Diet composition and prey selection in the lizard Lacerta monticola
We studied diet composition and prey selection in the lizard Lacerta monticola throughout its activity season. The most important prey groups in terms of numbers were Coleoptera, Diptera, Formicidae, and Araneae. Comparison of diet composition in the adult lizards with estimates of prey availability indicated that lizards exhibited precisely defined patterns of prey selection. Electivities were negative for prey < 3 mm in length and generally positive for larger prey, despite the higher relative abundance of the former group in the environment. Electivity scores for individual prey taxa were positively correlated with their length, and lizards preferentially consumed larger individuals belonging to the taxa containing smaller animals. Relative availability of the four major prey taxa fluctuated considerably throughout the year. In spite of these changes, monthly rates of consumption of Araneae and Diptera remained almost constant. Variations in monthly electivity scores were negatively correlated with relative availability of three (Coleoptera, Diptera, and Araneae) of the four major prey taxa. These results fit the predictions of prey-selection models based on nutrient constraints.