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Photo of red ants (Myrmica rubra) adult workers drinking from a water droplet.

Common red ants—shown here drinking from a water droplet—are native to Europe and Asia.

Photograph by Richard Becker, Alamy

Katie Langin

National Geographic

Published July 8, 2014

Housekeeping can be a matter of life and death—at least for social animals like ants, a new paper suggests.

According to a study published Tuesday in the journal Biology Letters, common red ants (Myrmica rubra) that were prevented from removing their nestmates' corpses died more frequently than those allowed to bring out their dead.

The tiny ants—each roughly the size of a medium-grain rice kernel—live under rocks and logs in densely packed colonies. More than a thousand worker ants can be found in a single nest.

These insects reap many benefits from group living, as they work together to gather food, care for their queen, and defend their nest.

But the situation also puts them at risk of being hit by disease epidemics: If one individual in the colony comes down with an illness, the blight can spread rapidly. This places a premium on good hygiene.

Dead Are Deadly

Many insects habitually remove dead nestmates from their colony. Scientists have long assumed that this behavior is based on a need to keep the rest of the colony healthy. But until now that idea hadn't been put to a formal test.

The new study, conducted by researchers at the Université Libre de Bruxelles and the Université de Liège in Belgium, tested the health benefits of corpse removal in common red ant colonies kept in artificial nests.

Some of the nests had wide exits. Others had narrow openings that made it difficult for the ants to transport and deposit corpses outside.

In each colony, the scientists fatally froze ten worker ants, placed their corpses back in the nest, and monitored the survival of the remaining workers.

The result: The ants in colonies that couldn't remove corpses didn't fare as well. By the end of the 50-day experiment, mortality had more than doubled in the corpse-littered colonies, from 6 percent to 13 percent.

Why the higher death rate? The researchers can't say for sure, but they speculate that "corpses artificially staying longer in the nest may have increased the occurrence of microorganisms, requiring a greater investment in the immune system for live ants and possibly resulting in a reduced lifespan."

The Benefits of Good Housekeeping

The study "shows a fundamental effect that … everybody thought we knew but nobody [had] really tested," wrote Olav Rueppell—an expert on social insects at the University of North Carolina at Greensboro who was not involved in the study—in an email to National Geographic.

The implications of corpse removal for group health may also apply to other social animals like honeybees and prairie dogs.

But for the common red ant, at least, the situation is clear: Dead ants beget more dead ants, so it's best to keep the nest nice and tidy.

Follow Katie Langin on Twitter.

15 comments
Gina Johnson
Gina Johnson

Belgium strikes again!

http://albaraak.com/ 

 No one ever noticed that our universities appear quite often in the media because of their discoveries?

Dwayne LaGrou
Dwayne LaGrou

I would like to see the little funeral procession with a tiny hearse. I wounded if have to put little bitty flags on their vehicles!!!

Ha Ha Ha!!,

Peter Staples
Peter Staples

In Australia, our red ants take their dead back to the nest.

Mario Gomez Sturmann
Mario Gomez Sturmann

Leaving sarcasm behind. I must say this is rather a dull paper. Everyone in the field of entomology, knows this fact. I've known this since i was 16 years old. Not particulary ground breaking. 

Never the less, keep on working, maybe this leads to a bigger knowledge.

Christopher Hancy
Christopher Hancy

Phone the press!  ground-breaking research from a Belgium university playing with ant farm! "Dead ants =more dead ants" Thanks guys for your tremendous contribution to global science!

Mathias Destrebecq
Mathias Destrebecq

Belgium strikes again! No one ever noticed that our universities appear quite often in the media because of their discoveries?

Brian Edwards
Brian Edwards

" mortality had more than doubled in the corpse-littered colonies, from 6 percent to 13 percent." Pity the poor scientist who has to scrutinize all those tiny little census forms :P Seriously though I have communal spiders about my home and they actively festoon their webs with corpses. Also assassin bugs wear their victims' corpses on their backs as camo. Do they trade off something for a stronger immune response?

Henry Major
Henry Major

Animals have carcasses. Only humans have corpses.

KENNETH LANE
KENNETH LANE

I have observed this corpse dumping often around our home when I have applied insecticides.  

J. Griffin
J. Griffin

They should do this with humans next and see if it has the same effect.

Notasdumb Astheyare
Notasdumb Astheyare

No, what we know is their interpretation of what they observed.  Nothing more.

Mayeso Gwedela
Mayeso Gwedela

Well, now we know it`s a fact...... love science!!!!

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