Dolphin Trivia, Part II

After yesterday's depressing post about the Chinese Yangtze River dolphin going extinct, I thought it'd be nice to wrap up the year on an "up" note.   So, in continuation of my previous installation of dolphin trivia, here's Part II:

  • Dolphins are bald — their skin contains no hair follicles, sebaceous or sweat glands. &nsbp; Their skin is 10-20 times thicker than human skin and is lined with hydrodynamic ridges that allow fast dynamic swimming.
  • Dolphins can sunburn easily and will often take advantage of shade to protect themselves.
  • Dolphins move their eyes independently (similar to a gecko lizard) which allows them to see from different angles at the same time when hunting or watching for predators.
  • Dolphins have a "chambered" stomach.   The forestomach does the mechanical breakdown of whole food.   Their conical teeth are only used to grasp (not chew) food.
  • Since they lack an olfactory nerve, dolphins have no sense of smell.   They do have a sense of taste, however, and often show personal preferences for certain kinds of fish.
  • Dolphins don't have vocal cords.   Instead, they use the muscles inside the blowhole produce squeaks, clicks, moans, warbles & other communicative sounds.
  • Dolphin mothers often whistle continuously for several days after giving birth.   Initially, the mother's whistle is uniform, but then it acquires a "signature" characteristic.   Scientists believe this is how she teaches her offspring its name.

Baiji Dolphin Deemed Extinct

The Baiji white Chinese river dolphin is now considered extinct.

Following 6 weeks of scouring a 3,400-kilometer segment of the Chinese Yangtze River, an expedition of 30 international researchers led by Swiss naturalist August Pfluger has declared that the Baiji, a rare white freshwater dolphin is effectively extinct.

Although there were several thousands of these dolphins fifty years ago, a 2004 report from a conservation workshop concluded that the number of Baiji in the river had declined rapidly since the 1970s.

Whereas fewer than 400 of the dolphins were reported in the mid-80s, a follow-up survey in 1997 recorded only 13.

Illegal overfishing and pollution from busy ship traffic are also considered culprits, but the construction of large dams is credited as the greatest contributor to the Baiji dolphin extinction and an ongoing threat to other marine life in the Yangtze river basin.

Scientists believe this to be the first instance of a cetacean species being pushed to extinction due entirely to human action. Wonder how many more species we’ll extinguish before wising up…

Gossip, Gossip, Gossip!

Dolphin couple gossiping

Oh, they saw us coming…   They drew us right in with their always-chipper smiles, perky chatter, and eternally-friendly dispositions.   We’ve been lulled into thinking of dolphins as our joyful & genial cousins in the sea.   But those sly devils had us fooled all along.   You see, dolphins are simply not to be trusted because, well… they gossip!

Not too long ago, I posted a blog entry about a group of Scottish researchers who had proved that dolphins have names.   Well, according to Bruno Maddox’s wry commentary in a recent Discover magazine article, the Scots have since gone on to show:

[Dolphins] gossip.   We know this because we know their names.   Each bottlenose individual identifies itself by a unique pattern of whistles and clicks.   What was not known until the Scottish research, however, is that a pair of dolphins use the name of a third dolphin when that third dolphin isn’t present.   In other words, dolphins gossip.

So, it’s not bad enough that our aquatic cousins are busybodies, but they’re rumormongers, too.   And just when we were starting to think they might truly be the superior species…
 

Dolphin Intelligence, Revisited

Despite recent half-baked claims to the contrary, it is widely accepted that dolphins are very smart. This is largely based on an estimation of brain power derived from the brain size to body size ratio or “encephalisation quotient”. Dolphins have an EQ that’s second only to humans. Although that’s certainly a compelling argument for brainpower, scientists have begun to adopt the view that behavior is an even more accurate measure of intelligence within a species.

And with that in mind, it seems like new, exciting dolphin behavioral discoveries are cropping up every few months lately that support an even greater estimation of dolphin intelligence. Nova Spicack’s interesting article “Dolphins are Smarter Than We Think” points to recent discoveries where dolphins have a sense of the future and are able to delay gratification.

Pierce Brosnan Is Saving Whales

A few years ago, Dede & I had the pleasure of seeing MacGillivray Freeman’s "Dolphins" at an Imax theatre in San Diego.   The film features narration by Pierce Brosnan, an awesome soundtrack of Sting’s jazzy songs & music, and strikingly beautiful visuals that live up to the Imax standard.   We loved the film so much that we bought the DVD and have watched it easily half a dozen times.

Apparently though, Pierce Brosnan didn’t just lend his talents to the film for a paycheck.   Nope, far from it.   Brosnan, together with his wife Keely Shaye Smith, is a environmental activist leader with a particular dedication towards marine ecology issues.

A tidbit on Ottmar Liebert’s blog pointed me to Pierce Brosnan’s official website where there’s some good info on his efforts with The Whaleman Foundation.   Together, they’ve launched a "Save the Whales Again!" campaign:

Most people believe that the whales were saved because of the very popular "Save the Whales" movement of the Seventies…   Unfortunately, dolphins and whales face even more threats today than ever before from toxic pollution, noise pollution, global warming, loss of habitat, lack of food, over-fishing, entanglement & ship strikes, and expanding whaling.   The "Save the Whales Again!" campaign is getting the truth out to the masses, in an effort to re-ignite the passion of the earlier "Save the Whales" movement.

Speed Is Skin Deep, Too.

speed limit sign in the waterAccording to a recent article on PhysOrg.com, dolphins were astounding us with their extraordinary swimming speed (nearly 25 m.p.h.) even as early as 350 B.C. when the Greek philosopher Aristotle marveled at their swiftness.

English zoologist Sir James Gray concluded in 1936 that, given the density of water and the amount of muscle dolphins have, the energy needed for a dolphin to swim so fast is nearly 10 times that which they can produce — an observation known as "Gray’s Paradox."

Gray theorized that to achieve this impossible feat the powerful motion of the dolphin’s tail must cause water to attach tightly to the dolphin’s skin due to a concept called "laminar flow," which eliminates turbulence.   Any moving object splits the medium through which it passes.   This turbulence increases friction, and thus drag.

Scientists searched for years for an answer to Gray’s Paradox — what mechanism stops the turbulence and allows for the dolphin’s seemingly impossible energy output?

Although it took several decades, his calculations were ultimately proven flawed because Sir Gray’s conclusions about the amount of energy output needed were based on sprinting speeds that dolphins can’t sustain.   But despite those flaws, scientist Frank Fish of West Chester University credits Gray’s Paradox for having brought about tremendous research focus on marine propulsion.   A number of mechanical factors have been discovered that all contribute to the ‘secret’ of the dolphin’s speed.

Most notably, this speed is made possible by the tapered body shape with ears, eyes, and blowhole that are flush with the skin.   Dolphin’s eyes, researchers say, secrete a mucus that lubricates skin surfaces for increased swimming speed.   This streamlined shape combined with large, powerful muscles that are mechanically linked to an oscillatory pair of crescent-shaped tail flukes enables dolphins to produce thrust with far greater efficiency than any man-made propulsion system.

Also part of the secret is the dolphin’s blubber, which is far more than simple fat.   Instead, dolphin blubber consists of a complex of fat cells and collagen fibers in a elastic criss-cross pattern that acts as a spring.

Other recent research highlighted in Discover magazine has revealed that dolphins constantly shed, replacing their entire outer layer of skin every two hours.   And while water flowing across the skin forms tiny vortices, the flakes of constantly shedding skin disrupt the vortices and dampen turbulence.

Yet another article at ThinkQuest offers insights about small folds in the dolphin’s skin, called dermal ridges.   These ridges run parallel to the length of the dolphin’s body and are constantly moving which goes to further allow the dolphin to propel effortlessly through the water.
 

Dolphin Names

Not content to simply do amazing things like sing, play games, or snoop on each other, now scientists have discovered that dolphins are now taking away yet another trait previously thought to be unique to humans — dolphins have names.

According to an article by Bjorn Carey published on MSNBC:

Humans are one of the few species 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.

A team of researchers led by Vincent Janik of the University of St. Andrews in Scotland has established that a dolphin will choose its own name as an infant and use that name throughout its life.   While scientists have long known that dolphins identify themselves with names, they had previously thought the animal’s unique voice to be a key ingredient of the call.   They’ve now discovered that dolphins recognize their names as patterns of variations in vocal pitch – rather than the voice itself.   Having (and using) names based on sound patterns rather than just a unique voice signature, is a behavior that had been thought to be common only to certain monkeys & humans.

Updated:   You can read additional coverage of this at the Times Online website.
 

Dolphin Eavesdroppers

dolphin pod

Scientists have long known that dolphins use short, broadband pulses of sonar-like echolocation sounds to create a three-dimensional acoustic picture of their surroundings and determine the size, shape, direction of movement and distance of objects in the water. Dolphins’ sonic imaging is so sophisticated that they can tell apart 2 small disks only 1/16th inch thick of differing metals. And since sound penetrates organic matter, there are even stories of dolphins detecting—and reacting to—human pregnancies! Recent research has also proven that they’re capable of listening in on and interpreting the echoes from another individual’s clicks.

Now a study conducted by Thomas Götz, a marine biologist at the University of Tübingen in Germany, takes this yet another step further. According to an article from National Geographic

Dolphins are eavesdroppers!

Götz’s study offers convincing evidence that not only are dolphins capable of understanding each other’s echolocation signals, but in fact they rely on this. The sole sound emissions of a lead dolphin are listened to & used by the all of the others when moving in tight, synchronous groups for cooperative food hunting strategies.

So, where before dolphins have always been considered playful and inquisitive animals, maybe now we know the truth behind their friendly facade… they’re just plain nosy!

Dolphins Get Connected

Vodafone, Ireland’s leading mobile phone service provider has teamed up with the Shannon Dolphin and Wildlife Foundation on Soundwaves, an innovative project that is establishing a hydrophone system in the Shannon Estuary. The Shannon Estuary is Ireland’s first marine Special Area of Conservation (SAC) and home to nearly 150 resident bottlenose dolphins.

SDWF’s Soundwaves system will transmit the underwater vocalizations of dolphins in the estuary, via cellular phone network, to a land station and will significantly enhance the current boat-based monitoring performed by dolphin conservationists.

Wonder if those Irish dolphins have to worry about “Anytime Minutes?” Dede has this vision of that annoying Verizon guy gurgling, “Can you hear me now?” underwater.

Dolphins & Humans – Fishing Buddies

In the resort town of Laguna in southern Brazil: a pod of bottlenose dolphins has developed a cooperative technique to herd mullet towards local fishermen.   The dolphins drive a school of fish towards the men, who cannot see the fish in the muddy, shallow water.   Relying on the dolphins’ cue, a conspicuous roll just out of net range, the fishermen cast their nets.   Those mullet missed by the fishing nets are momentarily disoriented, making them easy food for the well-positioned dolphins.

The dolphins were not trained for this behavior — in fact, the activity is initiated and led by the dolphins.   The fishermen don’t cast their nets until signaled to do so by their aquatic partners.   Town records indicate that this almost-daily collaborative partnership dates back to at least 1847.

As cited in the interesting paper, “Dolphins and the Question of Personhood”, marine researchers consider this further evidence that dolphins make conscious choices and thus should be considered sentient persons.