Preliminary comparative overview of the diet of brown frogs' tadpoles (Rana temporaria, Rana dalmatina, Rana graeca) (Anura: Ranidae) from several localities in the Republic of Serbia

The decline in consumer diversity in freshwater ecosystems is accelerating. Being both prey and predator in these ecosystems and dependent on aquatic habitats due to their complex life histories, amphibians are more vulnerable to pollution and global warming than other vertebrates. The life cycle of anuran amphibians includes a specific larval stage tadpole. During metamorphosis, tadpoles undergo dramatic changes in morphology, behavior, and diet, primarily accompanied by a transition from an aquatic to a terrestrial habitat. Consequently, anurans are important members of food webs and a link between these two habitats. Despite that, there is insufficient data on their nutrition, and understanding the nutritional requirements of a specific species or its developmental stage is essential for population survival. The primary aim of our study was to gather data on the nutritional types, feeding behaviors, and diets of tadpoles from several localities in the Republic of Serbia. Rana temporaria, R. dalmatina, and R. graeca are widely distributed in Serbia, occupying various habitats. We collected 572 tadpoles of these three species across 10 different localities and analyzed their intestinal contents. The results indicated quite diverse diets within and among species. The dominant food items were algae (especially diatoms), followed by detritus and pollen; some inorganic particles, such as microplastics, were also found. Animal prey was rarely found but was present in the intestinal content of some samples. These results significantly enhance understanding of tadpole nutrition and represent the first findings in our country with such a large sample size. Additionally, they provide an important foundation for future research.