Orbital angle in the Australian dingo

Wild and domestic canids differ in relation to their field of vision. Wolves (Canis lupus) have narrow binocular vision that favors the detection of prey over wide distances, whereas domestic dogs (Canis familiaris) have a wider binocular vision as a consequence of decreased predation behavior. Correlated with binocular vision is the orbital angle, which is a morphological ratio based on width and height of specific skull landmarks on the frontal and zygomatic bones. Wolves have acute orbital angles (42 ± 5.3 SD). Little is known about the orbital angle of other wild canids, such as the Australian dingo (Canis dingo), that have markedly different lifestyles and prey compared to the grey wolf. This study compares the orbital angles of dingoes (n=45, sourced from South Australian Museum) and greyhounds (n=52, sourced from University of Adelaide). Skulls were photographed in the dorsoventral position from the rostral view. ImageJ software was used to calculate orbital angle measurements. Orbital angles in dingoes and the greyhound were found to be symmetrical (p= 0.2); thus only the right-side orbital angles were analyzed. The mean orbital angle of dingoes and greyhounds (49 and 53 respectively) were statistically different, with overlapping ranges of 46.3 - 54.6 (t(95)=7.9, p<0.01). These findings are comparable to binocular field ranges with wild canids like dingoes and the wolf having narrower binocular fields of vision (70 ) than greyhounds (80 ). The difference in orbital angle and binocular field is likely reflective of direct or indirect consequence of domestication and paedomorphism.