WHEN THE HUNTER BECOMES THE HUNTED

There is a wide variety of frog predators, such as snakes, lizards, birds, and various small animals like hedgehogs. Even under water frogs can’t be safe from hungry sharp toothed fish, swimming mammals like water shrews, and even diving birds or other hungry frogs.

An example of these predators is the grass snake (Natrix natrix), a species wideley diffused in all Europe and middle-east countries, that usually reaches a lenght of 150cm. Their preferred prey is the common toad, but in scarsity of them, other frogs, especially brown frogs, form the food base. Small mammals, fish and birds as well as lizards and invertebrates are also often eaten. As the size of the vipers increases, so does the size of their prey: young snakes eat mainly newts, young frogs and smaller tadpoles, large female grass snakes feed mainly on the large-bodied female common toads. Larger frogs are often grabbed by the snakes first by one hind leg, then the other, and gradually gobbled down. The front legs are folded forward as easily as possible - if this is unsuccessful, they too are devoured piecemeal towards the head. The prey is detected visually by its movements and especially by its scent, which is transmitted to the Jacobson’s organ when it is tongued.

Another danger for frogs comes from the marsh harrier (Circus aeruginous), a bird of prey from temperate and subtropical western Eurasia and adjacent Africa. The name Circus is derived from the Ancient Greek kirkos (circle), referring to its circling flight, while, aeruginosus is Latin for “rusty”. The marsh harrier is 43 to 54 cm in length and has a wingspan of 115 to 130 cm. The strategy of the marsh harrier is to take its prey by surprise in a low “rocking” search flight with wings held in a v-shape. It usually seizes prey close to the ground, rarely on the water or in the air. The prey consists of mostly young songbirds and waterfowl such as ducks, pond and water rails. However, if available, the main part of the diet may also consist of fish, frogs, lizards and large insects. Although birds are part of its food spectrum, plucks of the marsh harrier are rarely found. It processes its prey where it has struck it. Unlike a number of other birds of prey, it has no fixed plucking sites.