Defensive colouration is not a reliable indicator of fungal infection in aposematic poison frogs

Color signals can be altered by pathogenic infections through different
pathways, potentially compromising their signaling functions. This
association has been widely examined in the context of sexual selection,
whereas little is known about its effects on aposematic coloration. We
measured dorsal skin color traits of the aposematic poison frog
Dendrobates tinctorius using multispectral digital imaging. For each
individual, we also quantified Batrachochytrium dendrobatidis (Bd)
infection status and load using droplet digital PCR (ddPCR). We compared
the brightness, saturation and hue from melanin- and carotenoid-based
coloration between frogs, using linear or bayesian circular regressions
models, and found no association between Bd infection status or
load and differences in coloration. Instead, body size influenced both
infection outcomes and colouration, with sex-specific patterns suggesting
potential ontogenetic or life-history trade-offs. Our findings
highlight that the links between colour expression and condition are more
context- and taxa-dependent than often assumed, and suggest that, in D.
tinctorius, defensive signals may remain stable despite pathogen exposure.
This dataset provides a detailed resource to explore the relationships
between pathogen infection, host traits, and color expression in an
aposematic species.