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Study Shows Monkeys Rubbing Urine On Hands Could Be For Attention
http://www.nature.com/news/2007/070903/full/070903-18.html
Published online: 7 September 2007

It may seem strange, but many monkeys wash their hands and feet with
urine. Researchers now think they know why.

Since this odd behaviour was first observed, explanatory theories have
varied wildly from suggesting that it helps monkeys improve their grip
when climbing to saying it is a method of cleaning. One widely
supported theory argues that monkeys use urine washing to cool
themselves down when temperatures get too high.

But new research hints that it's all about social communication.

The notion of animals using chemical scents to communicate with each
other is hardly new. Dogs classically use urine to mark their
territory, for example, as do many other creatures. But when it comes
to peeing on oneself, researchers had thought physiological reasons
might be as important as social ones. It seems they were wrong.

Primatologist Kimran Miller and her research colleagues at the
National Institutes of Health Animal Center in Poolesville, Maryland,
monitored capuchin monkeys for ten months in a captive environment.
The researchers would record daily the enclosure temperature and
humidity and then note rates of urine washing. Their report, to be
published in the American Journal of Primatology, shows that urine
washing behaviours did not change with either temperature or humidity.

Instead, Miller and her team noticed a link between urine washing and
attention-seeking.

Alpha males, for example, doubled their urine washing rates when being
solicited by females. The researchers think this might be how males
encourage females to continue paying attention once they've started.

And in 87% of fights or aggressive incidents, the loser of the battle
washed in urine. The team suspects that this is also an
attention-seeking behaviour — in this case seeking sympathy. But more
research is needed to be sure.

"This really challenges the dominant theory that urine washing in
capuchins is related to thermoregulation," comments primatologist
James Anderson at the University of Stirling in Scotland.

"We see antelope that pee on their throats, vultures that poop on
their feet, and monkeys that wash their hands in urine," says
behavioural endocrinologist Fred Bercovitch at the centre for
Conservation and Research for Endangered Species in San Diego. "It's
obvious that urination is about more than elimination and it is great
to see research like this that is figuring out why."