Stomach flushing affects survival/emigration in wild lizards: a study case with rainbow lizards (Agama agama) in Nigeria

Stomach flushing is one of the proposed techniques to study lizard diets. Apparently, it is ranged, together with direct observation and faecal analysis, as a non-harmful method for dietary studies. Some works explored the usefullness of stomach flushing, but we lack information about its effect on lizard's survival probabilities. In this paper we studied the effect of stomach flushing in an urban population of the rainbow lizard (Agama agama) from Calabar (Nigeria). During a period of five months of 2010, 147 lizards were noosed, sexed and individually marked. One group of lizards was stomach flushed only once, whereas the rest of lizards were not flushed. The flushed sample of lizards showed a lower survival than non-flushed lizards of all sex and age classes. In this study, the pictured diet from stomach flushing was very similar to results obtained with a faecal analysis of the same lizard population. Thus, both methods seem to be reliable to study the diet of the rainbow lizard. However, our results indicate that stomach flushing increases the probability of mortality (or at least emigration rates) in all age and sex classes, precluding its extensive use as a method to study lizard's diets.