How animals in groups interact when it comes to either increasing or decreasing fear in one another is an area relatively unexplored despite the great importance in relation to animal and human safety. Researchers form Aarhus University have now conducted a behavioural study with horses in order to make us wiser within this particular field.

“What we wanted to investigate in our study was whether a so-called demonstrator horse – a horse which has already been habituated to a ‘frightening object’ – can have a calming effect on the other herd members’ reactions when exposed to the same object”, says associate professor and project leader Janne Winther Christensen, Department of Animal Science.

First experiment with young demonstrators

The first experiment included 32 Danish Warmblood horses of the same age divided into eight groups of four horses each. The socially highest-ranking horse (determined through feeding tests) from each group was used as demonstrator. Half of the demonstrators were habituated to a sudden appearance of stimulus (a big, multi-coloured umbrella was unfolded) while fed in a test arena. The other half of the demonstrator horses were not habituated.

The same test arena was used when testing the entire group. Here, the four horses of each group were fed from individual troughs placed in a semicircle in order to be able to register the horses’ reactions and positions when the umbrella unfolded (see figure). The following registrations were collected for all young horses:

• Behavioural reactions (on a scale from 0-4 where 0 is no reaction and 4 is an escape reaction)
• Latency to resume eating behaviour after presentation of the umbrella
• Heart rate

Figure: Illustration of the set-up of the fear test in Experiments 1 and 2. The researchers registered the horses’ reactions and positions when the umbrella unfolded.    

The results from Experiment 1 showed that the strength of the young horses’ behavioural reaction was reduced in the groups including a habituated demonstrator. However, the latency to resume eating and the horses’ heart rates were unaffected.

The study showed that an experienced horse plays an important role in the regulation of fear reactions in groups of horses. Photo: Janne Winther Christensen.

Second experiment with adult demonstrators

In the second experiment, the researchers conducted the same set-up as in Experiment 1. However, this time with 32 Icelandic horses and with adult horses as demonstrators. The aim of the second experiment was to investigate the effect of the presence of an adult demonstrator in groups of four, including three 2-year-old horses in each group.

The results showed that the young horses, grouped with a habituated adult demonstrator, displayed fewer severe behavioural reactions, shorter latency to resume eating and a tendency to a lower heart rate compared to young horses in groups with a non-habituated demonstrator.

A habituated horse has a calming effect

“Both experiments have shown that a single habituated demonstrator horse can attenuate fear reactions in smaller groups of young horses. Thus, it seems that a certain level of social transmission takes place, meaning that an experienced horse plays an important role in the regulation of fear reactions in groups of horses”, explains Janne Winther Christensen.

The results also showed that there was a stronger fear-reducing effect of the habituated adult demonstrators in the second experiment compared to the first experiment in which young horses were demonstrators. As there were several varying factors between the two test rounds, including breed, time of year and feeding, it is not possible for the researchers to make a direct comparison.

“Further studies will be required before we can finally conclude whether adult horses have a greater influence as demonstrators than young horses. However, from our study, it seems that it is possible to attenuate fear reactions in groups of young horses by means of a single habituated demonstrator. And this knowledge has a huge potential regarding practical management within horse keeping, as fear reactions in horses cause many accidents every year in relation to human handling of horses”, concludes Janne Winther Christensen.

Read the full scientific article: “Attenuation of fear through social transmission in groups of same and differently aged horses”.

The study was funded by The Independent Research Fund Denmark | Technology and Production.    

Further information

Janne Winther Christensen, Department of Animal Science, Aarhus University.

Email: jwc@anis.au.dk