Bottlenose Dolphin

Bottlenose Dolphin

Mammalia

SCIENTIFIC CLASSIFICATION

COMMON NAME: bottlenose dolphin, Atlantic bottlenose dolphin, Pacific bottlenose dolphin, bottle-nosed dolphin
KINGDOM: Animalia
PHYLUM: Chordata
CLASS: Mammalia
ORDER: Cetacea
SUBORDER: Odontoceti
FAMILY: Delphinidae
GENUS SPECIES: Tursiops truncatus

FAST FACTS

DESCRIPTION: Bottlenose dolphins are light to dark gray over their dorsal surface, fading into a white or cream along their ventral region. They have a streamlined fusiform body shape. The source of their common name, bottlenose dolphins exhibit a pronounced anterior rostrum (often referred to as a beak), typically 7-8cm (3 in.) in length. Said rostrum generally contains 76-98 conically-shaped, homogenous teeth - with tooth counts varying among individuals. Their dorsal fin is falcate.

It should be noted that two distinct ecotypes are recognized. The coastal ecotype typically exhibits smaller average body size with relatively larger flipper size. Comparatively, the offshore ecotype typically exhibit larger average body size and darker coloration - among other morphological distinctions.
SIZE: Coastal ecotype = average 2.5-2.7 m (8.2-8.9 ft.)
Offshore ecotype = 3.7 m (12 ft.)

Atlantic bottlenose dolphins as a whole are typically smaller than Pacific bottlenose dolphins; however, bottlenose dolphins frequenting cooler, temperate waters in either ocean tend to exhibit sizes indicative of the relatively larger offshore ecotype.

Calves are approximately 106-132 cm (42-52 in.) at birth.
MALE Males may be slightly larger than females
WEIGHT: Coastal ecotype = average 190-260 kg (419-573 lbs.)
Offshore ecotype = average 454 kg (1,000 lbs.); maximum 650 kg (1,433 lbs.)

Newborn calves weigh approximately 20 kg (44 lbs.)
MALE Physically mature males tend to be more massive than physically mature females
DIET: Variety of fishes, squids, eels, and crustaceans
GESTATION: Approximately 12 months
ESTRAL PERIOD Roughly 12 month anestrus followed by an approximate 12 month polyestrus consisting of at least 3 distinct cycles, all of which are typically focused in the late spring
NURSING DURATION Up to 18 months (wean)
SEXUAL MATURITY: Typically exhibited as a function of age-dependent body size
MALE Sexual maturity for males is attained once body length reaches 2.4-2.6 m (8-8.5 ft.), generally between 9-13 years of age
FEMALE exual maturity for females is attained once body length reaches 2.3 m (7.5 ft.), generally between 5-12 years of age
LIFE SPAN: Approximately 20 years (average); Maximum lifespan appears to be in 45-50 year range (with 1-2% of population attaining maximum age)
MALE Maximum lifespan for males appears to be in 40-45 year range
FEMALE Maximum lifespan for females appears to be slightly greater (i.e. 5-10 years) than that of males
RANGE: Temperate and tropical marine waters worldwide; In the Pacific, they are found from northern Japan to Australia and from southern California to Chile; In the Atlantic, they are found from Nova Scotia to Patagonia and from Norway to the tip of South Africa; In the Indian Ocean, they are found from Australia to South Africa
HABITAT: Primarily temperate and tropical waters; coastal ecotype typically inhabits nearshore waters including harbors, bays, lagoons, gulfs, estuaries, with occassional forays into large rivers; offshore ecotype typically inhabits pelagic regions extending to the continental shelf as well as select atolls and ocean islands
POPULATION: GLOBAL Unknown
  LOCAL Eastern tropical Pacific = 243,500 (approximate)
Northern Gulf of Mexico = 35,000-45,000 (approximate)
Western North Atlantic = 10,000-13,000 (approximate)
STATUS: IUCN Data Deficient (DD)
CITES Appendix II
USFWS Protected in U.S. waters by the Marine Mammal Protection Act of 1972; not considered endangered or threatened

FUN FACTS

1. Dolphins frequently ride the bow wake or the stern wake of boats. They have been seen jumping as high as 4.9 m (16 ft.) out of the water and landing on their backs or sides, in a behavior called a breach.
2. Both young and old dolphins chase one another, carry objects around, toss seaweed to one another, and use objects to invite each other to interact. Such activity may be practice for catching food.
3. Bottlenose dolphins often cooperate when hunting and catching fish. In open waters, a dolphin pod sometimes encircles a large school of fish and herds them into a tight ball for easy feeding. Then the dolphins take turns charging through the school to feed. Occasionally dolphins will herd fish to shallow water where they are easy prey.
4. Bottlenose dolphins generally do not need to dive very deeply to catch food. Depending on habitat, most bottlenose dolphins regularly dive to depths of 3-46 m (10-150 ft.). They are, however, capable of diving to some depth. Under experimental conditions, a trained dolphin dove 547 m (1,795 ft.).
5. Bottlenose dolphins live in fluid social groups called pods. The size of a pod roughly varies from 2-15 individuals. Several pods may join temporarily to form larger groups called herds or aggregations. Up to several hundred animals have been observed traveling in a single herd.
6. 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. As it swims, a dolphin uses its pectoral flippers to steer and, with the help of the flukes, to stop.
7. Bottlenose dolphins routinely swim at speeds of about 5-11 kph (3-7 mph).
8. On average, a dive may last 8-10 minutes.
9. Group composition and structure often are based on age and sex. Adult males tend to group together in pairs or in threes. Females with calves associate with one another. Individuals may leave one group and join another.
10. Adults eat about 4-5% of their body weight per day. Bottlenose dolphins often cooperate when hunting and catching fish. In open waters, a dolphin group sometimes encircles a large school of fish and herds them into a tight, dense mass for easy feeding. The dolphins take turns charging through the school to feed while the others keep the fish from scattering. Occasionally dolphins herd fish to shallow water and trap them against a shore or sandbar.
11. For more information about bottlenose dolphins, explore the BOTTLENOSE DOLPHIN INFO BOOK.

ECOLOGY AND CONSERVATION

Dolphins are important predators of fish, crustaceans, and other marine fauna. They have been hunted in many parts of the world for meat and other by-products made from dolphin parts (such as fertilizer, and machinery lubricants made from their jaw oil). Possessing a larger brain than a human's, dolphins show a high degree of certain types of intelligence, making them popular subjects for research in fields such as cetacean physiology, psychology, and sociology. Their capacity for learning has also made them ideal trained performers in oceanarium and zoological shows.

Under the Marine Mammal Act of 1972, the taking of dolphins requires a special permit. Bottlenose dolphin populations were drastically reduced around the turn of the last century due to commercial fishing operations. The biggest problem still facing dolphins today is the indirect negative affect of commercial tuna fishing, which uses gigantic nets in which dolphins become easily entangled and killed.

Not only is it illegal, but it also may be dangerous to approach a wild dolphin. Marine parks like SeaWorld and Discovery Cove provide a safe environment for humans to interact with dolphins.

BIBLIOGRAPHY

Byrum, Jody and Nuzzolo, Deborah. Bottlenose Dolphins. Third Edition. SeaWorld Education Department, 1996.

Jefferson, T.J. Leatherwood, S. and M.A. Webber. FAO Species identification Guide. Marine Mammals of the World. Rome. FAO, 1993.

Leatherwood, Stephen, and Reeves, Randall R. The Sierra Club Handbook of Whales and Dolphins. San Francisco: Sierra Club Books, 1983.

Nowak, Ronald M. (ed.). Walkers Mammals of the World. Vol. II. Baltimore: Johns Hopkins University Press, 1991.

Nuzzulo, Debrorah. Dolphin Discovery: Bottlenose Dolphin Training and Interaction. SeaWorld Education Department Publication, SeaWorld, Inc., 2003.

Parker, S. (ed.). Grizmeks Encyclopedia of Mammals. Vol. IV. New York: McGraw-Hill Publishing Co., 1990.

Reeves, R. R., Stewart, B.S., Clapman, P.J., and J.A. Powell (Peter Folkens illustrator). National Audubon Society: Guide to Marine Mammals of the World. New York: Random House, 2002.

http://animaldiversity.ummz.umich.edu