Video: Crows recognise people’s faces

Grudge to bear (Image: Keith Brust)

Wild crows can recognise individual human faces and hold a grudge for years against people who have treated them badly. This ability – which may also exist in other wild animals – highlights how carefully some animals monitor the humans with whom they share living space.

Field biologists have observed that crows seem to recognise them, and a few researchers have even gone to the extreme of wearing masks when capturing birds to band (or “ring”) them, so that they could later observe the birds without upsetting them. However, it was unclear whether the birds distinguish people by their faces or by other distinctive features of dress, gait or behaviour. To find out, John Marzluff at the University of Washington in Seattle and colleagues donned a rubber caveman mask and then captured and banded wild American crows.

Whenever a person wearing the same mask approached those crows later, the birds scolded them loudly. In contrast, they ignored the same person wearing a mask of former US Vice-President Dick Cheney, which had never been worn during banding. “Most of the time you walk right up to them and they don’t care at all,” says Marzluff.


Long memories

The birds’ antipathy to the caveman mask has lasted more than three years, even though the crows have had no further bad experiences with people wearing it. The crows responded less strongly to other details of a person’s dress, such as the presence of a hat or a coloured armband.

In a second experiment, Marzluff’s team prepared six masks from casts of people’s faces, then wore different masks to capture crows in each of four locations. In each case, they found, the crows recognised and scolded whichever mask they had seen when they were captured, and ignored the others.

This shows that crows pay close attention to humans, noting which individuals pose a threat and which do not, says Doug Levey of the University of Florida in Gainesville, who was not part of the team.

“We may think they are just bystanders minding their own business – but we are their business,” he notes. “It’s likely that they’re incredibly perceptive of the dog and cat components of their environment, as well.”

Journal reference: Animal Behaviour, DOI: 10.1016/j.anbehav.2009.12.022