Richard Collins: Cross-species communication: yay or neigh? 

But is the film’s central conceit a valid one?

Mary Temple Grandin, a scientist who is autistic, revolutionised our understanding of cattle behaviour. She managed ‘to get inside’ a cow’s head and see the world from the animal’s point of view. Do some people have a similar gift with horses?

Dogs and cats can interpret the speech and body-language of their owners. Herd animals, such as antelope, respond to the alarm signals of species other than their own. So do birds. But does more elaborate vocal inter-communication take place?

In a paper just published, researchers at the University of Copenhagen argue that cross-species communication between hoofed animals is real. Their study focused on horses and pigs.

The domestic horse, the wild Przewalski’s horse, the farmyard pig and the wild boar acted as ‘guinea-pigs’. Recordings of horse and pig sounds were played to them over hidden loudspeakers in zoos. Some of the sounds transmitted were positively charged emotionally. Others were those of less happy individuals.

All four ungulates responded to the sounds — irrespective of the species whose calls were being transmitted. Not only that, they were able to distinguish between calls expressing positive emotions and those of negative ones.

But the order in which the sounds were transmitted also mattered. The domestic and Przewalski’s horses, as well as the domestic pigs, ‘reacted more strongly when the first vocalisation played was negative rather than positive’, the researchers found. The wild boars, however, didn’t.

Using recordings of an actor’s voice, the horses and pigs were then exposed to human speech. To exclude the possibility that the animals might react to specific words or phrases, only meaningless gibberish was played to them. Three of the four species could identify the emotional tone of the person speaking. The wild boar, once again, was the odd man out; it was unable to do so.

Interpreting the vocalisations of another species might be due to familiarity ‘following a process of learning with repeated exposure’.

Also, animals with particular ability to discriminate between human vocalisations may have been selected progressively during the process of domestication.

The Przewalski’s horse, however, has no significant history of domestication. Yet it was capable of interpreting the human sounds. An ancestral genetic inheritance may be at play here as both horse species are closely related.

The researchers remain agnostic as to whether ‘vocal emotional contagion’, the beginnings of empathy with other species, occurs.

They don’t endorse horse whispering as such, but their results do seem to leave the door open as to whether it is possible.

• Anne-Laure Maigrot et al. Cross-species discrimination of vocal expression of emotional valence by Equidae and Suidae. BCM Biology. 2022