Japanese researchers say urination is contagious among chimpanzees.

When one of the primates relieves itself, others in the group quickly follow suit. The pattern is consistent with other group imitation behaviors such as yawning or stretching.

Onishi Ena of the Kyoto University Wildlife Research Center and her colleagues observed 20 captive chimpanzees over 600 hours in Kumamoto Prefecture, southwestern Japan.

They found that the shorter the distance between chimps in a group, the more likely they would relieve themselves within just over three minutes after the first one.

The chance of chimpanzees within 50 to 60 centimeters of the first one urinating was twice as high as those three meters or further away.

They also found that lower-ranked members of a group were more likely to display this copycat behavior.

Onishi said the motives for this behavior remains a mystery, though they may be using it to try to establish relationships within the group.