To test the birds’ recognition of faces separately from that of clothing, gait and other individual human characteristics, Marzluff and two students wore rubber masks. He designated a caveman mask as “dangerous” and, in a deliberate gesture of civic generosity, a Dick Cheney mask as “neutral.” Researchers in the dangerous mask then trapped and banded seven crows on the university’s campus in Seattle. In the months that followed, the researchers and volunteers donned the masks on campus, this time walking prescribed routes and not bothering crows.
The crows had not forgotten. They scolded people in the dangerous mask significantly more than they did before they were trapped, even when the mask was disguised with a hat or worn upside down. The neutral mask provoked little reaction.
The effect has not only persisted, but also multiplied over the past two years. Wearing the dangerous mask on one recent walk through campus, Marzluff said, he was scolded by 47 of the 53 crows he encountered, many more than had experienced or witnessed the initial trapping. The researchers hypothesize that crows learn to recognize threatening humans from both parents and others in their flock. Bernd Heinrich, a professor emeritus at the University of Vermont known for his books on raven behavior, suggested that crows’ apparent ability to distinguish among human faces is a “byproduct of their acuity,” an outgrowth of their unusually keen ability to recognize one another, even after many months of separation.
First posted: TUESDAY, AUGUST 26, 2008