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Marine mammals "squeal" with delight when experiencing pleasure, according to a new study.

Lead researcher Sam Ridgway spent 50 years researching dolphins and whales. He would ask him various questions like how deep they can dive and how depth affects their hearing. He remembers that these cetaceans would also squeal when he rewarded them with tasty fish treats.

Ridgway first believed that the squeals were food signals or a type of communication that notifies nearby animals of the presence of food.

Upon further examination, researchers found that the time lag between dolphins and whales receiving a reward and their squeals is equivalent to the lag between a pleasant experience and dopamine release. Researchers said these findings suggest that dolphins and whales experience pleasure.

Researchers found that dolphins and whales still squealed when sounds like buzzes or whistles, replaced tasty food rewards.

"The [squealing] behavior had transferred over to another stimulus that wasn't food," Ridgway said in a news release. Researchers said the latest findings also reminded him of studies in the 1950s when animals appeared to feel the same amount of pleasure from electrical stimulation of a region of the brain that released dopamine as they did when receiving a food reward.

"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," added Ridgway.

After months of analysis, researchers believe that beluga whales and dolphins express their pleasure through their squeals.

"The dolphins take an average of 151 ms extra time for this release, and with the belugas...it's about 250 ms delay," said Ridgway.

"We think we have demonstrated that it [the victory squeal] has emotional content," he concluded.

The findings were published in the Journal of Experimental Biology.