101 Facts… Dolphins!

101 Facts… DOLPHINS! by IP Factly

Dolphins are some of the most recognizable creatures in the world. They are featured as the main attractions in marine parks all over the world, and can be seen playing in waves and around accompanying ships. Dolphins have so many amazing qualities: their intelligence, gentleness, and fun-loving nature are things that humans have been fascinated with for thousands of years.

101 dolphin facts

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Contents

General
History
Dolphin Species
Anatomy
Communication
Swimming, Jumping and Playing
Sleeping
Eating Habits
Courtship
Dolphin Calves
Dolphins and Humans
Threats
Final Facts
Photo Credits

General

The term “dolphin” comes from the Greek word “delphus,” meaning ”womb”, describing the dolphin as a ”fish with a womb”. Dolphins, however, are not fish, but marine mammals, and like other marine mammals, they give birth to live young which are developed in the womb.

Fresco of Dolphines from the bronze age excavations of Knossos on the greek island of Crete.

A dolphin was also once called a mereswine, another word for ”sea pig”.

Dolphins are closely related to whales and porpoises.

Close-up of a harbour porpoise.

A group of dolphins is called a ”school” or a ”pod”. Female dolphins are called ”cows” and male dolphins are called ”bulls”.

Oceanic dolphins live in pods of twelve to fifteen individuals. The members of the pod communicate via whistles and clicks, and have been seen helping each other when injured or ill. River dolphins are solitary animals, living on their own much of their lives.

A pod of spinner dolphins in the Red Sea.

Where there is plenty of food, pods come together to form a superpod, which can consist of up to 1,000 dolphins!

Superpod of dolphins.

Dolphins can be found all around the world – except for polar waters. However, they can endure water temperatures as low as ten degrees Celsius.

Dolphins can live for more than fifty years in captivity, but on average live up to twenty years in the wild.

History

Fossils of a dolphin with large, triangular teeth like a shark, and another with a 20 cm (7.9 inches) long tusk were discovered around New Zealand. They are believed to date back to the Oligocene period, roughly thirty-three to twenty-three million years ago.

Fossil of Eurhinodelphis, an extinct dolphin from Musee d’Histoire Naturelle, Brussels.

Scientists believe that dolphins evolved from land-dwelling animals, particularly those in the artiodactyl order, which includes pigs, deer, and camels.

Dolphin Species

There are almost forty species of dolphins in the world. Most dolphin species live in saltwater and are called oceanic dolphins, and a few species live in freshwater and are called river dolphins.

Oceanic dolphins that live in shallow waters are called coastal dolphins while those found in deep waters are called off-shore dolphins.

Killer whales, pygmy killer whales, false killer whales, melon-headed whales, long-finned pilot whales, and short-finned pilot whales are actually not whales but species of dolphins.

The common bottlenose dolphin is aptly the most common species of dolphin, and the most recognizable. It is found in all temperate and tropical oceans in the world, and in captivity in many marine parks worldwide.

A dolphin surfs the wake of a research boat on the Banana River – near the Kennedy Space Center.

The Hector’s dolphin is the smallest dolphin species in the world, measuring 1.6 meters (5 feet 3 inches) in length and up to 60 kg (130 pounds), at most.

Hector’s dolphin.

The killer whale is the largest dolphin species. A male killer whale can grow up to eight meters (or twenty-six feet) long and weigh more than six tonnes.

Single breaching orca.

The Burrunan dolphin, found in parts of Australia, is the newest dolphin species, recognized only in 2011.

Amazon River dolphins have very flexible necks and spinal cords that help them swim under tree trunks that have fallen into the river. They can even rotate their heads 180 degrees.

Feeding wild pink dolphins.

The Commerson’s dolphin has a very unique appearance – its head, dorsal fin, and flukes are black and its throat and belly are white. For this reason, it is also known as the panda dolphin.

A Commerson’s dolphin (Cephalarhynchus commersonii) off Argentina.

Anatomy

The shape of a dolphin’s body is called a fusiform, which is like the shape of a spindle or a round object that becomes narrower toward the ends.

White-sided Dolphin Skeleton articulated by Skulls Unlimited International, on display at The Museum of Osteology.

A dolphin’s beak is called a rostrum, though not all species have this. The Irrawaddy dolphin, for example, does not have a rostrum.

Large dolphin rostrums.

A dolphin’s tail consists of two fins or lobes called flukes. Flukes are made solely of thick, tough connective tissue without any bone, muscle, or cartilage.

All dolphins have a dorsal fin, a fin located on their backs, which is made of the same connective tissue as their flukes.

The rounded forehead of a dolphin is called a melon. It is packed with fat, and its unique shape plays an important role in echolocation.

Dolphin brains are larger than human brains!

Dolphins breathe through the blowholes on top of their heads, which are sealed with muscular flaps when underwater.

Dolphin with baby – blowhole clearly visible.

Dolphins normally surface every fifteen to twenty seconds to breathe, but can stay under water for up to twelve minutes.

It is nearly impossible to tell male and female dolphins apart at first glance, unless the female is traveling with her calf. Upon closer inspection, though, male dolphins have two slits on their bellies and females have four. So you need to turn them over to tell them apart.

Most dolphins have eighty to one hundred cone-shaped teeth. The long-beaked common dolphin, however, can have up to 120 small, sharp teeth.

All of a dolphin’s teeth are permanent and non-replaceable.

Harlold Bickford a mammal handler from Commander Task Unit brushes the teeth of a Bottle Nose Dolphin.

You can tell a dolphin’s age by the number of growth rings on its teeth.

The teeth of a dolphin are all shaped the same, and are not used for biting or chewing. Rather, they are used to grip objects and rake other dolphins.

Raking happens when a dolphin scratches another dolphin with its teeth as a way of saying “Watch what you’re doing!” or “I’m in charge here!.” This can often leave rake-like marks that lead to white scars.

Scarred Bottlenose Dolphin, Cromarty Firth, Scotland.

The teeth of a dolphin also act like antenna, sending sound waves that are transmitted from inside its lower jaw during the process of echolocation.

Dolphins have rubbery skin with no hair. They shed their outermost skin layer every two hours, so their skin stays smooth.

Dolphins have a thin layer of blubber under their skin that accounts for eighteen to twenty percent of their total body weight.

Dolphins have taste buds and have been observed to prefer some types of fish over others.

Dolphin eating fish at Sea World.

A dolphin’s eyes can move independently of each other.

Dolphins can produce ”tears” that protect their eyes from infection and help them to see more clearly, both above and in the water.

A dolphin’s ears are just small openings located behind its eyes.

Communication

Dolphins do not have a sense of smell, but have very good senses of sight and hearing, which they rely on to navigate through water, hunt, and communicate.

Dolphins have an ability called echolocation, which is the ability to locate objects by listening for echoes, which are sound waves bouncing off of objects.

Because dolphins are sensitive to sound, they can become disoriented, or ultimately lose their hearing when there are loud sounds underwater. Some of them can even die from the stress.

Commerson’s dolphins in the Strait of Magellan.

Dolphins do not have vocal cords. Rather, they produce sounds by moving air through their nasal passages.

Dolphins can produce a variety of sounds, classified into three types – click trains or a series of clicking sounds; burst pulses which are repeated clicks that humans hear as buzzing sounds; and whistles that vary in frequency.

Every bottlenose dolphin has a signature whistle.

Mother bottlenose dolphins whistle to their calves continuously after birth, in order to help them identify the sound. Bottlenose dolphin calves develop their own signature whistles as early as one month old.

Swimming, Jumping and Playing

Dolphins swim at speeds of five to eleven kilometers (three to seven miles) per hour, but can reach speed bursts of up to thirty-five kilometers (twenty-two miles) per hour.

Dolphins swim by moving their tails up and down, not from side to side.

Dolphins can jump as high as sixteen feet up into the air, and can land on their backs, bellies, or sides.

Bottlenose dolphin on mineclearance operations, with locator beacon.

Dolphins are known to frequently jump out of the water while swimming, which is called porpoising. They do this to save energy when traveling long distances, and also to play, to communicate, and to dislodge parasites.

Spinner dolphins are well-known for their acrobatics. They can jump out of the water and twist their bodies several times – up to five times – in the air before jumping back in.

Spinner dolphin jumping.

Dusky dolphins can perform head-over-tail leaps – they jump into the air, then position their backs in a curve and flip their tails before going back into the water, so they jump back in head-first.

A wild dusky dolphin named “Nox”.

Dolphins, both young and old, play by chasing each other, tossing objects to each other using different parts of their bodies, and throwing objects out of the water–then going after them.

Dolphins can be mischievous. While they generally do not eat birds, they can drag birds underwater as a form of play.

Sleeping

Dolphins spend thirty-three percent of each day, or roughly eight hours, sleeping, which they break down into naps of two to eight minutes. They are never fully asleep, though, since they still need to come up to the surface to breathe. Rather, only half of their brain is asleep, and only one eye is closed.

Indus River dolphins sleep in short bursts of four to sixty seconds since it must swim continuously in a river that has strong currents and potentially dangerous floating debris.

Eating Habits

Oceanic dolphins eat a wide variety of fish, squids, and shrimp. River dolphins eat catfish, crabs, and turtles.

The largest of the dolphin family, killer whales, eat other dolphins, fish, squid, seals, walruses, sea turtles, otters, penguins, birds, baby polar bears, and even moose!

Killer whales jumping.

Dolphins swallow their food whole, usually head-first. If the fish is too big, they will shake it or rub it against the ocean floor until it breaks into small pieces before eating.

Most dolphins eat approximately four to six percent of their body weight per day, while nursing mothers eat about eight percent.

Dolphins often hunt in groups. They surround the large school of fish, close in, and then take turns eating. They also herd fish toward mud banks, sand bars, and shorelines to trap them in shallow water.

Huge pod of playful spinner dolphins.

Some dolphins use their tails to flip fish out of the water, stunning them.

Some scientists believe that dolphins can use high-pitched sounds to stun their prey.

Some coastal dolphins have been observed using sea sponges as shields when looking for food on rocky bottoms, protecting them from spines, stings, and the sharp edges of rocks.

Courtship

Dolphins become sexually mature between five and twelve years of age.

Amazon River Dolphins at Duisburger Zoo.

Courtship between male and female dolphins can take place at any time of the year, and usually involves some head-butting and tooth-scratching.

During courtship, male Amazon River dolphins carry branches or balls of hardened clay in their snouts and present them to females as gifts.

Amazon river dolphin.

Dolphin Calves

Female dolphins give birth to just one baby dolphin, called a calf, every two to three years.

Dolphin calves are born after a gestation period – the period of being inside the womb – of roughly ten to fourteen months, depending on the species.

Dolphin calves are about 100 to 135 cm (thirty-nine to fifty-three inches) long and weigh ten to twenty kg (twenty-two to forty-four pounds).

Adult female Bottlenose Dolphin with two young at side, Inner Moray Firth, Scotland May 2005.

Dolphin calves are usually born tail-first to prevent them from drowning. As soon as the calf is born, its mother takes it to the surface to breathe.

Dolphin calves are connected to their mothers with an umbilical cord – the same cord that connects human babies to their mothers. In order to cut it, the mother dolphin has to quickly swim away after birth.

Often, when a female dolphin gives birth, there is another female dolphin nearby who assists her, pulling the baby out if it has to. That dolphin is the only one the mother allows near her calf during the first few hours after birth, although others are close by for protection.

Baby northern right whale dolphins are cream-colored or grayish brown when born, and stay this way for a year before turning black and white.

Northern right whale dolphin.

Baby Atlantic spotted dolphins and pantropical spotted dolphins are born without spots. In Atlantic spotted dolphins, the spots only appear after they are weaned, while pantropical spotted dolphins get their spots only upon reaching maturity, and sometimes not at all.

Photograph of Atlantic Spotted Dolphins off of Long Cay, near South Caicos in the Turks and Caicos islands.

Dolphin calves nurse for the first time within six hours after birth, and then as often as four times per hour for up to eight days, which comes as no surprise, since each nursing episode lasts five to ten seconds only.

A dolphin’s milk is composed of fifty-eight percent water, thirty-three percent fat and 6.8% protein, as well as small amounts of lactose. It is higher in fat and protein content than human breast milk.

Dolphin calves nurse for up to eighteen months, but stay with their mothers longer, for up to three to six years.

At birth, a dolphin calf’s flukes and dorsal fin are not firm and tend to flop, but they gradually stiffen.

Baby dolphin.

During the first few weeks, dolphin calves cannot swim very well, and so they follow their mother’s slipstream. A slipstream is a draft created by a moving object as it goes forward. Adult dolphins have a habit of following the slipstreams of boats, ships, and whales.

Mother and baby slipstreaming.

A dolphin’s first teeth appear at the age of three months, and fully erupt at five months.

Dolphins and Humans

In the town of Opononi, in New Zealand, there is a statue of a dolphin that was erected in honor of the dolphin, Opo, who became beloved to the local children in the summer of 1955, and was buried with full Maori honors.

Statue of Opo the dolphin.

In ancient Greece, dolphins were considered messengers of the god Poseidon, and seeing a dolphin following a ship was a sign of a fortunate voyage.

Dolphins are also considered sacred to the Greek god Apollo, who took their form when he established the oracle at Delphi.

Cupid Riding a Dolphin; at the Hermitage. 1st century Roman copy of Greek original.

The Ganges River dolphins are considered sacred because they are associated with the goddess of the river, Ganga, having carried her on their backs when she came down from the heavens.

Dolphins are not considered a threat to humans. There have never been any killer whale attacks on humans in the wild, but they have attacked their handlers in captivity, which scientists argue is not a result of natural aggression, but instead of stress.

There is only one recorded fatal dolphin attack on humans. In 1994, a man died off the coast of Brazil after being attacked by a bottlenose dolphin named Tiao. According to reports, Tiao was previously constantly harassed by humans, with some even trying to put ice cream cones in his blowhole.

Dolphins performing in a show at Palmitos Park in Gran Canaria.

Some dolphins have such a hard time adapting to life in captivity that they commit suicide by refusing to eat, or smashing their heads against walls.

Currently, the oldest dolphin in captivity is sixty years old. Her name is Nellie, and she lives in Marineland in Florida.

Threats

Sharks are the oceanic dolphins’ most common natural predators, particularly tiger sharks, bull sharks, dusky sharks, and great white sharks. River dolphins have no natural predators.

According to the International Union for Conservation of Nature (IUCN), four dolphin species are currently threatened by extinction – the Hector’s dolphin, Irrawaddy dolphin, South Asian river dolphin, and La Plata dolphin.

Hector’s dolphin is found in New Zealand waters.

The Baiji dolphin, once a common sight in the Yangtze River in China, is believed to have gone extinct in 2006.

The Maui’s dolphin, a subspecies of the Hector’s dolphin, is the most endangered species of dolphin, with only 55 adults remaining in the wild, as of 2012.

In the past, dolphins were hunted for their skin, meat, and oil, and in some countries like Japan, Peru, and Taiwan, they still are.

Many dolphins become entangled in fishing nets each year and end up drowning or getting injured. Others collide with boat propellers and die.

Final Facts

While the exact reason is unknown, dolphins can heal rapidly and recover completely, even from extreme shark bites.

According to Amazon folklore, if you stare into the eyes of an Amazon River dolphin, you will have nightmares for the rest of your life!

Amazon river dolphin.

Dolphins can make their own bubble rings, which are underwater bubbles that spin around.

Dolphins don’t seem to feel pain as intensely as we do.

Apart from keeping it warm, a dolphin’s blubber has compounds that help fight infections.

Photo Credits

Photo1 Fresco of Dolphines from the bronze age excavations of Knossos on the greek island of Crete.

Photo2 Close-up of a harbour porpoise. Author AVampireTear

Photo3 A pod of spinner dolphins (Stenella longirostris) in the Red Sea. Author Alexander Vasenin CC3.0

Photo3b Superpod of dolphins. Author lowjumpingfrog CC2.0 www.flickr.com/photos/jenorton/5643121091/

Photo4Fossil of Eurhinodelphis, an extinct dolphin from Musee d’Histoire Naturelle, Brussels.

Author Ghedoghedo CC3.0

Photo6 A dolphin surfs the wake of a research boat on the Banana River – near the Kennedy Space Center. Author NASA

Photo5 Single breaching orca. Author Minette Layne from Seattle, Washington, USA CC2.0

www.flickr.com/people/[email protected]

Photo7 Hector’s dolphin. Author TBjornstad CC2.5

Photo8 Feeding wild pink dolphins. Author Zemlinki! cc2.0

www.flickr.com/photos/zemlinki/256675975/

Photo9 A Commerson’s dolphin (Cephalarhynchus commersonii) off Argentina. Author Jan Kneschke cc2.0 flickr.com/photos/[email protected]/366160008

Photo10 White-sided Dolphin Skeleton articulated by Skulls Unlimited International, on display at The Museum of Osteology. Author Sklmsta cc1.0

Photo11 Large dolphin rostrums. Author Ryan Espanto cc2.0

www.flickr.com/photos/ryn413/3952952164/

Photo12 Dolphin Anatomy Author WikipedianProlific cc1.2

Photo13 Dolphin with baby – blowhole clearly visible. Jeremy Bradford cc2.0

www.flickr.com/photos/jtbradford/7934949822/

Photo14 Signalman 2nd Class Diver (DV) Harlold Bickford a mammal handler from Commander Task Unit (CTU-55.4.3) brushes the teeth of a Bottle Nose Dolphin. Author U.S. Navy photo by Photographer’s Mate 1st Class Brien Aho.

Photo15 Scarred Bottlenose Dolphin, Cromarty Firth, Scotland. Author Rene

Photo16 Dolphin eating fish at Sea World. Author Tammy Lo cc2.0 www.flickr.com/photos/tammylo/8027939892/

Photo17 Commerson’s dolphins in the Strait of Magellan. Author Miguel Vieira cc2.0

flickr.com/photos/[email protected]/6525826507

Photo18 Bottlenose dolphin (Tursiops truncatus) of the NMMP on mineclearance operations, with locator beacon. Author U.S. Navy photo by Photographer’s Mate 1st Class Brien Aho.

Photo19 Spinner dolphin jumping. Author Magnus Kjaergaard cc3.0

Photo20 A wild dusky dolphin named “Nox”. Author AllenMcC. cc3.0

Photo21 Killer whales jumping. Author Robert Pittman NOAA

Photo22 Huge pod of playful spinner dolphins. Author Steve Jurvetson cc2.0

www.flickr.com/photos/jurvetson/3236211824/

Photo23 Amazon river dolphin. Author Michelle Bender cc2.0

www.flickr.com/photos/-mbender/5354172843/

Photo24 Amazon River Dolphins at Duisburger Zoo. Author Stefanie Triltsch cc2.5

Photo25 Adult female Bottlenose Dolphin with two young at side, Inner Moray Firth, Scotland May 2005.

Author Peter Asprey, www.peter-asprey.com/ cc3.0

Photo26 Northern right whale dolphin. Author NOAA NMFS

Photo27 Photograph of Atlantic Spotted Dolphins off of Long Cay, near South Caicos in the Turks and Caicos islands. Author Bmatulis cc3.0

Photo28 Mother and baby slipstreaming. Author Steve Jurvetson cc2.0

www.flickr.com/photos/jurvetson/3235332805/

Photo30 Baby dolphin. Author snowlepard cc2.0 www.flickr.com/photos/[email protected]/6244058022/

Photo29 Statue of Opo the dolphin. Author Sas Cuyvers

Photo31 Cupid Riding a Dolphin; at the Hermitage. 1st century Roman copy of Greek original. Yair Haklai cc3.0

Photo32 Dolphins performing in a show at Palmitos Park in Gran Canaria. William Warby cc2.0

www.flickr.com/photos/wwarby/8190490359/

Photo33 Hector’s dolphin is found in New Zealand waters. Dr. Mridula Srinivasan, NOAA/NMFS/OST/AMD.

Photo34 Amazon river dolphin. Jorge Andrade cc2.0 www.flickr.com/photos/jorgebrazil/5715500965/