How does water come from frogs

info fauna
Coordination office for amphibian and reptile protection in Switzerland (karch)

The water frogs belong to the most conspicuous and best known amphibians. They are responsible for the loud frog concerts that can be heard at ponds and ponds in spring and summer. During the day they often sunbathe at the edge of the water, from where they can escape with a big jump into the water if they are disturbed. Thanks to the well-developed webbed feet, they are good swimmers.

The European water frogs form a complex of several closely related species and hybrid forms, of which only two are native to Switzerland: the little water frog, Pelophylax lessonae , and the pond frog, Pelophylax esculentus. The little water frog is an independent species, but the pond frog is a hybrid or bastard between the little water frog and the sea frog, Pelophylax ridibundus.

The sea frog did not originally exist in Switzerland, but was introduced in many places in the 20th century. The little water frog and the pond frog almost always appear together in a body of water, but it is not easy to distinguish them. The pond frog is the larger of the two forms, with the males reaching a body length of approx. 55 - 75 (max. 100) mm, the females even 65 - 85 (max. 120) mm. The little water frog remains significantly smaller at 45 - 55 (max. 65) mm for males and 50 - 65 (max. 75) mm for females.

The basic color of both forms is mostly grass green, more rarely yellow or blue-green, sometimes also brownish. The back and flanks are darkly spotted, on the thighs the spots converge to form bands. Often a light green stripe runs across the middle of the back. The small water frog is characterized by strong yellow spots in the groin area, which are usually missing in the pond frog.

The introduced sea frog is larger than both native water frogs, and it is usually darker and less contrasting in color. The most reliable distinguishing feature has turned out to be the inner heel hump, which differs in shape and size between the three forms. Good identification books contain illustrations of this feature, which are very helpful in distinguishing between them.