Abstract
In social insects, collective choices between food sources are based on self-organized mechanisms where information about resources are locally processed by the foragers. Such a collective decision emerges from the competition between pheromone trails leading to different resources but also between the recruiting stimuli emitted by successful foragers at nest entrances. In this study, we investigated how an additional nest entrance influences the ability of Myrmica rubra ant colonies to exploit two food sources of different quality (1M and 0.1M sucrose solution) and to select the most rewarding one. We found that the mobilisation of workers doubled in two-entrance nests compared to one-entrance nests but that ants were less likely to reach a food source once they exited the nest. Moreover, the collective selection of the most rewarding food source was less marked in two-entrance nests, with foragers distributing themselves evenly between the two feeders. Ultimately, multiple nest entrances reduced the foraging efficiency of ant colonies that consumed significantly less sugar out of the two available resources. Our results highlight that the nest structure, more specifically the number of nest entrances, can impede the ant's ability to process information about environmental opportunities and to select the most rewarding resource. This study opens new insights on how the physical interface between the nest interior and the outside environment can act upon collective decision-making and foraging efficiency in self-organized insect societies.
Highlights
Group-living animals have to share common goals, such as finding a suitable nesting place or exploiting a profitable food resource
In a previous study on Myrmica rubra ants, we found that an additional nest entrance segregated the pool of recruiters and hampered the formation of a collective foraging trail leading to a food source [31]
In mass recruiting ants such as M. rubra, these amplifying processes are based both on direct contacts, such as antennations and trophallaxis taking place at the nest entrance [29,30,31, 32, 34, 36], and on indirect interactions, via pheromone trails laid outside the nest [31,37,38]
Summary
Group-living animals have to share common goals, such as finding a suitable nesting place or exploiting a profitable food resource. The pay-offs of a collective decision obviously depend on their ability to integrate multiple–and sometimes conflicting–information sources in order to select the best option for the group as a whole [1,2,3]. In such situations where group coordination is beneficial, theoretical studies have demonstrated that pooling different sources of information in order to converge toward a shared decision could be more advantageous to all group members (as they are more likely to be correct) than decisions made by a few leaders [4,5,6,7,8].
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