Vienna Zoo Schönbrunn researches color change in exotic toads

The striking color change of male black-spotted toads during mating season apparently serves to avoid mismating. This is according to a recent study conducted under the leadership of the Schönbrunn Zoo in the natural habitat of the animals. The research results were presented on Thursday.

During the one to two-day spawning period, the male toads change from an inconspicuous brown to a bright yellow coloration. Females, on the other hand, remain brown. According to the study, the animals clearly recognize this color difference and use it to distinguish between potential mating partners and male competition.

Artificial Toad Models Provide Clear Results

To analyze the effect of coloration, 3D models in yellow and brown were placed in the water – while hundreds of toads were spawning simultaneously. The males showed significantly more interest in the brown models, which were meant to imitate females. The yellow, male dummies were embraced significantly less often.

“The yellow coloration does not serve attraction, but helps in the rapid distinction between males and females,” explained lead author Susanne Stückler, a scientific associate at the Schönbrunn Zoo. Neither body size nor weight of the males influenced mating success.

Color Change Controlled by Stress Hormones

As early as 2022, researchers at the zoo investigated the mechanism of color change. It was shown that stress hormones trigger the recoloring. The current study aimed to clarify the ecological function of this signal under natural conditions.

“Such reversible color signals seem particularly advantageous when mating is temporally limited and associated with strong competition,” said zoologist Doris Preininger. The contribution from Schönbrunn thus provides important insights into the reproductive biology of this amphibian species native to Southeast Asia.

(APA/Red)

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