Swimming Ants


Pachycondyla villosa

Our discovery of aerial gliding behavior in ants suggested that there is strong selection pressure for small, cursorial, canopy-dwelling animals to not fall into the forest understory.  To test this hypothesis, we dropped canopy ants onto forest floor leaf litter and into various aquatic settings, including flooded forest and slow streams in the Amazon, and Lake Gatun in Panama.  We then tracked the fate of the ants to determine their survival rates.  The results are summarized in Yanoviak et al. 2011 and Yanoviak & Frederick 2014.  Here are the highlights:


  • Many canopy ants can run (swim) across the surface of the water (videos).  This is not a new discovery, as other ants are known to do this.  However, whereas most other cases of swimming in ants are associated with specific habitats (e.g., mangroves and phytotelmata) our survey of 35 ant species showed that swimming behavior is widespread among tropical canopy ants.
  • Swimming appears to have independently evolved four times in ants.  Phylogenetic assessment of swimming and gliding behaviors suggests that most canopy ants either glide or swim.  Only the carpenter ants (Camponotus spp.) can do both.
  • Swimming ants use skototaxis (orientation to dark objects) to escape from the water surface.
  • The leg motions used by ants when swimming differ among species and are sometimes modified relative to the stepping patterns used on land.  In particular, the hind legs tend to function as rudders or stabilizers.  This was determined with high-speed videos in the lab (videos).
  • The high frequency of both swimming and gliding behaviors in arboreal ants shows that life in the canopy imposes specific challenges on the wingless organisms that live or forage in tree crowns.