Geometric Morphometric Analysis of Nasal and Orbital Regions in Mesocephalic Dogs: A Comparative Assessment Based on Climatic Origin

The nasal and orbital regions, in particular, exhibit remarkable variations in both respiratory functions and facial morphology. This study conducted a descriptive investigation of how morphological features in the nasal and orbital regions of mesocephalic dogs vary among individuals across different climates. This study does not aim to test the direct effect of climate on cranial morphology, but rather to evaluate whether a climate-based grouping of dog breeds corresponds to measurable shape variation. The skulls of 31 breeds were used in the study. Dogs were grouped according to whether they lived in harsh (n: 13), moderate (n: 11) and warm (n: 7) climates. The skulls were modeled using three-dimensional images provided by Kubinyi et al. (2024). 20 landmarks were marked in the nasal region (apertura nasalis ossea) and 22 in the left orbital region. The MorphoJ program was used. As a result of the PCA, it was observed that warm-climate dogs were partially separated according to the PC1 distribution graph. According to cross-validation scores, although not statistically significant, the harsh and warm climate dogs were correctly grouped with a high percentage (75%). The study reveals that there are certain morphological shape differences between different climate groups, and these differences show a remarkable trend towards climate-based separation. However, these differences are not at a level that would create a statistically significant separation. This situation points to a potential effect of climate on cranial shape variation, but suggests that the observed variation is largely related to breed-specific morphological characteristics.