You are here

Communication in ravens Corvus corax: again new aspects of an old problem [abstract]

Ueli Pfister (1997). Communication in ravens Corvus corax: again new aspects of an old problem [abstract]. Bioacoustics, Volume 8 (3-4): 256



The development of song in most songbirds depends upon learning processes. Only a few studies revealed the possibility that not only vocalisations might be learned, but also how to use them. We investigated the use of calls in interactions of 21 resident pairs of ravens Corvus corax and asked whether the use of calls depends on the call types. In our study area south of Bern (Switzerland) we found that 37 resident pairs had 81 different call types. The repertoire of an individual male or female raven contains a mean of 12 call types. Therefore the repertoires are only partially overlapping. In an experimental set-up we provoked interactions between a free-living and a caged pair. The sequences of calls of the free-living pair were analysed with row-wise matrix correlations and the results depicted with correspondence analysis. We found in all pairs a correlation between the transition matrices of preceding and following calls of the partner, which shows that the call behaviour of one individual influences that of the other. Therefore the partners are communicating. Comparing transition matrices of certain call types of different pairs, we found in some cases a high correlation between matrices of different call types, in other cases no correlation between matrices of the same call type. Comparing the results of the correspondence analyses among different pairs, we found that the same call types can be differently associated with the calls of the partner, although according to the repertoire composition the same associations would have been possible. This shows that certain pairs may use one and the same call type differently, and different call types the same way. How to use a call is therefore not dependent upon its type or acoustic structure. We conclude that acoustic communication in ravens is based mainly on conventions between the individuals. If not only the vocalisations are learned, but also how to use them in interactions, theoretical concepts of communication, which today assume that meaning relies on signals, have to be extended to include the possibility that the meaning of signals depends on relationships between individuals.