Ants do real estate the simple way

No site-versus-site comparison necessary, researchers suggest

For real-estate genius, look under a rock.

TAGGED A rock ant only a few millimeters long wears a radio-frequency identification tag. Researchers tracking the doings of individual ants propose a simplified version of how ants make real-estate decisions. IMAGE CREDIT: E. Robinson

Rock ants routinely pick the best in small, dark crevices, says Elva Robinson  of the University of Bristol in England. And the ant scouting system may be even simpler than researchers had thought.

When a colony of Temnothorax albipennis  needs to find a new home, some of the ants scurry out to scout the possibilities. After a series of lab tests, Robinson and her colleagues propose that individual ants aren’t directly comparing one possible site with another, as had been proposed before.

Instead, an individual ant decides merely whether a site is good enough or not, and the colony as a whole ends up in the best available place, Robinson and her colleagues suggest in a paper appearing online April 21 in Proceedings of the Royal Society B. Some ants are pickier than others, and the really particular ones are likely to keep searching. Their high standards push the colony toward the best choice, the team proposes.

Rock ants scurrying into dark protected crannies across Europe have become one of the major animal systems for testing ideas about collective decision making. Ants do have a queen, but she doesn’t squeak out orders. Individuals act, and out of their choices emerges a collective decision for the colony.

Paper coauthor Nigel Franks, also of the University of Bristol, rates ant house hunting as “fantastic.” Even when he and his colleagues put a mediocre nest near the ants’ original, ruined home and a really great nest nine times farther, the colony picks the good one.

The new paper “has been the first big rethink” since researchers eight years ago began describing how ants choose nests, Robinson says.

Another specialist in ant decision making, Stephen Pratt of Arizona State University in Tempe , says, “I think its most interesting claim is that individual ants do not ever compare the quality of two nests, even if they have the opportunity to do so.”

He adds, however, that he isn’t convinced because his earlier work using somewhat different tests on the same ant species found evidence for comparison. “I think the jury is still out.”

Robinson and her colleagues assembled massive amounts of data on house-hunting ants by fastening a tiny RFID tag, the kind stores use to foil shoplifters, onto each ant. Using the tags to monitor where the scouts went, researchers disrupted nine colonies and gave them each a choice between two potential nests — one darker and therefore preferable. But the subset of scouts visiting both sites didn’t show an apparent preference in bringing sister scouts to check out the better one.

When ants visit a nest, Robinson suggests, “they simply have to decide whether it’s good enough.” If it is, they return to recruit another scout to come take a look. If the nest site isn’t good, the individual scout keeps looking. When enough scouts encounter each other at a site, that’s the decision point. The scouts have achieved a quorum and it’s time to start moving in.

Susan Milius

Susan Milius is the life sciences writer, covering organismal biology and evolution, and has a special passion for plants, fungi and invertebrates. She studied biology and English literature.

More Stories from Science News on Animals

From the Nature Index

Paid Content