Sexual selection in a tropical toad: Do female toads choose brighter males in a species with rapid colour change?

Abstract

Conspicuous visual signals play an important role in animal communication, both within and between species. Bright, colourful signals allow animals to discriminate between individuals and can inform behavioural decisions and social interactions. In many instances, conspicuous colouration appears to have evolved through sexual selection via female mate choice or male–male competition. Male Neotropical yellow toads, Incilius luetkenii, display bright‐yellow colouration during their brief explosive mating events and then revert to a cryptic, female‐like, brown colour following amplexus and fertilization. Recent research has revealed that the yellow colouration of males may serve as a sex identification signal and that males remain yellow in the presence of both males and females but darken without conspecific stimulus. However, there is considerable variation in the brightness of yellow colouration in courting males, ranging from dull olive‐green to vibrant lemon‐yellow. The function of this variation remains unknown. In this study, we conducted two‐choice model presentation trials to test one mechanism of sexual selection that may drive this variation: intersexual selection. Specifically, we set out to determine whether females differentiate between males based on their colouration. We presented females with two hyper‐realistic robotic model toads, with one model painted to match a bright‐yellow male and the other a dull‐yellow male. Using several metrics of choice, we found that females did not show a preference for bright or dull colouration. Our research suggests that variation in the intensity of male breeding colouration is not driven by female choice in this species. Our study is consistent with the idea that there may be limited opportunity for female choice to influence male‐trait expression in explosive breeders. Future research will address whether intrasexual selection may influence colour variation in male yellow toads.

Sensory collectives in natural systems

“…Manipulations might involve the introduction of artificial cues or signals into a collective system, for example, via audio playback experiments, and presentation of visual or chemical stimuli. The use of robotics in multimodal communication studies has been extensive ( Gardner et al, 2021 ; Patricelli et al, 2007 ) as it enables individual unimodal components of signals to be presented to receivers in isolation, and then combined with components in other modalities, to investigate the influence of signals both separately and in combination (e.g. Swain et al, 2012 ).…”

Ecology of fear: predator avoidance reduces seed dispersal in an ant

“…The room was under a 12 : 12 white light cycle at 27°C and ca 55% humidity. I carried out the experiments on 6 April 2021 and I used identical 3D-printed models of R. ralata that were coloured with acrylic paint ( figure 2 a ), following approaches from other studies that used 3D-printed toads to study behavioural responses [ 28 ]. A Y-maze ( figure 2 b ) selection experiment was used to examine whether visual or non-visual cues drove the seed dispersal results.…”

Evidence that catecholaminergic systems mediate dynamic colour change during explosive breeding events in toads

“…Males consequently experience low rates of reproductive success, whereas females experience relatively high rates of mortality [10]. When dynamic colour change preceeds explosive breeding, it therefore likely regulates sexual recognition by helping males more easily distinguish each other from females [11][12][13]. In this way, we might consider sexual dichromatism that occurs prior to explosive breeding events an adaptive strategy that facilitates the speedy acquisition (and subsequent loss) of a signal for intense male-male competition [9].…”