Stress, corticosterone, and colour-change in a toad with dynamic sexual dichromatism

Abstract

Animals use colouration to serve diverse functions including camouflage, thermoregulation, and communication. Recent research has revealed that many anurans exhibit drastic colour changes and growing evidence supports that these changes are sexually selected signals. Male yellow toads, Incilius luetkenii, exhibit dynamic sexual dichromatism, changing from mud-brown to lemon-yellow during their brief breeding events. Toads darken when isolated in captivity, which is hypothesized to be a stress response, although the mechanisms driving this change have yet to be experimentally investigated. We confined breeding toads to small terrariums for four hours and predicted that colour and corticosterone levels would change in isolation. We found that toads darkened during isolation, but that corticosterone levels did not change with colour. Our correlational results suggest that corticosterone is not the main driver of colour change in yellow toads and highlight avenues for future research that may enhance our understanding of colour change in anurans.