Animals

Ants Enslave Each Other

There's a good chance that slave-maker ants are near you right now.

Slavery is widespread among certain ants in the United States and has even altered the genetic and chemical diversity of enslaved ant victims, a new study finds.

Some bees, wasps, beetles, crickets and other creatures also either enslave or trick others to do their work, showing the behavior persists in nature. As for slave-making Polyergus breviceps ants, they have been benefiting from the arrangement for years.

Co-author Neil Tsutsui explained to Discovery News that these ants "are successful. They produce more ants who do this and the behavior spreads. Evolution proceeds in basically the same way as for any other trait."

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"It's no more cruel than consuming other organisms as food, competing with another organism for resources, or the myriad other ways that organisms come into conflict in the natural world," added Tsutsui, who is a professor in the Department of Environmental Science, Policy & Management at the University of California, Berkeley.

He and co-author Candice Torres compared the chemical, genetic, and behavioral characteristics of enslaved and free-living colonies of the Formica altipetens ant, which is the target of Polyergus' slave-making.

They found the slaves were less aggressive toward non-nest mate ants than were their free-living counterparts. The findings, published in the journal PLOS ONE, suggest that slavery can dramatically change both the chemical and genetic context in which the kidnapped victims develop.

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During the summer, Polyergus conducts raids on Formica colonies, explains Tsutsui. During the raids, workers from the slave-making species leave the colony as a group and attempt to steal Formica pupae. The attacked adults do their best to defend themselves and the ant babies.

"There are cases of enslaved ants putting up a vigorous fight to try and repel the slave-makers when their colonies are being raided," he said.

Once stolen, the victim babies are brought back to the Polyergus colony. The attackers then continue to raid different Formica colonies, creating a highly diverse group of victims. As they grow older, the victim ants perform nest maintenance, brood care and foraging for their slaveholders, not even realizing their predicament.

"The way that ants normally develop a sense of colony identity makes them vulnerable to this type of slave-making behavior," Tsutsui said. "Normally, young ants emerge from pupation and imprint on the odors around them. They then use the memory of these odors to figure out who is a member of their colony versus who is an ant from a different colony."

The victim ants have no idea that they are enslaved. They appear to believe that they are in their home colony.

The scientists suspect the system in ants first evolved many years ago, after an ancestor of Polyergus might have occasionally raided other ant colonies, retrieving the larvae and pupae for food. This could have led to some of the raided pupae emerging as adult worker ants that, believing nothing was amiss, toiled away for the attackers. This would have then enhanced the survival and reproduction of Polyergus ants that practiced the raiding, making the behavior more common over time.

There seems to be no benefit for the enslaved ants, but the slave-makers do experience some risks. Some are killed during the raids.

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"There's also some evidence of the enslaved ants doing a bad job of caring for the slave-maker babies, and of laying their own eggs while enslaved," Tsutsui said.

James Trager, a myrmecologist (ant expert) and naturalist at the Shaw Nature Reserve in Missouri, says the ant study, "digs deeper into our understanding of the phenomena that are involved in making the system work."

This ant, Polyergus breviceps, is a slave-maker.

Real-life ants have powers beyond Hank Pym’s super-strength. They also float on water, build massive skyscrapers, dig crazy underground tunnels and will attack much larger creatures in huge numbers using massive jaws. With a nod to Marvel’s new film “Ant-Man,” here’s a look at some unusual abilities of our formic friends.

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Ants are nature’s excavators. They move pebbles, rocks and bits of soil in all kinds of conditions to help the colony survive, often one holding onto another like a tiny ant jackhammers. “If you put a fire ant in soil, it will begin to dig,” said Dan Goldman, physics professor at Georgia Tech who studies how animals build and move. “They do it over and over in any soil. They use their mandibles, limbs and antenna to shape and create these snowballs and move them thousands of body lengths onto the surface to create the mound.”

There is no fiercer predator than tens of thousands of army ants pouring across the jungle floor in search of hapless prey. These ants are among the largest species, and are either blind or have almost no eyesight. Yet they can still scour the forest floor for insects, small birds or, on occasion, unwary villagers. “They are the pack hunters of the tropics,” says Sean Brady, chair of the department of entomology at the Smithsonian Institution’s National Museum of Natural History in Washington.

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Ants build the equivalent of human skyscrapers with no blueprints and nobody telling them what to do. “Every construction worker is lifting their own stuff, all milling around, banging around in the complete dark relentlessly day in and day out,” said Georgia Tech’s Goldman.

Ants don’t vocalize, but they still talk amongst themselves, using their antennae. They also secrete chemicals called pheromones to either warn the colony of an attack, or to lay a trail to food for others to follow. “It’s all chemical and tactical,” says the Smithsonian’s Brady. “What they are saying to each other and how they figure out where to go, we don’t understand that yet.”

Here’s a video of two ants communicating

via antennae, a method biologists call “stimergy.”

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When Hurricane Katrina swamped much of the Gulf Coast, local residents not only had to worry about finding clean water or shelter, they also had to avoid bumping into huge floating mats of living fire ants.

Ants have big chompers. The bullet ant is so named because its bite feels like getting shot. The trap-jaw ant has such a powerful bite that researchers have watched them get pushed backward when chomping onto a hard surface, such as a wall or glass.

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Some ants have evolved a cooperative existence with other insects, such as aphids or scales. The ants watch over these plant-sucking critters, keeping predators away, while the aphids provide ants with a sweet liquid called honeydew. Beats getting in fights all the time.

When ants have to cross an obstacle, they build a living bridge, gripping each other to let the others crawl across. “A bridge may be several ant lengths long and they will be that way for hours,” said Michael Goodisman, associate professor of biology at Georgia Tech who also worked as a consultant on the new “Ant-Man” film. “Imagine a human chain would last a minute. They can hold onto each other and support many ants themselves.”

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Even though each ant has its own role -- worker, drone, soldier and queen, they behave more like one big insect with the goal of keeping the colony alive, well-fed and reproducing. “Ants have the most sophisticated social characteristic of any animals,” Goodisman said. “They need each other. They cannot survive on their own. It has to be associated with a colony to transfer its fitness to future generations. Ant colonies act as super-organisms.” This hive behavior was exploited in H.G. Wells' "Empire of the Ant," made into

this 1977 B-movie

.

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Most male ants are pretty useless -- they exist to mate (then quickly die) and take part in few defensive or care-taking roles, experts say. But male army ants do get to fly around. In fact, they are so big that call them “sausage flies.”