Chipmunks' unpleasant reminders.

Want to remember which kitchen cupboard is bare? Just urinate on it.

That may be the strategy among least chipmunks (Tamias minimus), suggest Lynn Devenport of the University of Oklahoma in Norman and his colleagues. Red foxes, coyotes, and wolves have been known to leave such marks at empty larders. A report in the March ANIMAL BEHAVIOUR, however, provides the first description of that behavior in a rodent, the authors say.

They noticed that chipmunks sometimes urinate, seemingly purposefully, after they dug up seeds. Otherwise, the animals rarely relieved themselves in open areas. Checking videotapes of laboratory chipmunks, the researchers saw none making wet spots farther than 4 centimeters from a wall or other sheltering object unless the animal had just found food. Then, the animals increased that distance to up to 18 cm. Chipmunks so marked about a third of the depleted patches, but they did not urinate on spots still holding goodies.

Researchers next put urine-laden sand on richly stocked patches that the lab chipmunks had already sampled but not depleted. All 16 of the test animals immediately moved on to an unmarked, skimpy patch. When none of the patches were marked, chipmunks harvested the bonanza first. In the wild, in a version of this experiment, chipmunks dug out the unmarked patches first in 15 out of 20 observations. All in all, Devenport sees the urine markings as a means of bookkeeping for foragers.