Abstract
Ant colonies are often considered to be highly efficient societies skilled at cooperating and sharing workload among workers. Yet, several studies have revealed low colony activity levels and a subgroup of specialized inactive individuals, raising questions about their role. This study investigates whether these inactive ants differ in their sensitivity to environmental cues compared to other worker groups. We monitored the behavior of individually tagged workers from Myrmica rubra ant colonies, categorizing them as foragers, nurses, domestics, or inactives. Approximately one-third of the workers exhibited high levels of inactivity, forming a distinct group that remains stable over several days. Subsequently, individual tests were conducted on these ants to compare their responses to intranidal or extranidal location cues, and to task-related stimuli such as larvae or prey. In individual tests, foragers displayed distinct responses compared to internal workers. They exhibited greater responsiveness to prey, but were less inclined to care for larvae, stay in colony-marked or shaded areas, or approach nestmates. Among internal workers, except for the inactive ants, responses to various stimuli did not significantly differ. Notably, inactives had a stronger attraction to colony odor and were more likely to carry larvae when compared to foragers. Our results suggest that the inactivity of some individuals is not due to a lack of sensitivity to surrounding stimuli. Furthermore, their high propensity to interact with larvae supports the hypothesis of a “reserve caste” function, where these workers become active during periods of increased colony workload.
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Data availability
The datasets generated and analyzed in this study are available in the Zenodo repository, https://doi.org/https://doi.org/10.5281/zenodo.8389599.
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Acknowledgements
We would like to thank Luc Dekelver for helping us collect ants in the field. We thank the FRIA “Fonds pour la formation à la recherche dans l’industrie et dans l’agriculture” for funding this research with the grant n°1.E.106.19F awarded to the author O.V.
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Fonds pour la Formation à la Recherche dans l’Industrie et dans l’Agriculture, 1.E.106.19F, Oscar Vaes.
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All authors contributed to the conceptualization and the methodology of the experiment, the formal analysis, and the investigation of data. Writing the original draft and the acquisition of funding were done by Oscar Vaes and Claire Detrain. Oscar Vaes and Quentin Avanzi performed the visualization and the curation of data. Software manipulation and the administration of the project were done by Oscar Vaes. Reviewing and editing the manuscript, supervision and validation of the work as well as providing the resources were done by Claire Detrain.
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Vaes, O., Avanzi, Q. & Detrain, C. Beyond busy workers: exploring the sensitivity of inactive ants to environmental cues. Insect. Soc. (2024). https://doi.org/10.1007/s00040-024-00959-2
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DOI: https://doi.org/10.1007/s00040-024-00959-2