Facts About Bottlenose Dolphins

 A few facts about bottlenose dolphins may help increase your enjoyment of these magnificent and endearing creatures found in the waters off Key Largo.

What is the scientific classification for dolphins? 
The scientific order of marine mammals known as Cetacea (see-tay-she-uh) includes dolphins, porpoises, and whales. Dolphins belong to the scientific family known as Delphinidae (del-fin-uh-dee). The bottlenose dolphin belongs to the genus Tursiops (ter-see-ops). It's unclear how many species of Tursiops there are (maybe just one), but any bottlenose around Key Largo is a Tursiops truncatus (trunk-kah-tuhs).

Is a dolphin also a porpoise? 
No. Porpoises are quite distinct from dolphins. Like all whales, dolphins, and porpoises, they're both cetaceans. But whereas scientists group dolphins into the family Delphinidae , porpoises belong to the family Phocoenidae (fo-seen-ee-dee). Porpoises are smaller and "squattier" than dolphins, and have no rostrum. Plus, porpoises have spade-shaped teeth, while the teeth of dolphins are cone shaped.

Where is the bottlenose dolphin found? 
Except for the polar regions, the bottlenose dolphin is found in most coastal waters around the world. Also, it can and does live far out to sea.

How big are bottlenose dolphins? 
Adults average around nine feet, and weigh around 500 pounds. A newborn dolphin calf might measure around four feet, and weigh around 30 pounds.

How long do bottlenose dolphins live? 
The average life span for bottlenose dolphins is about 25 years, although some may live to be 50, maybe even longer. One dolphin, Nellie, at Marineland near St. Augustine (Florida) is 57.

How fast can bottlenose dolphins swim? 
They can cruise at around seven miles per hour, and can burst up to 17 miles per hour or more over a short distance. When traveling fast dolphins tend to jump out of the water. Air offers less resistance than water, so by periodically jumping into the air dolphins can go faster.

What is echolocation, and how do dolphins use it?
Echolocation is the use of returning sound waves to detect things in the environment. By emitting a variety of sounds, and then listening for their echos, dolphins can know "what's out there," whether it be a school of fish or a large shark. Apparently, dolphins use echolocation to augment their visual senses, not to substitute for them entirely.

Do dolphins have social groupings? 
Dolphins are normally social animals, and form four types of groups:

1. Mother and calf
2. Young pre-adult dolphins form groups for play and exploring
3. Groups of females with their calves
4. Adult males form long-lasting groups of two or three

A dolphin grouping is called a "pod." A pod of bottlenose dolphins may consist of anywhere from two to hundreds of individuals, although pods of two to two dozen are more common. Dolphins living close to shore generally form smaller pods than those that live far offshore. Deep-water offshore dolphins may form larger pods as a way to deal with increased danger from predators.

What do dolphins eat? 
Bottlenose dolphins eat a wide variety of fish, plus eels, shrimp and other crustaceans. Their exact diet depends on what's available to them. Adult bottlenose dolphins normally eat 20 to 25 pounds of food daily, sometimes up to 40, maybe even 50.

When and how do dolphins sleep?
Dolphins sleep with half their brain at a time. Half their brain sleeps, while the other half stays awake. (I've observed that many college students can do this too, especially in class.) Dolphins alternate which side of their brains sleeps at any given time. Since dolphins must breathe consciously, this type of sleep allows them to partially sleep while still swimming and breathing.

How do dolphins catch their food? 
They use a variety of methods:

• In one method, called "kerplunking," the dolphin slaps a fish out of water with one of its tail flukes to stun it, making it easier to catch.

• In another kerplunking technique the dolphin slaps its tail flukes on the water to scare hiding fish into moving.

• In western Australia bottlenose dolphins display a form of tool use. The dolphins--mostly the females--hold sponges in their mouth to protect their noses while they root around in the sand looking for prey. This behavior is passed by a mother to her offspring. While the young females take to it quite readily, the young males mostly ignore the lessons. One speculation is that sponging is time consuming, and young males would rather socialize than forage with sponges, since socializing increases their chances of breeding.

• Dolphins often cooperate with one another--even to the point of acting as a team, especially when feeding. In the South Carolina's tidal waters, for instance, they have been observed beaching fish by running together as a group to create a head-on wave which washes the fish up on banks exposed by low tides. This technique is called "strand fishing."

Another fascinating dolphin-feeding method is called "mud-ring feeding." Researchers from the Dolphin Ecology Project--a non-profit research and education organization--have documented the occurrence of this behavior in Florida Bay. This feeding method is essentially a fish round-up, usually involving several dolphins. One swims in a circle in shallow water, using its tail to stir up a cloud of mud and silt which corrals a school of fish. Encircled by the large opaque cloud, the fish tend to remain in the cloud, refusing to penetrate it, and swimming in a tight group. Eventually, they panic and begin jumping--often into the mouths of hungry dolphins with their heads above water to catch what comes their way.