Prey synchronize their vigilant behaviour with other group members

Abstract

It is generally assumed that an individual of a prey species can benefit from an increase in the number of its group's members by reducing its own investment in vigilance. But what behaviour should group members adopt in relation to both the risk of being preyed upon and the individual investment in vigilance? Most models assume that individuals scan independently of one another. It is generally argued that it is more profitable for each group member owing to the cost that coordination of individual scans in non-overlapping bouts of vigilance would require. We studied the relationships between both individual and collective vigilance and group size in Defassa waterbuck, Kobus ellipsiprymnus defassa, in a population living under a predation risk. Our results confirmed that the proportion of time an individual spent in vigilance decreased with group size. However, the time during which at least one individual in the group scanned the environment (collective vigilance) increased. Analyses showed that individuals neither coordinated their scanning in an asynchronous way nor scanned independently of one another. On the contrary, scanning and non-scanning bouts were synchronized between group members, producing waves of collective vigilance. We claim that these waves are triggered by allelomimetic effects i.e. they are a phenomenon produced by an individual copying its neighbour's behaviour.

New perspectives in gaze sensitivity research

“…Other studies have used snapshots of group behavior to determine whether individuals were exhibiting vigilant behavior at the same time more or less than would be predicted statistically. These studies provide evidence that animals do monitor their neighbors, and tend of synchronize, rather than asynchronize their vigilance (Beauchamp, 2009;Ge, Beauchamp, & Li, 2011;Pays, Renaud, et al 2007). We suggest that measuring gaze following could also provide a direct measure of visual monitoring.…”

Catch the wave: prairie dogs assess neighbours’ awareness using contagious displays

“…Members of group-living species rely upon collective vigilance to detect predators [1], occasionally synchronizing vigilance so as to enhance the detection of potential threats [2,3]. As the number of individuals residing within a group increases, each individual can devote less time to vigilance and more time to other activities, for example foraging [1,4,5], owing, in part, to the cumulative effect of each individual's finite probability of detecting presumptive threats [6][7][8].…”

Negotiation may lead selfish individuals to cooperate: the example of the collective vigilance game

“…rodents [29]; marsupials [30]; ungulates [31]; passerines [18]; sea birds [32]; large flightless birds [33]), suggesting that prey living in groups often tend to imitate the vigilance of their companions. The present study shows that negotiation could regulate vigilance levels in these groups, in spite of the contagious aspect of vigilance.…”