All about Dolphins

Dolphins belong to the order of whales.

All dolphins, porpoises, and whales belong to the order Cetacea. They are often called cetaceans. Scientists group most dolphins (31 species) in the family Delphinidae, part of the suborder Odontoceti, or toothed whales. Delphinids include such well known dolphins as bottlenose dolphins and common dolphins as well as killer whales and pilot whales.

Another cetacean family, Plantanistidae, contains the river dolphins: small-eyed, long-snouted dolphins that live in fresh water. Porpoises belong to their own family, Phocoenidae. Porpoises are different than dolphins. They have shorter snouts, trangular tops fin, and spade-shped teeth. This fact sheet focuses on dolphins in the family Delphinidae.

Streamlined bodies slip through the water.

A dolphin has streamlined body parts that help it swim easily through the water. The dorsal fin, located on the center of its back, is made of dense fibrous connective tissue – there is no bone inside. The dorsal fin acts as a keel, giving the dolphin some stability as it swims.

Each lobe of a dolphin’s tail is called a fluke. Like the dorsal fin, flukes have no bone or muscle inside. A dolphin uses the powerful muscles along its back and tail stalk to move its flukes up and down. This motion moves the dolphin forward through the water.

As it swims, a dolphin uses its pectoral flippers to steer and, with the help of the flukes, to stop. Pectoral flippers are a dolphin’s forelimbs. If you looked at an X-ray picture of a dolphin’s pectoral flipper, you would see what looks like finger bones! Dolphins have no hind limbs, only ver small hip bones buried deep in the pelvic muscle and tissue.

A dolphin breathes through a single blowhole, located on top of its head. A muscular flap covers the blowhole, making a watertight seal when dolphins dive. To take a breath, dolphins contract the muscular flap. When dolphins relax the muscles, the flap stays tightly closed.

Dolphins live in all oceans.

Dolphins live in all oceans of the world. While some inhabit one particular geographical area of an ocean, others like killer whales are found worldwide. Coastal, or inshore, dolphins live close to land and are often seen by people on beaches and boats. Oceanic, or offshore, dolphins live farther out at sea. Many dolphins have a homerange, an area where they tend to stay.

Some dolphins, like these Commerson’s dolphins, swim in shallow coastal waters.

Fish is a common catch.

All dolphins are carnivores, or meat eaters. Many eat fishes and squids, while some, like killer whales, also catch seals, sea lions, walruses, and other dolphins. A dolphin grasps and tears food with its cone-shaped teeth. All dolphins swallow their food whole or in large chunks.

Although they sometimes feed by themselves, dolphins most often hunt in groups. Dolphins that live in the open ocean may swim in tight circles around a school of fish and take turns dashing in to catch a bite to eat. Closer to shore, a group of dolphins often herds fish into shallow water, keeping them trapped while group members feed.

Social dolphins stick together.

Dolphins live and travel in groups called pods, often family groups. In some species, individual dolphins enter and leave the pod over time. But others, like killer whales, have a stable group. Sometimes, several pods may join together to form a temporary herd. Several hundred individuals have been seen traveling in a single herd.

These social mammals commuicate by squeaking, grunting, trilling, and moaning. They also send messages through body language by leaping, breaching, smacking their tails against the water, butting heads, and jaw-snapping. Within each pod, some dolphins are more dominant than others.

Natural predators pursue dolphins.

Sharks are a dolphin’s main predator. Dolphin remains are often found in the stomachs of tiger sharks, dusky sharks and bull sharks. On occasion, killer whales may feed on some species of dolphins.

Human activities can harm dolphins.

In some parts of the world, humans hunt certain types of dolphins for food. Yet even where they’re not hunted, dolphins are threatened by some human activities.

Toxic chemicals that pollute nearshore waters may contaminate the fish on which dolphins feed. Scientists believe these chemicals might affect the health of dolphins and cause tumors. Pollution may have contributed to the deaths of dolphins that have washed up on beaches in recent years.

In the eastern tropical Pacific ocean, tuna travel under dolphin pods. When tuna fishermen set their nets around the dolphins to catch the tuna, the dolphins are trapped too. To help save dolphins, many tuna fishermen now use special nets and techniques to release the dolphins. From 1972 to 1994, dolphin deaths from purse seine fishing in the eastern tropical Pacific dropped more than 99%, from 423,678 to 4,095 individuals.

A more deadly type of fishing is done with gill nets. These nets stretch for miles across the ocean and extend deep under water. Once the fishermen have set the nets, they leave and return a few days later to haul them in. They remove the fish they were hoping to catch and discard all other animals that have died in the nets. Thousands of dolphins and other marine creatures drown in these huge nets each year.

Top 12 Facts about Dolphins that you must know

1. Dolphins are mammals. As all mammals, dolphins nurse their young from mammary glands.

2. Dolphins can swim up to 260 m. below the surface of the ocean. However they are mainly shallow divers as they need to reach the surface to breathe.

3. Dolphins can stay up to 15 minutes under water. They only do this some times as they usually stay only a few minutes diving before reaching the surface for air.

4. Dolphins use a technique called echolocation. This technique uses the same principles of a radar, and it is used to find food and navigate.

5. Dolphins are social beings. Dolphins live in groups and cooperate among each other for activities like getting food and calf rising.

6. Dolphins are Cetacenas. There are 32 species of ocean dolphins and 5 species of river dolphins.

7. The largest dolphin is the Orca, also known as “killer whale”. Orcas grow up to 6.1 meters long and they are named as whales because their size, but they really belong to the toothed cetacean family just like dolphins do.

8. The most popular dolphin is the “bottlenose dolphin”. Bottlenose dolphins are the ones we have seen in tv series, movies and aquatic shows. Bottlenose dolphins can grow up to 2.5-2.8 meters.

9. Dolphins are warm-blooded. As mammals, dolphins are warm blooded and their internal temperature is around 36 degrees. To conserve this temperature they are surrounded by a thick layer of fat called “blubber” just below the skin.

10. The botllenose dolphin brain weighs 1500-1600 grams. While average human brain weighs 1200-1300 grs. This is not a conclusive evidence of dolphin intelligence as many other factors might be the cause of intelligence according to scientists.

11. Dolphins communicate efficiently. Dolphins can make a unique signature whistle that may help individual dolphins recognize each other, collaborate and perform several other kinds of communication.

12. D olphins can swim 5 to 12 kilometers per hour. This will depend on the species and situation, although fastest dolphins can reach up to 32 km/h.

The Secret Language of Dolphins

Text by Crispin Boyer

Scientists are studying wild and captive dolphins to decipher their secret language. Photograph courtesy Augusto Stanzani/Ardea London Ltd

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Here’s a conversation worth talking about: A mother dolphin chats with her baby…over the telephone! The special call was made in an aquarium in Hawaii, where the mother and her two-year-old calf swam in separate tanks connected by a special underwater audio link. The two dolphins began squawking and chirping to each other—distinctive dolphin chatter. Cracking the Code “It seemed clear that they knew who they were talking with,” says Don White, whose Project Delphis ran the experiment. “Information was passing back and forth pretty quickly.” But what were they saying? That’s what scientists are trying to find out by studying wild and captive dolphins all over the world to decipher their secret language. They haven’t completely cracked the code yet, but they’re listening…and learning.

Chatty Mammals In many ways, you are just like the more than 30 species of dolphins that swim in the world’s oceans and rivers. Dolphins are mammals, like you are, and must swim to the surface to breathe air. Just as you might, they team up in pods, or groups, to accomplish tasks. And they’re smart. They also talk to each other. Starting from birth, dolphins squawk, whistle, click, and squeak. “Sometimes one dolphin will vocalize and then another will seem to answer,” says Sara Waller, who studies bottlenose dolphins off the California coast. “And sometimes members of a pod vocalize in different patterns at the same time, much like many people chattering at a party.” And just as you gesture and change facial expressions as you talk, dolphins communicate nonverbally through body postures, jaw claps, bubble blowing, and fin caresses.

Thinking Dolphin Scientists think dolphins “talk” about everything from basic facts like their age to their emotional state. “I speculate that they say things like ‘there are some good fish over here,’ or ‘watch out for that shark because he’s hunting,'” says Denise Herzing, who studies dolphins in the Bahamas. When the going gets tough, for instance, some dolphins call for backup. After being bullied by a duo of bottlenose dolphins, one spotted dolphin returned to the scene the next day with a few pals to chase and harass one of the bully bottlenose dolphins. “It’s as if the spotted dolphin communicated to his buddies that he needed their help, then led them in search of this guy,” says Herzing, who watched the scuffle.

Language Lessons Kathleen Dudzinski, director of the Dolphin Communication Project, has listened to dolphins for more than 17 years, using high-tech gear to record and analyze every nuance of their language. But she says she’s far from speaking “dolphin” yet. Part of the reason is the elusiveness of the animals. Dolphins are fast swimmers who can stay underwater for up to ten minutes between breaths. “It’s like studying an iceberg because they spend most of their lives underwater,” Dudzinski says.

Deciphering “dolphin speak” is also tricky because their language is so dependent on what they’re doing, whether they’re playing, fighting, or going after tasty fish. It’s no different for humans. Think about when you raise a hand to say hello. Under other circumstances, the same gesture can mean good-bye, stop, or that something costs five bucks. It’s the same for dolphins. During fights, for example, dolphins clap their jaws to say “back off!” But they jaw clap while playing, too, as if to show who’s king of the underwater playground. “I have not found one particular dolphin behavior that means the same thing every time you see it,” says Dudzinski. “If you like mysteries and detective work, then this is the job for you.” And who knows—maybe someday you’ll get a phone call from a dolphin.