Information Certainty Determines Social and Private Information Use in Ants

Abstract

Decision-making in uncertain environments requires animals to evaluate, contrast and integrate various information sources to choose appropriate actions. In consensus-making groups, quorum responses are commonly used to combine private and social information, leading to both robust and flexible decisions. Here we show that in house-hunting ant colonies, individuals fine-tune the parameters of their quorum responses depending on their private knowledge: informed ants evaluating a familiar new nest rely relatively more on social than private information when the certainty of their private information is low, and vice versa. This indicates that the ants follow a highly sophisticated ‘copy-when-uncertain’ social learning strategy similar to that observed in a few vertebrate species. Using simulations, we further show that this strategy improves colony performance during emigrations and confers well-informed individuals more weight in the decision process, thus representing a novel mechanism for the emergence of leadership in collective decision-making.

Social Learning Strategies: Bridge-Building between Fields

“…In addition to humans, uncertainty due to a lack of personal information has a powerful effect on increasing reliance on social learning across multiple taxa, including fish [27], chimpanzees [28] and ants [29]. Moreover, the opposite is also the case; children are more likely to innovate and devise a novel method when the demonstrated method is unreliable in providing rewards than when they observe reliable demonstration [17].…”

Tandem‐running and scouting behaviour are characterized by up‐regulation of learning and memory formation genes within the ant brain

“…For example, the waggle dance performed by honeybee workers benefits not only the individuals receiving the information—who are then able to more easily locate quality food sources—but also the colony as a whole for which the food is obtained (von Frisch, ). The benefits of social information usage depend on many extrinsic and intrinsic factors (Grüter & Leadbeater, ), including the costliness of acquiring private information (Wray, Klein, & Seeley, ), and the certainty of social information (Stroeymeyt, Giurfa, & Franks, ).…”

Copy when uncertain: Lower light levels result in higher trail pheromone deposition and stronger reliance on pheromone trails in the ant Lasius niger

“…This suggests that ants may also be following a ‘copy-when-uncertain’ strategy, only relying on chemical signals when memories are unavailable or unreliable. Such a strategy has been previously reported in other social insects in other contexts, such as flower choice in bumblebees [32] and during nest relocation in rock ants [33]. Reports also describe ants depositing pheromone to lower-quality resources only in the dark [34], or increasing pheromone deposition when learning was unsuccessful [15] or on hard-to-learn routes [16].…”

“…‘Copy when uncertain’ is an adaptive information use strategy in many situations, and is employed by vertebrates in a variety of situations [2,53–55]. Recently, behaviour consistent with ‘copy when uncertain’ has been described in the behaviour of Temnothorax rock ants during house-hunting, where informed ants rely more on social information about nest quality when their private information is uncertain [33]. Bumblebees in a foraging context have also reported to ‘copy when uncertain’, being more likely to land next to bee models in uncertain environments [32].…”