Science Spin September 2007

Chimps acquire 'road sense'

This phenomenon was recently described in the journal Current Biology by Kimberley Hockings, a psychologist studying for her PhD at the University of Stirling, and her colleagues.

Kimberley spent a year living in close proximity to a group of chimps while on field research in the Central African nation of Guinea, an experience she describes as amazing. She goes on to say, "I often found it quite humbling to observe their every movement and to see how we share so many similarities with them".

Kimberley's team recorded the behaviour of a small band of chimpanzees as they crossed two roads bisecting their forest territory. While one of the roads was a seldom-used track mainly travelled by pedestrians, the other was a much busier highway, regularly used by lorries and cars.

The band of chimps has reportedly used the same specific crossing points for decades so it was at these 'zebra crossings' that the researchers holed up, waiting for the chimps to appear.

The scientists hypothesised that the chimps would be able to assess the degree of risk as they came upon either road and they wanted to learn more about how they might respond to the varying level of risk encountered.

The data gathered are intriguing. As the first member in the line of chimps came upon the road it was observed to stop and scan the road for traffic. Perhaps unsurprisingly the scientists recorded that the time spent scanning was proportionate to the size of the road and the perceived level of danger. The chimps spent on average eight times longer assessing the risk on the larger road than on the smaller one (180 seconds versus 24 seconds).

The presence of both people and vehicles increased the time the chimps spent scanning before crossing the highway but interestingly, on the smaller road the brazen chimps paid no heed to the presence of human traffic, moving across when they saw fit, regardless of any remonstrations from their tall and clothed primate brethren.

This remarkable harmony between the local Manon people and the chimps is founded on a long history of peaceful co-existence. Indeed it would seem that the Manon people could have taught biology a few lessons about evolution long before Darwin set his pen to paper, as Kimberley explains, "The local Manon people believe that the chimpanzees are their ancestors and many families hold the chimpanzees as their totems".

The chimps cross in an orderly single file with the more dominant members of the group taking up the front and rear and the younger chimps in the middle, reminiscent of a scout troop out hiking along the road, with the leaders walking to the aft and fore and the young scouts in the middle.

On the larger road, one of the males was sometimes observed to remain behind, continuing to scan the road while his comrades crossed, only joining them after they had all started the crossing.

The positioning of dominant members to the front during group movement is a mechanism commonly used by primates as they move through dangerous areas. For example, in monkey troupes, the dominant males will often take a lead role as the group moves toward dangerous areas such as waterholes. The researchers believe that the chimps have adapted this type of behaviour to respond to the recent appearance of man-made roads and their associated dangers.

Fortunately, there have been no recorded traffic accidents involving the chimps but perhaps it is time that our road safety signs took into account the needs of our closest primate cousins. These chimps could even make the case for a renaming of one of our most iconic road safety markings, the zebra crossing. Based on the evidence presented here it seems that they might very well have the right of way to do so.

Reference:
Hockings, K.J., Anderson, J.R., and T. Matsuzawa, "Road crossing in chimpanzees: a risky business". Curr Biol, 2006. 16(17): p. 668-70.