"Lazy Slob" Mole Rats Are Key to Colony Growth, Study Says

Nicholas Bakalar
for National Geographic News
April 5, 2006

A few lazy rats are getting away with doing practically nothing while others do all the work. And no, this has nothing to do with what goes on in your office.

Between 60 and 75 percent of a population of Damaraland mole rats (Cryptomys damarensis)—rodents native to southern Africa (see map)—are "frequent workers."

These industrious rats perform 95 percent of the work, while the remaining "infrequent workers" enjoy the results, new research shows.

Damaraland mole rats, along with the closely related naked mole rats, are the only known mammals that are eusocial—that is, they live in social colonies with a division of labor among members.

A queen rat rules, and worker animals tend to her needs, including one or two males that mate with her.

But some of the workers carry more of a load than others, according to findings published in tomorrow's issue of the journal Nature.

Infrequent workers get busy only during wet seasons when the ground is soft enough to extend the burrows the animals live in. At these times the infrequent workers actually do more than the frequent workers.

"The real question is why the frequent workers put up with and feed these lazy slobs," said John R. Speakman, a professor at the University of Aberdeen in Scotland and co-author of the study.

"The answer is that some of their genetic material is locked up in the slobs as well, because all the members of a colony are related."

Rats in Overdrive

Speakman, tongue planted not too firmly in cheek, draws an analogy to explain.

"One way to think about this is to imagine the infrequent workers are like older teenagers. They do nothing around the house, and they eat all your food. Yet you tolerate them, because they are your only way to spread your genes into the wider world.

Continued on Next Page >>


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