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Cranial Shape Variation in Adult Kyrgyz Horses: Associations with Size and Sex.
Abstract: Cranial diversity within indigenous horse populations remains incompletely characterized. Cranial shape variation and its associations with skull size and sex were investigated in 37 adult Kyrgyz horses aged 4-5 years (18 females and 19 males). Three-dimensional configurations of 25 cranial landmarks were evaluated using Procrustes alignment, principal component analysis, and permutation-based multivariate models. Skull size was quantified using centroid size calculated from the landmark configurations. The first two principal components represented 29.41% of shape variance, with changes distributed across multiple cranial regions and substantial overlap between sexes. A 5.42% greater mean centroid size was observed in males ( < 0.001). In separate models, 5.17% and 4.92% of shape variance were explained by sex and allometry, respectively (both 0.05). Small, localized differences were observed between adjusted mean configurations. Cranial variation was therefore characterized by changes across several anatomical regions, a modest association with size, and limited evidence for additional sexual shape differentiation after size adjustment.
Publication Date: 2026-10-11 PubMed ID: 42939119PubMed Central: PMC13700652DOI: 10.3390/ani16203188Google Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
Summary
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Cranial shape variations in adult Kyrgyz horses were studied to understand how skull size and sex contribute to differences. The research used 3D analysis of skull landmarks to find associations between shape, size, and sex.
Objective and Population Studied
- Analyzed cranial shape variation in indigenous Kyrgyz horses.
- Sample: 37 adult horses aged 4-5 years; 18 females and 19 males.
Methods Used
- Collected three-dimensional data on 25 cranial landmarks from each horse’s skull.
- Applied Procrustes alignment to normalize the skull shapes for comparison.
- Performed principal component analysis (PCA) to identify main axes of shape variation.
- Used permutation-based multivariate models to test associations between shape, size, and sex.
- Calculated centroid size as a measurement of overall skull size based on landmark configurations.
Findings on Cranial Shape Variation
- The first two principal components accounted for 29.41% of total cranial shape variation.
- Shape changes were distributed across multiple cranial regions rather than localized to a single area.
- There was substantial overlap between male and female shape variation, indicating no strong sex-based shape difference.
Associations with Skull Size and Sex
- Males had a significantly larger mean centroid size, about 5.42% larger than females (p < 0.001).
- Sex explained 5.17% of the variance in cranial shape, showing a modest shape difference attributable to sex.
- Allometry (shape changes associated with size) explained 4.92% of shape variance, indicating modest effects of size on shape.
- When adjusting shape differences for size, only small localized differences remained between sexes.
Conclusions
- Cranial shape variation in Kyrgyz horses involves complex changes across various skull regions, not limited to one area.
- Skull size contributes modestly to shape variation, with males having larger skulls but only slight shape differences after size adjustment.
- Sex has a limited influence on cranial shape beyond its association with size.
- This study enhances the understanding of morphological diversity in indigenous horse populations, showing that size rather than sex drives most cranial shape differences.
Cite This Article
APA
Arı HH, Pasicka E, Korkmazcan A, Akta A, Gündemir O.
(2026).
Cranial Shape Variation in Adult Kyrgyz Horses: Associations with Size and Sex.
Animals (Basel), 16(20), 3188.
https://doi.org/10.3390/ani16203188 Publication
Researcher Affiliations
- Faculty of Veterinary Medicine, Kyrgyz-Turkish Manas University, Bishkek 720044, Kyrgyzstan.
- Department of Biostructure and Animal Physiology, Faculty of Veterinary Medicine, Wrocław University of Environmental and Life Sciences, Kożuchowska 1/3, 51-631 Wroclaw, Poland.
- Institute of Graduate Studies, Istanbul University-Cerrahpasa, Istanbul 34320, Türkiye.
- Institute of Graduate Studies, Istanbul University-Cerrahpasa, Istanbul 34320, Türkiye.
- Department of Anatomy, Faculty of Veterinary Medicine, Istanbul University-Cerrahpasa, Istanbul 34320, Türkiye.
Grant Funding
- KTMU-BAP-2026.FB.01 / Kyrgyz-Turkish Manas University Scientific Research Projects
- SGALP-2025-38519 / Scientific Research Projects Coordination Unit of Istanbul University-Cerrahpasa Rectorate
Conflict of Interest Statement
The authors declare no conflicts of interest.
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