For the first time, some of the squeals dolphins emit have been linked to feelings of happiness.

Sam Ridgway, president of the National Marine Mammal Foundation, led a study published in the Journal of Experimental Biology, which found that bottlenose dolphins and beluga whales would give out a “victory squeal” upon anticipation of receiving a reward.

And these findings don’t just apply to dolphins and whales, but also extend to all delphinoids, which include dolphins, belugas and porpoises.

“When we train dolphins and belugas, we reward them with fish for correct responses,” he said. “Usually we cannot give them a fish reward right away. Therefore, we give them a whistle immediately and the fish later. We were surprised that animals then gave the squeal after our whistle. We called this a victory squeal.”

Ridgway and his team explored the time delay of the squeal after the whistle and the animals’ behavior, and concluded that the dolphins were responding with delight for being correct and expecting a reward.

Based on these findings, Ridgway speculated that the sounds were a result of the release of dopamine, a chemical that stimulates the sensation of pleasure and is associated with reward centers in the brain — similar to processes experienced by humans and other mammals.

A dopamine release takes from 100 to 200 milliseconds, so Ridgway hypothesized that if the time between the sounding of the whistle and the animals’ squeals was longer than the time it takes dopamine to be released, the animals could be expressing happiness. After his findings showed the response results of dolphins at an average of 151 milliseconds and belugas at an average of 250 milliseconds, Ridgway concluded that the sounds were emotional in nature.

The dolphins and belugas also emitted the sounds when tasked with diving hundreds of meters to switch off a noise, thus transferring the behavior to a stimulus other than food.

As for how the squeals are produced, Ridgway explains that they’re actually rapid “clicks” that sonar dolphins and other toothless whales produce as part of the sonar they use to find food, navigate and avoid predators. Dolphins in the wild click as they hunt for fish, with the clicks becoming more frequent as they close in. Similar to Ridgway’s findings, wild dolphins can be heard squealing with happiness after they seize a fish. And there’s nothing fishy about that.