Are Chestnuts really ‘nuts’?

Coat color, one of the most prominent horse features, has fascinated and intrigued us for centuries. Resulting from genetic mutations that affect pigment producing cells (melanocytes), some coat colors are often seen as more desirable than others and can affect the value of an animal. In the horse industry particularly, some breeds are predominantly defined by the color and color patterns of their coats (e.g. American Paint & Appaloosa). Widespread stereotyping also surrounds horses of certain colors, most notably chestnut horses, and particularly those that are female, are often described as “crazy”.

Studies testing the hypothesis that chestnut horses are “crazy” are limited at best (Brunberg et al., 2013). Researchers from the University of Sydney, Australia have investigated possible associations between the chestnut coat color and behavioral responses in the horse. Their study provides insight into potential genetic associations between coat color and adverse behaviors in horses. The benefit of this is that equine industry professionals can better understand why horses may have completely polar reactions to similar stimuli.

Coat color differentiation – A Bay, B Chestnut

The researchers designed and distributed an owner questionnaire to investigate a range of horse behaviors which was used for the behavioral assessment of each horse. The questionnaire was composed of sections pertaining to the respondent’s horse handling experience, basic horse information, equipment used when handling or riding the horse, and behavioral responses in general and to specific circumstances. The questionnaire was promoted by printed advertisements in horse industry retail shops, online using social media and by word of mouth.

Completed questionnaires were received on 905 horses; however, only horses reported as having the bay or chestnut phenotype (n = 477) were included in the analyses.


Significant (P < 0.05) differences in behavioral responses between bay and chestnut horses were present in the models for four questions (from a possible 90). See table below.

Chestnut   Bay
Mean S.D. Mean S.D. P-value
Does the horse allow its feet to be picked up by a stranger * 0.45 0.68 0.35 0.69 0.018
How does the horse approach familiar stationary objects ** 2.25 0.89 2.50 0.79 0.001
How does the horse approach unfamiliar animals ** 2.39 0.87 2.58 0.95 0.025
How does the horse approach familiar motorized objects ** 2.50 0.94 2.63 0.82 0.039

Possible answers & scores:

*Never (0), Seldom (1), Sometimes (3), Usually (4) or Always (5)

**Approach Rapidly (1), Approach Slowly (2), Generally Stays still (3), Moves Slowly Away (4) or Moves Rapidly Away (5).

There was no compelling evidence that chestnut horses are any more likely than bay horses to display ‘difficult’ behaviors.  In fact, the only time chestnut horses were more likely to display this type of behavior was when having their feet picked up by a stranger.

The results actually suggest that chestnut horses were more likely to approach objects and animals in their environment, regardless of their familiarity. This is particularly worth noting as prior to domestication and selection, the vast majority of horses expressed the bay phenotype and the increase in coat-colour variability is thought to be a direct consequence of domestication (Cieslak et al., 2011; Ludwig et al., 2009; Pruvost et al., 2011).

It is possible then, that selection for the chestnut phenotype may have inadvertently involved selection for boldness as well. You could understand how boldness differences between bay and chestnut horses might have led to the notion of “crazy chestnuts”. Chestnut horses may seem “crazy” simply because they might get themselves into situations that are more frightening or dangerous.

This perception would gain even more support if boldness presented in some horses as self-confidence or assertiveness. Any horse that resists a new command or cue in a more forceful manner than other horses might be labelled as difficult or “crazy”.

This study refutes the theory that chestnut horses are more inclined to perform adverse behaviours associated with training difficulties. Despite this, 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. Owners of chestnut horses with training problems might need help on a case-by-case basis, rather than being told that all chestnuts are just crazy!


Finn, J.L., Haase, B., Willet, C.E., van Rooy, D., Chew, T., Wade, C.M., Hamilton, N.A. and Velie, B.D., 2016. The relationship between coat colour phenotype and equine behaviour: A pilot study. Applied Animal Behaviour Science, 174, pp.66-69.


Brunberg, E., Gille, S., Mikko, S., Lindgren, G. and Keeling, L.J., 2013. Icelandic horses with the Silver coat colour show altered behaviour in a fear reaction test. Applied Animal Behaviour Science146(1), pp.72-78.

Cieslak, M., Reissmann, M., Hofreiter, M. and Ludwig, A., 2011. Colours of domestication. Biological Reviews86(4), pp.885-899.

Ludwig, A., Pruvost, M., Reissmann, M., Benecke, N., Brockmann, G.A., Castaños, P., Cieslak, M., Lippold, S., Llorente, L., Malaspinas, A.S. and Slatkin, M., 2009. Coat color variation at the beginning of horse domestication. Science324(5926), pp.485-485.

Pruvost, M., Bellone, R., Benecke, N., Sandoval-Castellanos, E., Cieslak, M., Kuznetsova, T., Morales-Muñiz, A., O’Connor, T., Reissmann, M., Hofreiter, M. and Ludwig, A., 2011. Genotypes of predomestic horses match phenotypes painted in Paleolithic works of cave art. Proceedings of the National Academy of Sciences108(46), pp.18626-18630.