Age is a basic demographic characteristic vital to studies of mammalian social organization, population dynamics, and behavior. To eliminate potentially confounding ontogenetic variation, morphological comparisons among populations of mammals typically are limited to mature individuals (i.e., those assumed to have ceased most somatic growth). In our morphometric studies of treeshrews (Scandentia), adult individuals are defined by the presence of fully erupted permanent dentition, a common criterion in specimen-based mammalogy. In a number of cases, however, we have had poorly sampled populations of interest in which there were potentially useful specimens that could not be included in samples because they lacked associated skulls. Such specimens typically are associated with external body and weight measurements recorded by the original collectors, and we sought to determine whether these data could be used successfully as a proxy for age or at least to establish maturity. We analyzed four traditional external dimensions (head-and-body length, tail length, hind foot length, and ear length) and weight associated with 103 specimens from two allopatric populations of the Lesser Treeshrew (Tupaia minor Günther, 1876) from Peninsular Malaysia and from Borneo, which we treated as separate samples (populations). Individuals were assigned to one of eight age categories based on dental eruption stage, and measurements were compared among groups. In general, mean sizes of infants and subadults were smaller than those of adults, but the majority of subadults fell within the range of variation of adults. The large overlap among infants, subadults, and adults in external measurements and weight indicates that such measures are poor proxies for age in this species, probably for treeshrews in general, and possibly for other small mammals. This has significant implications for any investigation wherein relative age of individuals in a given population is an important consideration.

中文翻译：

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老化小型哺乳动物外部测量的局限性：小树鼩的警示例子（Scandentia: Tupaiidae: Tupaia minor Günther, 1876）

年龄是对哺乳动物社会组织、种群动态和行为研究至关重要的基本人口特征。为了消除潜在的混杂个体遗传变异，哺乳动物种群之间的形态比较通常仅限于成熟个体（即那些假定已停止大部分体细胞生长的个体）。在我们对树鼩（Scandentia）的形态测量研究中，成年个体的定义是恒牙列完全萌出，这是基于标本的哺乳动物学中的常见标准。然而，在许多情况下，我们对感兴趣的人群进行了不良采样，其中有潜在有用的标本由于缺乏相关的头骨而无法包含在样本中。这些样本通常与原始收集者记录的外部体重和体重测量值相关，我们试图确定这些数据是否可以成功地用作年龄的代表，或者至少可以确定成熟度。我们分析了四个传统的外部尺寸（头和身体的长度、尾巴长度、后脚长度和耳朵长度）和与来自马来西亚半岛的小树鼩（Tupaia minor Günther，1876 年）的两个异域种群的 103 个标本相关的重量和来自婆罗洲，我们将其视为单独的样本（种群）。根据牙齿萌出阶段将个体分配到八个年龄类别之一，并在各组之间比较测量值。一般来说，婴儿和亚成人的平均大小小于成人，但大多数亚成人在成人的变异范围内。婴儿、亚成人、而成年人的外部测量值和体重表明，这些测量值不能代表该物种的年龄，可能是一般的树鼩，也可能是其他小型哺乳动物。这对任何调查都具有重要意义，其中给定人群中个体的相对年龄是一个重要的考虑因素。