Bottlenose dolphins are well known as the intelligent and charismatic stars of many aquarium shows. Their curved mouths give the appearance of a friendly, permanent smile, and they can be trained to perform complex tricks.

In the wild, these sleek swimmers can reach speeds of over 18 miles (30 kilometers) an hour. They surface often to breathe, doing so two or three times a minute. Bottlenose dolphins travel in social groups and communicate with each other by a complex system of squeaks and whistles. Schools have been known to come to the aid of an injured dolphin and help it to the surface.

Bottlenose dolphins track their prey through the expert use of echolocation. They can make up to 1,000 clicking noises per second. These sounds travel underwater until they encounter objects, then bounce back to their dolphin senders, revealing the location, size, and shape of their target.

When dolphins are feeding, that target is often a bottom-dwelling fish, though they also eat shrimp and squid. These clever animals are also sometimes spotted following fishing boats in hopes of dining on leftovers.

Bottlenose dolphins are found in tropical oceans and other warm waters around the globe. They were once widely hunted for meat and oil (used for lamps and cooking), but today only limited dolphin fishing occurs. However, dolphins are threatened by commercial fishing for other species, like tuna, and can become mortally entangled in nets and other fishing equipment.

All dolphins, including the bottlenose, are porpoises. Although some people use these names interchangeably, porpoises are actually a larger group that also includes animals like the orca and the beluga whale.

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Above:   Boto

Below:  Bottle Nose Dolphin

Dusky Dolphins

REUTERS/Fatih Saribas
Three-year-old Turkish girl Ayse suffering from cerebral palsy touches a dolphin's fin as she is assisted by diver-pedagogue Murat Cicek during a therapy session in Antalya, Turkey June 12, 2005. Children suffering autism or cerebral palsy are treated under the supervision of Dr. Murat Kemaloglu with the help of Murat Cicek and Yusuf Yurdasiper, both divers and pedagogues, in Dolphinland pool in Turkey's Mediterranean coastal city of Antalya. The dolphins are also attractions for visitors to the resort city.

How Dolphins Spin, and Why
[LiveScience 2006-03-27]

[Photo] A spinner dolphin maybe trying to shake a sucker. Credit: Bob Pitman

By Corey Binns

Spinner dolphins work hard to earn their name. In one astounding leap into the air, they can spin around up to seven times. With underwater movie footage and a mathematical model, scientists can now explain just how dolphins manage the acrobatic feat.

Before takeoff, the animal begins its spin underwater.

Using its flippers like wings, it starts a gentle barrel roll. The movement is slow because the dolphin's fin and flippers drag against the water, which adds a lot of resistance.

Try this at home

It's like having your hand in the bathtub, says West Chester University physicist Anthony Nicastro. "You can feel resistance, due to all that water you're pushing around," Nicastro explained. "The dolphin has flippers, a dorsal fin, and other surfaces dragging water. Underwater, they generate 1 or 2 spins per second."

Once a dolphin breaks the surface, everything changes.

As it enters the air, the dolphin sheds all of the resistant forces that slowed it down in the water. And that's when things really get dizzy.

Airborne, the spinner dolphin can make up to seven revolutions in as little as a second.

Previous studies suggested that a dolphin generated the spins by the way it twisted its body, once it broke the surface. "You're not going to spin much at all from a flat jump. It just doesn't make sense in a real world model," says biologist Frank Fish, also from West Chester University.

By using calculus, the mathematical model that Nicastro came up with correctly describes how the spin works. The results were published in the January 2006 issue of the Journal of Experimental Biology.

But why?

Nobody knows for sure why spinner dolphins spin. There could be all kinds of reasons: to display dominance, to communicate their location, to hunt, or just for fun.

It could also be an easy way to shake off fish taking a free ride.

Remoras, fish with dorsal fins that acts like suction cups, stick to sharks and whales. The suckers add extra drag to a dolphin's streamlining, says Fish the biologist. Curious to learn what it felt like to have a remora suck him, Fish stuck one on his back. "They went into my skin—it hurt!" he says.

Dolphins have sensitive skin with lots of nerve endings, so remoras may be an irritant to the animals, Fish figures.

When a dolphin jumps into the air and spins, remoras flail out. And when the dolphin lands on the surface, with a huge splash, it will knock off the pesky pisces.

"If the dolphin weren't spinning, the remoras would stay on. The spinning action is what knocks off the remora," Nicastro said.

The Marine Life Oceanarium in Gulfport training staff member, Shannon Huyser, left, works with a dolphin along with NOAA researcher Jeff Foster, second from left, and Marci Romagnoli, right, in Gulfport Miss., Sept. 15, 2005. The dolphins were washed out of the Oceanarium's tank during Hurricane Katrina. More than a dozen dolphin evacuees from Hurricane Katrina are on their way to their new home in a luxury resort in the Bahamas. The dolphins used to live at the Marine Life Oceanarium in Gulfport. (AP Photo/Steve Helber, File)

Dolphins Name Themselves
[LiveScience 2006-05-08]

[Photo] The dolphins are being fed from a boat. Credit: Marine Life Oceanarium


A high-pitched "wee-o-wee-o-wee-o-wee" whistle might not sound like much to you, but it's exactly how a dolphin might introduce itself.

Because sight is limited in the ocean, dolphins create individual "name" calls to communicate their whereabouts to friends and families.

But it's not as simple as just recognizing a voice, as with most animals. A new study reveals that the calls contain frequency changes that dolphins recognize.

Digital dolphins

Humans are one of the few animals that use sound modulation instead of simple voice differences to identify individuals. For example, a person can recognize the name "John" whether it's being said by Gilbert Gottfried or James Earl Jones.

Scientists have long known that dolphins identify themselves with names, but the belief was that, like some monkeys, the animal's voice was the key ingredient of the call.

A team of researchers led by Vincent Janik of the University of St. Andrews in Scotland temporarily captured seven male and seven female bottlenose dolphins in Sarasota Bay in Florida. Janik and his crew recorded the name calls of each dolphin, and digitally removed the voice features of each call.

They then played the computerized calls and digital versions of other random calls through underwater speakers where the dolphins were held.

In nine of 14 cases, the dolphin would turn more often toward the speaker—an established technique for gauging a dolphin's interest—if it heard a whistle resembling the name of a close relative.

"Every dolphin has its own voice," Janik told LiveScience. "But we removed those features and showed that the animals are actually paying attention to the modulation and not the voice."

Naming game

A dolphin chooses its own name as an infant and uses it throughout its life.

"It seems like the animals hear what's around them, and then they make up their own whistle," Janik said. "They either develop something original ... or they base it on parts of the whistles around them."

Regardless of the method, the young dolphins want to make their call stand apart from the calls of their closest relatives. Communicating by sight is difficult underwater, so dolphins use these calls to let other dolphins know they're nearby. A dolphin will also call out its name if it's lost and distressed, hoping relatives will come to its aid.

Dolphins are some of the most talkative animals around, even though we don't know what they're saying.

"Their repertoire of calls probably numbers in the hundreds," Janik said. "Some of them are food calls, but for most of them we have no ideas what they're for."

The study is detailed in this week's early online edition of the journal Proceedings of the National Academy of Sciences.

Source: LiveScience - http://www.LiveScience.com

[Photo] Toadfish can eavesdrop on the calls of dolphins to avoid getting eaten. Credit: Midge Marchaterre

Fish can eavesdrop on the calls of dolphins to avoid getting eaten, a new study suggests.

"Probably a lot of fish can do this," said lead researcher Luke Remage-Healey, a behavioral neuro-endocrinologist at University of California, Los Angeles.

A bottom-dwelling fish found off the coast of Florida called the gulf toadfish is prime prey for dolphins, which often listen to toadfish calls to find their targets. In fact, 80 percent of bottlenose dolphin diets containing sound-producing fish. But whether the toadfish peels its “ears” toward dolphins has remained a mystery.

Remage-Healey first suspected that gulf toadfish could listen in on hungry dolphins' calls two years ago while recording the mating calls of the male toadfish off the Gulf coast of Florida.

"Then, they all stopped calling," Remage-Healey recalled. "My field assistant noticed dolphins foraging right over the toadfish site, and we heard we were recording dolphin sounds instead."

The researchers captured toadfish and placed each in its own cage and rested the cages on the seabed in the breeding patch. From underwater speakers, they played recordings of snapping shrimp sounds or dolphin sounds — both high frequency "whistles" that dolphins use to communicate with each other, and low frequency "pops" likely used to locate a quarry. The shrimp sounds mimicked a common background noise in the bay.

Results showed that the toadfish ignored the snapping shrimp sounds and dolphin whistles and continued on with their mating calls. But when the fish heard dolphin pops or combinations of pops and whistles, they drastically reduced their calling rates.

Prior research revealed toadfish hear low frequency sounds best, consistent with the drastic response to the recordings of low frequency pops.

As confirmation, measurements of toadfish blood taken immediately after the dolphin sounds were played revealed that levels of the stress hormone cortisol shot up after they heard pops.

Remage-Healey, Douglas Nowacek of Florida State University and Andrew Bass of Cornell University in New York report their findings in the Nov. 15 issue of the Journal of Experimental Biology.