All Things Considered

'Hey I'm Dead!' The Story Of The Very Lively Ant

By Robert Krulwich

Published April 1, 2009 12:00 AM

E-MAIL
|

Here's a question — not one that's on everybody's lips, granted — but a question nonetheless: How do ants know when another ant is dead? E.O. Wilson, now the most celebrated, most eminent ant scholar in the world, wanted to know.

When Ed Wilson was a young assistant professor at Harvard in the 1950s, he observed that when ants die — and if they're not crushed and torn apart — they just lie there, sometimes upside down, feet in the air, while their sister ants (almost all ants in a colony are ladies) walk right by without a glance. That is until about two days after an ant's passing, Ed discovered, when the corpse appears to emit a chemical signal that changes the living ants' behavior dramatically.

All of a sudden what was once a pile of gunk on the colony floor becomes a "Problem to Be Solved." Once the signal is in the air, any ant that happens by grabs the corpse and carries it through the colony to a refuse pile designated the graveyard and dumps it on a mound of also-dead ants.

Ed, who would revolutionize the study of ants by exploring their ability to communicate with smell, decided to figure out what chemicals equal "I am dead" to an ant.

In his autobiography, Naturalist, he wrote: "I thought, maybe with the right chemicals I could create an artificial corpse."

In our broadcast on All Things Considered, Ed describes how he researched the likely chemical constituents of "I am dead."

"They included skatole, a component of feces; trimethylamine, one of the essences of rotting fish; and several of the more pungent fatty acids that contribute to rancid human body odor," Ed says. "For weeks, my laboratory smelled like the combined essences of sewer, garbage dump and locker room."

Finally, after much sifting and mixing, Ed discovered that oleic acid — just a teeny drop of it — was all the ants had to sniff to think "DEAD!" And, because he could — Ed had a colony parked in his Harvard lab so he could watch them endlessly — one day he took a drop of the chemical and gently deposited it on an ant that had the misfortune of walking by.

That poor ant is the main subject of our radio story. (Click the listen button above.) Ed describes how as soon as he dabbed the ant, the next ant that came near grabbed his ant, slung it on its back, hiked over to the graveyard and though the ant was very much alive — "kicking, you know," says Ed — flung it onto the refuse pile.

Dead is what you smell — not what you see — if you are an ant. So, though it tried to clean itself over and over, the minute it returned to the colony, it was grabbed, carried and slung back on the pile.

"Didn't you take pity?" I asked Ed. "You started it! Didn't you give it a shower or something?"

"No, I was trying to see if I could create the 'Living Dead,'" he says, while making zombie motions with his head and hands. He confesses that it took the ant "roughly an hour or two" to get clean enough to return to regular business.

Yes, Ed was naughty, and yes he had a wonderful time offending all the folks on his floor in the biology department. But what Ed was discovering is that most organisms on Earth do not communicate by sight and sound. He was among the first to realize that an enormous number of creatures — ants included — share information by taste and smell, even if those smells are what technological sophisticates would call "yucky."

Related Links

View Transcript

MELISSA BLOCK, host:

This is not your usual April Fool's story because in this case, the fool was an ant - an innocent, unsuspecting little ant who happened to be living at Harvard University in the Biology Department, a very big mistake.

NPR's Robert Krulwich tells the tale.

ROBERT KRULWICH: People don't get this about ants, says ant scholar E.O. Wilson, world famous biologist. When we people communicate with each other, we talk.

(Soundbite of laughing children)

KRULWICH: We talk, and talk, and listen, and look.

Dr. E.O. WILSON (Biology Department, Harvard University): Humans are the most audio-visual creatures on Earth.

KRULWICH: But most animals do not communicate our way, not at all.

Dr. WILSON: We are highly unusual. The vast majority of creatures on Earth communicate the way the ants do, by chemicals, pheromones.

KRULWICH: Look closely and you will find little glands on the surface of an ant.

Dr. WILSON: One hair produces one signal. Another one up here produces another signal. They're loaded with glands that they use to communicate with.

KRULWICH: So, if an ant wants to say something to another ant, it chooses a gland to squeeze out a chemical message at a second ant, who then would go?

(Soundbite of sniffing)

Dr. WILSON: I think I smell it, an ant.

(Soundbite of sniffing)

KRULWICH: And that's how they talk. Fifty years ago, Ed Wilson made his reputation figuring out which chemicals produce specific ant messages. For example, he was fascinated by what happens when ants die.

Dr. WILSON: If an ant dies, it just falls over. It may be lying with its feet sticking up.

KRULWICH: And that dead ant will be ignored pretty much by everybody in the colony for about two days, until the corpse is programmed to release a chemical signal, which says I'm dead. At which point, the next ant comes along and immediately grabs the body, carries it off to an ant graveyard. And apparently, every ant knows the I'm dead smell.

Dr. WILSON: So I decided to find out what substances it was smelling.

KRULWICH: Ed told me on stage at the 92nd Street Y in New York City recently that he knew the smell was a very repugnant, stinky odor, a very specific chemical combination.

Dr. WILSON: So, what I did, I got a large array of these substances. I tried?

KRULWICH: The rancid sock smell and poop smell and?

Dr. WILSON: Oh, I - let's see: rotting fish, that's trimethyl amine. I had the essence of feces that's skatole, an indole, and I had all these in pure forms.

KRULWICH: So, his lab was not exactly the favorite spot in the building, but he did have a little ant colony right there in his lab, plus, some plastic ants. And what he'd do is he'd take a few drops of foul smelling chemicals and then apply them?

Dr. WILSON: In very tiny amounts, I was putting them on dummies.

KRULWICH: ?waiting to see what smell would make the ants treat those dummies as corpses.

Dr. WILSON: Until finally, I hit the key substance. And that alone, that does it.

KRULWICH: It was oleic acid.

Dr. WILSON: When they sniff oleic acid, and that's a corpse, so I said, well, if that's the way they do it, will they treat one of their live, healthy nest mates as a corpse?

KRULWICH: So, Ed waited until a little ant just happened along on his tabletop, and he leaned over and he squirted her with the I'm dead signal. And then, the next ant that came along grabbed our ant immediately, says Ed.

Dr. WILSON: Poor thing would be lifted up, kicking, you know, and take it out to the cemetery and dumped.

KRULWICH: And it would pick itself up?

Dr. WILSON: Oh, it would start, yeah, cleaning itself, you know, like a dog trying to get itself cleaned. And then, it would try to re-enter the colony. And if the ant does a good enough job?

KRULWICH: Then the next, the ant would pick it up and slap it back onto a pile of really, truly dead ants, and then it would have to clean itself all over again.

Dr. WILSON: Probably, it would clean out all that oleic acid.

KRULWICH: Then you take, because you started it. Didn't you like to give it a shower or something?

Dr. WILSON: Well, no, I was trying to see if I could create the living dead, you know, a?

(Soundbite of laughter)

KRULWICH: A zombie ant.

Dr. WILSON: You know, an ant that would come back, you know, like this. No, I'm just kidding. I was creating the living dead?

KRULWICH: How long did it take for this very unfortunate, not dead, dead ant to get accepted as alive again?

Dr. WILSON: Well, actually, I'm just, you know, it cleans itself furiously as soon as it's got the stuff on it. It knows it's got a contaminant.

KRULWICH: But after washing and then re-washing, and re-re-washing, Ed thinks?

Dr. WILSON: Roughly an hour or two.

KRULWICH: Science finally had the chemical formula for I'm dead. And the little ant, she resumed her ordinary life presumably unaware of what had just occurred.

Ants, it seems safe to say, have no chemical signals for you wouldn't believe what just happened to me.

Robert Krulwich, NPR News, New York. Transcript provided by NPR, Copyright National Public Radio.

Source: NPR

WBUR Topics

SUPPORT