Horses appear capable of recognising themselves in mirrors, according to researchers, revealing a level of self-awareness in the species traditionally associated with humans and primates.
The researchers at the University of Pisa in Italy reported that a majority of the 14 horses used in the study tried to rub off cross-shaped marks deliberately drawn on their cheeks.
The findings by Paolo Baragli and his colleagues are reported in the journal Animal Cognition.
The researchers described a study in which a large mirror was installed in an indoor arena.
Fourteen horses were introduced to the space one at a time for their behaviour to be monitored in a four-phase experiment.
The first two phases involved monitoring their reaction to mirror exposure, either open or covered.
“We found that in the presence of the reflective surface the behavior of the horses clearly differed when compared to the condition in which the surface was covered.”
Their attention to the mirror and exploratory activity increased when the mirror was open.
Eleven horses even checked behind the mirror and appeared to watch their reflections as they moved their heads in peek-a-boo fashion.
In the next phase, the researchers used transparent medical ultrasound gel to put an “X” on both cheeks of the horses. The reactions of the horses to the presence of the mirror were again followed.
In the final phase, odorless yellow or blue paint was added to the gel, so that the crosses put on their cheeks stood out.
The study team said the behavior of a majority of the horses suggested they recognised from their reflection that they had something on their face.
The marks could only be seen by the horses with the aid of a mirror.
“Our horses used the mirror surface to guide their movements towards their colored cheeks, thus showing that they can recognize themselves in a mirror.”
Looking at the data on a group level, the horses spent longer scratching their faces on poles situated in front of the mirror when they were marked with the visible mark compared to the non-visible mark.
This indicated that the horses did not see the non-visible mark, suggesting the presence of mirror self-recognition in horses.
The study team said recent evidence for research, including their own experiment, indicated that mirror self-recognition was not an all-or-nothing phenomenon that appeared once in the evolutionary tree.
A convergent evolution mechanism can be at the basis of its presence in distantly related species, they said.
They said their results amounted to the first evidence of mirror self-recognition at the group level in a non-primate species.
Baragli, P., Scopa, C., Maglieri, V. et al. If horses had toes: demonstrating mirror self recognition at group level in Equus caballus. Anim Cogn (2021). https://doi.org/10.1007/s10071-021-01502-7