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

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."



This National Geographic video captures on film a good example strand fishing dolphins in action.



• 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.

Do wild dolphins ever act cooperatively with humans?
Yes. In Laguna, Brazil, a most fascinating alliance has developed between bottlenose dolphins and local fishermen. The dolphins herd schools of mullet toward fishermen waiting to throw their cast nets. Apparently, the dolphins even signal to the fishermen exactly when to throw.

This is a WIN-WIN situation for both man and dolphin. The fishermen catch more fish, and the dolphin catch the herded fish escaping the nets. By most accounts, this cooperation has been going on for more than 100 years. This learned behavior--on the part of humans and dolphins--is passed down from one generation to the next.

Do dolphins have any natural enemies?
Yes. Their enemies include killer whales (orcas), and certain large sharks such as the tiger shark and the bull shark.

How do dolphins protect themselves?
A lot of dolphin self defense relies on strength in numbers. When a predator threatens, the entire pod may take part in neutralizing the threat. For example, dolphins will ram a shark's soft underbelly to kill it or drive it away. Dolphins are also adept at communicating danger to one another through the various sounds they produce.

If you see a dorsal fin in the water, how can you tell if it belongs to a dolphin or a shark?
Dolphins swim by flapping their tails up and down, alternately surfacing and diving. A dolphin seems to "roll" through the water, bowed backs and fins showing one second, disappearing the next, then reappearing. This "now-you-see-it, now-you-don't" pattern is what you'll normally see when you spot a dolphin dorsal fin. A shark, on the other hand, swims with a side-to-side motion of its tail, and its dorsal fin tends to cut straight through the water without the dolphin's rolling pattern.

How do dolphins communicate?
They use a variety of sounds described as clicks, squeaks, creaks, buzzing clicks, chuffs, screams, squawks, pops, chirps, and whistles. Plus, like humans, they communicate with body language which can include play biting, petting, smacking, and so on. No doubt dolphins can communicate with one another, but so can dogs, cats, and probably most other animals for that matter. Perhaps the most interesting question regarding dolphin communications is "Do they have a language?" If you mean a human-type language based on symbols, and capable of describing abstract ideas, the short answer according to experts is no.

Why do dolphins jump?
Nobody knows for sure, but scientists speculate that dolphins jump for a variety of reasons, including the following:

• Because it's fun. They are naturally playful, so maybe they're just jumping for joy.
• Because it's easier to travel through air than through water.
• To get a good look at the above-water world around them--maybe to help them navigate.
• To get away from sharks.
• To help them regulate breathing.

How do dolphins chew their food?
Their cone-shaped teeth are used for catching food, not for chewing. They swallow their food whole.

Do dolphins have good vision?
Yes. The design of their eyes allows them to see well above and below water, and in bright as well as dim light. Their may, however, be more or less color blind. Unlike humans, dolphins have monoscopic vision in each eye, allowing them to see two different images at the same time. Within limits, they can also focus both eyes on the same image, allowing them to "see in stereo" the way we humans do.

Do dolphins have good hearing?
They have excellent hearing. Like dogs, bottlenose dolphins can hear a wide range of high-pitch sounds that we humans can't. But dolphins can hear much higher frequencies than even dogs can. Oh, and in case you're looking for a dolphins ears, they're the little dimples down there behind their eyes.

How intelligent are dolphins?
Dolphins are highly intelligent, capable of tool use. They can also recognize themselves in a mirror, thereby displaying self-awareness. Groups of dolphins can work together in amazingly cooperative patterns, for example, to defend against a shark. They have even been noted displaying a sense of humor by playing "tricks" on other animals-- rolling sea turtles in the water, and sneaking up to scare unsuspecting pelicans, for instance.