A method of obtaining dietary data for slow worms (Anguis fragilis) by means of non-harmful cooling and results from a Danish population

Diet composition of slow worms (Anguis fragilis) from a Danish population was recorded from May to September 2006. Slow worms were maintained in cool conditions (at 8C) for a maximum of 126h, which made approximately half of the animals regurgitate. The method worked equally well on juveniles and adults. The regurgitations revealed that the slow worms preyed on small snails, slugs, pill millipedes (Glomeris marginata), earthworms and Lepidoptera larvae. There were seasonal changes in taxon composition of the diet but no ontogenetic or sex-related differences. The food quality of selected prey types was tested on juveniles in a laboratory experiment. Mealworms gave a significantly lower gain in mass and snout-vent length than slugs, earthworms and a mix of all three prey types. A supplementary experiment revealed that slow worms from the present population completely rejected mealworms as prey. Earthworms seemed to be nutritionally inferior to molluscs.