Pulling Ant Castles From the Ground

Walter Tschinkel's office is filled with castles built by thousands of workers. Long tunnels connect large chambers in an intricate web of architecture that reflects the efforts of master craftsmen.

Tschinkel didn't have to go to Europe to find his castles. But he had to do a lot of digging.

Tschinkel [pronounced chinkel] is an ant biologist at Florida State University and he found his castles buried in the sandy soil near Tallahassee.

The tools of his trade are a shovel, a cement trowel, and buckets of dental plaster. The product is a series of plaster casts of ant nests — "colossal structures," as he puts it — that reveal complex hidden worlds that harbor no slackers.

The astonishing casts, some of which are more than 8 feet tall, aren't unique because scientists have been pouring plaster down ant holes for decades now. But Tschinkel has honed the process to an art form, and each new cast tells something new about the social structure of ant colonies.

Dental Plaster's the Trick

We humans would be hard pressed to match their skills at cooperative ventures on a grand scale. Tschinkel knew he wanted to become a biologist when he was only 6 years old. He spent much of his time collecting insects in the forest, but it wasn't until he was in graduate school that he learned what he wanted to do with his life.

He was studying the emerging field of chemical communication, the method by which animals produce secretions and odors to communicate with each other, when he heard the eminent biologist Edward Wilson give a talk on ants.

"I realized that social insects presented the most interesting and complex examples of chemical communication," Tschinkel says, so when he finished school he dove head first into the world of ants.

He started pouring plaster of paris down ant holes to see if he could produce a cast of the nest, and it worked fairly well, but not spectacularly. Then about 15 years ago a colleague introduced him to dental plaster, which flowed easily down the hole and hardened within an hour.

Tschinkel has to dig a hole much bigger and deeper than the nest itself, and then he carefully removes pieces of the plaster which breaks apart during the excavation process. One huge nest that had recently been abandoned by harvester ants (Pogonomyrmex badius) came out in 185 pieces.

Entombed, Muscular Ants

The difficult part, he says, is reassembling the cast by figuring out which piece broke off from what, and then gluing them back together. That takes a lot longer than it took the ants to build the nest.

"It only takes them four or five days," he says. Harvester ants move once or twice a year, and the huge cast in his office was made shortly after the ants vacated their home. More often, he says, the ants are still in the nest, and they are called upon to make the supreme sacrifice.

"They get entombed in the plaster," he says. "That's sort of an unfortunate thing."

It took about 5,000 ants to make the nest. They had to remove more than 40 pounds of sand. And then they moved, possibly because the nest had become contaminated with some sort of pathogen. They don't always move very far, sometimes only a few meters.

The fact that they are able to do so much in such a short period of time speaks volumes about ants. For openers, they are very powerful for their size. An ant has six times the muscles of a cat, Tschinkel says, so "it's a complex animal."

What's truly amazing is each ant has its own chores to do, and it does so without supervision.

"There's no boss in the ant world," Tschinkel says.

The most basic division of labor is based on age. The younger ants take care of the newly hatched ants. Middle aged ants do most of the nesting chores. And only the oldest ants venture out of the safety of the nest to forage for food.

"They are only foraging toward the end of their lives," he says. "That makes sense because foraging is by far the most dangerous activity.

"It's the opposite of what we do. We take our youngest men, the ones with the highest reproductive future, and send them off to war. Ants don't do that."

The foraging process involves the area of science that got Tschinkel into ants in the first place — chemical communication.

When a foraging ant finds a food source, it literally leaves a chemical trail for other members of the nest to follow when they head out to harvest the new resource. Nearly all species of ants have that capability, but it developed in different ways.

"We know that because different ants use different glands" to produce the chemicals, Tschinkel says.

Chemical Communication

Some excrete chemicals, leaving an odor for their colleagues to follow, and some apparently have sneaker feet, "literally leaving a footprint trail" that other ants can follow, he says.

"There's dozens of variations on this basic theme," but nearly all ants have figured out a way to communicate chemically with their co-workers, he added.

Some ants are even more resourceful. There's a symbiotic relationship between aphids and ants. As any gardener knows, aphids dine on plants, but plant tissue contains much less nitrogen than animals need.

"It's mostly sugar," Tschinkel says. So aphids excrete the excess sugar in order to concentrate the nitrogen. The excreted sugar, called "honeydew," is prized by a wide range of insects, including ants.

As a result, some ants become aphid ranchers, herding and tending their flocks of aphids so they can have a steady supply of honeydew. The ants, in turn, protect the aphids from parasites.

"Some are so dependent on each other that the ants actually take the aphids underground in the winter," assuring their survival, Tschinkel says.

Once underground, they enter a castle that is so intricate and so functional that it is a marvel to behold.

Lee Dye’s column appears weekly on ABCNEWS.com. A former science writer for the Los Angeles Times, he now lives in Juneau, Alaska.