ABSTRACT
The locomotor behavior of an animal strongly depends on the distribution of its body mass. Whenever changes occur in this distribution, the displacement of the body center of mass (CoM) may lead to a loss of balance. Ants are an interesting biological model with which to investigate how an animal copes with such changes because, when they transport food, their CoM may be displaced from its usual position. We studied the ant Formica rufa, whose diet consists mainly of liquid food, stored in the abdomen, but also includes prey transported in the mandibles. We investigated the kinematics of locomotion of the same individuals while walking unloaded and while transporting food internally or externally. We found that the kinematics of locomotion slightly differed in the two types of transport. Ants transporting food in their mandibles adopted a more erect posture and tended to be more often in static instability than ants transporting food internally. In addition, the amplitude of the vertical oscillations of their CoM was higher, which led to a jerky locomotion. However, owing to their erect position, the position of their overall CoM was actually not different from that of unloaded ants. Finally, the mechanical work achieved by ants to rise and accelerate their CoM was smaller in ants transporting food internally than in ants transporting food externally or in unloaded ants. This suggests that the morphology of F. rufa could make the transport of food in the gaster more mechanically efficient than the transport of food in the mandibles.
Footnotes
Author contributions
Conceptualization: V.F.; Data curation: V.F.; Formal analysis: H.M., V.F.; Funding acquisition: V.F.; Investigation: G.B., H.M., V.F.; Methodology: G.B., H.M., V.F.; Project administration: V.F.; Resources: V.F.; Software: H.M., V.F.; Supervision: V.F.; Validation: V.F.; Visualization: H.M., V.F.; Writing – original draft: G.B., V.F.; Writing – review & editing: V.F.
Funding
H.M. was funded by a doctoral grant from the French Ministry of Higher Education, Research and Innovation through the SEVAB graduate school of the University of Toulouse. The image acquisition equipment was financed by the project Serious GaRS (ref no. 16004115/MP0007086) funded by FEDER-FSE Midi-Pyrénées et Garonne 2014–2020.
Data availability
Dataset and R script to analyze the data and generate the figures of this paper are available on Zenodo (https://doi.org/10.5281/zenodo.13844044).