Foraging through multiple nest holes: An impediment to collective decision-making in ants

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 selforganized insect societies.

Acorn Ants May Create and Use Two Entrances to the Nest Cavity

“…Using entrances from two opposite sites could have an influence on the foraging activity. For example, it was shown that for the red ant Myrmica rubra, the number of nest entrances influenced the collective foraging of the colony: multiple nest entrances reduced the foraging efficiency [42] but favored the simultaneous exploitation of several sources. It has been suggested that multiple entrances appear as a way for small-or medium-sized colonies to benefit from some of the advantages conferred by polydomy [38]-i.e., the simultaneous use of several nest sites by one colony-and T. crassispinus colony might use more than one nest (seasonal polydomy) [43].…”

Embodiment in distributed information processing: “Solid” plants versus “liquid” ant colonies

“…Many species of ants create their own transport and information processing networks using pheromone trails. These trails are created through foragers that leave the nest in search of food and upon returning with food, deposit pheromone trails on their way back to the nest (Beckers et al, 1992 ; Lehue & Detrain, 2020 ; Wendt et al, 2020 ). These trails encode quality: the better the food source, the more pheromone the successful foragers deposit.…”

“…For example, the information sharing between returning foragers to new recruits is an independent process at each nest entrance (Lehue et al, 2020 ). Therefore, having multiple nest entrances instead of one interferes with path optimisation, reducing the chances of finding food, establishing stable pheromone trails and effectively choosing the highest quality food source, resulting in a lower overall food gathering (Lehue et al, 2020 ; Lehue & Detrain, 2020 ). On the other hand, an increase in nest entrances facilitates the discovery of more food sites, which is useful for species harvesting many small, scattered packets of food, and exploiting more resources simultaneously is also a good bet-hedging strategy against losing resources, for example, to competing colonies or by depletion (Lehue et al, 2020 ; Lehue & Detrain, 2020 ).…”

Salivary gland substances of the arboreal termite Nasutitermes corniger induce worker aggregation and gnawing of food substrate

“…One of the most complex collective efforts of these societies is foraging behavior (Anderson & Ratnieks, 1999; Bonabeau & Theraulaz, 1999; Laloi et al, 2000; Aredes et al, 2022). Social foraging in insects depends on individual behaviors triggered by positive and negative stimuli, which, according to their frequency and intensity, may amplify or attenuate different behaviors (Detrain & Deneubourg, 2008; Lehue & Detrain, 2020). In termites, social foraging behavior involves interactions among individuals of different castes and is essentially regulated by chemical signals released by nestmates and the food source (Costa‐Leonardo, 2002; Costa‐Leonardo et al, 2009; Traniello & Leuthold, 2000; Bagnères & Hanus, 2015; Leonhardt et al, 2016; Costa‐Leonardo et al, 2023).…”