Spatial distancing by fungus-exposed Myrmica ants is prompted by sickness rather than contagiousness

Behavioural defences against parasites across host social structures

“…Notably, while resulting in the same outcome, prevention of social contact between infectious and healthy group members in this case is not driven by the healthy but by the infectious individual (in contrast to classical avoidance of infected conspecifics, see Gibson & Amoroso, 2022). This contact reduction also occurs at non-infectious disease stages (Bos et al, 2012;Conroy & Holman, 2022;Detrain & Leclerc, 2022) and in generally moribund individuals (Heinze & Walter, 2010;Ruepell et al, 2010), where it has been suggested to result from impaired perception of social cues (Kralj & Fuchs, 2006;Leclerc & Detrain, 2017) or sickness behaviour.…”

“…Notably, while resulting in the same outcome, prevention of social contact between infectious and healthy group members in this case is not driven by the healthy but by the infectious individual (in contrast to classical avoidance of infected conspecifics, see Gibson & Amoroso, 2022). This contact reduction also occurs at non‐infectious disease stages (Bos et al, 2012; Conroy & Holman, 2022; Detrain & Leclerc, 2022) and in generally moribund individuals (Heinze & Walter, 2010; Ruepell et al, 2010), where it has been suggested to result from impaired perception of social cues (Kralj & Fuchs, 2006; Leclerc & Detrain, 2017) or sickness behaviour. More work is needed to distinguish sickness behaviours such as reduced locomotion (Alciatore et al, 2021; Richard et al, 2008, but see Geffre et al, 2020) or reduced performance of colony tasks (Scharf et al, 2012) from altruistic self‐removal, even though both may contribute to lower contact rates and parasite spread (Figure 1).…”