Social clues in risky pools: Perceived conspecific rivals strongly modify individual oviposition decisions in response to larval predation and competition

ABSTRACT Reproductive choices are imperative in shaping organismal fitness across diverse taxa. Such choices are particularly critical in organisms with biphasic lifecycles, as females must maximize offspring survival pre-oviposition, with no parental care extended afterward. Consequently, females face strong site selection pressures to effectively respond to offspring competition and predation risks. Ovipositing females encounter yet another challenge during site selection: assessing future competition for their offspring from potential conspecific rivals. Our current knowledge, based on average social versus solitary behaviours, fails to clarify how social signals influence individual behavior within groups. To address these challenges, we leveraged the unique oviposition biology of the mosquito Aedes aegypti where only blood-fed females can lay eggs. By tracking individual behaviour in a social setting, we ask: how does social information from perceived conspecific rivals influence an individual’s oviposition site selection? In our lab-based experiment, we examined oviposition strategies at two spatial scales under varying larval competition and predation risk. Our findings reveal that social information exerts a stronger influence on egg-laying behavior at larger spatial scales, i.e., at the scale of pool networks, than between neighboring pools. Social cues facilitated oviposition with increasing larval predation, as social females transitioned from rejecting to accepting pool networks. Conversely, under larval competition, social cues led to inhibition, with females withholding their eggs likely in anticipation of future competition. At finer spatial scales, social information only weakly modified oviposition behavior despite potential negative fitness consequences for the offspring. Thus, perceived conspecific risk strongly modifies oviposition—facilitation, inhibition, or no effect—and is scale-dependent.