Dolphins, whales express pleasure through squeals

Just like humans, dolphins and whales too while experiencing pleasure squeal with delight to savour moments of joy, says a study.

The time delay between dolphins and whales receiving a reward and their squeals is the same as the delay between a pleasant experience and dopamine release - suggesting that dolphins and whales experience pleasure, the study noted.

Dopamine is a neurotransmitter that helps control the brain's reward and pleasure centers. Once dopamine is released, a person usually feels good and may get a boost of self-confidence.

"We think we have demonstrated that it (the victory squeal) has emotional content," said lead author Sam Ridgway, president of the National Marine Mammal Foundation, US.

Over his five-decade career Ridgway has asked these cetaceans various questions, including how deep they can dive and how depth affects their hearing.

As he trained each animal to answer his questions, he rewarded them with fish treats, and each time that they received a reward he remembers that they squealed.

"Normally we worked in open waters in the San Diego Bay or out in the ocean. Our recordings sometimes have a lot of background noise, so most of the analysis has to be done by hand using the human ear," Ridgway added.

When humans squeal out of happiness there is a 100-200 millisecond delay from the time of the event and the happy sound.

"The dolphins take an average of 151 milliseconds extra time for this release, and with the belugas it is about a 250 millisecond delay," Ridgway said.

The study appeared in the Journal of Experimental Biology.