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Why Dolphins Are the Second-Smartest Creatures on the Planet

These big-brained marine mammals are chatty, playful creatures that we humans find it easy to identify with, but scientists are just starting to understand everything that they're capable of.

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tursiop dolphin portrait detail of eye while looking at you from oceanAndrea Izzotti/Shutterstock

They have big brains

Members of the dolphin family—which includes dozens of species, including familiar bottlenose dolphins and killer whales—have the second-largest brain size relative to body size, after humans, says Richard C. Connor, a professor in the biology department at the University of Massachusetts Dartmouth. “Big brains are very expensive energetically,” he says. “They cost a lot so they have to be doing something important.”

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Group of cute smart dolphins in the oceanNataSnow/Shutterstock

They talk to each other

Dolphins have an elaborate system of clicks and whistles that they use to communicate with one another, Connor says. “They produce clicks for their remarkable sonar, but for social communication, they have highly modified click trains, which to our ear sound like growling, screaming, and squeaks.” He adds that while researchers don’t know what most of these sounds mean, a population of male bottlenose dolphins he’s been studying in Shark Bay, Western Australia, for the past three decades makes a specific low-frequency click pattern called “pops” to herd females.

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Dolphins swim in the poolPshevlotskyy Oleksandr/Shutterstock

Dolphins have names for each other

Dolphins have “signature whistles” that function as identifiers, shares Jason N. Bruck, a teaching assistant professor of biology at Oklahoma State University. “We know that dolphins have these because when they separate from each other they will start to produce the signature whistles at high rates,” he says. “This is how they rejoin their social groups.” What’s more, Bruck’s research has recently shown that dolphins remember other signature whistles for as long as two decades. “That’s the best memory seen so far in a non-human animal,” Bruck adds.

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dolphin portrait detail of eye while looking at you from oceanAndrea Izzotti/Shutterstock

They might be able to communicate with humans

We know dolphins can learn to interpret detailed commands from trainers, but that’s not so different from what dogs or sea lions can do, says Bruck (who adds that his lab has even trained a crab to follow cues for food). But he says that some scientists are using underwater speakers to play dolphin sounds back to them in an attempt to understand their communication better. “In some ways, this represents our best ability to communicate with dolphins under their terms,” he says.

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dolphin family swimming, underwater shotbluehand/Shutterstock

They cooperate to hunt

Because it can be tricky to swim after a single fish and catch it, dolphins often cooperate to get fish to clump together. “They will work together to corral fish into a ‘bait-ball,'” Bruck says—when the fish are congregated in one place, they’re easy prey.

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Man hand touch a dolphinNataSnow/Shutterstock

They’ve been said to help humans in distress at sea

Connor says the most interesting story he’s heard involved a human who wasn’t really in trouble. A group of false killer whales floating in a shallow area stayed packed together except when a snorkelling oceanographer came near them. “Three times, a flanking whale broke off and pushed him to shore,” Connor says. “Without the snorkel, they did not. He thought the snorkel may have made it sound like he was having trouble breathing.”

Bruck says a wise researcher cautioned him about assuming dolphins always have good intentions toward people. “While you might hear from the people dolphins rescue, one wouldn’t necessarily hear from the people that dolphins drag out to the middle of the ocean.”

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dolphin underwater portrait while looking at youAndrea Izzotti/Shutterstock

Dolphins have passed the “mirror test”

Only a few animals recognize their own images—researchers test them by marking their bodies in a place they can’t see without a mirror. Species that pay attention to the mark or try to touch it are thought to be aware that they’re looking at themselves. The New York Times recently described an experiment showing that young dolphins got interested in their reflections as young as seven months (that’s earlier than human babies, who typically pass the milestone around 12 months), and tried to get a better look at the mark on their bodies at two years old. But what does it really mean? “The trouble with the mirror test in dolphins is that they do not have hands to wipe off markings on their face like chimps do,” Bruck says. Connor agrees that the mirror test isn’t particularly useful: “There is no evidence it demarcates a key cognitive boundary like ‘self-awareness,’ and it has no relevance to their lives in the wild,” he says.

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Seascape of coral reef / Caribbean Sea / Curacao with big tube sponge and various hard and soft coralsnaturepics.li/Shutterstock

They use tools

Much like apes use sticks to dig insects out of the ground, dolphins sometimes grab an implement to help them access food sources. “Dolphins in Australia have been shown to use sponges to dig for flatfish in the sand,” Bruck says. “It is a behaviour passed down the generations and some dolphins even have a preferred sponge that they use repeatedly.”

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Sea Grass Background UnderwaterRich Carey/Shutterstock

They play with seaweed as a toy

Dolphins are playful, too. They often joy-ride the bow waves of passing boats and have been observed passing seaweed back-and-forth, or moving it from their beaks to their flippers to their tail fins. “Play in many species releases neurotransmitters and neurohormones in the brain that feel good,” Bruck says. “There may not be more meaning than that.”

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Two cute dolphins smimming in the blue ocean over the coral reef, selective focusvkilikov/Shutterstock

Dolphins appear to mourn their dead

Recently, an orca was observed carrying her dead calf through the water for 17 days before she gave it up. “Many in the press and even some scientists treated this as conclusive evidence of grief in whales and dolphins,” Bruck says. “I remain skeptical. Dolphins have a rough first day of life. They have to be born, swim to the surface and take their first breath. Mom will often help steer her calves during this difficult task. Because whale moms invest so much in gestation, this long-term carrying behaviour might not really be grief but rather the dolphin stuck in a loop, unaware their calf is really dead.”

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Spinner Dolphins Mauritius Indian Ocean Summer Stenella longirostrisChristopher Berthelot/Shutterstock

They have a complicated social structure

It’s easy to anthropomorphize dolphins because of their cleverness and playful nature, but researchers say that their social networks are probably the way that they’re most like us. Among the Shark Bay dolphins Connor has been studying in Australia, there are three levels of alliances among males: At the most basic level, the dolphins swim in consistent pairs or trios to herd females; the second-order alliances happen when these pairs gang up with other small groups; and after tracking the animals for decades, Connor and his team discovered that there was an even larger group dynamic at work, evident from the ways males move into and out of their first- and second-order alliances. “Our studies in Shark Bay have revealed the most complex non-human society on the planet,” Connor says. “The only other species with three levels of alliances within a large social network is humans.”

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Dolphin SwimmingPaula Cobleigh/Shutterstock

Their complex social systems make their intelligence similar to ours

These social networks might explain why dolphins have such large brains. “Many people think that the largest brains evolved because of benefits they provided in the social realm, as individuals need to cooperate with those they are also in reproductive competition with,” Connor says.

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Dolphin Swimming at Sri Lanka South Sea'sUdaynga Lakmal/Shutterstock

Comparing intelligence across species is probably not productive

Scientists don’t really rank animal intelligence, Bruck says: “Rather, we look for how animals perform on certain tasks and relate those results back to why they may have evolved those skills.” For example, chimpanzees have remarkable short-term memories and can beat humans in testing situations. “Being good at thinking and remembering things quickly makes chimps more likely to survive,” Bruck says. Likewise, pigeons are much better than humans at mastering tasks of spatial rotation, because it’s a skill they need to navigate in flight.

But the types of intelligence that impress us humans most are those we can directly relate to. “Dolphins, elephants, some apes, hyenas, crows, ravens, and parrots all have an intelligence we can easily identify with,” Bruck says. “That’s why we think they are smart. We see ourselves in them. They actually share our social system, where social groups are fluid and brain-power is needed to keep track of social partners and complex relationships.” Dolphins also do one not-so-great “human” thing.

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Originally Published on Reader's Digest