title: The mane effect in the horse (Equus ferus caballus): Right mane dominance enhanced in mares but not associated with left and right manoeuvres in a reining competition.
abstract: A human physical asymmetry is the near 90% clockwise occipitoparietal scalp hair-whorl direction in Europeans, an incidence that approximates the left lateralization of speech and right-handedness. Hair-whorl direction is also asymmetric in horses, Equus ferus caballus and placement is proposed to be related to temperament and lateralized skill in equitation manoeuvres. We describe a hair-whorl asymmetry in the horse, mane direction. Of 526, 3-year-old American Quarter horses, 69% of horses had mane directed to the right and 31% had mane directed to the left. The bias was larger in females, with 74% of females vs. 65% of males having mane directed to the right. Mane direction was unrelated to coat colour. The behavioural significance of mane asymmetry was investigated using judges' scores from a reining competition requiring symmetrical maneuvers of spin, circle and roll-back to either the left or to the right. There was no relation between mane asymmetry and overall reining performance and no relation between mane direction and scores for left or right manoeuvres. The results are discussed in relation to the significance of morphological asymmetries, neural function and the influence of planar cell polarity genes, such as Frizzled, that influence epidermal hair cell patterning.
authors.affiliation: a Department of Neuroscience , Canadian Centre of Behavioural Neuroscience, University of Lethbridge , Lethbridge , AB , Canada.
authors.forename: Ian Q
authors.initials: IQ
authors.lastname: Whishaw
authors.affiliation: a Department of Neuroscience , Canadian Centre of Behavioural Neuroscience, University of Lethbridge , Lethbridge , AB , Canada.
authors.forename: Bryan
authors.initials: B
authors.lastname: Kolb
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D003163:Competitive Behavior / Q000502:physiology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D005868:Gestures; D006736:Horses; D008124:Locomotion / Q000502:physiology*; D008297:Male; D011597:Psychomotor Performance / Q000502:physiology*; D012737:Sex Factors; D012919:Social Behavior; D013694:Temperament
keywords: Mane asymmetry in performance horses; hair-whorl direction in the horse; laterality in horses; laterality in skilled behaviour; reining horse laterality; sex differences in mane asymmetry