Lia Schlippe Justicia Lia Schlippe Justicia Carolin Dittrich Carolin Dittrich Ossi Nokelainen Ossi Nokelainen Bibiana Rojas Bibiana Rojas Oxford University Press 2026 The expression of visual signals such as coloration can be altered by parasitic or pathogenic infections through multiple pathways, including resource reallocation, impaired tissue structure, and reduced pigment acquisition. These effects may compromise the functions of coloration and overall fitness. Conversely, the link between pigments and immunological defences can aid differently colored individuals in coping with infection. While the pigmentation-condition association has been widely studied in the context of sexual selection, far less is known about how pathogens affect defensive coloration, such as aposematic signals. Here, we investigated whether infection by the fungal pathogen Batrachochytrium dendrobatidis (Bd) is reflected in characteristics of the melanin- and/or carotenoid-based coloration of the aposematic poison frog Dendrobates tinctorius in the wild. Using ddPCR to identify the frogs' infection status, and multispectral digital imaging to quantify their coloration traits, we show that neither type of coloration is a reliable indicator of Bd infection. Instead, body size influenced both infection outcomes and coloration, with sex-specific patterns suggesting potential ontogenetic or life-history trade-offs. Our findings highlight that the links between color 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. PDFDocument eng 2026-06-23T10:12:35.077533582Z 2026 Amazon Carotenoids Chytrid Fungus Dendrobates Tinctorius Melanin Pathogens Poison Frog Visual Signal 1408117 b application/pdf http://creativecommons.org/licenses/by/4.0/