Assessing Age Related Cranial Characteristics and Morphometrics of the Egyptian Rousette (Rousettus aegyptiacus) from Central Africa

This study assessed and related quantitative age determination methods based on cranial bone fusion and dental development to linear morphometrics in Rousettus aegyptiacus. Five growth development stages were identified based on cranial suture fusion and degree of second molar tooth eruption. Expressing these growth development stages in measurement size showed a linear growth pattern, with little overlap between smaller (stages 1, 2, and 3) and larger (stages 4 and 5) individuals. Total skull length (TSL), mastoid breadth (MB) and forearm length (FAL) had the highest influence on variation along the first and second principal components, accounting for 93% of variation. Advanced size was confirmed to relate to aging owing to development of cranial suture fusions and dental development. The smallest and largest individuals were significantly (P < 0.05) separated by measurements of TSL, MB and FAL. Meanwhile, some intermediate sized individuals overlapped despite being in different stages of cranial suture development. Species specific reliability in morphological approaches to age determination can be achieved by establishing a baseline reference, which may be directly related to the quantitative cementum growth assessment method.