reduced by the turn of the century. The U.S. National Marine Fisheries Service estimated that there were 3,000 to 10,000 Bottlenosed dolphins off the east coast of the United States in 1981. In the eastern tropical Pacific the population is estimated to be 243,500, while in the waters of Japan the population estimates are as low as 37,000. The biggest threat now to dolphin populations is probably commercial fishing for tuna. Dolphins school with tuna and sometimes become trapped in nets set by fisherman. In 1990, "Dolphin Safe" labels (certifying that no dolphins were encircled to catch tuna) were placed on tuna cans, reducing dolphin deaths in tuna nets by 97 percent. Fisherman sometimes shoot Bottlenose dolphins because they believe the dolphins are competing with them for fish and other desirable catch. Dolphins have been hunted by people in many parts of the world for meat and products (such as fertilizer, body oil for cooking and illumination, and jaw oil used as a lubricant in fine machinery) made from dolphin parts.

Distinguishing Characteristics

 

· The dolphin's sleek, fusiform body, together with its flippers, flukes and dorsal fin adapt this animal for ocean life.

· A dolphin's forelimbs are pectoral flippers, which it uses to steer and with the help of the flukes, to stop.