Juvenile agile frogs spatially avoid ranavirus-infected conspecifics, but do not show generalized social distancing or self-isolation

Abstract

ABSTRACTExposure to contagious pathogens can result in behavioural changes, which can alter the spread of infectious diseases. Healthy individuals can express generalized social distancing or actively avoid the sources of infection, while infected individuals can show passive or active self-isolation. Amphibians are globally threatened by serious contagious diseases, yet their behavioural responses to infections are very scarcely known. We studied behavioural changes in agile frog (Rana dalmatina) juveniles upon exposure to aRanavirus(Rv). We performed classic choice tests in chambers containing a conspecific infected withRvin one end compartment and a non-infected conspecific in the other end, with anRv-infected or non-infected focal individual in the central compartment. We found that both non-infected andRv- infected focal individuals spatially avoided infected conspecifics, while there were no signs of generalized social distancing, nor self-isolation. Spatial avoidance of infected conspecifics may effectively hinder disease transmission. On the other hand, the absence of self-isolation by infected individuals may facilitate it. Our finding that infected individuals spent more time near the non-infected than infected conspecifics suggests that the strong behavioural drive to avoid infected conspecifics may not be silenced by infection, possibly to prevent secondary infections. The observation that infected focal individuals did not spend more time near conspecifics than non-infected focals renders it unlikely that the pathogen manipulated host behaviour to aid disease spread. More research is urgently needed to understand under what circumstances behavioural responses can help amphibians cope with infections, and how that affects disease dynamics in natural populations.GRAPHICAL ABSTRACT