FEEDING-HABITS OF TRITURUS-VULGARIS, TELENOMUS-CRISTATUS AND T-ALPESTRIS (AMPHIBIA, URODELA) IN THE NORTHERN APENNINES (ITALY)

Although the aquatic cycle of some newts spans the entire year with various life stages, newt diet had only been studied during single phases of the cycle. We analyzed the diet of the warty newt, alpine newt and smooth newt, living syntopically in the same pond, during all the life stages (larvae, juveniles, neotenics, adults) and throughout one entire annual cycle. Food samples were obtained by stomach-flushing 876 newts. The newts were found to exploit a large variety of prey, mainly aquatic insects (imagoes and larvae), and other aquatic invertebrates, together with small numbers of terrestrial Arthropoda that had fallen into the pond. The dietary similarity among species and life stages was high. Although newts were able to exploit most of the range of available prey sizes, on average they selected prey size in relation to their own weight. The frequency of capture of some prey differed significantly between day and night. The six most frequent prey, equivalent to 83% of prey items, were captured with marked seasonal variations. Gastropoda, Collembola, Homoptera and Diptera were captured in relation to their cycles of availability in the pond, while the other variable prey were continuously available, and were probably exploited only when the fluctuating prey were absent. The patterns of dietary similarity among species and of seasonal and diel plasticity, indicate that newts are opportunistic and do not select specific prey taxa. Prey are selected on the basis of size, although all newts may catch a wide range of prey, with some limitations for large items. In newts, as in the other Urodela, food size is more important than type in the partitioning of feeding resources.