DEPARTMENT OF BEHAVIOURAL ECOLOGY

Evolution in Africa everyday

Do corncrake males ue social information gained by eavesdropping on interactions between rivals?

Project duration: 2013-2016

Project head: Lucyna Wojas

Supervisor: Tomasz Osiejuk

Co-workers: PaweĊ‚ Podkowa

Purpose of research/hypothesis.
The main aim of this research is to experimentally verify whether vocal communication in territorial corncrake males has the characteristics of a communication network and to demonstrate how social eavesdropping affects subsequent decisions by males during territory defence. We will apply an experimental approach to test the following hypotheses:
Hypothesis I. Corncrake males eavesdrop on vocal interactions between opponents, and eavesdropping has a
social character.
Hypothesis II. Corncrake males eavesdrop on interactions between opponents in a limited range because of limitations on individual vocal recognition due to attenuation and because of distortions affecting calls during propagation.
Methodology
The hypotheses will be verified using interactive playback experiments conducted using a small microphone array within a focal male territory. First, a simulated interaction between two rivals will beplayed back from a set of four speakers in order, including a signal exchange, approach and fight. In the second part of the experiment, we will simulate the intrusion of the territory of the focal male by playing back the recording of the winner or the loser of the previously presented vocal fight. This simulated conflicting will enable the eavesdropper to extract social information. Simulated conflicts will be played at different distances from the territory of the focal birds to enable or prevent individual recognition. A control experiment will be conducted in which the simulated interaction does not have a clear winner or lose r so that no social information will be provided to eavesdroppers. Impact of the results. Social eavesdropping in a territorial context involves gathering information on opponents based on the interactions that occur between them and the effects of those interactions. For an individual eavesdropper, this behaviour is
evolutionarily advantageous because it minimises the cost of defending the individual’s territory by matching the defence strategy with the characteristics of the (eavesdropped) rival and the individual’s own capabilities. This intraspecific eavesdropping seems to be a natural animal behaviour, but so far, little work has been conducted to study its mechanisms, functionality and impact on the fitness of individuals. This project is the first to examine the functioning of the communication network and its most important consequences (i.e., social eavesdropping) in a non-songbird that does not learn to sing. The acoustic communication of corncrakes has been intensively studied over the last few years, and it seems to be an ideal model for research on communication networks. We have good knowledge about the meaning of particular signals used during territorial defence and about direct conflicts preceding physical contact and risky fights. It is likely that vocal fights of corncrakes are subject to eavesdropping because their calls are very loud and reach many conspecifics.
Whereas territorial calls enable individual recognition, earlier propagation experiments suggest that this recognition is limited in range. Finally, corncrake males live in a dense environment and call at night, which limits their information exchange to a single acoustic channel, simplifying the interpretation of the results and the testing of thehypotheses.