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Saving Up for a Rainy Day

Why do frequent workers tolerate these freeloaders? Well, infrequent workers actually do pull their weight, but only when the time is right.

mole rat

Photo: Sharry Goldman

These rodents live in underground burrows, and labor is divided among groups called castes.

Are you annoyed by that guy in your office who plays solitaire all day and never actually accomplishes anything?

Then you’d really be aggravated in the work environment of the Damaraland mole-rats of the Kalahari Desert, where up to 40% of a colony is that guy.

These rodents live in underground burrows, and labor is divided among groups called castes. This social structure is similar to ant colonies and beehives where a single queen aided by a few males produces offspring for the group. Everyone else belongs to the worker caste that tends the young, maintains tunnels, and forages for food.

The worker caste is further subdivided into two groups: frequent workers and infrequent workers. Like the names imply, frequent workers labor continually and do 95% of the colony’s work, while infrequent workers mostly spend their days relaxing and getting fat on food their more industrious compatriots have collected.

This seems like a raw deal. Why do frequent workers tolerate these freeloaders? Well, infrequent workers actually do pull their weight, but only when the time is right.

The rock-hard Kalahari Desert soil is only soft enough to tunnel through following rainfall. Therefore, during the one or two rains that fall each year, mole-rats must work overtime to build tunnels so they can reach nearby colonies with new mates. When it rains, the infrequent workers quickly mobilize their extra fat stores and shift their metabolisms into high gear. The extra energy conserved by lazing away may translate into a surge of burrowing power that exploits the softer soil in a way other colony members cannot. Thus, laziness is really a clever strategy that helps the colony reproduce.

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