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Dolphins, Whales Squeal When Happy

Aug 14, 2014 11:44 AM EDT
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Almost like giggling children, dolphins and whales squeal with joy when presented with a fishy treat, a new study finds.

While initially these gleeful sounds were thought to be signals communicating the presence of food, scientists now suggest that these squeals are in fact displays of emotion.

"We think we have demonstrated that it (the victory squeal) has emotional content," Dr. Sam Ridgway, president of the US National Marine Mammal Foundation in San Diego, said in The Journal of Experimental Biology.

To investigate further, Ridgway and his colleagues analyzed decades of recordings of experiments involving dolphins and beluga whales. They also trained bottlenose dolphins (Tursiops truncatus) and belugas (Delphinapterus leucas) to perform various tasks such as diving, and used a whistle or buzzer to signal that the animal would be rewarded with a fishy morsel later.

These marine mammals are known to use buzzing sounds to navigate and communicate when hunting for food, but they also emit what researchers call "victory squeals" in response to a reward, or merely the promise of one.

"We noticed that each time an animal took a fish, it would make this particular pulsed sound," Ridgway told Live Science.

Ridgway and his team also trained dolphins and belugas to dive in ocean waters and turn off an artificial buzzer, later to be rewarded if they completed the task. Once they shut off the buzzer, scientists noticed that the animals emitted their victory squeals well before reaching the surface and seeing their fishy treat.

"The (squealing) behavior had transferred over to another stimulus that wasn't food," Ridgway added, according to Mail Online.

When humans emit cries of joy there is a 100-200 millisecond delay from the time of the event and the happy sound. But with dolphins it took an average of 151 milliseconds extra time for this release, and with the belugas it was about a 250 millisecond delay, researchers wrote.

Animals other than dolphins and whales that use echolocation also have been known to produce similar sounds. Bats, for instance, make what scientists call a "terminal buzz" when they zero in on their prey. Beaked whales also buzz when they close in on squid, and sperm whales have been known to make creaking sounds when catching their food.

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