MORPHOMETRIC CHARACTERISTICS OF THE CERVICAL, THORACIC, AND LUMBAR VERTEBRAE OF THE BROWN BEAR (URSUS ARCTOS): SEXUAL DIMORPHISM AND SIZE VARIATION

The vertebral column plays a significant structural and functional role in supporting the brown bear's (Ursus arctos) greater body mass, locomotion, and behavioral ecology. However, detailed morphometric ob-servations of the ursid axial skeleton remain limited. This presented study delivers an extensive morphological and morphometric analysis of the cervical, thoracic, and lumbar vertebrae in eight adult brown bears from the Belitsa Dancing Bear Sanctuary, Bulgaria. Five males and three females (24–39 years; 100–300 kg) were examined. Each vertebra was measured for width, length, and height using digital calipers, and statistical anal-yses were performed to evaluate the influence of sex, body weight, and age. The typical vertebral formula (C7–T14–L6) was found in seven individuals, while one female exhibited a T15/L5 configuration with a con-stant thoracolumbar total of 20 vertebrae. Sexual dimorphism was evident, with males possessing significantly larger vertebrae across multiple regions. Markedly distinct differences were identified at T7 and L5. Body weight had a clear effect, with heavier bears demonstrating significantly larger vertebral dimensions. Occa-sional intervertebral ossifications were observed and excluded from quantitative evaluation. This evidence points to strong functional links between vertebral morphology, biomechanical demands, and life-history char-acteristics in brown bears. This analysis delivers baseline anatomical data relevant for evolutionary interpre-tation, comparative morphology within Carnivora, and clinical assessment of spinal pathology in captive and wild bears.