Figure 1.

Stress transmission in animal collectives. Individual attributes make members of social groups more or less susceptible to external stressors in their environment by shaping their propensity to encounter stressors and their physiological responses. If the stress response is activated in one individual, changes in its behaviour and physiology can provide cues causing a stress response in conspecifics. Individual and social attributes, or behavioural context, can determine whether a stress response is transmitted (amplified), buffered (attenuated), or if there is no effect. Changes in the composition of the group, or in the interactions among individuals, can alter group performance in collective tasks and other emergent collective properties. The impact on group performance could then feed back onto how individuals interact with their environment, for example by increasing predator alertness or reducing social cohesion, potentially altering their state (e.g. changed reproductive status or health) and shaping their future response to stressors. (Online version in colour.)