Dolphin hear, dolphin doCaptive dolphins base their whistles on human
21 August 2002
|Dolphins add dinner bell to their repertoire.|
Young captive dolphins mimic their trainer's whistle in their calls to other
dolphins, researchers say1. The finding is some of
the first evidence that animals use imitated sounds to communicate with each
"In developing their whistle, young dolphins are incorporating sounds they
hear in their environment into their vocalization," says Peter Tyack, who
studies animal behavior at the Woods Hole Oceanographic Institution,
When separated from their social group, dolphins whistle in short, unique
bursts to signal their location and identity. They whistle through their
blowholes at frequencies almost too high for humans to hear. Their human
trainers use a dog whistle to communicate with the dolphins.
The whistles of wild dolphins trill up and down, but dolphins born in
captivity tend to whistle long stretches of one pitch, Tyack's team found. These
stretches closely matched the dog whistle - the training signal for "come get a
Choosing to mimic this signal might not be a coincidence, Tyack says. Young
calves may learn that adding the dinner bell to their call elicits a rapid
response from other dolphins.
Dolphins' musical skills may become more sophisticated with age. Captive
dolphins' signature whistles become more variable as they get older, notes
Jennifer Miksis, another member of the Woods Hole team.
Dolphins also communicate using head jerks, teeth baring and jaw claps. "They
can use incredibly subtle body language and sounds to convey very detailed
information about their intentions," says Miksis.
Anyone can whistle
Zoologist Diana Reiss of Osborn Laboratories for Marine Science in New York
taught dolphins sounds using an underwater keyboard that produced distinct
whistles when the dolphins pushed differently shaped keys2.
All captive-born baby dolphins have relatively monotonous
"After the nineteenth time they heard the whistle associated with ball, they
repeated it back," says Reiss. The dolphins repeated only the ending of the
whistle at first, much as a child might repeat "nana" after hearing "banana".
They also whistled when they played with balls outside keyboard sessions.
But Reiss disputes that dolphins use unique calls to identify themselves -
their contact calls are all based on a rising whistle, she says. She thinks that
all captive-born baby dolphins have relatively monotonous whistles, regardless
of their training, that become more complex with age.
Even the oldest captive dolphin in their study, which was 35 years old, had a
less variable whistle than the wild dolphin of the same age, Miksis counters.
Individuals of other species, such as bats, also have signature calls, she