Meerkats in the semi-desert Kalahari. The animals belonging to the mongooses warn their conspecifics against predators with disharmonious warnings in order to increase their attention. Photo: Stephen Le Quesne
Vorlesen Meerkats use disharmonic warning calls to make the signals more surprising and therefore more effective for their conspecifics. A research team from the University of Zurich found this out in the observation of meerkat colonies in the semi-desert Kalahari in South Africa. They played the little predators a repertoire of characteristic warning cries of their conspecifics. The animals responded to so-called non-linear tone sequences in which, in addition to the fundamental tone, other notes resonated more than they did linear ones: they interrupted their foraging. The fact that the animals adapt their behavior to nonlinear warning patterns underpins for the first time the so-called unpredictability hypothesis: the disharmonious alarm, which is known from numerous animal species, prevents a failure to comply with and calls for a situation-appropriate behavior. For the approximately 50 centimeters large meerkats (Suricata suricatta) have warning signals of great importance, because they live in open deserts and their view is limited in the search for food on the ground. Over a period of several months, scientists in the Kalahari experimented with eight groups of animals. The secure identification of the group members was achieved by tiny transponders, with which the position of the meerkats could be determined to one meter exactly.

The researchers now presented the animals with nine different warning signals via loudspeakers, registering five forms of behavior: no reaction, heightened vigilance, watchful standstill, general running away and deliberate escape into the building. The meerkats adapted their behavior in each case the type of reproduction, which was selected by the biologists. While warning signals that consisted only of a clear keynote, the animals hardly distracted the foraging, they stopped their food procurement in non-linear alarm. Also, they then calmed down more slowly. The alarmed meerkats also fled into the building only when the disharmonic cries had been played to them before.

The behavioral changes were clearly directly related to the different warnings, the biologists report. This observation is, in their estimation, a testament to the unpredictability hypothesis: According to this, the nonlinear calls characteristic of many animal species prevent the receivers from simply ignoring the alarm.

Simon W. Townsend (University of Zurich) et al .: Proceedings of the Royal Society: Biology Letters, online pre-publication, doi: 10.1098 / rsbl.2010.0537 ddp / science.de? David Köndgen ad

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