Sheep recognize each other by their faces and can remember faces for more than two years. Livestock farmers might not be surprised — animals form bonds with each other and a newcomer to a flock certainly stands out. But the surprising part of this finding is that it was based on pictures of sheep faces without any social interaction.
Sheep were shown pictures of other sheep faces, two at a time, and food was placed under one of the faces. The animals in the study quickly learned to link specific faces with food.
Later the researchers showed the test subjects pictures of sheep faces. The photos were face shots of current flock mates, sheep that were no longer part of the flock and individuals the test subjects had never encountered. The sheep vocalized at the sheep they knew, including faces of individuals they hadn’t seen for two years, but responded differently to unknown sheep. The findings were similar with human images. In total, the researchers found sheep could remember 50 sheep faces and 10 human faces for at least two years.
Source: Sheep don't forget a face. Keith M. Kendrick, Ana P. da Costa, Andrea E. Leigh, Michael R. Hinton & Jon W. Peirce. Nature. 414, 165-166. Nov. 8, 2001.
- Janet Wallace