Why individual vigilance declines as group size increases

@article{Roberts1996WhyIV,
  title={Why individual vigilance declines as group size increases},
  author={Gilbert Roberts},
  journal={Animal Behaviour},
  year={1996},
  volume={51},
  pages={1077-1086}
}
  • G. Roberts
  • Published 1 May 1996
  • Psychology
  • Animal Behaviour
A reduction in individual vigilance with an increase in group size is one of the most frequently reported relationships in the study of animal behaviour. It has been argued that this phenomenon may not be a direct consequence of an increase in group size but may be due to other factors relating to increased group size, such as increased foraging competition. However, there is evidence for a direct relationship between group size and vigilance where other variables have been controlled. The aim… Expand
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References

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PREDATOR VIGILANCE AND GROUP SIZE IN MAMMALS AND BIRDS: A CRITICAL REVIEW OF THE EMPIRICAL EVIDENCE
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  • Psychology, Medicine
  • Biological reviews of the Cambridge Philosophical Society
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TLDR
Most of the studies fail to adequately demonstrate an unambiguous relationship between vigilance behaviour and group size, but many studies reveal interesting features of the relationship between Vigilance and Group size that should provide fruitful avenues for future research. Expand
Back to the basics of anti-predatory vigilance: the group-size effect
Abstract A negative relationship between group size and levels of individual vigilance is widespread in socially feeding vertebrates. The main explanation of this ‘group-size effect’, the many-eyesExpand
Vigilance does not covary with group size in an island population of silvereyes (Zosterops lateralis)
TLDR
There was no relationship between scanning behavior and group size under Heron Island's predator-free environment, and covariation between group size and vigilance is not expected in the absence of predators. Expand
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A simple model was developed to examine the relationship between vigilance while feeding and several determinants of the risk of predation. It was found that the relationship between vigilance andExpand
Evolutionarily stable levels of vigilance as a function of group size
An animal's level of vigilance is usually interpreted as a trade-off between gaining food and reducing the danger of predation. In the context of a group of animals, vigilance has been analysed usingExpand
From individual to collective vigilance in wild boar (Sus scrofa)
Vigilance behaviour of captive wild boars at feeding points was investigated using films. Results show that individual vigilance decreased with increasing group size, especially between solitaryExpand
The effects of mixed-species flocking on the vigilance of shorebirds: Who do they trust?
TLDR
The effect of mixed species flocking on vigilance is investigated in two species of wading bird wintering on rocky shores, finding that both turnstones and purple sandpipers ‘share’ vigilance with conspecifics, but also with some other waders; the extent of sharing appears to depend on the relative size of, and habitat overlap with, the other species. Expand
Should co-operative groups be more vigilant than selfish groups?
We develop four simple models of group vigilance that illustrate the conditions under which co-operative groups should be more or less vigilant than selfish groups. In the first model, preyExpand
Vigilance and group size in ostriches
Abstract Wild ostriches were observed while feeding alone or in groups of up to four birds, and their vigilance (proportion of time with the head up) recorded. Individual vigilance declined as groupExpand
Group Vigilance and Shoal Size in a Small Characin Fish
TLDR
The importance of the enhanced predator detection ability of fish shoals and the social transmission of alarms within them is discussed in relation to predator avoidance behaviour and other activities of fish in shoals. Expand
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