Animal Vocalizations

The Semantic Properties of Animal Vocalizations
By Sharon White

It is well-known and widely accepted, that the main attribute which distinguishes human kind from other living creatures is language. But animal vocalizations also do contain semantic properties. Let’s consider several examples.

Gibbons are several species of our closest surviving non-human kin. Like humans, they communicate in various ways, including posturing and gesturing, but the most language-like of their communication is their system of calls. Investigations of the gibbons of northern Thailand have shown that these gibbons have a stock of at least nine different calls. One of these is emitted typically when the group is surprised by a possible enemy and takes the form of a high pitched shout; it is often repeated by those who hear it and all act accordingly in order to avoid the danger of the enemy. An entirely different sort of call occurs in connection with friendly approaches among young gibbons, and reinforces the notion of play. A third call seems to serve to keep the members of a group close enough together as they move through the woods in search of food. The most important property of this system of communication is its lack of flexibility. Whatever the exact number of calls is, it is finite and small. Whilst any one of the calls can be varied in loudness or in the number of repetitions, no matter what situation a gibbon may encounter, its vocal reaction is constrained to be one of this small finite number: a gibbon does not react to a new situation by producing a new call or putting together two or more of the calls already available.

It has been suggested that language grew out of a primate call system, like the ones used by apes today and the one I have described that is used by gibbons. It is assumed that humans started out with a simple set of cries in which each one meant something different, such as, “Danger!” or “Follow me!”. These cries gradually became more elaborate and eventually evolved into language. A possible intermediate stage is seen in the cries of the vervet monkey. This monkey has several alarm calls which distinguish between different types of danger. The chutter announces the presence of a snake, the rraup gives warning of an eagle, a chirp is used for lions and leopards and the less panic-stricken utterance uh signals the presence of a spotted hyena. According to some, it is a very short step from an alarm call warning of a poisonous snake to using the chutter as a ‘word’ signifying a poisonous snake. However, another interpretation of these signals is possible; a distinguishing between the intensity of different types of danger. However an experiment in which a concealed loudspeaker plated recordings of the alarm calls showed that when each sound was heard, a specific response was seen. For example, when they heard the chutter, the vervets stood on their hind legs and looked around for a snake. This implies that the monkeys clearly have a special signal for each type of enemy; each signal has semantic properties.