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

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 account for the inter-individual variation in oviposition within social settings. 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. Together, our study integrates two decades of findings on social information in reproductive choice, revealing that the effects of social facilitation, inhibition, or no effect on oviposition are dependent on risk and spatial scale.

Does mom know best when it comes to selecting egg-laying sites? In insects like mosquitoes, females must make crucial decisions to maximize offspring survival, as no parental care can be extended after egg-laying. During egg-laying, individuals also face threats from neighboring females competing for the same egg-laying pools. Our study investigates how perceived risks from neighbouring females impact individual behavior within a group. Studying egg-laying in groups can be tricky, especially since it's hard to track individual behavior. To tackle this uniquely, we studied Aedes mosquitoes, where only blood-fed females can lay eggs, allowing us to track individual egg-laying among non-laying females. By tracking individuals in a 'social' setting, we found that social cues substantially modified egg-laying behavior across larval competition and predation risks. Social cues had a stronger effect at the larger spatial scale, where the types of risks in the network of pools played a key role, than at the finer scale of decisions between neighbouring pools. Surprisingly, social information promotes egg-laying under high predation risk network but suppresses it under competitive risk. At finer spatial scales, social information weakly modified oviposition behaviour, despite potential negative consequences for offspring fitness. Our study provides evidence that the effect of social information – facilitation, inhibition or no effect – both in magnitude and direction is risk and spatial scale dependent. Thus, even the ‘best laid plans’ can be influenced by social clues.