Domesticated horse (Equus ferus caballus) tool use

Around five and half thousand years ago, in what we now call Kazakhstan, someone put the first bridle on a horse. That person was part of the Botai culture, a semi-mobile group of early herders who also seem to have been the first to adopt horse milk as part of their regular diet.

The path from then to now is not a straight one—involving massive changes in human warfare, farming and transport—but the end result is a close bond between modern domesticated horses and those who care for them. We now know a huge amount about equine behaviour and temperament, and we have a long artistic record of horses that gives us a clear picture into their past behaviour too. And in all those paintings, all those sculptures over thousands of years, not one shows a horse casually using a tool.

Surely we would know by now if these creatures were tool-users, wouldn’t we?

This is the question that Konstanze Krueger and her colleagues have spent much of the last decade exploring. And they have done so using a thoroughly modern tool: crowdsourcing.

Stable minds

Krueger is Germany's first Professor of Horse Management, based at Nuertingen-Geislingen University. Her team studies the ways that horses learn about, interact with and understand the world. She noted that reports of clever horse behaviour would appear sporadically in the news or on social media, but no-one was working to bring all these individual cases together to see if they added up to anything more than amusing tales.

From mid-2012 to late 2021, Krueger used questionnaires, conferences, horse journals, Facebook and Youtube to track down the source of those reports. She also set up a specific website of her own—innovative-behaviour.org—to which people could add their own observations.

All this searching resulted in descriptions of over 1000 equid behaviours across 635 reports, from horse owners around the world. Of those behaviours, 13 fitted the definition of tool use. A small sample to be sure, but enough to suggest that this wasn’t a case of a few over-enthusiastic horse owners exaggerating or anthropomorphising their animals’ achievements. Plus, modern reports come with videos, helping the researchers to verify the activities.

In this film, for example, an Arab gelding uses a stick tool to scratch his chest and stomach:

And in this one a foal grooms her mother using a human (brush) tool:

Every one of the types of tool use that the scientists found involved a horse holding something in its mouth. As useful and durable as they are for trotting and galloping, horse hooves just aren’t built for object manipulation. Horses held, moved and threw buckets, halters, and sticks, each time with a clear purpose. And they had four main targets: other horses, their owners/trainers, themselves, and food.

Here are two clips that show the kind of stick-tool reaching and feeding behaviour familiar from wild chimpanzees, capuchin monkeys and various bird species. In the first video, from which the image at the top of this post was taken, a mare uses a stick to rake hay towards herself, while her companion looks on:

A second example of hay raking is also a possible example of social learning. A horse, Corado, became expert at bringing sticks from the paddock to his shared stall beside the hay barn. There, he would use them to rake hay from beneath the barn out into the open. His stablemate, a mule named Otello, saw this happen many times, but didn’t actually do any raking himself. Until Corado took ill, and Otello found that the only way to continue getting surreptitious access to hay was to start doing the job himself:

Hans and hooves

For some of you, the mention of smart horses will immediately turn your mind to another German, Clever Hans. Hans was a stallion born in the late nineteenth century, owned and trained by retired school teacher Wilhem von Osten. Here’s Hans with von Osten with some of the training materials they used:

In that picture you can see both counting and reading aids. When von Osten began to exhibit Hans around his home town of Berlin, Hans proved able to answer questions put to him in both verbal and written form, as long as he could tap the answer with his hoof. In the words of a journalist from the New York Times, who viewed a demonstration in 1904,

The versatility of Hans…is astonishing. He can distinguish between straw and felt hats, between canes and umbrellas. He knows the different colors. One beholds several colored rags fastened on a string. A cavalry officer places himself before the horse and Hans is asked to state the color of his cap. The horse answers by stamping his foot down three times, the color of the third rag, which like the cap, is red.

Hans has also been taught to distinguish tones. The various tones of the musical scale are numbered, and he recognises their position by his usual method.

Hans can tell the time on a watch and can indicate the exact hour. At the test yesterday he recognised persons from photographs.

Anything that involved a counted response, whether to indicate an actual number such as the answer to a mathematics problem, or to indicate the position of a reference scale, Hans mastered.

Of course, if you’ve heard of Hans, you’ll know that ultimately his abilities turned out to be astonishing, but not in the way that the journalist and others believed. In 1907, psychologist Oskar Pfungst proved that Hans was reading subtle and unconscious clues from von Osten’s face and body. Hans would begin tapping, and when he saw von Osten react to the correct number, he stopped. Tellingly, when von Osten didn’t know the correct answer to a question, neither did Hans.

Despite not being actually able to communicate about cavalry cap colours, Hans did display a deep ability to read human cues. He picked up on minor movements that went unnoticed by other humans, including von Osten himself. Ultimately the tale of Clever Hans tells us more about his species’ social acuity than their numerical one, but it is a valuable insight into the equine mind nonetheless.

Crowded thoughts

I’ve included Hans here because it can be tempting to dismiss the actions of domesticated and trained animals as the result of human interaction, even in the case of unwitting clues given by honest owners. However, horse perception and abilities differ significantly from our own. None of the horses in the videos above was trained to rake hay or scratch themselves by a human holding a stick in their mouth. Instead, the animals have invented their own techniques, and perhaps for Corado and Otello even shared it with others.

It is true that captive animals and pets often show greater tool using abilities than their wild relatives, but that should not lead us to automatically downplay the difficulties of cross-species learning and functional physics faced by equids. We should also be wary of past assessments of any animal as a non-tool-user, even one as well documented in literature and art as the horse.

Krueger and her team were careful to note that their findings should be taken as provisional and suggestive, rather than definitive, until the biases associated with crowdsourced information can be fully assessed. Despite rigorous vetting of each response to ensure that the horses are actually displaying the claimed behaviour, the videos and descriptions provided by each informant have not been through the same level of analysis that would take place in a controlled experiment. Still, at the very least, we can expect more crowdsourced revelations in the future, powered by the internet and citizen scientists. Perhaps the next animal to be discovered using tools is the one you film today!

Sources: Outram, A. et al. (2009) The Earliest Horse Harnessing and Milking. Science 323: 1332-1335. || Librado, P. et al. (2021) The origins and spread of domestic horses from the Western Eurasian steppes. Nature 598: 634–640. || Krueger, K. et al. (2022) Tool use in horses. Animals 12:1876. || Heyn, E. (1904) Berlin’s wonderful horse. New York Times September 4. (https://timesmachine.nytimes.com/timesmachine/1904/09/04/101396572.pdf)

Main image credit: Krueger et al. (2022) || Second image credit: Wikipedia; https://en.wikipedia.org/wiki/Clever_Hans#/media/File:Osten_und_Hans.jpg || Video credits: Krueger et al. (2022) Supplementary Information