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Dolphin intelligence

How intelligent are dolphins?

A growing body of scientific research is revealing that dolphins and whales have intelligence and culture more sophisticated than humans have previously assumed. According to Dr Diana Reiss, one of the world's foremost experts on cetacean intelligence, the last few decades of research tell us that dolphins are fully conscious, creative, highly communicative animals with complex inner and social lives, and an intelligence rare in nature. Indeed, in some respects, it surpasses our own. "I've worked closely with dolphins for 35 years," Dr Reiss says, "and I can tell you that they have an intelligence which I revere".

Take, for instance, Kelly, a female dolphin at the Institute for Marine Mammal Studies in Mississippi. Dolphins at the institute have been trained to keep their pool clean by collecting floating litter and passing it to a trainer. When dolphins turn in rubbish, they are rewarded with fish.

But Kelly has devised a novel way to make sure she is paid top rates for her litter collecting work. When Kelly finds a piece of paper in her pool, she swims it down to the bottom and hides it underneath a rock. When a trainer passes by, she swims down to the rock, tears off a small piece and takes it to the trainer. Once she has been rewarded with a fish, Kelly swims down and rips off another small piece of paper and takes it straight back to the trainer for another fish!

And indeed, this is not Kelly's only innovation. One day when a bird flew into Kelly's pool, she collected it in her mouth and gave it to a trainer, for which she was rewarded with a generous serving of fish. The experience seems to have sparked an idea, as the next time Kelly was given a fish, she did not eat it as usual but took it to the bottom of her pool and hid it under the rock where she would normally hide pieces of rubbish. Later, when no trainers were present, Kelly brought the fish to the surface and used it to lure birds overhead, which she grabbed and delivered to a trainer in return for another generous serve of fish. Having proven to be highly profitable, Kelly taught her bird baiting strategy to her calf, who in turn taught the other calves in the pool.

While such inventiveness and forward planning suggests a high capacity for reasoning, we don't yet know how intelligent dolphins really are. As dolphins evolved in an aquatic environment unlike our own, dolphin brains were naturally selected for different functions to those human brains were selected for, with different cognitive abilities favouring life in the sea rather than on land. As dolphin intelligence is likely to take forms not directly comparable to our own, it is difficult for scientists to know how to test the intellectual abilities of dolphins, or even which abilities should be tested.

Scientists approached the question of intelligence in animals early on by looking at the physical structure of the brain. Large brains, particularly a large cerebral cortex, are associated with higher intelligence, and an adult bottlenose dolphin has a brain about 25% heavier than the average adult human brain (with 10-40% more neurons). Sperm whales have the largest brains of all animals, but, scientists thought, this brain might be required to operate the whale's vast body, rather than for particularly sophisticated cognitive functions. So they developed another measure of intelligence, the "encephalization quotient" (or EQ), which measures the ratio of an animal's brain and body size relative to other similarly sized animals. According to this measure, dolphins rank immediately below humans, and above our closest relatives, the other great apes (indeed, the EQ of a bottlenose dolphin is more than double that of, for example, a chimpanzee). The problem remains, however, that we don't know enough about the functioning of the brain to be sure of how these anatomical measures equate to intelligence. Most scientists are now of the view that behaviour is a more reliable guide for understanding the intelligence of species.

One of the most interesting behavioural tests conducted with dolphins is the mirror self-recognition test. As pet owners reading would likely confirm, dogs and cats do not seem to recognise, or demonstrate any interest in, their own reflections. In contrast, dolphins understand and are fascinated by their reflections. In the footage below, Presley, a dolphin at the New York Aquarium who has just been exposed for the first time to a mirror, is behaving as a human child might on making the same discovery. He is making deliberate movements to test whether these are copied in the reflection. The researchers have drawn a black mark on Presley's head, and he can also be seen orientating his body to view the mark in the mirror, indicating that he knows the mark is on his body, and not only in the reflection.

The ability of dolphins to recognise themselves, as Presley does, indicates that they possess self-awareness, which is thought to be a precursor to advanced thinking processes normally associated with humans (incidentally, dolphins are interested not only in reflections, but also in watching television. As part of the BBC's "Dolphins – Deep Thinkers?" programme, presenter David Attenborough was beamed to Akeakamai the dolphin, who watched him on an underwater television screen. Not only did Akeakamai respond correctly to Sir David's sign language, she also attempted to imitate him).

Pilot Whale
A pilot whale approaches an underwater photographer, fascinated by its reflection in the camera lens. Image courtesy of Rory Moore

In the wild, dolphins live in complex societies with many features that resemble human societies. For instance, female friends help out by "babysitting" each other's calves. Young males tend to hang out together in pairs, while calves stick very close to their mothers. Recent observations of dolphins refusing to abandon the bodies of dead family members have led scientists to suggest dolphins are capable, like humans, of experiencing grief at the loss of a friend.

A mother carries her dead calf on her back. Video length = 1:43

Also like humans, dolphins have developed sophisticated forms of cooperation to master their environments. In the video below, dolphins in the waters off Florida are seen working together to catch fish. A lead dolphin swims in a circle beating its tail, creating a sandy wall around a school of fish. When the fish try to jump over the wall, the rest of the dolphins rush in and catch them in their mouths.

Dolphins invent unique strategy of hunting using rings of mud. Source: BBC Video length = 2:03

Feeding strategies vary greatly across different dolphin populations. For example, in Galveston Bay in Texas, bottlenose dolphins do not form sand rings, but rather take advantage of passing fishing boats, skillfully wriggling in and out of their nets to steal captured shrimp. In Shark Bay off Western Australia, dolphins forage for food using sponges they rip from the seafloor to protect their sensitive beaks. Interestingly, the use of sponges as tools is taught to calves by their mothers, providing scientists with the first hint that dolphins may have cultures.

In order to have such complex societies, dolphins need a method of communication, which they achieve through a series of complex whistles and clicks - their own language. If you watch the video below, you can imagine what it is like to swim amongst a pod of dolphins communicating with each other. As of yet, we have not been successful in decoding what dolphins are "saying", or determining to what extent they have a language resembling human languages. We do know that their communication system is sophisticated, and that they are able to use syntax (they comprehend past, present and future tense, and understand the significance of the order of words in a sentence).

Courtesy of BlueVoice.org. Video length = 1:32

Dolphins also have the capacity to learn human languages, with some dolphins in captivity capable of understanding several thousand English sentences. This may not seem like a lot relative to the unlimited number of sentences humans can construct, but as the American astrophysicist Carl Sagan famously pointed out, it is interesting to note that no human has been reported to learn even a single sentence of "Dolphinese".

It is tempting to put dolphins' ability with human languages down to their ability to memorise sentences, much like a dog who has been taught several sentences by a trainer. But dolphins appear to be able to comprehend English sentences even when new elements are introduced or the word order is shuffled, indicating that they genuinely understand what is being said to them.

Another hallmark of intelligence in a species is the ability to flexibly solve problems, and in this regard dolphins are again impressive. It may seem to us that dolphins live relatively carefree lives cruising in the surf, but imagine the dolphin facing the issue of a stubborn moray eel who won't come out from the crevice it is taking cover in. Researchers have observed a dolphin inventively solve just this problem by killing a scorpion fish and using its spiky body to poke the eel until it reluctantly exited its hiding place.

As is well known, dolphins often channel their creativity into entertaining themselves. Dolphins have developed, for instance, many different ways of creating bubble rings to play with and each dolphin seems to have a style it prefers. At SeaWorld in Orlando, dolphins taught themselves to create perfectly vertical bubble rings by angling their heads in a particular way and blowing a puff of air out of their blowholes. Bayley, a dolphin at the National Aquarium in Baltimore, prefers to create bubble rings by kicking the water with her tail. Shiloh, on the other hand, likes to blow two bubbles at once. When one meets the other, they create a hoop, which she swims through. Such games, which require advanced planning, tell us that dolphins are capable of thinking about the future.

The ability to blow bubble rings may seem insignificant relative to the civilisations humans have built. But, as Swedish biological scientist Karl Erik Fichtelius points out, the assumption that other large-brained mammals do not measure up to humans in intelligence because they have not developed a culture equivalent to our own is a superficial one. After all, our species has had its large brain and its potential for probably 250,000 years – a blink on the evolutionary timescale – and only suddenly began cultivating the soil and developing a written language, with the rapid acceleration in technology this brought, perhaps 10,000 years ago.

Essential to the relatively recent development of human civilisation has been our ability to preserve information from generation to generation through the use of tools such as the printing press. The development of our hands gave us an enormous advantage in the use of such recording tools. Dolphins, in contrast, evolved in an environment which favoured a streamlined body over dexterity. Is it possible that dolphin civilisation could, like in the case of humans, take off if only dolphins had hands?

That dolphins do not have a civilisation similar to human civilisation is clearly not proof that they don't have a comparably high intelligence. But do they? Scientists don't yet know, but what they do say is that, from the evidence we have, dolphins deserve their reputation for being highly intelligent, and for having complex personalities and social bonds.

We certainly know enough to say that dolphins, like other feeling creatures, deserve our protection from suffering.

Why does intelligence matter in regard to dolphin hunting?

Dolphin hunting is an unfortunate practice because it causes suffering - you would probably agree that if it were perpetuated on unfeeling objects, we'd have no cause for concern. The first thing we think of is the physical pain, and we know dolphins, like other mammals, have developed nervous systems and can feel pain similarly to the way we do.

So even if dolphins weren't known to be especially intelligent, dolphin hunting would be unacceptable on the basis of the physical pain it causes. However, that they are so advanced, with complex thoughts and language and friendships, may add a further psychological element to their suffering.

For instance, if dolphins are able to think about the future – which it seems that they are – they may be able to anticipate what is coming during the several days they are trapped before being slaughtered. If this is the case, the capture period would presumably be one of terror for the dolphins.

The social complexity of dolphins introduces the likelihood that dolphins suffer from witnessing the mistreatment of other dolphins with whom they share a social bond. If scientists are correct, for instance, in suggesting that mother dolphins can grieve the death of their calves, then we should consider that mother dolphins could suffer enormously when they see their calves ripped from them and brutally slaughtered before their eyes.

The ability of dolphins to communicate with each other also potentially enhances their suffering beyond physical pain. For instance, at the time of the slaughter, dolphins are lined up next to each other in close proximity (a practice which would not be allowed in any modern slaughterhouse in the developed world). The dolphins can be heard whistling to each other over the sounds of thrashing animals during the slaughter. What if they are able to communicate to each other the level of pain they are experiencing, or tell the next dolphin in line what is coming?

To reiterate, even if dolphins were not particularly intelligent or social, their capture and slaughter would still cause them extreme distress and physical pain. That their suffering might be enhanced beyond even this is just another reason why dolphin hunting has to be brought to an immediate and permanent end.

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