Vienna, Austria - October 08, 2025 Schönbrunn Zoo has unveiled fascinating new insights into the dramatic color change of black-scarred toads during India’s monsoon season. During the brief one- to two-day spawning period, male toads shift from brown to bright yellow, creating a striking spectacle in the water. “During the two days of spawning, things get heated for the toads. The males, who are in the majority, cling to the few females as quickly as possible, thus quickly securing a mating partner at the water's edge,” explains Susanne Stückler, PhD, lead author of the study and research associate at Schönbrunn Zoo. To investigate the role of coloration, researchers placed 3D toad models—yellow to mimic males and brown to mimic females—into the water during natural spawning events involving hundreds of toads. Males were observed clinging to the brown female models significantly more often than to the yellow male models, demonstrating that the vivid yellow coloring helps males quickly distinguish females from rival males. The study also revealed that body size, weight, and male coloration did not affect a male’s ability to secure a mate. “This reversible, conspicuous color signal appears to be particularly advantageous in time-limited reproductive events with high competition, as is the case with black-scarred toads,” said Dr. Doris Preininger, research associate at the zoo. Previous research at Schönbrunn Zoo in 2022 showed that stress hormones trigger this rapid color change. The latest study confirms the critical role of the yellow hue in natural mating behavior, highlighting how basic research contributes to understanding these unique amphibians in the wild.