Impacts of fungal disease on dyadic social interactions in a wild agamid lizard

ABSTRACT

Emerging infectious fungal diseases are responsible for the extinction of myriad species across a range of phyla. As recently shown by the COVID-19 pandemic, social transmission can be key to disease spread, and in this context, humans are not alone in trying to be alone. In group-living species, individuals have been shown to use social behaviour to avoid infection;diseased individuals can isolate from the group, or healthy animals can avoid diseased conspecifics. However, little is known about social behaviour as a mechanism to avoid fungal infection. In this study, we investigated the extent to which wild urban eastern water dragons, Intellagama lesueurii, a gregarious reptile, modify their social behaviour as a response to infection with a recently emerged infectious fungal disease, caused by the pathogen Nannizziopsis barbatae. Using individual data from a long-term study population inhabiting Roma Street Parkland in Brisbane's Central Business District (QLD, Australia) and focal sampling, we tested whether dragons exhibit self-isolation and social-distancing behaviours in the context of dyadic social approach events. Our results suggested that while the presence of the fungal disease had no effect on individuals' social behaviour, its severity did. Specifically, we found that (1) diseased individuals were no less social than their nondiseased conspecifics, (2) nondiseased individuals did not avoid or spend less time with diseased conspecifics, and (3) models considering the severity of skin lesions caused by N. barbatae, instead of their presence or absence, suggested that individuals avoided more severely diseased conspecifics regardless of their own disease status. © 2023 The Author(s)