Bottlenose Dolphin Facts

A bottlenose dolphin breathes through a blow hole. The
A bottlenose dolphin breathes through a blow hole. The "bottle" on its head is really its rostrum. David Tipling / Getty Images

Bottlenose dolphins are known for the elongated shape of their upper and lower jaws or rostrum. They are the most common type of dolphin, found everywhere except the Arctic and Antarctic. The bottlenose's so-called "nose" is actually the blowhole on the top of its head.

There are at least three species of bottlenose dolphins: the common bottlenose dolphin (Tursiops truncatus), the Burrunan dolphin (Tursiops australis), and the Indo-Pacific bottlenose dolphin (Tursiops aduncus). These playful mammals have the largest brain mass per body size of any animal except humans. They display high intelligence and emotional intelligence.

Fast Facts: Bottlenose Dolphin

  • Scientific Name: Tursiops sp.
  • Distinguishing Features: Large gray dolphin characterized by its elongated upper and lower jaws
  • Average Size: 10 to 14 ft, 1100 lbs
  • Diet: Carnivorous
  • Average Lifespan: 40 to 50 years
  • Habitat: Worldwide in warm and temperate oceans
  • Conservation Status: Least Concern (Tursiops truncatus)
  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Mammalia
  • Order: Artiodactyla
  • Family: Delphinidae
  • Fun Fact: After humans, the bottlenose dolphin has the highest level of encephalization, leading to high intelligence.

Description

On average, bottlenose dolphins reach a length of 10 to 14 ft and weigh around 1100 pounds. The dolphin's skin is dark gray on its back and pale gray on its flanks. Visually, the species is distinguishable from other dolphins by its elongated rostrum.

A dolphin's flukes (tail) and dorsal fin consists of connective tissue, lacking muscle or bone. The pectoral fins contain bones and muscle and are analogous to human arms. Bottlenose dolphins living in colder, deeper waters tend to have more fat and blood than those living in shallow water. The dolphin's streamlined body helps it swim very quickly — over 30 km/hr.

Senses and Intelligence

Dolphins have sharp eyesight, with horseshoe-shaped double-slit pupils and a tapetum lucidum to aid vision in dim light. The bottlenose has a poor sense of smell, since its blowhole only opens for breathing air. Dolphins seek food by emitting clicking sounds and mapping their environment using echolocation. They lack vocal cords, but communicate via body language and whistles.

Bottlenose dolphins are extremely intelligent. While no dolphin language has been found, they can comprehend artificial language, including sign language and human speech. They display mirror self-recognition, memory, understanding of numbers, and tool use. They exhibit high emotional intelligence, including altruistic behavior. Dolphins form complex social relationships.

Distribution

Bottlenose dolphins live warm and temperate oceans. They are found everywhere except near the Arctic and Antarctic Circles. However, the dolphins living along shallow coastal waters are genetically distinct from those living in deeper water.

Bottlenose dolphin range
Bottlenose dolphin range. maplab

Diet and Hunting

Dolphins are carnivorous. The feed mainly on fish, but also hunt shrimp, cuttlefish, and mollusks. Groups of bottlenose dolphins adopt different hunting strategies. Sometimes they hunt as a pod, herding fish together. Other times, a dolphin may hunt alone, usually seeking bottom-dwelling species. Dolphins may follow fishermen for food or work cooperatively with other species to catch prey. A group offshore from Georgia and South Carolina uses a strategy called "strand feeding." In strand feeding, the pod swims around a school of fish to trap prey in the current. Next, dolphins charge toward the fish, pushing themselves and the school onto a mud flat. The dolphins crawl around on land to collect their prize.

Predators

Bottlenose dolphins are preyed upon by large sharks, such as the tiger shark, bull shark, and great white. In rare cases, killer whales eat dolphins, although the two species swim together in other regions. Dolphins protect themselves by swimming in a pod, evading attackers, or mobbing predators to kill them or chase them away. Sometimes dolphins protect members of other species from predators and other dangers.

Reproduction

Both male and female dolphins have genital slits that conceal their reproductive organs to make their bodies more hydrodynamic. Males compete with each other to mate with females during the breeding season. Breeding occurs at different times, depending on geographic location.

Gestation requires about 12 months. Usually, a single calf is born, although sometimes the mother bears twins. The calf stays with its mother and nurses for between 18 months and 8 years. Males mature between ages 5 and 13. Females become mature between the ages of 9 and 14 and reproduce every 2 to 6 years. In the wild, bottlenose dolphin life expectancy ranges from 40 to 50 years. Females typically live 5 to 10 years longer than males. About 2% of dolphins live to 60 years of age. Bottlenose dolphins hybridize with other dolphin species, both in captivity and in the wild.

Bottlenose Dolphins and Humans

Dolphins display curiosity about humans and have been known to rescue people. They can be trained for entertainment, to aid fishermen, and to help find sea mines.

Interactions between humans and bottlenose dolphins are usually friendly.
Interactions between humans and bottlenose dolphins are usually friendly. George Karbus Photography / Getty Images

However, human-dolphin interactions are often harmful to dolphins. Some people hunt dolphins, while many die as bycatch. Dolphins are frequently injured by boats, suffer from noise pollution, and are adversely affected by chemical pollution. While dolphins are often friendly toward people, there are cases of dolphins injuring or killing swimmers.

Conservation Status

Some local populations are threatened by water pollution, fishing, harassment, injury, and food shortages. However, the common bottlenose dolphin is listed as being of "least concern" on the IUCN Red List. Dolphins and whales enjoy some level of protection in most parts of the world. In the United States, the Marine Mammal Protection Act of 1972 (MMPA) prohibits hunting and harassing of dolphins and whales, except in special circumstances.

Sources

  • Connor, Richards (2000). Cetacean Societies: Field Studies of Dolphins and Whales. Chicago: University of Chicago Press. ISBN 978-0-226-50341-7.
  • Reeves, R.; Stewart, B.; Clapham, P.; Powell, J. (2002). Guide to Marine Mammals of the World. New York: A.A. Knopf. p. 422. ISBN 0-375-41141-0.
  • Reiss D, Marino L (2001). "Mirror self-recognition in the bottlenose dolphin: a case of cognitive convergence". Proceedings of the National Academy of Sciences of the United States of America. 98 (10): 5937–5942. doi:10.1073/pnas.101086398
  • Shirihai, H.; Jarrett, B. (2006). Whales Dolphins and Other Marine Mammals of the World. Princeton: Princeton Univ. Press. pp. 155–161. ISBN 0-691-12757-3.
  • Wells, R.; Scott, M. (2002). "Bottlenose Dolphins". In Perrin, W.; Wursig, B.; Thewissen, J. Encyclopedia of Marine Mammals. Academic Press. pp. 122–127. ISBN 0-12-551340-2.