Scientists from the University of Bristol Woodland Road wanted to learn more about rock ants (Temnothorax albipennis). Specifically, they had noticed that the ants seem to be able to pick out the best possible nest sites when they decide to move. As a collective group, the entire colony chooses where to settle in, though scouts fan out and look around to see what's available. At first, they thought that the ants just directly compared options. But ants that never see the worse sites still help the colony decide on the better one - and researchers wanted to know how.
The researchers decided to create artifical nests and watch the ants while they made a decision. They made sites that either were darker (a condition the ants like) or not, thus creating a choice between a "low" and "high" quality nest. They also varied the distance that th ants had to travel to reach the two types of nests, to see if the colonies would be willing to travel further for the best choice. The key was that the researchers wanted to see how individual ants contributed to the colony's final decision, and whether the ants directly compared sites. But, as you might imagine, it's not exactly easy to watch what individual ants in a colony of look-alikes are doing. So they did something that just looks really, really cool to track the ants movements. They fitted ants with a micro version of a radio collar. These mini-radios relayed the ants location, so the scientists could see what sites the ants visited before making their choice.
The results, published in the journal Proceedings of the Royal Society B, were almost as cool as the methods. They found that the ants were willing to travel over 9 times as far for a good nest as a bad one, even without directly comparing any two nests. Instead of having to travel and compare, ants are simply more willing to abandon a poor nest area and look for somewhere else to live. When they evaluate a site, they choose to either camp there or move onward based on its quality. Those ants that visited the poorer quality choice decided to move on 41% of the time - the ones who visited the higher quality one left only 3% of the time. The appearance of directly comparing nests, the study suggests, is simply a side effect of ants visiting a low-quality site, deciding against it, and finding a better one. These findings impact how we view the intelligence, memory, and nest selection in insects in general.
It might be the complete and total nerd in me, but I think studies like this are totally amazing because they combine sexy gadgetry with important, ecological science. That, and they make for really, really cool pictures.
Robinson, E., Smith, F., Sullivan, K., & Franks, N. (2009). Do ants make direct comparisons? Proceedings of the Royal Society B: Biological Sciences DOI: 10.1098/rspb.2009.0350