When most people think of a dolphin, this is the animal that comes to mind. It may surprise some people that, scientists have actually classified over 35 different species of marine and freshwater dolphins. These different dolphin species display a wide variety of body shapes, sizes and color patterns, however, the "classic" gray bottlenose dolphin (Tursiops truncatus) is certainly the one most widely recognized. Not only is this the species most often found in zoological parks and aquariums, but it is also the one usually featured in the popular press, television shows and movies, such as "Flipper".  

Many people are surprised to learn that killer whales (Orcinus orca) are really dolphins.  In fact they are the largest members of the Delphinidae family of  marine dolphins; the very same family as bottlenose dolphins.  (For some more information about killer whales and about how they got their "killer reputation" click here.)

Much of what we know about cetacean physiology, reproduction, nutritional requirements, medical care, behavior, cognition and learning, has been derived from working with and observing bottlenose dolphins in modern marine parks and aquariums. Members of this species adapt and do very well in these environments. They live long, healthy lives and reproduce extremely well. They are naturally curious, playful animals and form strong bonds with their human caregivers.

Scientific Classification:

Although most scientists today only recognize one species of bottlenose dolphin (T. truncatus) they usually describe at least three subspecies or races. These include the Atlantic bottlenose dolphin (T. truncatus), the Pacific bottlenose dolphin (T. truncatus gilli), and the Southern Hemisphere bottlenose dolphin (T. truncatus aduncus). Some physical characteristics vary so much between these groups that some scientists believe that they should actually be classified as completely separate species. There may also be significant differences between populations within the same subspecies, such as nearshore and offshore groups. For the purposes of this website we will consider all bottlenose dolphins as a single species.

General body shape: The dolphin body is "torpedo" shaped to provide a hydrodynamic profile and reduce resistance as the animal glides through the water. Midway down the back is a prominent sickle-shaped dorsal fin which provides stabilization (something like the keel of a sailboat). Just behind the head area are two medium sized pectoral fins that help with steering and direction (similar in function to the forward planes on a submarine). The vast majority of the animal’s propulsion comes from its powerful tail flukes. The flukes are located at the end of the extremely muscular tail stock or peduncle. (It may be interesting to note that the tail flukes of all cetaceans lay in a horizontal plane. The tail fins of fish, on the other hand, lay in a vertical plane.) The upper and lower jaws extend out past the melon area and together are called the rostrum. In this species the rostrum extends out several inches and serves as the basis for its common name "bottlenose dolphin". In reality, the nose is no where near this area. As in all cetaceans, the nose is actually located on top of the head and is called a "blowhole". This positioning allows the animal to exhale and inhale without having to lift its head above the surface of the water. It functions in the same way that a skin diver uses a snorkel.

Color: The primary color of the bottlenose dolphin varies from very dark to light gray. This color is darker on the top or dorsal surface of the animal. It gradually lightens as it moves down to the belly area. The belly or ventral surface of the animal may be pure white, although at times it may range from pink to yellow. This pattern of dark on top and light on the bottom is a classic example of "counter-shading", which is common in many cetaceans. It is thought that this coloration pattern helps serve the animal to avoid being seen by both predators and prey alike. When viewed from above the dark dorsal surface of the dolphin blends in with the dark waters and sea floor below. When viewed from below the light underside blends in with the bright sky and shimmering surface of the water above.

Size: Depending upon the subspecies and individual population, adults may attain lengths of up to 13 feet (4 meters) and weights of 1,450 lbs (650 kg). The most common subspecies found in US oceanariums, the Atlantic bottlenose dolphin, however is generally a much smaller animal. Adult lengths of this subspecies generally range from 6 – 9 feet (1.8 – 2.7 m) and weights range from 300 – 500 lbs (135 - 225 kg). At birth, calves are usually 35 – 50 inches (90 – 130 cm) in length and may weigh from 30 – 90 lbs (13.5 – 41 kg).

Bottlenose dolphins are found in temperate and tropical waters around the world.

Diet:

The primary diet of this species is small fish which they usually catch and swallow whole. Depending upon the availability of prey species they may also eat larger fish, squid, octopus, crabs and shrimp. Large food items may be torn into pieces to make swallowing easier. Larger subspecies, such as the Pacific bottlenose dolphin, may eat up to 35 lbs (16 kg) per day. Pregnant or nursing mothers may consume even more.

Maximum speed is approximately 20 miles per hour (32 kph).

Reproduction:

Sexual maturity: Males: 7 – 12 years of age. Females: 5 – 10 years of age.

Gestation period: Approximately 12 months.

Calf size: Length: 35 – 50 inches (90 – 130 cm). Weight: 30 – 90 lbs (13.5 – 41 kg).

Number of calves: Normally one calf per pregnancy. While twin fetuses have been reported, this is thought to be very rare and none are known to have survived.

Calving period: Usually spring and summer

Nursing process: Female dolphins posses two mammal glands which produce a rich milk to nourish her young. The calf feeds on this milk by placing its rostrum against one of the two mammal slits located on the ventral surface of the mother's body. It then cups its tongue around the nipple which lies beneath the mammary slit.  A tight seal is formed between the calf's tongue and the mother's nipple.  The mother can physically eject milk into the calves mouth to help speed the nursing process.  This is very helpful since the whole process takes place under water while both animals hold their breath.    

Nursing period: Young calves may begin eating fish within a few months after birth, but may continue to nurse for 1 to 2 years or more.

Calving interval: Approximately every 2 to 4 years.

Calf survival rate: Approximate average is 50%. Maternal bond and experience are extremely important to calf survival and all three increase with the mother’s age and with each successive pregnancy. Infant survival is much lower with very young and/or inexperience mothers.

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Revised: August 27, 2011.