Interspecies communication

Interspecies communication, interspecific communication, or heterospecific communication refers to communication among animals, plants, microorganisms, or other organisms of different species. Although researchers have explored the topic for many years, only recently has interspecies communication been recognized as an established field of inquiry.

Eavesdropping Heterospecific eavesdropping occurs when an organism of one species gleans information from a signal emitted by an organism of another species for the purpose of conveying information to conspecifics. In some cases, two species may exhibit bidirectional eavesdropping, in which organisms of both species acquire information from signals originating from organisms of the other. Eavesdropping is sometimes not considered a form of communication, but other models include it. Heterospecific eavesdropping allows organisms to obtain and benefit from information they might not otherwise be able to access as quickly, and may occur as part of mutualistic, commensal, competitive, parasitic, or predator-prey interactions.

Alarm signals

Responses to heterospecific alarm calls have been documented in over 70 mammalian, avian, and even reptilian species, some of which produce no alarm calls themselves. When alarm calls contain more detailed information, their comprehension by heterospecifics varies, with some eavesdroppers extracting information on predator type or degree of danger. For instance, Diana monkeys appear to distinguish between Campbell's monkey alarm calls indicating leopards and those indicating eagles. Furthermore, when one species elicits an alarm signal specific to a certain predator, the other species react in the same pattern as the species that called. For example, leopards hunt both species by capitalizing the elements of stealth and surprise. If the monkeys detect the leopard before it attacks (usually resulting in mobbing), the leopard will typically not attack. Therefore, when a leopard alarm call is given, both species respond by positioning near the leopard signaling that it has been found out. Eavesdropping on alarm calls can occur bidirectionally, as with redfronted lemurs and Verreaux's sificas, which both exhibit mixed alarm call systems and respond differently to distinct alarm calls of the other species. Beyond distinguishing among distinct alarm calls, superb fairy-wrens and white-browed scrubwrens mutually understand variations in single calls as establishing degrees of danger. Responses to heterospecific alarm calls have been identified in species that do not otherwise interact with one another, such as between the yellow-bellied marmot and golden-mantled ground squirrel. Animals also engage in alarm signal eavesdropping across classes, with mammals and the Galapagos marine iguana documented eavesdropping on the alarm calls of birds and bird species found to eavesdrop on the alarm calls of mammals. Red squirrels' acoustic response to raptors is near-identical to that of birds, making the latter also aware to a potential predatory threat, while eastern chipmunks are keen to mobbing calls by eastern tufted titmice. Whether heterospecific understanding is a learned behavior or not is unclear. Alarm signal eavesdropping may benefit the signaling species as well as the eavesdropper, either by depriving a shared predator of prey and causing it to leave an area, or by leading eavesdroppers to participate in mobbing. For instance, black-capped chickadees produce mobbing calls that detail size and location information on predators, to which 24-50 different species are known to respond by participating in the mobbing. One of these species, the red-breasted nuthatch, has been shown to selectively respond only to chickadee mobbing calls indicating more dangerous predators in order to save energy, demonstrating comprehension of complex heterospecific signals.

Eavesdropping has been found in túngara frogs and their sympatric heterospecifics. The scientists posit that mixed-species choruses may reduce their risk of predation without increasing mate competition.

In predation Heterospecifics may benefit from information obtained from eavesdropping differently from the intended conspecific receivers, and signalers may modify their behavior to combat effective eavesdropping. Fringe-lipped bats hunt by eavesdropping on frog mating calls, using these acoustic signals both to identify suitable prey species such as túngara frogs and to locate individuals. Because of this, male túngara frogs are known to produce less effective mating calls which are not preferred by fringe-lipped bats, but which are also not preferred by female túngara frogs.

Development of interspecific eavesdropping In 2000 it was found that age and interspecies experience were important factors in the ability for bonnet macaques to recognize heterospecific calls. Macaques who were exposed longer to other species' alarm calls were more likely to correctly respond to heterospecific alarm calls. Key to this early learning was the reinforcement of a predatory threat, when an alarm call was given a corresponding threat had to be presented in order to make the association. Interspecies communication may not be an innate ability but rather a sort of imprinting coupled with an intense emotion (fear) early in life. Other species, such as the fringe-lipped bat, display social learning of new signals associated with prey in maturity. Interspecies communication between an older caretaker animal and a younger animal is observed in the animal world only rarely. In the case of Owen and Mzee, a orphaned baby hippopotamus bonded with a 130-year-old Aldabran tortoise named Mzee (Swahili for a wise old man). According to staff at their animal sanctuary, they vocalized to each other in neither a stereotypical tortoise nor a hippopotamus fashion. Owen does not respond to hippopotamus calls. It is likely that when Owen was first introduced to Mzee he was still young enough to be imprinted.

Intentional signaling

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