Using osteological measurements to estimate body length in Amazonian manatees

ABSTRACT Body length is an important parameter in morphological, ecological and behavioral studies of a species and contributes to the understanding of the body condition of individuals. This parameter is essential for conservation and management strategies by informing studies evaluating growth rates, physical maturity and classification of individuals into age groups, promoting better accuracy for the biological parameters of the species. The aim of this study was to identify predictors of body length for Amazonian manatees (Trichechus inunguis) using metric characters of osteological materials. Eleven linear measurements of skull, jaw, scapulae and humeri were collected from 41 Amazonian manatee skeletons of different age classes (calf, juvenile and adult). Data were analyzed by simple linear regression. The condylobasal length was the best predictor of body length for the species (R = 0.943), however, all bones evaluated showed at least one measurement with the capacity to predict body size (R2 > 0.9). Results of this study are useful for inferring body length of Amazonian manatees using bones deposited in museums and biological collections, expanding the informative potential of these materials.摘要：体长是物种形态学、生态学与行为学研究的核心参数，有助于深入解析个体的身体状况。该参数可为物种保护与管理策略提供关键支撑：通过为生长速率评估、生理成熟度判定及个体年龄组划分等研究提供科学依据，能够提升该物种生物学参数估算的准确性。本研究旨在利用骨骼材料的测量特征，确定亚马逊海牛（Amazonian manatee, Trichechus inunguis）体长的预测因子。研究人员从41具分属不同年龄组（幼崽、亚成体及成体）的亚马逊海牛骨骼标本中，采集了头骨、下颌骨、肩胛骨（scapulae）、肱骨（humeri）共11项线性测量数据，并采用简单线性回归（simple linear regression）方法开展数据分析。结果显示，颅基底长（condylobasal length）是该物种体长的最优预测因子（相关系数R=0.943）；不过所有被测骨骼均至少存在一项可用于预测体尺的测量指标（决定系数R²>0.9）。本研究结果可为利用馆藏于博物馆及生物标本馆的骨骼标本推断亚马逊海牛的体长提供参考，进一步拓展此类标本的科研应用潜力。