Anna Dornhaus, a University of Arizona researcher, painted ants different colors to study them. Great differences were found in the speed of ants’ work, and about 50 percent were found to do no work.
Anna Dornhaus is peering into a cardboard nest box only an inch on a side, at a “family” of 100 or so European rock ants. Known as Temnos, the ants — painted in primary colors — are going about their ant chores hauling, foraging, nursing the glistening maggoty brood.
Next to a color-coded Temnos, a rice grain would look like an old-growth log. When the lid on an ant colony is raised, a whiff of dead cockroach — ant chow — wafts by. A quiescent larger queen is a study in brown. “She’s hardly a head of state,” Dr. Dornhaus said. “More like an ovary.”
Nearby are bumblebee hives under glass in which each bee sports a number from 1 to 100 on tiny price-tag-like label attached to its back.
To understand what is really going on in a colony of ants or bees, Dr. Dornhaus, an assistant professor of ecology and evolutionary biology at the University of Arizona, tracks the little creatures individually — hence the paint and the numbers. Individual ants, she said, have “their own brains and legs, as well as complex and flexible behaviors.” She continues, “Each ant’s behavior and the rules under which it operates generate a pattern for the colony, so it’s crucial to discover its individual cognitive skill.”
Dr. Dornhaus, 34, a tall, blond German-born scientist, has great patience, a prime requirement in her trade, and a feel for the creatures she studies. When people find out that “I study ants, bees and other crawly things, the first thing they ask is do I know how to kill them.”
She added, “I wouldn’t tell them if I knew.”
The social insects, she said, are “the most interesting creatures evolution has produced.”
Dr. Dornhaus is breaking new ground in her studies of whether the efficiency of ant society, based on a division of labor among ant specialists, is important to their success. To do that, she said, “I briefly anesthetized 1,200 ants, one by one, and painted them using a single wire-size brush, with model airplane paint — Rally Green, Racing Red, Daytona Yellow.”
After recording their behavior with two video cameras aiming down on an insect-size stage, she analyzed 300 hours of videotape of the ants in action. She discovered behavior more worthy of Aesop’s grasshopper than the proverbial industrious ants.
“The specialists aren’t necessarily good at their jobs,” she said. “And the other ants don’t seem to recognize their lack of ability.”
Dr. Dornhaus found that fast ants took one to five minutes to perform a task — collecting a piece of food, fetching a sand-grain stone to build a wall, transporting a brood item — while slow ants took more than an hour, and sometimes two. And she discovered that about 50 percent of the other ants do not do any work at all. In fact, small colonies may sometimes rely on a single hyperactive overachiever.
Why do some worker ants lean on their shovels and let the rest of the workers do all the work? “It’s like students living together — you’ll always find one will have a lower threshold for doing the washing up and will end up always doing it all,” she said.
Perhaps the division of labor — which the economist Adam Smith linked to human achievement — may not be the key to ant success. Possibly, Dr. Dornhaus said, “the lazing ants are resting, or are waiting in reserve in case something goes wrong.” Or the laggards may be cooking up some biochemical nest protection. (All ant species manufacture a fungicide to stave off mold in their nests.) Or, she said, “It’s possible they aren’t doing anything at all.”
Dr. Dornhaus was born in Cologne, Germany. Her father was a physicist and her mother an artist, and, from the age of 10, she wanted to be a biology researcher. A high school whiz in math and chemistry, she breezed through an undergraduate biology degree at the University of Freiburg. From there, she headed to the University of Massachusetts, Amherst, for a year as an exchange student. She worked with Dr. Melinda Novak studying cognition in monkeys.
“We were trying to discover if rhesus monkeys recognized themselves in a mirror as chimps do,” she said. (They apparently do not.) “At that point I knew I wanted to study animal social behavior.”
Dr. Dornhaus returned to Germany to find an animal behavior research group and discovered the Behavioral Physiology and Sociobiology Department at the University of Wurzburg, headed by Dr. Bert Hölldobler, the co-author, with E. O. Wilson at Harvard University, of the classic “The Ants” and the recently published “The Superorganism.”
Her thesis adviser was Dr. Lars Chittka, an expert on the ecology of insect sensory and cognitive abilities, who was studying bumblebees.
Dr. Chittka — who said that the bumblebee group, although highly social, was regarded as primitive in social habits — wondered why a single bumblebee, after returning to the nest, beat its wings excitedly and ran around crazily in circles. Soon the other bees would get excited and leave the nest. He asked Dr. Dornhaus to find out what was going on.
“I knew that when I looked at this crazy bee it knew something the others didn’t,” Dr. Dornhaus said.
Dr. Dornhaus has shown that bees are capable of complex communication.
She designed an experiment, which revealed that the crazy bee was making and broadcasting a pheromone in the hive that alerted other bees: “Hey, there’s food out there.” (The bumblebee, unlike its more sophisticated honeybee relatives, did not indicate the food’s location.)
But, as Dr. Dornhaus said, “Bumblebees don’t have to meet in person to communicate; they leave a note behind on a blackboard for other bees that food can be found.”
Dr. Dornhaus realized that the bumblebees communicate in ways that resemble a waggle dance. The idea that bumblebees were so primitive that they were incapable of complex communication was “destroyed by Anna’s work, and was published in Nature,” Dr. Chittka said.
The honeybee waggle dance, performed in tight figure eights — in which a bee returns to the hive to inform its nest mates where the food is — is one of the most remarkable discoveries in animal communication. It is the closest approach to symbolic language of any creature apart from humans.
But Dr. Dornhaus questioned what the honeybees actually got out of the waggle dance communication. Many scientists had studied the dance but no one had questioned its basic function.
The waggle dancers depend upon a vertical dancing platform for direction and orientation, but Dr. Dornhaus flipped some beehives on their sides at her study site among agricultural fields in Germany. Deprived of the appropriate stage, the honeybee scouts still danced, but it was random. “Every night after the bees were asleep, I weighed the flipped hives,” she said, but the bees continued to haul in as much nectar as ever.
The next spring, Dr. Dornhaus moved her study to the well-flowered thyme, lavender and wild rose shrublands of Spain, repeating her experiment and refining it. “I weighed each returning bee, but my results were the same,” she said.
Because honeybees evolved in the tropics, Dr. Dornhaus’s next field site was in the Nilgiri Hills in the Western Ghats in India. In Bangalore, she said, “I bought some Indian-hive-bee hives, transporting them in a taxi to my cabin.”
But the recalcitrant Indian bees “just packed up and left,” she said. Local farmers — braving considerable stings — tried to replace them by stealing a nest from a tree. Again, the Indian bees deserted. Dr. Dornhaus resorted to European honeybees, also used there for honey making, and they stayed put.
Tropical forests are well known for biological diversity, but from a honeybee’s perspective, they are a green desert, because flowering trees are widely spaced.
“A honeybee is less than an inch long,” Dr. Dornhaus explained. “If it flies 20 kilometers that equals 787,400 body lengths. If we say a human is two meters tall, then in human terms, that would be like traveling 394 kilometers and back, possibly several times a day.”
Again, the flipped hives interrupted the informative dances. The bees could not find the flowering trees and went hungry. Dr. Dornhaus concluded that the value of the waggle dance depended on the environment.
When she is off duty from her research and teaching, she concentrates on nature photography, shooting at the macro and landscape levels. She and her fiancé also coach her two “large size, mixed breed dogs” in the fast-growing sport of agility training.
Dr. Dornhaus’s own agile work on social insects has attracted the attention of computer scientists and engineers because “they need such algorithms to design artificially distributed problem-solving systems.”
“It’s fascinating that many cognitive functions — learning, planning, using tools — can be solved by brains several orders of magnitude smaller than ours,” Dr. Dornhaus said. “It shows that we should never underestimate an animal because it is small.”
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Full article and photos: http://www.nytimes.com/2009/04/28/science/28prof.html
