Abstract
Leaf cutter ants are model organisms in studies of central place foraging, but these ants carry smaller than optimal leaf fragments for their body size. Laboratory experiments show that load ratios (leaf fragment mass/ant mass) are higher on extreme downhill trails than on extreme uphill trails, which could explain deviations from optimality in the wild. Here we examine how trail gradient affects load size selection in the field for the first time. We measured load ratios on extreme natural gradients in the mountains of Monteverde, Costa Rica. In general, load ratios were found to be higher on downhill trails than on uphill trails as found in laboratory studies. Not all colonies showed this pattern, indicating that other factors may interact with trail gradient to determine load size selection. The results confirm that extreme trail gradients can contribute to determine optimal load sizes in central place foraging in natural conditions.
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Acknowledgements
We thank Orlando Torres, Jorge Torres, Myriam Scally, the Green Tree B and B and the Calandria Reserve for letting us sample on their property. This study is a result of the CIEE Study Abroad Program in Tropical Ecology and Conservation in Monteverde, Costa Rica. We thank the Costa Rican National Conservation System for allowing us permission to conduct research in Costa Rica (permit number M-P-SINAC-PNI-ACAT-021-2018).
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Finger, C., Chaves-Campos, J. Trail Gradient Influences Load Size in Wild Leaf Cutter Ants. J Insect Behav 33, 7–13 (2020). https://doi.org/10.1007/s10905-020-09740-2
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DOI: https://doi.org/10.1007/s10905-020-09740-2