Body weight and snout-vent length (SVL) data of 3006 individual Leptodactylus latrans frogs collected over ten years in the Pampa Region of Argentina were analyzed to evaluate the best approach for expressing body condition and to characterize the natural variability of this parameter. Two different methods for expressing body condition were compared: the scaled mass index (SMI) and the residuals methods. Body weight of L. latrans was related to SVL through an allometric relationship described by the power function: Y = 0.00006 X^3.11. The shape of the weight-length relationship was not affected by neither the sex of the animal nor its date or site of capture. A truly size-independent SMI value was more easily obtained when defining the scaling exponent through a non-linear regression of mass on length rather than when performing a standardized major axis regression of lnweight on lnlength. Overall, it was proved optimal to use a single scaling factor equal to 3.11 to compute SMI of all L. Latrans from the Pampa Region, irrespective of their gender and month or site of capture. Altogether, obtained results showed that SMI is a more performant indicator of body condition than residuals because it is less variable and it allows a better detection of effects. SMI and residuals condition factors deviated from each other in the extremities of L. latrans size range because scaling is not considered when calculating residuals. Body condition of females, males and juveniles was significantly lower in December/January compared to October/November and February/March. Moreover, juveniles consistently exhibited a lower body condition compared to both males and females. Based on the natural inter- and intra-annual variability observed for L. latrans SMI values, it should be possible to detect a 10% difference in SMI in an intra-annual study by sampling 14 to 17 frogs per group, whereas a 15% difference in SMI could be detected in an inter-annual study by sampling 23–29 animals per site. These numbers show that alterations of body condition should be straightforwardly identifiable in field studies with L. latrans when using SMI. The determination of SMI body condition factor during amphibian monitoring programs could be of great value, as it would provide information on amphibian health together with population abundance numbers.

分析了阿根廷Pampa地区十年来收集的3006只Laeptodactylus latrans蛙的体重和口鼻长度（SVL）数据，以评估表达身体状况的最佳方法并表征该参数的自然变异性。比较了两种表示身体状况的方法：缩放质量指数（SMI）和残差法。Latrans的体重通过幂函数描述的同种异形关系与SVL相关：Y = 0.00006 X ^3.11。体重长度关系的形状不受动物的性别，捕获日期或地点的影响。通过质量对长度的非线性回归来定义比例指数时，而不是对长度对长度进行标准化的主轴重量回归时，更容易获得与尺寸无关的SMI值。总体而言，事实证明，使用最佳比例因子等于3.11来计算潘帕地区所有L.Latrans的SMI ，无论其性别，捕获的月份或地点如何都是最佳的。总体而言，获得的结果表明，SMI比残差更能代表身体状况，因为它的可变性较小，并且可以更好地检测效果。SMI和残差条件因子在四肢的末端相互偏离L. latrans大小范围，因为在计算残差时不考虑缩放。与十月/十一月和二月/三月相比，十二月/一月的女性，男性和青少年的身体状况明显降低。此外，与男性和女性相比，青少年的身体状况始终较低。基于观察到的L. latrans SMI值的自然年际和年际变异性，应该在年内研究中通过每组采样14至17只青蛙来检测SMI的10％差异，而15％在一项年度研究中，可以通过在每个站点采样23-29只动物来检测SMI的差异。这些数字表明，在L. latrans的田间研究中，应该可以直接识别出身体状况的改变。使用SMI时。在两栖动物监测程序中确定SMI身体状况因素可能具有很大的价值，因为它可以提供有关两栖动物健康状况以及种群数量的信息。