The #1 source for news about monkeys and apes

[Josh Greenman <josh.greenman AT gmail.com>]

http://www.newscientist.com/article/dn16744-chimps-use-geometry-to-navigate-the-jungle.html

Chimps use geometry to navigate the jungle

12 March 2009 by Ewen Callaway

If you're ever lost in the jungle, follow a chimpanzee. New research
suggests the great apes keep a geometric mental map of their home
range, moving from point to point in nearly straight lines.

"The kind of striking thing when you are with the chimpanzees in the
forest is that we use a compass or GPS, but obviously these guys know
where they are going," says Christophe Boesch, a primatologist at the
Max Planck Institute for Evolutionary Anthropology in Leipzig.

With the aid of GPS, he and colleague Emmanuelle Normand shadowed the
movements of 15 chimpanzees in Côte d'Ivoire's Taï National Park for a
total of 217 days.

In a given day, a single animal might visit 15 of the roughly 12,000
trees in its 17-square-kilometre range, Boesch says. "They are kind of
nomads."
Chimp tracking

Each morning, researchers woke before a chimpanzee, and then tailed
the animal until it went to sleep at day's end – often in a different
nest. Researchers recorded their GPS position once a minute.

"We were able to do this study now because of the new GPS technology
that works perfectly in the tropical forest. That was not the case
five years ago," Boesch says.

After analysing all this data, he and Normand found good evidence that
the animals chose their routes using a mental map built around
geometric coordinates, as opposed to a navigation style based on
landmarks for well-travelled routes.

While darting from fruit tree to fruit tree, individuals tended to
move in straight lines, slowing only once they neared their
destination. Chimps also visited trees from an angle that depended on
current location.

This suggests the chimpanzees do not rely exclusively on landmarks
such as specific trees and streams to navigate. These markers could
come in handy once a chimp nears its destination.
Travelling in styles

Previous research and everyday experience suggests that humans, too,
employ both styles of navigation, depending on their environment.

"In a city you can use roads, which are the classical landmarks,
whereas if you are a Pygmy in the tropical rainforest or an Eskimo in
the Arctic, where you have nothing as a landmark, then you will learn
to get by using more sophisticated means," Boesch says.

Paul Garber, a biological anthropologist at the University of Illinois
in Urbana-Champaign, thinks that point-to-point distance might not be
the only factor involved in a chimpanzee's choice of route.

Quantity and quality of food, as well as competition, could play a
role in route choice. Also, like travelling salesmen who optimize
their travels, chimpanzees may be thinking about navigation with an
eye to the future, Garber says. "They may be planning not just one
step in a route, but many, many steps ahead."

Journal reference: Animal Behaviour (DOI: 10.1016/j.anbehav.2009.01.025)