Identifying effects of toe clipping on anuran return rates: the importance of statistical power

Toe clipping is a common method of marking anurans for population studies. We re-analysed data from four published studies investigating the relationship between return rate and number of toes clipped for three anuran species: Bufo fowleri, Crinia signifera and Hyla labialis. Although these studies claimed contradictory results, a re-analysis of the data with proper attention to statistical power demonstrated a statistically significant decline of 6-18% in the probability of return for each toe removed after the first, in three of the four studies examined. The probability that the fourth study would detect a statistically significant effect of toe clipping was low unless the size of the effect was overwhelming. These results provide consistent evidence that toe clipping decreases the return rate of marked anurans, and demonstrates the importance of considering statistical power during data analysis. Use of toe clipping for mark-recapture studies may produce estimates of population parameters that are biased by the same magnitude as the return rates, unless researchers control for the effect of this marking method.