Killer whales bunch together when they socialize or resttouching, rubbing, resting, and rolling on the surface. They spread out to find food. But even when they separate they remain in acoustic range.
There are between 7 and 17 calls in the repertoire of the average killer whale matriline. However, during the dialogues that Miller recorded, the call produced by the first individual was copied almost immediately by the respondera phenomenon that the scientists dubbed "call-matching."
At one point they noted such an exchange between a mother and calf.
But it is not yet clear what these exchanges mean. It could signal that the responder is aware of the first caller and is paying attention, or that the message might simply have been received.
"Call-matching has been found in a number of species, and probably has a variety of meanings," Deecke said.
In primates, call-matching can be used as a sign of reconciliation after a nasty situation or fight. In some songbirds, song-matching signals a "stay away" territorial warning.
"Miller's work is the first step to understanding the function of these calls in the context of killer whale behavior," Deecke said.
The fact that call-matching behavior is seen in other species suggests there might be basic rules of communication, Miller said. He intends to follow the call-matching observations with underwater playback experiments to see how killer whales respond to a range of calls.
The ability to identify individual callers and calls also provides an opportunity to study how vocalizations are passed from one generation to the next, opening a window into killer whale culture. Now the trick is to figure out what these creatures are saying.
National Geographic Channel Presents airs on Sundays at 8 p.m. ET/PT in the United States and is available only on the National Geographic Channel.
Got a high-speed connection? Watch National Geographic Channel Presents video clips in streaming video.
Uncovering Secrets of Blue Whale's Song
Killer WhalesKilling Other Whales
Human Noise May Disturb Whales' "Love Songs"
Killer Whale "Willy" Shows Reluctance to Be Free
Ancient Walking Whales Shed Light on Ancestry of Ocean Giants
Related Web Sites
National Geographic Channel
National Geographic Presents: Program Schedule
Be The CreatureExplore A Creature!
Crittercam Interactive Feature
Photo ID of Killer Whales