Flood’s rising? Quick, start peeing!

Rainforest ants fight floods in their nests with a last-resort effort that scientists have now dubbed communal peeing.

The Malaysian ant Cataulacus muticus nests only inside the hollows of stalks of giant bamboo, which thrives in tropical humidity. When heavy rains pelt the bamboo, water can sluice into the ant nests and threaten the colony’s larvae.

During a storm, ant workers cluster at the nest entrance as if plugging the hole with their heads, report Ulrich Maschwitz and Joachim Moog at J.W. Goethe University in Frankfurt, Germany. Some of the water gets by the insects, however.

In the December 2000 issue of Naturwissenschaften, the researchers describe the ants’ version of bailing. Workers sip from the growing puddle in the nest and then scurry out into the storm and excrete a droplet onto the bamboo stem.

The researchers flooded a laboratory colony with several milliliters of colored water, a serious flood for the small creatures. The workers bailed it out over the course of 2 days by sipping and then excreting more than 3,000 droplets.

Creating minifloods in laboratory ant nests of two other species in the same genus failed to prompt such urinary heroics. These other species construct nests in places that are less flood-prone, such as twigs and rotten wood. So, the internal bailing of C. muticus, the researchers say, may be an adaptation to life in rainforest bamboo.

Susan Milius is the life sciences writer, covering organismal biology and evolution, and has a special passion for plants, fungi and invertebrates. She studied biology and English literature.