April 21, 2013 The Incredible World of Dolphins
I’ve watched many dolphins from the Malibu shoreline lately. They are playful, affectionate, curious, intelligent, social and vocal. Are they the creatures humans would have been had we not left the water?
Dolphins are aquatic, top-predator mammals classified as a type of whale or cetacean. There are two types of cetaceans. Baleen whales filter massive amounts of small oceanic organisms, called krill, with comb-like sieves in their mouths. Toothed whales, on the other hand, grab prey with their teeth. Dolphins and their mistaken twin, the porpoise, are a type of toothed whale. There are about 70 kinds of toothed whales, and about 45 species of dolphins, porpoises and false whales, such as killer whales or orcas.
Dolphins are miraculously adapted to murky rivers, as in the Amazon River dolphin, shallow coasts like Hector’s dolphins of New Zealand or in massive packs of 10,000 bottlenose dolphins roaming the open oceans.
Like humans, dolphins are exceptionally tactile creatures and their skin conveys different levels of information or signals to each animal. Excellent sight enables them to see in the dark, while their range of hearing is 10 times that of humans. They keep the kids in line: Adult dolphins discipline their misbehaved juveniles by driving them to the ocean floor and momentarily holding them there.
Dolphins are innovative when faced with a new scenario or situation. This goes beyond genetic programming of behavior. Innovation allows rapid assessment of a new situation and reactions to it. Dolphins clearly understand gestures, similar to sign language that chimpanzees are also able to learn. Humans and dolphins appear to be the only known animals to spontaneously interpret images on a screen without prior teaching. Dolphins are capable of highly flexible behavior, and therefore are considered intelligent.
Moreover, they’re individualists. Each animal has its own signature whistle, which is used to keep in contact with its peers.
Dolphins constantly send out noises called “click trains” which sound, to the untrained ear, like old creaky doors. These complex series of sounds are the most sophisticated, advanced forms of sonar, called echolocation, and are unrivalled by anything on the planet—man-made or otherwise. As the sonar waves move through water they encounter objects, bouncing back shapes and contents to be deciphered by the dolphin’s large brain (which is bigger than a human’s). Sometimes the sonar is so potent it actually stuns its prey.
Dolphins are able to quickly shift their food-gathering techniques by either hunting alone or in larger groups that herd shoals or bait balls of schooling fish. Killer whales, the largest of the dolphins, teach their young how to hunt sea lions, seals and porpoises by herding and then isolating them.
Like crows and ants, dolphins use tools to assist when foraging. In Australia, bottlenose dolphins scour the ocean bottom using echolocation and probing their nose or rostrum up to 30 inches into the floor. But in order to protect their nose and face from spines and stingers, they wisely use a sponge while hunting for buried bottom-dwelling fish.
Most fish tend to move sideways like the sinuous movement of a snake. Dolphins and other whales, on the other hand, move up and down as their strong bodies flex like a bounding deer. Incredible strength comes from their tail or fluke, which is horizontal rather than vertical.
Plus, dolphins are a well-rested bunch, sleeping as much as one third of each day. But how do they do this when their predators are always hunting them? The answer is teamwork. Dolphins usually rest in groups that bunch tightly together. One lazy eye per dolphin remains open and, although asleep, their slow methodical echolocatory clicks scan their environment for sharks and other predators. The group essentially forms a sensory integration system of relying on each others’ sonar system to detect any trouble while they rest.
Scientists have been able to listen to cetaceans with special underwater sound equipment called hydrophones. And the renowned OrcaLab on Hanson Island in British Columbia’s Johnstone Strait has been studying intelligence 24/7 for the past 20 years. They record and track many pods off the west coast of Vancouver Island and know each killer whale by its signature whistle. These complex, exquisite creatures share common fishing grounds and belly-rubbing rituals on shallow pebble beaches, escort other pods through the strait and gather with an intricate timeless symphony of undecipherable dialects that plays underwater along the southwest coast of British Columbia.
However, despite their wonderful architecture, dolphins have suffered just like other sea creatures from the presence of humans. Overfishing, marine and agricultural pollutions, and plastic bags clogging intestines have all taken a deadly toll on dolphins. Even today, some countries still allow the use of 40 mile-long drift nets that senselessly kill all life in its wake, including cetaceans.
From 2010 to 2012 more than 700 dolphins have turned up dead in the Gulf of Mexico, washing up along coastal Louisiana to Texas through to Florida. From February to April of this year alone, more than 800 dead dolphins washed ashore in Peru.
Clearly these exquisite top-predators are telling us something is very wrong. Whether the toxicity is bacterial, man-made chemicals or geo-chemical sound-induced exploration (which there is sufficient evidence from at least a dozen necropsies), we must not continue to desecrate our oceans and all life within.
Wild dolphins, like all other animals, including humans, are entitled to the right to life on our blue planet.
Text © by Dr Reese Halter 2013. All rights reserved.
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