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: 5.29). 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
 · 
100 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The group augmentation (GA) hypothesis states that if helpers in cooperatively breeding animals raise the reproductive success of the group, the benefits of living in a resulting larger group - improved survival or future reproductive success - favour the evolution of seemingly altruistic helping behaviour. The applicability of the GA hypothesis remains debatable, however, partly owing to the lack of a clear conceptual framework and a shortage of appropriate empirical studies. We conceptualise here the GA hypothesis and illustrate that benefits of GA can accrue via different evolutionary mechanisms that relate closely to well-supported general concepts of group living and cooperation. These benefits reflect several plausible explanations for the evolutionary maintenance of helping behaviour in cooperatively breeding animals.
    Trends in Ecology & Evolution 07/2014; 29(8). DOI:10.1016/j.tree.2014.05.013 · 15.35 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: To maximise survival, animals should adjust their behaviour flexibly in response to indicators of predation risk. Predation risk is affected by a range of ecological, social and individual variables, which can fluctuate over different time scales. In general, current risk levels are known to influence the behaviour of sentinels, individuals that adopt a raised position to scan for danger while group-mates are engaged in other activities. However, there has been little consideration of whether decisions made at different stages of a sentinel bout are affected in the same way by perceived predation risk and whether the same level of behavioural plasticity is exhibited when making these different decisions. Here we use detailed behavioural observations and a playback experiment to investigate the behavioural choices of dwarf mongoose (Helogale parvula) sentinels at three different stages of a bout (before, start, during). Individuals were more likely to begin a bout, and did so sooner, following alarm calls, which are immediate, direct indicators of elevated risk. Sentinels selected an initial height from which to guard depending on factors that tend to vary in the medium-term (hours), choosing higher positions in denser habitat and less windy conditions. In contrast, decisions about bout duration were made in relation to short-term (seconds/minutes) changes in information, with sentinels guarding for longer when an alarm call was given during a bout, and terminating bouts sooner when group-mates moved out of sight. Our results demonstrate that sentinel decisions are influenced by both direct and indirect indicators of likely predation risk and that sentinel behaviour is adjusted flexibly with regard to information presented on various time scales, highlighting the complexity of decision-making processes.
    Animal Behaviour 11/2014; 98:185-192. DOI:10.1016/j.anbehav.2014.10.012 · 3.07 Impact Factor
  • Source
    Behaviour 01/2013; 150:691-712. · 1.40 Impact Factor

Full-text

Download
29 Downloads
Available from
May 21, 2014