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Should I stay or should I go? A slight difference changes the meaning of a songbird alarm call| old_uid | 15774 |
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| title | Should I stay or should I go? A slight difference changes the meaning of a songbird alarm call |
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| start_date | 2015/06/10 |
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| schedule | 14h30 |
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| online | no |
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| summary | Predation is a powerful force shaping alarm acoustic signals. In many birds, the flee and the mobbing alarm calls are both used to announce a predator but elicit opposite responses from receivers, respectively a quick fly to cover or an approach and an harassment of the predator. Although previous studies have reported structural differences between both signals in bird species, there is a lack of investigations aiming to understand the acoustic basis of the switch between both functional types of alarm signals. In the superb fairy-wren Malurus cyaneus, flee and mobbing calls present strong similitudes. They are both characterized by the same high-pitched carrier frequency on which is applied a broad and fast frequency modulation, with the mobbing call presenting a low-pitched and short introductory element. By playback experiments with synthetic calls, we examined which structural details drive the functional difference between mobbing and flee calls. We showed that the functional switch between both calls is due to a simple variation of the slope of the carrier frequency, and does not depend on the other parameters composing both signals. Our result highlights the importance of the carrier slope in determining the meaning of alarm calls and supports the idea of a broadly shared coding rule among birds. Due to their importance for survival, alarm calls have evolved under strong constraints. We hypothesize that, in the evolutionary history of alarm calls, both signals have a common ancestor but that the mobbing call has diverged from a pre-existent flee call possibly in the context of social cooperation. |
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| responsibles | Devaud |
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