One Rainbow Trout Had Eaten Three Juvenile Grass Snakes in a Bavarian Stream

January 16, 2026

Juvenile grass snake in shallow water in Bavaria

Research · Ecology

A rainbow trout (Oncorhynchus mykiss) caught in the Ammer River in Bavaria, Germany had eaten three juvenile grass snakes (Natrix natrix), according to a short communication published on 16 January 2026. The observation is one of the few confirmed Central European records of a salmonid consuming reptiles and is unusual because three snakes were found in a single fish.

The trout was caught near Peißenberg on 14 May 2025 and measured 39 cm in total length. When it was dissected shortly after capture, three dead juvenile grass snakes were found in its stomach. Each snake was estimated to be about 20 cm long.

Reptiles are unusual prey for salmonids

Rainbow trout in this section of the Ammer originate from regular stocking for recreational fishing. The species has a highly flexible diet, but most dietary studies are dominated by aquatic invertebrates, fish and terrestrial insects; amphibians can also become important in some places or seasons. Reptiles have been reported only occasionally.

Three snakes show how flexible the trout’s diet can be

The authors regard the event as very rare and most likely incidental. Even so, finding three juveniles in one trout shows that snake predation need not always be limited to a single encounter when small snakes are locally available.

Juvenile grass snakes can spend time close to the shoreline or swim at the water surface in spring. In those situations they may be conspicuous to visually hunting trout. The record therefore fits the broader picture of rainbow trout as an opportunistic predator able to exploit unusual prey when an opportunity arises.

A rare interaction between a stocked fish and a native reptile

The authors stress that such an unusual prey record does not by itself imply a negative ecological effect on the snake population. Its biological value is more specific: it documents a direct trophic interaction between a regularly stocked fish and a native semi-aquatic reptile, and adds to the sparse evidence that salmonids sometimes consume reptiles.

Sources and image credit

Vogelmann, C., Wendt, P., & Martens, A. (2026). Three juvenile Natrix natrix (Reptilia) as prey of Oncorhynchus mykiss (Actinopterygii, Salmoniformes, Salmonidae) in a Bavarian stream. Acta Ichthyologica et Piscatoria, 56, 23–25. https://doi.org/10.3897/aiep.56.176058Primary open-access short communication published 16 January 2026; CC BY 4.0.

Image: Bertl 85 — juvenile grass snake in a waterhole at the Ehemaliger Standortübungsplatz Landshut mit Isarleite nature reserve, Bavaria, Germany, 15 August 2012. Representative photograph, not one of the snakes found in the trout. Wikimedia Commons; CC BY-SA 3.0. · https://creativecommons.org/licenses/by-sa/3.0/ · Source