For a long time scientists thought the fact that pigeons in urban environments often lost their toes was due to some form of infection, or was a reaction to chemical pollutants.

But now researchers in France believe they’ve stumbled upon the real culprit: human hair.

The team from the National Museum of Natural History and the University of Lyon recorded the occurrence and extent of toe mutilations from pigeons eking out their time in 46 sites across Paris.

They found that human pollution likely played a part in nearly all cases of missing toes and that pigeons living in areas with higher rates of air and noise pollution tended to have fewer digits than those that lived in leafier environs.