Dr. Steve Yanoviak, University of Texas
Part of the show Science of Sex, Smell and Pheromones...
Chris – Your work is normally carried out at the top of trees. Tell us your story about how you have discovered some very interesting behaviour in ants living in the canopy.
Steve – I’ve done a variety of different studies over the years, but the most dramatic part occurred two years ago. I was trying to catch a mosquito, and so had to sit very still so they would come up to me to feed on my blood. While sitting there, I saw some ants nesting in the branch. They weren’t happy with my presence and so started to crawl all over me and bite! As the ants were spiny, I brushed them off the branch rather than squashing them. Instead of falling straight down to the ground, they made a J-shaped trajectory that took them straight back to the tree trunk.
Chris – How do they do that?
Steve - Good question! About 85 out of 100 ants will do it, but the mechanism is still a mystery. What we do know is that they do it by sight. We tested this by painting nail varnish over their eyes. When they were stopped from seeing, they couldn’t get back to the trunk.
Chris - Why would ants need to do that?
Steve - Ant workers are important to their colonies. They forage for food and bring it back for the rest of the colony to eat. If a worker goes out and gets lost or eaten, the colony incurs a direct cost because not only do they have less food but they must also replace him. If an ant falls from the canopy into the leaf litter, it will have travelled the distance of about 3000 body lengths. From this distance, it may be difficult to find the chemical trails to lead them back again. Being able to fly back to your own leaf or tree trunk is therefore very advantageous.
Chris - How did you know it was the same ant that landed on the tree?
Steve – We painted the ants white so we could spot them on a video tape. This showed us that once they had fallen, it took on average about ten minutes for them to get back.
Chris - Where is this going to lead now?
Steve – It will go in a couple of directions. We want to find out some of the more specific details and the biomechanics behind it. How are they making the turns? How many different species of ants do this? What are the evolutionary origins? We are also going to look at other insects, including those in the Asian and African tropics.