Early whaling logs often referred to whales as ‘singers’. All whales use sounds for communication, and most use recognisable patterns, ranging from the haunting tones of bowhead whales to the fast echolocation. Bowheads and bottle nosed dolphins use ‘names’ to identify each other and their clan, have ‘conversations’, and copy each other’s calls.
Bowheads are second only in size to the blue whale, and are very long-lived. Stone harpoon heads, which went out of use at the turn of the 19th century, have been found lodged in the bodies of some individuals of today. Listen to their calls here.
Whales’ land-based ancestors made sounds as we do, using the throat and mouth. But try singing under water! Whales call during dives; whilst holding their breath, and with their mouths closed. Calling is essential for these highly social animals; this is evident because independently both baleen and toothed whales have evolved new ways to produce and transmit sound in the sea.
How are whale sounds made?
We produce sound in a tubular organ in our throats; the larynx. This organ is an air valve, closing off the lungs when we swallow, and controlling the outward flow of air. Sound is generated by vibrating paired membranes in the larynx; these ‘chop up’ the airflow into pressure waves. This is then modified by resonating in the chambers of the chest, nose and throat before being released through the mouth.
A humpback’s larynx does not sit across the windpipe. Instead it straddles the opening to an additional air sac located beneath the throat. These whales make sounds by passing air between this sac and the windpipe, vibrating the vocal folds of the larynx. These deep notes are modified and amplified by resonating in the laryngeal sac and nasal cavity, and are thought to be transmitted into the water through the sac, which vibrates the flexible throat pleats somewhat like a hi-fi speaker cone.
Dolphins have evolved a secondary set of vocal folds inside their nasal cavities, called ‘phonic lips’. These vibrate like our vocal chords and generating pressure waves.
Because during deep dives the air volume in their nasal cavities becomes very small, their clicks, rasps and whistles do not resonate in inner cavities. Instead, a lens of fatty material on the front of the skull known as the ‘melon’ acts as an underwater ‘speaker cone’, amplifying and transmitting these calls.
Why do whales ‘sing’?
The repetitive, phrased songs of humpback whales are a means of male display. Whilst both genders make sounds, only the males produce song patterns. They copy the signature calls of their clan, serenading unaccompanied females during seasonal migration and at the winter breeding grounds.
Their behaviour suggests that these breeding areas are a form of ‘floating lek’, where females ‘browse’ amongst available mates. Humpbacks also use other non-singing signals, e.g. when hunting together, females call to communicate with their offspring.
Bottle-nosed dolphins develop their own distinctive signature whistle in the first few months, and exchange these ‘names’ when meeting other dolphins. Females keep their whistle throughout life, whilst males change their signature calls when they move between social groups. Like baleen whales, they also communicate during foraging dives and to maintain social ties.
What can we learn from whale song?
Biologists classify ‘song’ as following ‘a repeating, predictable acoustic pattern’. Most songbirds mimic the calls of their peer group as juveniles. When they mature, this song pattern becomes ‘fixed’. Whales are unusual; they can copy and learn new sounds throughout their lives. Like us, they have a brain structure that continuously learns and can adapt to changes.
The diversity of signature calls and unique song patterns used by clans reveal that whales have a complex and sophisticated system of learnable language. Studying the language and culture of whale populations can thus provide clues about how own language and social complexity may have evolved.
Text copyright © 2015 Mags Leighton. All rights reserved.
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