The gazelle's leaping behavior, the begging of the nestlings, the expensive suit - all of these things are signals. All are intended to convey information about a signaller , to a signal receiver . Biologists have argued that the stotting display serves as a signal of quality to potential predators. It would be a waste of your time and energy to chase after me. Similarly, baby birds, through their begging behavior, may be informing their parents about how badly they need to be fed.
Additional examples are easy to find.
Bull elks may signal their quality to rivals and to potential mates with a loud bugling call . A peacock's fine tail probably serves to advertise the high quality of its bearer to potential mates. Expensive suits, fast cars, wine, or jewelery are not cheap in terms of that all-important human currency, money. By leaping up and down, a gazelle is expending the very energy that it will need desperately should a chase ensue. A field of evolutionary biology called signalling theory examines the nature of communication behavior, and attempts to answer these sorts of questions.