Pathogen growth rate
At the time of collection in early hibernation, 88.89% (n=40) of
individuals from Persisting 1 (Cold + Dry) had detectable P.
destructans from swab samples, as did 97.78% (n=44) from Persisting 2
(Cold + Wet). All cages in each site had at least one infected bat at
the beginning of the experiment. Additionally, at the time of
collection, bats captured in Persisting 1 (Cold + Wet) had higher
pathogen loads than bats that originated in Persisting 2 (Cold + Dry)
(generalized linear model with gamma error distribution and log link
function: β = 1.371 ± 0.428 SE, p = 0.002; Supplemental Fig. 3).
Over the course of the experiment, the highest on-host pathogen growth
rates were recorded in the previously extirpated site (Warm + Wet),
which was at least 4° C warmer than either of the two persisting sites,
on average. Pathogen growth rates in Persisting 2 (Cold + Wet) were
slightly higher than in Persisting 1 (Cold + Dry), likely attributable
to the 1° C warmer and more humid conditions in the former. We also
detected an interactive effect of origin site (the site from which bats
were collected at the beginning of the experiment) and translocation
site on the pathogen growth rate, such that within the previously
extirpated site (Warm + Wet), bats originating in Persisting 2 (Cold +
Wet) had lower pathogen growth rates than bats that originated in
Persisting 1 (Cold + Dry) (Fig. 2; Supplemental Table 1).
Correspondingly, we detected an interactive effect of average roosting
temperature and origin site on pathogen growth rate (Fig. 2;
Supplemental Table 2). Across all bats, the pathogen growth rate
increased with average roosting temperature, consistent with the
sensitivity of P. destructans to ambient thermal
conditions24,66. However, due to the effect of origin
site, the estimated relationship between average roosting temperature
and pathogen growth rate was positive for bats that originated in
Persisting 1 (Cold + Dry) but did not increase for bats that originated
in Persisting 2 (Cold + Wet) (Fig. 2). Interestingly, we observed a
decrease in pathogen loads on five bats in Persisting 1 (Cold + Dry),
four in Persisting 2 (Cold + Wet), and one in Extirpated (Warm + Wet).