COMMUNICATION

The meaning of sounds

There are many ways of communicating, some totally silent. ‘Talking' apes answer their observers in sign language, bees express themselves in dance and many animals modulate their calls. Some species, including birds and cetaceans, possess extraordinarily complex singing talents.

Killer whale near Unimak Island, in Alaska. Certain killer whales are bilingual and speak not only the common language, but also a sort of dialect specific to their group, that reinforces the community’s identity. © CNRS Photothèque/CEBC/Christophe Guinet
Killer whale near Unimak Island, in Alaska. Certain killer whales are bilingual and speak not only the common language, but also a sort of dialect specific to their group, that reinforces the community’s identity. © CNRS Photothèque/CEBC/Christophe Guinet
Communication via song is a characteristic of birds, which in some circumstances is coupled with a more aesthetic seduction technique. Here a cock-of-the-rock parades on its chosen site, where the bright light shows off its brightly coloured plumage. © CNRS Photothèque/Marc Thery
Communication via song is a characteristic of birds, which in some circumstances is coupled with a more aesthetic seduction technique. Here a cock-of-the-rock parades on its chosen site, where the bright light shows off its brightly coloured plumage. © CNRS Photothèque/Marc Thery

Very recently, Yosuke, a Gabon grey parrot living in a Tokyo suburb, escaped from home. It was captured by the police and taken to a veterinary clinic, where it insistently repeated the name and address of its owner until it was finally taken home. While this was just a case of imitating human speech, some birds and marine mammals are able to use language that is just as complex as human language.

Detail and shades of meaning

Birds teach their young to sing in different ways, depending on the species. It is generally agreed that bird song is associated with mating and territory. For instance, Thierry Aubin, an ethologist and researcher at the French National Centre for Scientific Research (CNRS) Laboratory for the Neurobiology of Learning, Memory and Communication (NAMC)(1) believes that a skylark can say all in one go: "I belong to the skylark species, I am a male, I live in Brittany and I am located near a large dune by the sea."

A bird will sometimes sing for days at a time before it attracts a mate and will not stop even if an intruder bursts on the scene. On the contrary it will listen to the intruder. All the experts agree that birds sing out of a sense of aesthetic pleasure, and many have drawn an analogy between bird song and human music: rhythm, repetition, intensity.

The singing of marine mammals, which was unknown until the 1960s, is equally full of nuances. Sound travels roughly four times faster under water than it does through the air. Cetaceans use sound in a variety of circumstances: for echolocation (2), whistles and calls denoting different types of communication, not forgetting their famous songs, so named on account of their length and their complex and repetitive structure.

This varied voice communication evolves over time and differs not only from one species to another but also within individual species. Researchers are convinced that it is a form of culture and a way of transmitting behaviour from one generation to the next.

Chants and dialects

The humpback whale has been studied extensively. Only the males sing and they do this solely during mating season. As with birds, scientists believe that these melodies are part of the mating ritual and/or serve as signals to rivals in the vicinity. Australian cetologist Michael Noad, has also noticed that songs evolve from season to season and, most importantly, are transmitted rapidly across wide expanses of ocean. The result is that all whales in that area sing from the same musical score.

Killer whales (Orcas) even speak different dialects. This surprising discovery relates only to sedentary populations. Unlike the less talkative migratory killer whale, the sedentary type has developed a sort of private language that is understood only by the members of its pod (a small group of animals living together). To communicate outside the pod, these bilingual killer whales use a common language that is understood by all killer whales, which reinforces the community's cohesion and identity.

Unfortunately, a shadow has been cast over this underwater hit parade. Human-generated noise in the marine environment (propellers, seismic sounding, offshore drilling and various types of sonar) are becoming invasive. The noise pollution appears to be doubling every decade, shrinking the auditory domain of marine mammals. It is a worrying development for those animals that rely on their sense of hearing to find, among other things, their bearings, food and a mate.

Kirstine de Caritat

  1. Laboratoire de Neurobiologie de l'Apprentissage, de la Mémoire et de la Communication, CNRS, Université Paris-Sud (FR).
  2. This biological orientation and guidance mechanism allows certain animals, such as bats, to emit high-frequency sounds that are reflected back from surrounding surfaces, indicating the relative distance and direction of these surfaces

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