Associations between Domestic-Dog Morphology and Behaviour Scores in the Dog Mentality Assessment.

Holly R. Stone,Bjorn Forkman,Melissa J. Starling,Paul D. McGreevy,Carlos E. Ambrósio

doi:10.1371/journal.pone.0149403

Abstract

The domestic dog shows a wide range of morphologies, that humans have selected for in the process of creating unique breeds. Recent studies have revealed correlations between changes in morphology and behaviour as reported by owners. For example, as height and weight decrease, many undesirable behaviours (non-social fear, hyperactivity and attention seeking) become more apparent. The current study aimed to explore more of these correlations, but this time used reports from trained observers. Phenotypic measurements were recorded from a range of common dog breeds (n = 45) and included cephalic index (CI: the ratio of skull width to skull length), bodyweight, height and sex. These data were then correlated with results from the Dog Mentality Assessment (DMA), which involves trained observers scoring a dog’s reaction to stimuli presented over 10 standardised subtests. Each subtest is designed to evoke a behavioural response. Backward elimination and weighted step-wise regression revealed that shorter dogs demonstrated more aggressive tendencies, reacting defensively toward both assistants dressed as ghosts (p = 0.045), and to a dummy (p = 0.008). Taller dogs were more affectionate when greeting and being handled by humans (p = 0.007, p = <0.001, respectively). Taller dogs were also more cooperative (p = <0.001), and playful (p = 0.001) with humans than shorter dogs. Heavier dogs were more inquisitive toward a dummy (p = 0.011), to the source of a metallic noise (p = 0.010) and to an assistant (p = 0.003). Heavier dogs were also more attentive to the ghosts (p = 0.013). In comparison, lighter dogs were cautious of a dummy (p = <0.001) and fearful of the sound of a gunshot (p = <0.001). Lighter dogs were also cautious of, and demonstrated prolonged fearfulness toward, the source of metallic noise (p = <0.001, p = <0.034, respectively). With a far larger sample and the advantage of third-party reporting (which overcomes potential owner bias), the current findings build on previous studies in this field, further supporting covariance between morphology and behaviour.

Highlights

Throughout the process of domestication, the dog has been transformed to meet many of the functional and emotional needs of humans [1]
The breeds selected were recognised by the Australian National Kennel Council (ANKC) and had a minimum of 30 annual registrations
Bodyweight was positively correlated with chase proneness, while brachycephalic dogs demonstrated grabbing behaviours on the second test, but not in the first test

Summary

Introduction

Throughout the process of domestication, the dog has been transformed to meet many of the functional and emotional needs of humans [1]. Selective breeding has produced a broad spectrum of dogs occupying various niches as herders, hunters, protectors, trackers, assistance dogs, athletes and, commonly, as companions. Their relationships with humans, their ongoing journey to domestication and their morphological diversity have captured the interest of geneticists, anatomists and ethologists. Retzius (1840) provided the first classifications of human cranial morphology, dolichocephalic and brachycephalic [9]. Dolichocephalic is a long and narrow head, mesaticephalic is a head of medium proportions and brachycephalic is a head of short and wide proportions [10]

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Discussion

Conclusion