Ants tumble but keep marching in microgravity

Learn more about the citizen science lesson plan here. "We will compare the results from different species and may learn about some new algorithms for collective search that no one has thought of yet," says Deborah Gordon. (Credit: "Tetramorium" via Shutterstock)

Last year, eight groups of ants flew to the International Space Station. Results from their trip show that the collective search behavior of ants in microgravity had some interesting twists.

The ISS experiment, reported online in Frontiers in Ecology and Evolution, used the pavement ant, a species that searches by spreading quickly to the boundary of the area they are exploring. This search algorithm may explain why pavement ants often end up in conflict with neighboring colonies along sidewalks.

“In the extreme condition of microgravity in space, the pavement ants did the same thing they did on Earth, but not as well,” says Stanford University biologist Deborah M. Gordon, who studies collective behavior.

However, microgravity gave the ants another, unexpected opportunity to shine: They showed a remarkable ability to walk on the surface of their enclosure, and a capacity to regain contact with the surface after they lost hold, tumbling around or skidding rapidly in a Michael Jackson-type move, Gordon says.

But not all ants search the way pavement ants do. “An earlier experiment showed that another species, Argentine ants, do not move toward boundaries,” says Gordon.

“Instead, they search thoroughly all over the new area. Comparing the search behavior of different species can show us how evolution has shaped collective behavior to fit extreme conditions.”

Smelling the perimeter

An ant’s world harbors food, water, and shelter, as well as enemies. An ant colony needs to monitor its surroundings to find out what is going on. To monitor the colony’s world, ants have to move around, because an ant has to get close to something to smell it—most ants have poor vision.

Over millions of years of evolution, different ant species have evolved in different environments, and they have probably evolved interesting and diverse ways of keeping track of what is going on, says Gordon.

For instance, when Argentine ants are more crowded, they search more thoroughly, using a path that winds around in a small area. But ants that are less crowded cover more ground by walking farther in straight lines. They find out whether there are many other ants nearby through smelling each other when they touch antennae.

Species that are successful invaders outside their native habitats, such as the Argentine ants and pavement ants, may be especially good at searching. Perhaps that is why they are so quick to find the crumbs on our kitchen counters, says Gordon.

Ants now, robots later?

Now Gordon is inviting high school students to collaborate in further research on collective search by ants on Earth, through a new “citizen science” lesson plan. Younger students could try it too.

The lesson plan guides students as they investigate new collective search algorithms in species of ants that haven’t been studied—and there are more than 14,000 species to learn about.

Ants may not encounter microgravity on Earth, but they search in every other kind of environment. The results might offer suggestions on how to program robots for rescue and exploration. Collective search algorithms are used to program rescue robots to search efficiently. When robots search dangerous territory for humans, it may be most effective, and cheapest, to mimic ants and not require the robots to report back to a central controller.

Teacher-tested by Tammy Moriarty, a professional development associate at Stanford’s Center to Support Excellence in Teaching, the lesson plan integrates science, technology, engineering, and math, known collectively as the STEM subjects.


Students will investigate, on Earth, the same underlying question Gordon asked in the Ants-in-Space project: What techniques can be used to thoroughly explore a novel area, without any central control or plan for how to coordinate the search?

Data and results will be posted on a public website. “We will compare the results from different species and may learn about some new algorithms for collective search that no one has thought of yet,” says Gordon.

“Deborah Gordon is a scientist who wants to reach out to classroom teachers who are preparing our future scientists and citizens,” Moriarty says. The lesson plan engages students with a scientific inquiry that does not have a predictable answer. As a result, the students are actually doing science, including collecting and observing wild ants, and looking for patterns in their behavior.

Source: Leslie Willoughby for Stanford University