Encoding Messages

Animals have a variety of ways of encoding information. Firstly, for an animal to get its signal across to receptive parties, it must avoid as much interference as possible. One example of this phenomenon, known as channel partitioning, is in beach crabs. On a single beach there may be multiple species of crabs, all of whom wave their claws to attract females. By waving their claws at different intervals and frequencies, the females are able to distinguish conspecific males from heterospecific males. Signals can also be encoded based on their form, such as with begging in birds. Hatchlings have a begging behaviour that involves opening their mouths towards their parent, which correlates well with the actual act of eating, which involves the hatchling opening its beak. However, there are many signals without a relation between form and meaning, as with the extension of the dulap in anoles, which signals aggression but has no correlation with aggressive actions. Messages can also be encoded via discrete or graded methods. A discrete message retains the same form all the time, as in an alarm call. A graded message has different forms on a continuum that express different levels of a behaviour, such as in Steller’s jay which angles its crest higher if it is more likely to engage in aggressive behaviour. Signals can be encoded acoustically, such as with different times intervals in between syllables, the order of syllables and phrases, and the order of entire songs. A good example of acoustic encoding is with bird trilling. Trilling can be measured by trill rate, or the speed at which the notes are sung, and trill bandwidth, or the difference between the maximum frequency and the minimum frequency. There is a biophysical limit which prevents birds from singing beyond a certain trill rate to trill bandwidth ratio, and the closer males get to that limit, the higher females rate their quality. Lastly, messages can be encoded chemically, which occurs more frequently in mammals than other classes of species. Mammals generate an odour image, which is a scent pattern composed of different chemicals at different concentrations. Individuals generate different odour images, with chemicals differing between different species, and concentrations of species-specific chemicals being different in different individuals. This allows for conspecifics and heterospecifics to recognise each other and to leave scent-based messages in the environment.