生物谷報道 按照特定組合去掉蛙類和蟾蜍的腳趾是生態(tài)學(xué)家識別不同個體的一種常用方法,。實驗者認(rèn)為這樣做是無害的。然而,，最近的一項研究卻表明：失去的腳趾越多,，標(biāo)記青蛙被再次找到的可能性越低。
利用一種名為“貝葉斯分析”的復(fù)雜統(tǒng)計技術(shù),，澳大利亞墨爾本皇家植物園的生態(tài)學(xué)家Michael McCarthy和Kirsten Parris檢驗了剪趾法對蛙類或蟾蜍存活狀況的影響,。6位同事把自己的記錄交給他們，包括兩種分別來自于澳大利亞和南美洲的蛙類,，以及一種北美蟾蜍,，共有約3700只剪掉腳趾的個體,。隨后，McCarthy和Parris檢查了為給個體編碼而去掉的腳趾數(shù),，以及該個體是否重新被發(fā)現(xiàn)等情況。
結(jié)果一清二楚：每多剪掉一個腳趾,，個體的重捕機(jī)會就會減少一些,。比起那些僅缺少1個腳趾的個體，缺少8個腳趾的個體被重捕的機(jī)會大約是前者的1／4,。盡管其他解釋——例如這種粗暴的對待讓它們逃離研究區(qū)域——也是可能的,，但研究人員推測，失蹤的個體死于感染,。McCarthy指出,，無論哪種解釋，這些新發(fā)現(xiàn)都表明剪趾對動物造成了傷害,，可能使實驗結(jié)果出現(xiàn)偏差,。他說，這對研究人員和他們的課題來說很不幸,，因為還沒有令人滿意的替代性標(biāo)記方法,。
這項新研究令澳大利亞悉尼大學(xué)研究兩棲類和爬行類的進(jìn)化生態(tài)學(xué)家Richard Shine感到進(jìn)退兩難。他表示,，通常,，生物學(xué)家用剪趾法來研究瀕危物種，現(xiàn)在這種方法本身可能會傷害動物,，“動物倫理委員會……能否痛痛快快允許研究人員剪趾”成了一個問題,。
相關(guān)研究成果發(fā)表在8月份的《應(yīng)用生態(tài)學(xué)雜志》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
