Why individual vigilance declines as group size increases

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…

Examined whether the reduction in rate and/or duration of scanning of the environment found in mammal and bird species also occurred in humans. 821 students at a German university were observed in student dining halls for 2-10 min periods, and the…

Levels of anti-predator vigilance often decrease with group size in birds and mammals. Vigilance may also serve other purposes such as scrounging. While scrounging, individual adopt the vigilant posture to locate and eventually exploit the food…

Abstract  The mean vigilance of animals in a group often decreases as their group size increases, yet nothing is known about whether there is individual variability in this relationship in species that change group sizes frequently, such as those…

We studied the effect of group size on the proportion of time that greater rheas, Rhea americana , allocated to vigilance and feeding during the non-breeding season. We tested whether: (1) the proportion of time that one bird allocates to vigilance…

Buggy Creek (BCR) virus is an arthropod-borne alphavirus that is naturally transmitted to its vertebrate host the cliff swallow (Petrochelidon pyrrhonota) by an invertebrate vector, namely the cimicid swallow bug (Oeciacus vicarius). We examined how…

Social foragers can benefit from others' success by joining and sharing their food discoveries. In a producer-scrounger (PS) system, foragers can either search for food themselves (play producer) or search for joining opportunities (play scrounger),…

Vigilance has been predicted to decrease with group size due to increased predator detection and dilution of predation risk in larger groups. Although earlier literature reviews have provided ample support for this prediction, an increasing number…

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 using the evolutionarily stable strategy (ESS) concept.…

In this paper a general ESS model of vigilance as function of group size is developed. The model can be used to investigate the effects of the attack rate, the probability that the foraging process is terminated prematurely by environmental events…