Effects of load mass and size on cooperative transport in ants over multiple transport challenges

Helen F. McCreery, Jenna Bilek, Radhika Nagpal, Michael D. Breed

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


Some ant species cooperatively transport a wide range of extremely large, heavy food objects of various shapes and materials. While previous studies have examined how object mass and size affect the recruitment of additional workers, less is understood about how these attributes affect the rest of the transport process. Using artificial baits with independently varying mass and size, we reveal their effects on cooperative transport in Paratrechina longicornis across two transport challenges: movement initiation and obstacle navigation. As expected, object mass was tightly correlated with number of porters as workers adjust group size to the task. Mass affected performance similarly across the two challenges, with groups carrying heavy objects having lower performance. Yet, object size had differing effects depending on the challenge. While larger objects led to reduced performance during movement initiation – groups took longer to start moving these objects and had lower velocities – there was no evidence for this during obstacle navigation, and the opposite pattern was weakly supported. If a group struggles to start moving an object, it does not necessarily predict difficulty navigating around obstacles; groups should persist in trying to move ‘difficult’ objects, which may be easier to transport later in the process. Additionally, groups hitting obstacles were not substantially disrupted, and started moving again sooner than at the start, despite the nest direction being blocked. Paratrechina longicornis transport groups never failed, performing well at both challenges while carrying widely varying objects, and even transported a bait weighing 1900 times the mass of an individual.

Original languageEnglish (US)
Article numberjeb206821
JournalJournal of Experimental Biology
Issue number17
StatePublished - 2019
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Insect Science
  • Ecology, Evolution, Behavior and Systematics
  • Aquatic Science
  • Animal Science and Zoology
  • Molecular Biology
  • Physiology


  • Collective behaviour
  • Decentralized coordination
  • Emergent behavior
  • Formicidae
  • Self-organization


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