Body condition and acoustic noise modify female responses to uni- and multimodal signals emitted by a male-mimicking robot frog

Mate choice is shaped by both intrinsic and extrinsic factors, including
signal conspicuity, receiver body condition, and environmental properties.
Multimodal signals are generally more conspicuous than unimodal ones and
are expected to elicit stronger responses. However, variation in body
condition and background noise modulate receivers’ responsiveness. We
investigated how signal type (uni- or multimodal) interacts with body
condition and background acoustic noise to influence female responses to
male displays in the stream-breeding frog Crossodactylus schmidti. In a
field experiment using a male-mimicking robot frog, females were exposed
to acoustic (advertisement calls), visual (toe flags), and multimodal
(advertisement calls + toe flags) stimuli, while their behavioral
responses, body condition, and environmental acoustic noise were recorded.
Females responded preferentially to multimodal stimuli over acoustic or
visual ones. Those in poorer body condition were more responsive overall,
reacting more readily to all stimulus types, indicating
condition-dependent mate choice. High levels of acoustic noise generally
reduced responses to visual signals, suggesting cross-modal sensory
interference. However, when exposed to unimodal acoustic stimuli in
noisier sites, females increased their visual signaling, possibly as
compensatory behavior in response to auditory masking. These findings
highlight the adaptive significance of multimodal signals in noisy
environments and emphasize the role of female condition and background
noise in shaping intersexual communication during mate choice.