Humans have long wondered about the meaning of the high pitched noises made by dolphins and whales but scientists have finally unveiled why these animals squeal. It appears that the marine mammals squeal to show their pleasure and happiness the same way that humans whoop with laughter when they are happy or excited.
National Marine Mammal Foundation president Sam Ridgway, who has been studying bottlenose dolphins and beluga whales for most of his life, initially assumed that the marine mammals create the sound, which is marked by swift series of pulses that often come with upsweeping tone, to signal other animals that food was nearby. The assumption is based on observations that every time these marine animals take a fish, they make this particular sound. Ridgway, however, decided to learn more about these squeals after his wife said that the sound resembles those produced by happy children.
It appears that the animals' squeals are indeed an expression of delight. For their study published in the Journal of Experimental Biology on Aug, 15, Ridgway and colleagues trained dolphins and whales to perform particular tasks and used a buzzer or whistle as signal to indicate that the animal would receive a reward later. They observed that the marine animals consistently produced squealing noises when they hear the signal regardless when it is made long before the reward comes.
"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 shared.
The researchers also observed a spike of the hormone dopamine, which is known to stimulate the sensation of pleasure, in the animals whenever they receive a reward. Ridgway and colleagues likewise noted that the dolphins squeal 151 millisecond after hearing the reward signal. Whales, on the other hand, take much longer to make their victory squeals at 250 milliseconds but the delay suggests that the marine mammals squeal in response to a surge in their dopamine levels.
"In laboratory animals, there is a 100 to 200 ms delay for dopamine release. [Victory squals] delay in our animals is similar and consistent with vocalization after dopamine release," the researchers wrote. "Our novel observation suggests that the dopamine reward system is active in cetacean brains."
Ridgway believes that the study demonstrated that the victory squeals of the animals have emotional content and expressed his interest to find out more about the cognitive abilities of these marine mammals.