How do animals communicate?
Animal communication is the transfer of information between individuals and groups of animals. This could be intraspecies communication, such as sounds and vocalisations produced by whales in a pod. But it also includes interspecies communication, which can be seen in cases of great apes being taught to use sign language.
Both of these examples imply a certain degree of intentionality, not to mention intelligence. However, not all animal communication is like this.
Besides the five traditionally recognised human senses (taste, sight, touch, smell, and sound), some species are also capable of exchanging thermal, seismic and electric information.
When information leads to some kind of behavioural change by the receiver, this communication may be referred to as ‘signalling’. Animal signals can have a range of functions, from marking territory and finding a mate, to warding off predators and locating food.
What is signalling theory?
Signalling theory predicts that for a signal to be maintained in the population, the interaction should benefit both the sender and receiver. In Madagascar, for example, red-fronted lemurs and sifakas, can recognise one another’s alarm calls. The selective advantage of being able to detect the alarm calls of another species ensures this ability is passed down to future generations.
Honest vs. dishonest signalling
It’s important to note that the terms ‘honest’ and ‘dishonest’, when used in conjunction with signalling, are not meant in the human sense. There is no intent here, rather a signal is considered ‘honest’ if it truly conveys useful information to the receiver.
A prime example of this is the aposematic warning signal of a poisonous or otherwise dangerous animal. Take the black and yellow colours of a poison dart frog. This is an honest signal, as it tells the predator of the imminent risk. Again, the signal is mutually beneficial. Predators that are able to detect the risk will survive and the trait will be selected.
Dishonest signalling doesn’t imply conscious deception, just that the signal may convey information that is not true. In fact, there are certain species that mimic the colouring of aposematic animals. Take the harmless milk snake, for example. Its red, white and black bands are ever so similar to those of the (highly venomous) coral snake.
The fiddler crab offers another example of dishonest signalling. Males of this species are known for having having one large claw, which they use when fighting for a mate. If a fiddler crab loses its claw in the fight, another claw will grow back in its place. This replacement claw is the same size, but tends to be lighter and weaker than the original. However, it remains a (dishonest) visual signal, which can be used to scare off other male and attract a mate.
In some cases, when producing a signal, there is direct relationship between the cost and benefit. A prime example of this, and one that got Darwin scratching his head, is the peacock’s elaborate tail feathers.
Darwin famously wrote “the sight of a feather in a peacock’s tail, whenever I gaze at it, makes me sick.”
A peacock’s tail challenged his theory of natural selection, as the adaptation seemed to be more of a hindrance to the bird’s survival than a help. The coloured feathers serve to attract a potential mate, however, by opening their colourful tails, they also become more visible to predators.
Another example of this is the act of stotting, performed by gazelles. This is when they bound in the air, with all four legs off the ground. Leaping like this in the air consumes a lot of energy and makes the gazelle more visible, so why do they do it? It’s been observed that gazelles are more likely to do this when predators are nearby. It’s believed that stotting is a demonstration of the gazelle’s strength, which deters the predator from attacking. Once more, signalling provides an advantage to both parties. The gazelle is less likely to be attacked and the predator avoids a long, unproductive pursuit.