Swarming Ants Offer Robot Rescue Tips

Ants use antennae to slow their tumbles, could robots do the same?

Much of the South has been living with fire ants for decades, and most youngsters there know to avoid trampling their giant underground nests unless they are looking for a swarm of painful bites. It turns out that these pesky insects are extremely good at running through tunnels without clobbering each other and even using their antennae as extra limbs.

And researchers believe these new findings about their curious locomotion could give engineers lessons for building automated search-and-rescue robots designed to hunt for human victims trapped underground.

Scientists at Georgia Tech have been studying fire ants as they scurry through their nests, some of which can hold up to 100,000 individuals and become evacuated in minutes if they are flooded with water or attacked by larger predators. The ants are an invasive species, brought to the United States from South America where their native habitat is often subject to natural cycles of floods.

After several years of watching ants in two-dimensional and three-dimensional nests constructed in his laboratory, Nick Gravish, a postdoctoral student in the Department of Physics, found that tight spaces and jam-packed passageways didn't seem to bother them. In fact, with a top speed of 9 body lengths per second, they are basically sprinting past their fellow drones or workers inside the colony.

"We were so surprised to see them move so fast," said Gravish, first author on a study appearing today in the Proceedings of the National Academy of Sciences. "And their motion was filled with slips and missteps. You get a sense that slipping and falling is not a problem. We see that ants can run over the top of each other, and lift each other up. They can scramble as fast as possible and there's no penalty for that."

Gravish and collaborators professor Daniel Goldman and Michael Goodisman, and researcher Daria Monaenkova used X-ray tomography to study tunnels the ants built in the test chambers. They also used video tracking equipment to watch them move through tunnels made between two clear plates. This scientific ant farm was mounted on an air piston which was fired, dropping the maze so the ants would lose their footing and fall. The ants used their antennae as extra limbs to stop their descent. Nobody had really seen them doing that before, he said.

The same kind of crawling and falling movements will likely be faced by search-and-rescue robots in the future.

"We're very interested in how the next generation of robotics, which is going to be at the millimeter scale, will move through torturous complex environments," he said. "These ants are a good system to look at locomotion and this is one of the first studies to look at locomotion of ants in their own environment."

However, one robotics expert agreed that studying insects like ants can give good clues for building some kinds of autonomous devices, but cautioned not to be too optimistic that engineers can duplicate what nature has done over millions of years.

"The characteristics of the animals and response of the (robot) sensors are typically so different that it is problematic to just copy what you see in their behavior to run it on the robot," said Achim Lilienthal, director of the Mobile Robot and Olfaction Laboratory at the University of Orebro in Sweden.

Lilienthal recently build a "gas-bot" that can follow traces of methane escaping from a landfill using special laser sensors, and is working on problems of robot sensing and smell.

"The world looks very different for the robot," q he said.

Fire ants can evacuate a nest with impressive speed.

Tragedies like the Boston Marathon bombings remind us how important first responders are. Animals come to the rescue of members of their own species too.

Dolphins, for example, form "living rafts" to keep ill or injured dolphins buoyant, according to a paper published in Marine Mammal Science. Up to 12 dolphins, working together in a pod, may swim together to try and keep one of their own afloat.

Meerkats have one of the animal kingdom's most efficient security operations. A sentinel stands guard, watching for any potential threats. Should an intruder approach, an entire clan -- from elderly grandmas to younger dads -- mob the unwelcome visitor.

"Non-dangerous terrestrial animals most often ran away when they were approached and mobbed by the meerkats," explained Beke Graw and Marta Manser of the University of Zurich. More threatening animals, such as poisonous snakes, were also mobbed, but the meerkats often had to back down and leave, knowing they might be safer doing so.

Risking their own lives, vervet monkeys make loud alarm calls when they spot a predator, saving others from harm. According to Robert Seyfarth of the University of Pennsylvania and colleagues, the monkeys even identify, the specific type of predator in the loud calls.

"Animals on the ground respond to leopard alarms by running into trees, to eagle alarms by looking up, and to snake alarms by looking down," the researchers explained.

American bison are formidable animals, both in terms of size and weight, so they are usually only taken down by large predators, such as mountain lions, wolves and humans. According to Animal Diversity Web, bison travel in lines led by dominant adults. If they detect a predator, a meaningful bison-emitted grunt or snort tells the herd to be wary. Mother bison, as for many animal moms, will also fight to the death to save their young.

Male wild chimpanzees living in Bossou, Guinea, have figured out how to deactivate, and sometimes even destroy, snares set out by human hunters, according to Gaku Ohashi of the Japan Monkey Center and colleagues. The researchers documented instances where the chimps set free trapped individuals and took steps to deactivate snares, such as by shaking or hitting the devices.

Vampire bats starve to death if they do not feast on a blood meal after two nights. Roost-mates come to the rescue during famines, according to biology Gerald Wilkinson of the University of Maryland. "A buddy system ensures that food distribution among the bats is equitable," he explained. Bats seem to have BFFs with whom they regularly share blood meals via regurgitating. Barfing up blood may be a stomach churner for humans, but for these bats, it's a lifesaver.

Ants, well known for their complex societies, put the preservation of the overall colony above their individual needs. They identify colony members by scent, according to Gregg Henderson and colleagues from the USDA. Intruders who literally stink -- not matching the colony's signature scent -- will be attacked with as much force as an ant can muster.

Walruses breed during harsh Arctic winters, with mothers giving birth to just one offspring per season. If disaster strikes and the infant becomes an orphan, another walrus female may adopt it, according to The Encyclopedia of Earth. Communal care of young by multiple female walruses has also been documented.

There are many accounts of cats saving members of their own species and humans. One example of the former was Scarlett, a calico owned by Karen Weller of New York. When Scarlett and her litter of five kittens became trapped in a Brooklyn garage fire, the mother feline carried out each of her kittens to safety. During the five separate trips, Scarlett sustained severe burns to her eyes, ears and face, but she forged ahead until all kittens were out of danger.

In fiction, Lassie came to the rescue of seemingly everyone and everything. Fiction in this case mirrors fact, as there are countless reports of heroic dogs saving the day. A video on Animal Planet, for example, (http://animal.discovery.com/tv-shows/weird-true-and-freaky/videos/dog-rescues-dog-on-highway.htm) captured footage of a dog in Santiago, Chile, pulling another injured dog to safety. This first responder canine had to navigate through heavy traffic, but the brave dog managed to pull off a happy ending