Breaking down the Species Boundaries: Selective Pressures behind Interspecific Communication in Vertebrates

Studying heterospecific communication provides an opportunity to examine the dynamics of cross‐species social behaviour. It allows us to ask questions about the extent to which the transfer of information is adaptive or accidental and provides an empirically tractable context for manipulating relationships. To date, most studies of heterospecific communication have focussed on receivers. However, the selective pressures on signallers can be as important in determining the dynamics of interspecific communication. Here, we propose a simple framework for thinking about cross‐species information transfer, which (i) considers whether information exchange is either accidental or adaptive and (ii) whether it is unidirectional or bidirectional. To clearly classify interactions, it is necessary to quantify all of the payoffs of interspecific communication to both signallers and receivers. This requires accurate characterisation of the currency influenced by cross‐species communication (e.g. weight gain, foraging success, survival). However, quantifying the payoffs may be difficult, because each side may be benefiting via different currencies. To date, studies on heterospecific communication have focussed on only one dimension of a niche (usually antipredator or foraging signals). However, because niches are multidimensional, investigations should incorporate multiple aspects of a species’ niche, to get a better perspective on why we see certain patterns of information use between species.