Longitudinal Thoracic Growth and Emerging Sexual Dimorphism in Dromedary Camel Calves

Dromedary camels (Camelus dromedarius) exhibit distinctive anatomical adaptations that support survival in arid environments; however, longitudinal data on early thoracic development are scarce. This study characterised postnatal growth and structural changes of the thoracic cage during the first year of life and evaluated sex-related differences in growth trajectories. A total of 120 clinically healthy, full-term calves (60 males, 60 females) were enrolled within 24 h after birth and examined at birth and at 1, 3, 6, 9 and 12 months of age. Morphometric measurements included body weight, thoracic circumference, thoracic depth and thoracic width. Thoracic shape was assessed using the thoracic index (TW/TD × 100) and the costal curvature ratio (TW/TC). Longitudinal changes were analysed using linear mixed-effects models. All thoracic dimensions increased significantly with age (p < 0.001). Thoracic circumference increased from 72.1 ± 3.4 cm at birth to 140.6 ± 7.8 cm at 12 months. Significant age × sex interactions were observed for body weight and thoracic circumference (p < 0.01), with males showing greater transverse thoracic expansion after 6 months. The thoracic index increased progressively (p < 0.001), indicating proportionally greater growth in width than in depth, whereas the costal curvature ratio remained relatively stable. Strong positive correlations were found between body weight and thoracic measurements (r = 0.92-0.96; p < 0.001). These data provide reference values for early thoracic development and demonstrate the emergence of sexual dimorphism in thoracic morphology during the first postnatal year.