Chestnut horses do not deserve their reputation for crankiness, say researchers, but they did find them generally bolder than their bay counterparts in an Australian study.
University of Sydney researchers have published their findings from a pilot study that explored the relationship between coat colour genetics and equine behaviour.
They found that the breed, sex and age of a horse significantly influenced many behaviours, but their findings refuted the notion of the “crazy chestnut”.
They reported major behavioural differences between bays and chestnuts, but the latter were not more likely to display undesirable behaviours.
Brandon Velie and his colleagues, writing in the journal, Applied Animal Behaviour Science, said mutations in genes influencing melanocytes – mature melanin-forming cells, especially in the skin – not only affected the colour of an animal, but were also believed to influence physiological and behavioural functions.
On that basis, the common perception among horse owners that chestnut coat colour was linked to bad behaviour seemed plausible.
The study team set out to explore the perception by seeking out potential genetic associations between coat colour and bad behaviour.
The study team ran an online questionnaire, with 90 questions focused on behaviour, which generated data for analysis on 477 horses across a range of breeds, ages, and disciplines.
To avoid biased responses, questions were worded in a neutral way and horse owners were not told about the aims of the study.
Respondents were asked to provide details on their horse’s behaviour during general handling and while being exercised, as well as how they reacted towards different stimuli. The study also asked how the animal behaved when separated from other horses.
Breed, sex, and age significantly influenced many of the behaviours assessed in the questionnaire, they reported. However, significant differences in behavioural responses between bay and chestnut horses were present in only four questions.
“Chestnut horses were more likely to approach objects and animals in their environment, regardless of their familiarity,” they said.
“This suggests that selection for the chestnut phenotype in horses may have inadvertently involved selection for boldness and altered the way horses interact with their surroundings.”
Discussing their findings, the study team said one might expect that age, breed, and sex would influence horses’ behaviour. “However, no compelling evidence was found to support that chestnut horses are any more likely than bay horses to display behaviours often associated with a difficulty to train.
“In fact, the only time chestnut horses were more likely to display this type of behaviour was when having their feet picked up by a stranger.
“That being said, no significant differences between bay and chestnut horses were present for any other question that would involve either familiar or unfamiliar people picking up the horse’s feet. This strongly suggests that the difference is attributable to sampling rather than a real difference between the two phenotypes.”
However, the presence of significant differences in how bay and chestnut horses approached different stimuli in their environment was potentially more interesting, they said.
Chestnut horses were found to be more likely to approach objects and animals in their environment, regardless of familiarity.
This was worth noting, they wrote, as before domestication most horses were bay. The increase in coat-colour variability in today’s horses is widely considered a direct result of domestication.
It was possible, they said, that selection for the chestnut phenotype may have inadvertently involved selection for boldness as well.
“That said, associations between breed, sex, and age with behavioural responses and the few significant links with colour phenotype clearly refute the notion of ‘crazy chestnuts’.
“However, it is easy to understand how boldness differences between bay and chestnut horses may have led to this perception.
“Chestnut horses may seem ‘crazy’ simply because they get themselves into situations that tend to be more frightening or dangerous,” they suggested.
Such a view would gain even more suppoort if boldness presented in some horses as self-confidence or assertiveness, they suggested.
The findings suggested a plausible link between melanin-based colouration and behaviour, they said, but the theory that chestnut horses were more inclined to perform badly during training was not supported, they said.
Future studies would benefit from involving greater numbers of horses and genetically testing the animals to determine their coat color genes.
Bay horses, they point out, may carry a chestnut allele, creating a potential intermediate phenotype. An inability to discern this intermediate phenotype in the pilot study may have weakened the associations examined in the research.
They concluded: “The stereotype that all horses of a particular coat colour show certain behaviours can alter the perception of the horse and perhaps limit people from seeking help if needed.
“Objective data is needed if these myths are to be disproved so that people who have chestnut horses with training problems actually get help on a case-by-case basis, rather than being told that all chestnuts are crazy.”
The relationship between coat colour phenotype and equine behaviour: A pilot study
Jessica L. Finn, Bianca Haase, Cali E. Willet, Diane van Rooy, Tracy Chew, Claire M. Wade, Natasha A. Hamilton, Brandon D. Velie.
The full study can be read here.