I admit it. I have serious geek tendencies. Sometimes I read scientific papers for no apparent reason. One in the Journal of Zoology caught my attention recently: "Does human pedestrian behaviour influence risk assessment in a successful mammal urban adapter?" by P. W. Bateman and P. A. Fleming.
In the study, researchers examined eastern grey squirrels (Sciurus carolinenesis), called "successful urban exploiters" by the authors, foraging on the grounds of an apartment project in lower Manhattan that was dissected with footpaths and well stocked with the grey rodents. The observers were told to walk towards and by foraging squirrels in such a way as to remain two meters from the critters when they passed. They did so using two variants of this approach.
The first variant required the observers to stay on the footpath and thus only approach squirrels within range of the footpath. Half the time the observers were instructed to avert their eyes and half the time they were told to look at the squirrels. The second variant involved the observers leaving the footpath and approaching the squirrels directly with the same split between looking at the varmints and averting their eyes. The observers then recorded what proportion of squirrels fled before they reached the two-meters-away point.
The results aren't really surprising. Squirrels have intuitive "radar" of sorts that alerts them to potential danger and bids them flee when the danger is deemed too great. Generally speaking, squirrels stayed put when the observers stayed on the footpath, but fled readily when the observers went out of their way to approach the squirrels off the footpath.
In both cases the squirrels flee a lot more often when you're looking at them, which is the only part of the study that's all that interesting. It shows that squirrels can tell when people are looking at them.
The study also measured three things in each of the four treatments: the distance at which the squirrels sit up and take notice; the distance from the observers at which the squirrels begin to flee; and the distance that the squirrels ran before starting to forage again.
The key results follow.
-
When the observers didn't look at the squirrels and stayed on the path, the squirrels stayed put, being used to humans. Their radar didn't kick in.
-
When the observers looked at the rodents but stayed on the footpath, the squirrels became alert when the observers reached about five meters away, but they didn't run away, probably because people in the apartment complex generally stay on the footpaths. They were alert to potential danger but didn't flee.
-
When the observers left the path but averted their gaze, the squirrels got alert from about eight meters out, but they didn't flee. The squirrels were concerned a bit—people generally stay on the paths—but they didn't scram. The presence of people is a normal thing for them.
-
But when the observers left the path and stared at the squirrels, squirrel radar puts them on high alert. The critters get alert from about seven meters away and flee shortly thereafter; they tend to run about six meters away before again going about their business.
Ready to Bolt
The key point is that it makes a big difference whether or not people are looking at the squirrels, although staying on the footpaths also keeps them calmer. In truly dreadful scientific prose that tries desperately to sound authoritative, the researchers conclude as follows:
"We have identified cues that are likely to be important for risk perception by an urban animal species monitoring its environment. Together with direction of attention of people, urban squirrels were more reactive to pedestrians that showed a divergence from 'usual' behaviour (e.g. pedestrians entering areas which are usually human-free), even when not associated with closer approach or changes in speed. In addition to being arboreal (which can include use of anthropogenic structures), which minimizes vulnerability to diurnal terrestrial 'predators' (see Herr, Schley & Roper, 2009), general trophic and social flexibility (Baumgartner, 1943; Don, 1983; Koprowski, 2005) may help explain why eastern grey squirrels are successful urban adapters."
