生物谷报道 按照特定组合去掉蛙类和蟾蜍的脚趾是生态学家识别不同个体的一种常用方法。实验者认为这样做是无害的。然而，最近的一项研究却表明：失去的脚趾越多，标记青蛙被再次找到的可能性越低。
利用一种名为“贝叶斯分析”的复杂统计技术，澳大利亚墨尔本皇家植物园的生态学家Michael McCarthy和Kirsten Parris检验了剪趾法对蛙类或蟾蜍存活状况的影响。6位同事把自己的记录交给他们，包括两种分别来自于澳大利亚和南美洲的蛙类，以及一种北美蟾蜍，共有约3700只剪掉脚趾的个体。随后，McCarthy和Parris检查了为给个体编码而去掉的脚趾数，以及该个体是否重新被发现等情况。
结果一清二楚：每多剪掉一个脚趾，个体的重捕机会就会减少一些。比起那些仅缺少1个脚趾的个体，缺少8个脚趾的个体被重捕的机会大约是前者的1／4。尽管其他解释——例如这种粗暴的对待让它们逃离研究区域——也是可能的，但研究人员推测，失踪的个体死于感染。McCarthy指出，无论哪种解释，这些新发现都表明剪趾对动物造成了伤害，可能使实验结果出现偏差。他说，这对研究人员和他们的课题来说很不幸，因为还没有令人满意的替代性标记方法。
这项新研究令澳大利亚悉尼大学研究两栖类和爬行类的进化生态学家Richard Shine感到进退两难。他表示，通常，生物学家用剪趾法来研究濒危物种，现在这种方法本身可能会伤害动物，“动物伦理委员会……能否痛痛快快允许研究人员剪趾”成了一个问题。
相关研究成果发表在8月份的《应用生态学杂志》上。
ORIGINAL TEXT：
Don't Touch My Toes
Removing a unique combination of toes in frogs and toads is a common way for ecologists to ID individuals. Experimenters have assumed that this is harmless. But now, a study in the August issue of the Journal of Applied Ecology shows otherwise: The more toes gone, the less likely a marked frog is to ever hop into sight again.
Ecologists Michael McCarthy and Kirsten Parris of the Royal Botanic Gardens Melbourne in Australia used a sophisticated statistical technique called Bayesian analysis to check for effects of toe clipping on frog and toad survival. Six colleagues gave them their records for a total of almost 3700 toe-clipped individuals of two species of frog, one from Australia and one from South America, and a North American toad species. McCarthy and Parris then looked at the number of toes removed to create each animal's digital code, and whether or not it was ever seen again.
The results were clear-cut: With each additional toe missing, an animal's chances of recapture dropped. An individual missing eight toes was almost one-fourth as likely to be retrieved as one with only one toe gone. The researchers suspect that the missing animals die from infection, although other explanations are possible; for instance, the maltreatment could make them flee the study area. Either way, McCarthy says, the new findings show that toe clipping hurts the animals and can potentially lead to biased results. Unfortunately for researchers and their subjects, he says, there are no satisfactory alternative marking techniques.
Evolutionary biologist Richard Shine, who works on amphibians and reptiles at the University of Sydney, Australia, is put in a quandary by the new study. He points out that toe clipping is used by conservation ecologists to study populations of endangered amphibians. Now that the technique itself may be harming the animals, he says, it is doubtful that an "animal ethics committee ... would allow a researcher to chop toes off willy-nilly."
--MENNO SCHILTHUIZEN
Related sites
Froglog Newsletter subscribers debate toe clipping amphibians here ...
... and here
U.S. National Wildlife Health Center's page on toe clipping
National Academies Press page on alternative marking systems for amphibians
