The livestock animal trained to recognize human faces from photographs is the sheep.
In a 2017 study, researchers trained eight female Welsh Mountain sheep to distinguish photographs of familiar and unfamiliar human faces. The animals learned the task through food rewards and could recognize learned faces even when the photographs showed the people from a different angle.
The study also tested images of well-known people, including Barack Obama, Emma Watson, Jake Gyllenhaal and Fiona Bruce. The sheep’s performance demonstrated more than a simple response to one fixed picture: they could generalize a familiar identity across changes in viewpoint, a feature associated with face recognition.
This does not mean sheep recognize faces exactly as humans do, nor does it show that every sheep naturally identifies people from photographs without training. The animals were carefully conditioned, and their accuracy declined when images were tilted or otherwise altered. Still, the result challenged the stereotype that sheep have little visual or social sophistication.