Estación Biológica Cocha Cashu
Vocal communication in the white-winged trumpeter
Principal Investigator: Dr Nathalie Seddon, Research Fellow of Newnham College, University of Cambridge, UK.
Contact details: Department of Zoology, Downing Street, University of Cambridge CB2 3EJ, U.K. Tel: +44 1223 336600; Fax: +44 1223 336676
Co-workers: Dr Joe Tobias and Adriana Alvarez del Villar D´Onofrio
Two fundamental features of intelligent vocal communication are the ability to use auditory signals to refer to external objects and the capacity to modify vocal signals with respect to social context (Cheney & Seyfarth 1990). Until recently, these abilities were deemed unique to human communication (Bickerton 1990). Research over the past two decades has, however, revealed that other social mammals including monkeys (e.g. Cheney & Seyfarth 1988, 1990) and carnivores (e.g. Rasa 1989) are also capable of referential signaling. Specifically, these studies demonstrated one class of vocalisations (alarm calls) are often used to denote specific external objects (predators). Furthermore, various studies have also shown that the use of such alarm calls can vary with respect to social context, such as the proximity of related offspring to the caller (Hoogland 1983). Evidence that birds are also capable of using vocalisations in this way is much more limited, and no study has hitherto investigated if birds are able to control their vocalisations according to more subtle and variable social contexts. Just how does the cognitive ability of birds compare to that of mammals?
In groups of communally breeding birds there is a fine balance between conflict and cooperation, and social interactions within groups can be complex and varied. Group-living birds therefore make good subjects in which to investigate the ability to modify vocal behaviour according to social situation. In recognition of this, Nathalie and her team plans to investigate the interaction between social system and vocal behaviour in a terrestrial, communally breeding bird found at Cocha Cashu: the white-winged trumpeter. It is an ideal species in which to address the forgoing issues for three reasons. Firstly, trumpeters have a varied vocal repertoire including several structurally different alarm calls, begging calls given by young birds and adults during social interactions, and choruses produced by all group members during territory defence (Sherman 1996). Secondly, they live in groups of 4–13 individuals and practice cooperative polyandry, a rare breeding system in which several males copulate with a single female and cooperate to help to raise a single brood (Sherman 1995). Thirdly, trumpeters habituate to human observers making it possible to clearly observe social interactions, including how copulations are allocated amongst group members. As such there is enormous potential to investigate the link between the social and vocal communication systems in this species.
In order to evaluate the cognitive abilities of white-winged trumpeters, the following questions will be addressed:
To what extent are trumpeter vocalisations self-referent?
To what extent do trumpeter vocalisations refer to external stimuli?
To what extent can trumpeters control their vocal behaviour?
During this first field season (August-October 2001) these questions will be addressed using one class of vocalisations: alarm calls. However, the research will be conducted with a view to developing a long-term investigation into the link between social behaviour and vocal communication in white-winged trumpeters. Such a study may provide new and interesting insights into cognition in social animals.
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Cheney, D. L. & Seyfarth, R. M. (1988) Assessment of meaning and the detection of unreliable signals by vervet monkeys. Animal Behaviour, 36: 477-486.
Cheney, D. L. & Seyfarth, R. M. (1990) How Monkeys See the World. University of Chicago Press, Chicago, USA.
Hoogland, J. L. (1983) Nepotism and alarm-calling in the black-tailed prairie dog (Cynomys ludovicianus). Animal Behaviour, 31: 472-479.
Rasa, O. A. E. (1989) Behavioural parameters of vigilance in the dwarf mongoose: social acquisition of a sex-biased role. Behaviour, 110: 125-145.
Seddon, N. (2001). The Ecology, Communication and Conservation of the Subdesert Mesite Monias benschi. Ph.D thesis, University of Cambridge, UK.
Sherman, P. T. (1995) Social organisation of cooperatively polyandrous of white-winged trumpeters Psophia leucoptera. Auk, 112(2): 296-309.
Sherman, P. T. (1996) Family Psophiidae. In Handbook of the birds of the world, Volume 3 (eds. del Hoyo, J., Elliott, A. & Sargatal, J.), pp. 96–107. Lynx editions, Barcelona, Spain