Oral traditions suggest that differences in the position and number of facial hair whorls on horses may be linked to temperament.
Scientists have investigated the heritability of forehead whorls – an important step towards learning more about any relationship they may have with temperament.
In general, horses have 2cm-long hairs on their body. Hair whorls can be seen in various places. Their number and position have been used for individual identification of horses because they are quite individual.
Almost all horses have one or more hair whorls on their forehead, and these facial whorls are classified into high, medium and low, based on their position (see the graphic).
Facial whorls may be related to temperamental traits, if oral accounts from generations of horse owners prove to be true. Horses with a whorl in the low position might be difficult to handle, and horses with multiple facial hair whorls tend to fear novel items and environmental conditions.
Several recent studies have examined the relationships between facial hair whorls and behaviors. The direction of rotation of facial hair whorls has been linked with the turning response. Horses that favor the right were found to have more clockwise facial hair whorls, whereas left-favoring horses had more counter-clockwise ones.
Japanese researchers Teruaki Tozaki and Takuya Itou devised an experiment to examine heritability around both the number and position of facial hair whorls in Japanese Thoroughbreds.
The pair, together with their colleagues, delved into the facial whorl characteristics of 4845 Thoroughbreds in Japan, all registered with the Japan Racehorse Association (JRA). Information on the number and position of whorls was already held in the JRA database.
They delved back three generations in the database in order to estimate heritability.
The Thoroughbreds were found to have between one and four forehead whorls. The majority, 81.07%, had just one, while 18.65% had two. Just 12 of the 4845 horses – that’s 0.25% – had three, and only one had four.
The study team, writing in the journal BMC Research Notes, found that 55.77% of the horses had one whorl at the high position, 22.93% at the medium position, and 2.37% at the low position.
Their findings indicated that genetic factors contributed more to the variability of facial whorl position rather than the number. Indeed, position proved to have high heritability.
The researchers noted that a similar study in Konik horses – a primitive Polish horse breed – also reported high heritability of this trait.
Since a similar result was obtained independently in two different breeds, it is likely that a large proportion of the variation in facial hair whorl positions in horses is due to genetic factors.
In contrast, heritability around facial whorl numbers was low.
It was possible, they said, that future genetic testing may identify the genes responsible for whorls, which could become a de facto test for temperament if links with character traits are confirmed.
However, they acknowledged it was difficult to distinguish between inborn and potentially acquired temperament.
Knowing more about the genetic basis for temperament in individual horses had the potential to optimize their life after racing retirement, they said.
“These findings could be useful for designing a rational plan of racehorse management.
“We also expect that these results will stimulate future studies to elucidate the relationship among temperamental traits and facial hair whorls in all horse breeds.”
The full study team comprised Yokomori, Itou, Teruaki Tozaki, Hiroshi Mita, Takeshi Miyake, Hironaga Kakoi, Yuki Kobayashi and Kanichi Kusano, from a range of Japanese institutions.
Heritability estimates of the position and number of facial hair whorls in Thoroughbred horses
Tamu Yokomori, Teruaki Tozaki, Hiroshi Mita, Takeshi Miyake, Hironaga Kakoi, Yuki Kobayashi, Kanichi Kusano and Takuya Itou
BMC Research Notes 2019 12:346 https://doi.org/10.1186/s13104-019-4386-x