Only in the case of the hornbills and mongooses is the relationship more mutualistic. The hornbills, which send the signals, have the added benefits of easier access to their prey as the mongooses flush the prey into the open. The mongooses have to give up some of their food that they find; they also have to trust that the hornbills will in fact alarm for their predators, as well. The mongooses gain a better warning system: hornbills, from their stations in the sky or trees, can see more terrain and therefore more predators. This system of sentry duty allows the mongooses more time to forage while the hornbills exert less energy in foraging, benefitting both while both contribute to the association.
Social eavesdropping in great tits
The two types of eavesdropping are interceptive, which we have discussed in this paper, and social. Social eavesdropping occurs when animals are paying attention not only to the signals one animal gives, but instead to the interplay of at least two different signal systems (Peake 2005). An interesting example of a social eavesdropper is the great tit.
Male great tits are territorial, defending their areas of forest from intruders, including other male great tits. They are very intelligent in their guarding, however, making use of information other than that they gain from their own confrontations. By judging from a series of interactions whether or not a male poses a threat, the great tit is able to save energy that does not need to be spent on defense.
Let’s say male great tit B trespasses into male great tit A’s territory. Male A is able to quickly defeat tit B, chasing him out of his territory and into his neighbor’s, tit C. If tit C is then defeated by tit B (who tit A beat with ease), then tit A realizes that tit C is not actually a dangerous threat. The next time tit C intrudes, tit A will expend less energy in his attempts to drive him out. (Peake et al 2002)
Glossary
Animal communication – the method animals use to transfer information between one another. The method may include a visual cue, a sound, a smell, a touch, or a chemical release. For animal communication to evolve, the sender of a signal must always benefit; the receiver, not necessarily.
Alarm call – in many species of animals, an individual or individuals will keep a lookout for predators while the others go about the usual tasks of the species. If a predator approaches, the lookout(s) communicates their presence to the rest of the community via one of the methods listed above.
Eavesdropping – eavesdropping occurs when an individual other than the sender or the intended receiver receives a communication. The two types of eavesdropping can generally be categorized as being interceptive or social (Peake 2005).
Interceptive Eavesdropping – occurs when an individual receives a call directed at another animal(s), thereby keeping the message from reaching the intended audience. This type of eavesdropping is rare with regards to visual and auditory communications.
Social eavesdropping – occurs when an animal overhears a signal directed at another animal(s), but does not prevent the signal from reaching the intended recipient. This type of eavesdropping often occurs with regards to visual or auditory signals.
Conspecific – if two animals are conspecific, they belong to the same species. If a type of communication or eavesdropping is conspecific, it occurs between two animals of the same species.
Heterospecific
– if two animals are heterospecific, they belong to different species. If a type of communication or eavesdropping is heterospecific, it occurs between two animals belonging to different species.
Sympatric – if two groups of animals are sympatric, they share the same living area or territory. For example, red squirrels are sympatric with Eurasian jays.
Allopatric – if two groups of animals are allopatric, they do not share the same living area or territory. For example, the polar bear, found within the northern Arctic Circle, is allopatric with the penguin, found in Antarctica.
Fitness – if an animal has increased fitness, it has an increased ability to pass on its genetic material, usually by producing more offspring. Most traits, including eavesdropping, develop because the ancestors who developed the gene for that trait had increased fitness over other animals of the same species, leading to more of their genes in the species’ gene pool. The fitness of members of a species over one another is known as relative fitness.
Mobbing – a defensive response in social animals. After one animal gives an alarm call, alerting the group to the presence of a predator, other members of the group join him or her, then together attack (“mob”) the predator.
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