Amphibians
The famously noisy Natterjack toad (Bufo calamita) makes a ratchet-like sound usually heard at night and often acts as a pioneer species, primarily on floodplains but increasingly today on brownfield sites such as the far larger waters found in the Ruhr area. Its preferred spawning grounds include shallow waters such as flooded grassland, shallow bog pools or wheel ruts filled with water. Natterjack toads are often concentrated in small areas as suitable spawning grounds have become scarce on cultivated land nowadays. Its spawning grounds are often completely free of vegetation and only carry water for a few weeks, making the spawn chains easily identifiable, but the short incubation period of the tadpoles enables the species to reproduce successfully.
Equally conspicuous is the chorus of the pool frog (Rana lessonae), which can also be heard on warm days during daylight. In contrast to the Natterjack toad, the pool frog tends to frequent larger, sunnier, well vegetated waters, where it sits in the shore vegetation and leaps into the water to feed, where it then remains secreted. It carefully surveys its surroundings before climbing back out and resuming its concert once more. In contrast to the vocal sac on the chin of the Natterjack toad, the pool frog’s two vocal sacs are located on each side of its head. Typically for indigenous frogs, the pool frog lays its eggs in clumps.
If frogs and toads are often easy to identify by their calls during mating season, the same cannot be said of the newts, which are significantly less conspicuous and can only be found by chance or after a concerted search. On the Rhine bend at Orsoy, the great crested newt (Triturus cristatus) has been discovered by chance in two small ponds. The great crested newt is the largest of the indigenous newts. With its large jagged crest, the males appear extremely imposing during the mating season, when they primarily appear in well vegetated waters. Females stick individual eggs to aquatic plants – an arduous task with around 200 eggs to distribute.
