Disease-Dependent Social Responses to Local Disease Composition in a Wild Reptile

Felix Requena-Garcia , Nicola Jackson, Angela C Mitchell, Celine Frere

Emerging infectious diseases can generate persistent and locally heterogeneous patterns of risk across animal populations, yet how animal social behaviour varies under these conditions remains poorly understood. When pathogens persist in the environment, individuals may need to respond to disease conditions at fine spatial and temporal scales rather than rely on fixed social strategies. Here, we examine how individual disease status and local conditions relate to social behaviour in a free-ranging population of eastern water dragons (Intellagama lesueurii) affected by the fungal pathogen Nannizziopsis barbatae (Nb). Using 16,855 sightings of 201 individually identified lizards collected between 2018 and 2023, we quantified gregariousness at each observation and tested how it varied with local conspecific abundance, local disease composition, and individual disease status. Gregariousness increased strongly with local conspecific abundance and varied with local disease composition according to individual disease status. Among diseased individuals, gregariousness decreased with increasing local disease composition, whereas healthy individuals showed no clear relationship across the same gradient. Together, these findings suggest that social behaviour under persistent fungal disease pressure varies with fine-scale local conditions and individual disease status, highlighting the context-dependent nature of social behaviour in wildlife disease systems.