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Dryad

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

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May 11, 2023 version files 192.95 KB

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, to date, little is known about social behaviour as a mechanism to avoid fungal infection. In this study, we investigate 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 test whether dragons exhibit self-isolation and social distancing behaviours in the context of dyadic social approach events. Statistical analyses of data collected from 633 observations of 123 unique individuals (78 non-diseased, 45 diseased) during 2020 – 2021 suggested that while the presence of the fungal disease had no effect on individuals’ social behaviour, the severity of the fungal disease did significantly affect individuals’ social behaviour. Specifically, we found that (i) diseased individuals were no less social than their non-diseased conspecifics, (ii) non-diseased individuals did not avoid or spend less time with diseased conspecifics, and (iii) models considering the severity of skin lesions caused by Nannizziopsis barbatae, instead of their presence or absence, suggested that individuals avoided more severely diseased conspecifics regardless of their own disease status These findings warrant further investigation, given the evidence that many species have displayed behavioural adaptations to disease, and the increasing risk posed by emerging infectious fungal diseases.