The Pelophylax esculentus complex comprises three species that are morphologically indistinguishable: P. lessonae, P. ridibundus, and the hybrid species P. esculentus. Most studies investigating the diet and trophic niche of green frogs have considered the three species as a unique entity, without providing insights into trophic niche differentiation in mixed populations. However, when living in sympatry, the three species are expected to show at least some degree of differentiation in their trophic habits, to lessen competition and promote coexistence. 

In a paper that will soon be published in Acta Herpetologica, the stomach content of 317 adult green frogs from three mixed populations from the South Banat district (Serbia) was analyzed. 1477 prey items, belonging to 17 different taxonomic groups, were identified. The study found that the staple diet, consisting of ground-dwelling and aerial species (namely, Hymenoptera, Coleoptera and Lepidoptera), is the same for the three species. P. lessonae, however, has a narrower trophic niche, dominated by the staple prey groups. P. ridibundus, on the other hand, was found to consume a wider spectrum of prey, including small invertebrates and vertebrates. Thanks to its larger body size, the species consumed larger, but fewer, prey. The hybrid species P. esculentus shows an intermediate trophic niche width.

Diet varied significantly among individuals, reflecting the opportunistic nature of green frogs, and was influenced by locality, suggesting that the local abundance of prey categories is more important than active selection. A preference for adult invertebrates over larvae, however, was observed: a finding that might arise from the “sit and wait” hunting strategy of green frogs, that skews their preference toward more active prey. Finally, cannibalism on newly metamorphosed individuals was observed in the population with the lowest availability of other food sources.  

The finding of a similar but region-specific diet for the three species is particularly important for understanding the dynamics of syntopic and marginal populations. In particular, this ecological information is vitally important for the conservation of P. lessonae, which is regionally threatened in the study area.

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