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Humpback Whale Calls Are Love Songs, Biologist Suggests

Stephanie Peatling in Sydney
for National Geographic News
September 15, 2006
 
Even among whales, it seems, the best singers get the girls.

Joshua Smith, a doctoral student at the University of Queensland in St. Lucia, Australia, has spent three migration seasons collecting the songs of humpback whales.

It's during this time that male humpbacks emit vocalizations that sound, at least to human ears, like barks, chirps, and moans.

(See a Crittercam video of humpback whales.)

"Singers are joining females with calves more often and singing for a much longer duration with them than with any other group," Smith said.

Some theories have suggested that male humpbacks, like insects and birds, could be using their songs to either warn off other males or to attract females.

But Smith now thinks it's more likely that the songs are used as a courtship display directed at females, who may also size up males based on their singing ability.

"The way they structure their songs, perhaps using elements like higher or lower frequencies and how they do that, could reflect attributes of that male, such as his fitness or his age," Smith said.

Through his research, Smith hopes to decode the relationship between the songs and the social interactions between the singing males and other whales.

Getting the … Guy?

While male humpbacks sing most often in the presence of a female, there is still little evidence that females are overtly attracted to or join males that sing.

With the help of a large number of volunteers, Smith and his supervisor, Michael Noad, recorded and tracked male humpbacks that sang for up to 23 hours, as well as other males that sang for just ten minutes.

Using underwater microphones called hydrophones, the team was able to record the songs from whales up tens of kilometers away.

Among their findings, the researchers noticed that, rather than repel rival males, singing appears to attract other males.

The scientists suggest this may be a potential strategy for male humpbacks to locate a female, since another singing male may often have a female present.

"Song acts as a broadcast signal, and males in the environment around can hear the song as well as the females," Smith said.

"But if another male interacts with a singer, then that singer will typically stop."

Smith says he is confident that male humpback songs are used to woo mates.

Less clear, he says, are the types of information relayed in their songs and how female humpbacks respond when interacting with a singing male.

Smith's research is part of an international project called the Humpback Acoustic Research Collaboration, jointly funded by the United States Office of Naval Research and the Australian Defense Science and Technology Organization.

Noise Pollution

Smith's academic supervisor, Michael Noad, is a whale expert at the University of Queensland's School of Veterinary Science. Noad has collected thousands of hours of whale songs to better understand them.

"There's a lot of concern about the potential harm to marine mammals from underwater sounds," Noad said.

"We have very little idea of what sounds they do or do not like; [whether] sounds harm them; and if they do, at what level."

In Australia, concerns have been raised that naval exercises using sonar equipment might hurt the whales as they migrate along the coastline.

But Noad says so little research has been done that it is still too early to tell.

(Related story: "Whales Could Be Harmed by Oil-Search Noises, Report Says" [June 2006].)

"We need to learn more about how whales interact with the acoustic environment. Acoustics is their primary sense."

He says learning how whales use and respond to sound needs to be established before researchers can determine whether there are dangerous levels or types of sound.

Once that has been worked out, scientists will then be able to look at whether defense exercises, underwater seismic tests, or even commercial shipping activities are disturbing the humpbacks, Noad says.

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