Carlesso, D. | bioRxiv Science

bioRxiv2023

Leaderless consensus decision-making determines cooperative transport direction in weaver ants

Animal groups need to achieve and maintain consensus to minimise conflict among individuals and prevent group fragmentation. An excellent example of a consensus challenge is cooperative transport, where multiple individuals cooperate to move a large item together. This behavior, regularly displayed by ants and humans only, requires individuals to agree on which direction to move in. Unlike humans, ants cannot use verbal communication but most likely rely on private information and/or mechanical forces sensed through the carried item to coordinate their behaviour. Here we investigated how groups of weaver ants achieve consensus during cooperative transport using a tethered-object protocol, where ants had to transport a prey item that was tethered in place with a thin string. This protocol allows the decoupling of the movement of informed ants from that of uninformed individuals. We showed that weaver ants pool together the opinions of all group members to increase their navigational accuracy. We confirmed this result using a symmetry-breaking task, in which we challenged ants with navigating an open-ended corridor. Weaver ants are the first reported ant species to use a wisdom of the crowd strategy for cooperative transport, demonstrating that consensus mechanisms may differ according to the ecology of each species.

animal behavior and cognition↗

bioRxiv2020

Nectar non-protein amino acids (NPAAs) do not change nectar palatability but enhance learning and memory in honey bees

Floral nectar is a pivotal element of the intimate relationship between plants and pollinators and its chemical composition is likely to have been shaped by strong selective pressures. Nectars are composed of a plethora of nutritionally valuable compounds but also hundreds of secondary metabolites (SMs) whose ecological role is still not completely understood. Here we performed a set of behavioural experiments to study whether five ubiquitous nectar non-protein amino acids (NPAAs: {beta}-alanine, GABA, citrulline, ornithine and taurine) interact with gustation, feeding preference, and learning and memory in the pollinator Apis mellifera. We showed that harnessed foragers were unable to discriminate NPAAs from water when only accessing antennal chemo-tactile information and that freely moving bees did not exhibit innate feeding preferences for NPAA-laced sucrose solutions. Also, dietary consumption of NPAAs did not alter food consumption or longevity in caged bees over 10 days. Taken together our data suggest that ecologically relevant concentrations of NPAAs did not alter nectar palatability to bees. Olfactory conditioning assays showed that honey bees were more likely to learn a scent when it signalled a sucrose reward containing either {beta}-alanine or GABA, and that GABA also enhanced specific memory retention. Conversely, when ingested two hours prior to conditioning, GABA, {beta}-alanine, and taurine weakened bees acquisition performances but not specific memory retention, which was enhanced in the case of {beta}-alanine and taurine. Neither citrulline nor ornithine affected learning and memory. Our study suggests that NPAAs in nectars may represent a cooperative strategy adopted by plants to attract beneficial pollinators, while simultaneously enhancing pollen transfer among conspecific flowers. Future work should validate these results in more ecological scenarios and extend the study to as many nectar SMs as possible, alone and in combination, as well as to other species of pollinators.

animal behavior and cognition↗