Effects of snake fungal disease on short-term survival, behavior, and movement in free-ranging snakes

Pathogenic fungi are increasingly associated with epidemics in wildlife
populations. Snake fungal disease (SFD) is an emerging threat to snakes,
taxa that are elusive and difficult to sample. Thus, assessments of the
impacts of SFD on populations have rarely occurred. We used a field
technique to enhance detection, Passive Integrated Transponder (PIT)
telemetry, and a multistate capture-mark-recapture model to assess SFD
effects on short-term (within-season) survival, movement, and surface
activity of two wild snake species, Regina septemvittata (Queensnakes) and
Nerodia sipedon (Common Watersnakes). We were unable to detect an effect
of disease state on short-term survival for either species. However, we
estimated Bayesian posterior probabilities of >0.99 that R.
septemvittata with SFD spent more time surface-active and were less likely
to permanently emigrate from the study area. We also estimated
probabilities of 0.98 and 0.87 that temporary immigration and temporary
emigration rates were lower in diseased R. septemvittata. We found
evidence of elevated surface activity and lower temporary immigration
rates in diseased N. sipedon, with estimated probabilities of 0.89, and
found considerably less support for differences in permanent or temporary
emigration rates. This study is the first to yield estimates for key
demographic and behavioral parameters (survival, emigration, surface
activity) of snakes in wild populations afflicted with SFD. Given the
increase in surface activity of diseased snakes, future surveys of snake
populations should explore longer-term demographic consequences of SFD and
recognize that disease prevalence in surface-active animals may exceed
that of the population as a whole.