Eighty-five percent of falling C. atratus workers glide back to their home tree. Marked ants often came right back to the branch where they started within ten minutes of falling or being dropped off!
"I first noticed directed descent behavior on BCI [the Smithsonian's Barro Colorado Island field station in Panama] in 1998 while working on a canopy ant project with Mike Kaspari. Some spiny C. atratus workers got stuck in my hand while I was sitting in a tree crown. When I brushed them off, they appeared to glide rather than fall haphazardly," Yanoviak recalls.
"Early on, when Steve was dropping ants from the radio tower on BCI I got really excited because I could see their very clear 'J' trajectory." explains Kaspari, zoology professor at the University of Oklahoma and Research Associate at the Smithsonian. Kaspari introduced Steve to Robert Dudley, physiologist at the University of California, Berkeley and also a Smithsonian Research Associate.
Yanoviak's caught the ants' initial vertical drop, a quick swivel to orient the hind legs in the direction of the "trunk" and a steep, directed glide and landing on the vertical surface on video he recorded in Peru. Dudley's high-speed video enabled the authors to quantify the velocity and angle of the glide trajectory as Yanoviak dropped ants from the balcony of the lab on Barro Colorado against a backdrop of white bedsheet.
Additional experiments at Yanoviak's field sites in Costa Rica and near I
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Contact: Mike Kaspari
mkaspari@ou.edu
405-325-3371
Smithsonian Tropical Research Institute
9-Feb-2005