A group of scientists have devised a basis on which equine anatomy could be used to compare horse facial expressions to those of other animals including humans. The scientists discovered that horse facial expressions could resemble those of cats, dogs, chimps and could also have some similarities to human facial expressions. The horses also used their nostrils, lips and eyes to alter their facial expressions just as humans do. The research has led to a simple-to-use standardisation using the muscles of equine anatomy.
The team analysed hours of video footage of horse facial expressions, using FACS (Facial Action Coding Systems) which is a standardised way of describing facial movements based on the underlying muscle actions. It was initially devised to describe human facial expressions, but has since been used to describe cats, dogs and chimps’ facial movements too. The team also carried out their own anatomical study of equine facial muscles, thoroughly documenting all the muscles on a horse’s face. Through their research a standardised code to describe the horse anatomy of equine facial movements has been devised which can be used for further research.
Horses are visual animals which have large eyes positioned laterally on a long face and better eyesight than a cat or a dog. They belong to the order of Perissodactyla and are one of the nine species of Equus within this. Horses are now completely domesticated – feral species no longer exist in the wild – and they are social animals with a complex social structure within the herd. They live within several small groups that share space and resources. The members of the group stay loyal to the group, but territory can overlap so horses do come into contact with other groups and reveal fission fusion dynamics, which is a variation of complex social organisation which is found in chimpanzees, bonobos, elephants, spotted hyenas and humans.
Such social groups would require social interactions. The use of head and body posture to communicate in horses has been well-documented, but although it has been noted that horses can use facial expressions to react, there has not been thorough research on whether horses use the same facial movements to express the same reactions to similar stimuli. The team of scientists discovered that horses had a total of 17 action units or different facial movements. This compares favourably to orang utans who had 15, or dogs who have 16. Cats have more at 21 because of ear and whisker movement while humans have 27. The scientists discovered that many of the equine facial movements were similar to those of other animals including humans. It has been documented that some of the horse’s facial movements can be related to pain. Now it can be shown whether equine facial expressions can also be related to positive experiences using the EquiFACs.
Original Research available to read online:
Jen Wathan, Anne Burrows, Bridget M Waller and Karen McComb. EquiFACS: The equine Facial Acting Coding System; PLOS ONE; August 2015