The humble goat can recognise when humans are smiling... just like dogs and horses, according to new research.

And the ruminant mammal, known for its intelligence and remarkable ability to scale mountains, prefers happy to sad faces, say British scientists.

It is the first evidence a species of livestock can differentiate between moods - just like man's first and second best friends.

The ability of animals to perceive emotional expressions is not limited to those with a long history of domestication as companions.

So the skill may be far more widespread than previously believed, reports Royal Society Open Science.

Dr Alan McElligott, who led the study at Queen Mary University of London and is now at the University of Roehampton, said: "The study has important implications for how we interact with livestock and other species, because the abilities of animals to perceive human emotions might be widespread and not just limited to pets."

It is well known that human facial expressions are highly informative for dogs and horses.

But whether domestic species tamed mainly for the purpose of providing food - such as milk, butter, cheese, wool and meat - are capable of this had remained a mystery.

First author Dr Christian Nawroth, now at Leibniz Institute for Farm Animal Biology, Germany, said: "We present the first evidence that a livestock species, the goat, can differentiate between happy and angry human faces.

"Not only can they distinguish between these emotional expressions, but they also generally prefer happy faces.

"The ability of animals to perceive human emotional expressions is thus not limited to those with a long history of domestication as companions, and therefore may be far more widespread than previously believed."

Writing in the journal, the team described how 20 goats interacted with images of positive, or happy, and negative, or angry, human facial expressions.

The study, which was carried out at Buttercups Sanctuary for Goats in Maidstone, found the animals preferred to look at and interact with the former.

It involved Dr Alan McElligott, now at the University of Roehampton, south west London, and colleagues showing the goats pairs of unfamiliar static human faces of the same individual - showing happy and angry expressions.

They reacted more excitedly to the former, approaching them and exploring them with their snouts.

This was particularly the case when the happy faces were positioned on the right of the test arena - suggesting goats use the left hemisphere of their brains to process positive emotion.

Goats can't see red so the pictures were in a format called 'grey scale' that removes the colour.

Dr Nawroth said: "We already knew goats are very attuned to human body language, but we did not know how they react to different human emotional expressions, such as anger and happiness.

"Here, we show for the first time that goats do not only distinguish between these expressions, but they also prefer to interact with happy ones."

The research has implications for understanding how animals process human emotions.

"The study has important implications for how we interact with livestock and other species, because the abilities of animals to perceive human emotions might be widespread and not just limited to pets" - Dr Alan McElligott

Co-author Natalia Albuquerque, from the University of Sao Paulo, said: "The study of emotion perception has already shown very complex abilities in dogs and horses.

"However, to date, there was no evidence that animals such as goats were capable of reading human facial expressions.

"Our results open new paths to understanding the emotional lives of all domestic animals."

Goats are believed to have first been domesticated around 10,000 years ago in the Middle East.

Goats are now also used to make gelatin, and their manure is used for fertiliser.

They are also used for research models in biological studies, to pull carts and for pack animals. Goats are bovines and are closely related to cows and antelopes.

They can climb near verticle mountains to reach salt at the summit that they love to snack on, and are said to be among the cleverest of animals.

The researchers said: "Facial expressions are rich sources of social information for humans and thus have an important role in regulating social interactions.

"In addition, facial expressions are also prevalent in non-human animals and the question of whether and how animals perceive emotional facial expressions is of major interest to understand their underlying ultimate functions and origin."

They added: "We present the first evidence that goats can discriminate human facial expressions with different emotional information.

"Not only can they distinguish them, but they also generally prefer happy faces, regardless of the gender of the human faces or the sex of the goats."