Diet and trophic niche overlap of two ranid species in northern Italy

Abstract

Diet of two syntopic populations of Rana dalmatina and R. synklepton esculenta were studied in order to collect data about competition and niche overlap in relation to habitats frequented. Field observations confirm previous ecological researches and show that the former species has a short aquatic phase during the mating period; it lives in woods after breeding relatively far from water. The edible frog, on the contrary, remains near damp areas during the whole activity period. Trophic niche breadth proved greater in R. dalmatina than in R. synklepton esculenta. Niche overlap between species was low, because of the different kind of habitats frequented, while that between sexes was low in R. dalmatina, because males and females show different activity patterns during the year. On the contrary, overlap was complete in R. synklepton esculenta. No correlation was found between the size of frogs and preys. In conclusion, frogs are opportunistic predators and our results suggest that maintaining a highly diversified habitat is useful for avoiding competition between species.

Keywords:

• Amphibians ecology
• Diet
• Niche overlap ‐Niche breadth
• Prey biomass
• Competition.