Article

The higher the better: sentinel height influences foraging success in a social bird.

School of Biological Sciences, University of Bristol, Woodland Road, Bristol BS8 1UG, UK.
Proceedings of the Royal Society B: Biological Sciences (Impact Factor: 5.68). 05/2009; 276(1666):2437-42. DOI: 10.1098/rspb.2009.0187
Source: PubMed

ABSTRACT In all social species, information relevant to survival and reproduction can be obtained in two main ways: through personal interaction with the environment (i.e. 'personal' information) and from the performance of others (i.e. 'public' information). While public information is less costly to obtain than personal information, it may be inappropriate or inaccurate. When deciding how much to rely on public information, individuals should therefore assess its potential quality, but this possibility requires empirical testing in animals. Here, we use the sentinel system of cooperatively breeding pied babblers (Turdoides bicolor) to investigate how behavioural decisions of foragers are influenced by potential variation in the quality of anti-predator information from a vigilant groupmate. When sentinels moved to a higher position, from where their probability of detecting predators is likely to be greater, foragers reduced their vigilance, spread out more widely and were more likely to venture into the open. Consequently, they spent more time foraging and increased their foraging efficiency, resulting in a profound increase in biomass intake rate. The opposite behavioural changes, and consequent foraging outcomes, were found when sentinels moved lower. A playback experiment demonstrated that foragers can use vocal cues alone to assess sentinel height. This is the first study to link explicitly a measure of the potential quality of public information with a fitness measure from those relying on the information, and our results emphasize that a full understanding of the evolution of communication in complex societies requires consideration of the reliability of information.

0 Bookmarks
 · 
83 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Wherever individuals perform cooperative behaviours, each should be selected to adjust their own current contributions in relation to the likely future contributions of their collaborators. Here, we use the sentinel system of pied babblers (Turdoides bicolor) to show that individuals anticipate contributions by group mates, adjusting their own contribution in response to information about internal state broadcast by others. Specifically, we show that (i) short-term changes in state influence contributions to a cooperative behaviour, (ii) individuals communicate short-term changes in state, and (iii) individuals use information about the state of group mates to adjust their own investment in sentinel behaviour. Our results demonstrate that individual decisions about contributions to a cooperative effort can be influenced by information about the likely future contribution of others. We suggest that similar pre-emptive adjustments based on information obtained from collaborators will be a common feature of cooperative behaviour, and may play an important role in the development of complex communication in social species.
    Proceedings of the Royal Society B: Biological Sciences 11/2010; 277(1698):3223-8. · 5.68 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Ecological conditions can influence decisions relating to antipredator behaviour through impacts on the likelihood of detecting predators and the ability to hear vocalizations. Previous studies of antipredator behaviour have tended to focus on foragers, whose vigilance behaviour may be confounded by the type of food they are eating, and on receivers in vocal communication networks. We examined the impact of habitat and wind conditions on the behaviour of sentinels, individuals that suspend their own foraging to adopt a raised position to scan for danger while groupmates continue feeding, and that produce a variety of calls used by foragers to adjust their antipredator behaviour. Sentinels of the pied babbler, Turdoides bicolor, a cooperatively breeding bird, started guarding sooner and guarded for longer in long grass compared to more open habitats, and also initiated sentinel bouts sooner in high wind, probably because of the increased predation risk in such circumstances. Sentinels also selected positions that were both lower and closer to the foraging group when it was windy, potentially improving transmission of vocal signals that are valuable to foragers. Our results demonstrate that sentinel behaviour can be influenced by extrinsic factors, as well as the intrinsic factors previously shown, and suggest that ecological variation may affect decisions bearing both selfish and cooperative benefits.
    Animal Behaviour 01/2011; 82(6):1435-1441. · 3.07 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Efficient cooperation requires effective coordination of individual contributions to the cooperative behaviour. Most social birds and mammals involved in cooperation produce a range of vocalisations, which may be important in regulating both individual contributions and the combined group effort. Here we investigate the role of a specific call in regulating cooperative sentinel behaviour in pied babblers (Turdoides bicolor). 'Fast-rate chuck' calls are often given by sentinels as they finish guard bouts and may potentially coordinate the rotation of individuals as sentinels, minimising time without a sentinel, or may signal the presence or absence of predators, regulating the onset of the subsequent sentinel bout. We ask (i) when fast-rate chuck calls are given and (ii) what effect they have on the interval between sentinel bouts. Contrary to expectation, we find little evidence that these calls are involved in regulating the pied babbler sentinel system: observations revealed that their utterance is influenced only marginally by wind conditions and not at all by habitat, while observations and experimental playback showed that the giving of these calls has no effect on inter-bout interval. We conclude that pied babblers do not seem to call at the end of a sentinel bout to maximise the efficiency of this cooperative act, but may use vocalisations at this stage to influence more individually driven behaviours.
    PLoS ONE 01/2011; 6(10):e25010. · 3.53 Impact Factor

Full-text

View
24 Downloads
Available from
May 21, 2014