The Grudge That Lasted Seventeen Years
In 2006 a researcher trapped seven crows while wearing a caveman mask. The birds scolded that face for seventeen years — and taught it to offspring that had never seen the trapping.
Seven Crows, One Face, Seventeen Years
In 2006, John Marzluff, an environmental scientist at the University of Washington, put on a rubber caveman mask and trapped seven crows on campus. He banded them and let them go. He never harmed them again.
The birds did not let it go. For the next seventeen years, that mask could not walk across campus without being screamed at.
The Control That Made It a Study
The detail that turns this from an anecdote into an experiment is the second mask. Researchers also wore a commercially sold Dick Cheney mask, walking the same routes, trapping nobody.
The crows ignored it. At each of the five sites, the birds reacted to one face and one face only — the particular mask that had been worn during their banding — greeting it with loud scolding cries and small mobs. They were not reacting to humans, or to masks, or to strangers. They were reacting to a specific face associated with a specific bad day.
The Grudge Grew Instead of Fading
The strange part is what happened to the numbers over time. If this were ordinary memory, the response should have decayed as the original seven birds aged and died.
It did the opposite. About 1.25 years after the trapping, roughly 30 percent of the crows encountered on a masked walk scolded consistently. Nearly three years in, that figure had more than doubled, to around 66 percent. On one later walk, Marzluff was scolded by 47 of the 53 crows he passed — far more birds than had ever been present at a trapping in the first place.
The hostility was spreading to birds that had no personal reason for it.
Three Ways to Learn a Face You Never Met
The spread happened along three routes, and only one of them involves first-hand experience.
Some crows learned the face directly, by being trapped. Others learned it by watching — the birds circling and calling in the mob overhead during a capture picked it up without ever being handled. And young crows that had never witnessed a trapping at all scolded the mask on their own, having taken the cue from their parents.
That third route is the striking one. A bird born years after 2006 could identify and harass a specific human face purely on inherited social information. The grudge was being taught.
September 2023: Silence
Seventeen years after it started, Marzluff put the caveman mask on again and walked the campus.
Not one crow scolded him.
As the original birds died and generation after generation replaced them, the response had thinned out and finally stopped altogether. Marzluff took the silence as the natural end of the experiment and planned to conclude it. The face that a population of crows had warned each other about for nearly two decades had, at last, been forgotten.
