Aggression is a common occurrence in the world of marine mammals. Aggressive displays, or agonistic interactions, are often seen among members of a group or between individuals of different species. Sounds that declare a readiness to fight may be produced during aggressive displays. Animals can listen to these sounds to assess an opponent's willingness to fight or fighting ability. Loud sounds may also be used to startle or defend against a predator. The best description of aggressive displays come from species that can be kept in captivity such as small cetaceans (bottlenose dolphins and beluga whales) and pinnipeds. Many of these sounds are also used by large and small marine mammals in the wild.

Beluga whales may exhibit aggressive displays that include jaw claps and tail slaps. Photo courtesy of Peter Scheifele. (Go to larger version)

Threat displays are typically given during agonistic interactions between dolphins and between dolphins and their predators. These displays start as a vocalization composed of a burst or pulsed sound. As the aggression escalates, the vocalizations are often accompanied by jaw claps and/or tail slaps. Jaw claps are made by opening the mouth and clapping the upper and lower jaws together with force. Tail slaps are made by thrusting the tail out of the water and then slapping it down on the water's surface. Both of these actions create very abrupt sounds that have a rapid onset and offset. These sounds can be analyzed by viewing a waveform picture. This picture depicts the relative intensity of the sound over time. The following waveform picture and corresponding spectrogram depicts a series of four jaw claps from a captive beluga whale.

The four claps of sound in the spectrogram line up with the four blue pulses in the waveform directly above. The waveform is aligned with the spectrogram in time on the x axis and shows energy, in relative units, on the y axis.

Now listen to a series of jaw claps and burst pulsed sounds recorded from three aggressive beluga whales. Can you hear the difference between the jaw claps and the pulsed sound?

	QuickTime (25K) Click this button to use any media player Courtesy of Jennifer Miksis, University of Rhode Island

For more information on how specific marine animals communicate using sound, use the following links:
Marine Mammals	Fish	Invertebrates