Interspecies Communication - Parasitic Communication and Eavesdropping

Parasitic Communication and Eavesdropping

Unlike cooperative communication, parasitic communication involves an unequal sharing of information (parasitism). In terms of alarm calls, this means that the warnings are not bi-directional. However, it would be faulty to say that the eavesdroppers are not giving any information in return. It may be that the other species has simply not been able to decipher the eavesdroppers’ calls. Much of the research done on this type of communication has been found in bird species, including the nuthatch and the great tit. In 2007, Templeton and Greene found that nuthatches are able to discriminate between subtle differences in chickadee alarm calls, which broadcast the location and size of a predator. Since chickadees and nuthatches typically occupy the same habitat, mobbing predators together acts as a deterrent that benefits both species. The team also found that nuthatches screen chickadee alarm calls in order to determine whether it is cost-efficient to mob a particular predator. This is because not all predators pose the same risk to nuthatches as to chickadees. Templeton and Greene speculate that screening may be most important in the winter when energy demands are the highest.

Work by Gorissen, Gorissen, and Eens (2006) has focused on blue tit song matching (or, “song imitation”) by great tits. Blue and great tits compete for resources such as food and nesting cavities and their coexistence has important fitness consequences for both species. These fitness costs might promote interspecific aggression because resources need to be defended against heterospecifics as well. So, the use of efficient vocal strategies such as matching might prove to be effective in interspecific communication. Hence, heterospecific matching could be a way of phrasing a threat in the language of the heterospecfic intruder. It could equally be well argued that these imitations of blue tit sounds have no function at all and are merely the result of learning mistakes in the sensitive period of great tits because blue and great tits form mixed foraging flocks together. While the authors agree with the first hypothesis, it is plausible that the latter also being true given the data on age and experience in primates.

In addition to birds, eavesdropping has been found in tungara frogs and their sympatric heterospecifics. The scientists posit that mixed-species choruses may reduce their risk of predation without increasing mate competition.