Researchers working in Hawai'i waters have reported the first confirmed evidence that humpback whale calves produce sounds.

The purpose of the grunts and squeals recorded by the Cetos Research Organization has not been deciphered, but they could be alarm calls to summon the calf's mother or an expression of curiosity, said Ann Zoidis, director of the research project.

"We found that calves make sounds most often when separated from their mothers, but they are not always alarm calls. Sometimes they occurred when curious calves approached the divers and even made eye contact with them," she said. "In those cases, the sounds appeared to be in reaction to a novel object."

Marine scientists for years have been using single hydrophones to collect sounds from whale pods that included calves, Zoidis said, but it was difficult to pinpoint the individual animals responsible for the noises.

Cetos built a two-element hydrophone array that allowed researchers to do angular measurements to the sound source.

Zoidis, who also heads the Cetos Research Organization, said the study verified for the first time that humpback whale calves, both male and female, make sounds.

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