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

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.