The Effect of Parasitism on Personality in a Social Insect

It has been recognised for some years that animals differ consistently in various aspects of their behaviour, a phenomenon that has come to be referred to as animal personality. Recent work has attempted to investigate the ecological factors that shape personality, including the forms of stress that affect its expression. One of these – disease – is known to exert a considerable effect on host behaviour, yet its impact on animal personality has been relatively understudied. This study demonstrates that wood ants, Formica rufa, show consistent individual differences in three personality traits: boldness, sociability and aggressiveness; however there was little evidence of substantial correlations between these traits at the group level (known as behavioural syndromes). There was only limited evidence that exposure to the parasitic fungus Metarhizium anisopliae had an effect on the mean personality traits, with challenged ants showing marginal changes in boldness and sociability at high doses of fungus but no change in aggressiveness even when close to death. The results suggest that individual personality in F. rufa is very resilient to the physiological stress caused by pathogenesis. This may be because, as social insects, higher-order behavioural variation such as casteand colony-level personality may play a larger role in host-parasite interactions.