Journal of Comparative Physiology A

, Volume 196, Issue 7, pp 471–480 | Cite as

Foraging grass-cutting ants (Atta vollenweideri) maintain stability by balancing their loads with controlled head movements

  • Karin MollEmail author
  • Flavio Roces
  • Walter Federle
Original Paper


Grass-cutting ants (Atta vollenweideri) carry leaf fragments several times heavier and longer than the workers themselves over considerable distances back to their nest. Workers transport fragments in an upright, slightly backwards-tilted position. To investigate how they maintain stability and control the carried fragment’s position, we measured head and fragment positions from video recordings. Load-transporting ants often fell over, demonstrating the biomechanical difficulty of this behavior. Long fragments were carried at a significantly steeper angle than short fragments of the same mass. Workers did not hold fragments differently between the mandibles, but performed controlled up and down head movements at the neck joint. By attaching additional mass at the fragment’s tip to load-carrying ants, we demonstrated that they are able to adjust the fragment angle. When we forced ants to transport loads across inclines, workers walking uphill carried fragments at a significantly steeper angle, and downhill at a shallower angle than ants walking horizontally. However, we observed similar head movements in unladen workers, indicating a generalized reaction to slopes that may have other functions in addition to maintaining stability. Our results underline the importance of proximate, biomechanical factors for the understanding of the foraging process in leaf-cutting ants.


Terrestrial locomotion Load Static stability Adaptation Atta 



This study was funded by a Dissertation Grant from the UK Biotechnology and Biological Sciences Research Council, by the German Academic Exchange Service (DAAD), by the Cambridge European Trust, by the Balfour Fund of the Department of Zoology (University of Cambridge), and by the German Research Foundation (DFG, Sonderforschungsbereich SFB 554/TPE1). We thank Martin Bollazzi for helpful discussions and Thomas Endlein for technical support. We are much indebted to Alejandro G. Di Giacomo and the Götz family for allowing the collection of the ant colony at the Reserva Ecológica El Bagual (Alparamis SA - Aves Argentinas) in Eastern Chaco, Province of Formosa, Argentina.


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Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  1. 1.Department of ZoologyUniversity of CambridgeCambridgeUK
  2. 2.Department of Behavioural Physiology and Sociobiology, BiocenterUniversity of WürzburgWürzburgGermany

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