Even the scientific name hints at why this species is so interesting to humans: "esculentus", meaning "edible". The Edible Frog was formerly found in huge numbers in lakes and streams and was considered a delectable treat.
Description
Like both of its parental species, the Edible Frog lacks the dark eye-patch exhibited by the brown frog group of species (Agile Frog, Common Frog, and Moor Frog). Only rarely does a dark area extend from the temporal area to the top of the foreleg; this can lead to misidentification. The best form of identification in the field is in fact the mating call, whereby considerable practice is required. The call of the quite noisy Edible Frog can be described as "growling" to "rattling" with rapid delivery of a "re-re-re-re-re-re" pattern. Twenty to thirty "tones" are emitted per second, with each sequence lasting approximately 1.5 seconds. In contrast, the Marsh Frog emits harsh sounds with a much slower pace, while the Pool Frog's are even faster.
Dorsal colouration is varying shades of green-brown. There is almost always a green area, at least around the head or on the sides of the body. The underside is usually whitish or light grey, yet may sometimes be darkly marbled. The vocal sacs of the male Edible Frog are greyish (Marsh Frog's are white and the Pool Frog's are blackish). The best way to identify Green frog group of species is the form of the metatarsal tubercle around the heel area. This however requires capturing the animal, which is forbidden by conservation laws.
Distribution
Range of the Edible Frog is the entire Donau-Auen National Park.
Endangerment and Conservation Status
Green frogs are still frequently sighted in the Danube wetlands, but they are now rarely seen in the surrounding agricultural areas. All amphibians are protected by environmental protection acts.
Behaviour
In the summer, these amphibians are almost always found in the immediate vicinity of water. Here they eat (most) everything they can get a hold of, in particular insects, worms and spiders. Younger animals also like to eat mosquitoes. Edible Frogs hibernate between September and October on land and less frequently under water. They may go considerable distances in their search for suitable hibernation spots. It is thus essential that a variety of landscapes near water exist offering piles of leaves, deadwood, crevices in the earth, fallen trees and other structures.
Special Characteristics
Up until recently, the Edible Frog was considered to be a full species. Evidence was produced at a late stage, however, to show that it is in fact a hybrid form of two parental species, the Marsh Frog (Pelophylax ridibundus), and the Pool Frog (Pelophylax lessonae). However, the Edible Frog is not likely produced by crossing the two parental species. The Edible Frog may mate with its parental species without completely mixing the genetic material. This extremely complex procedure for the production of gametes and initial phases following fertilization has yet to be exhaustively explained. In addition, triploid organisms have developed which have received an extra set of one chromosome set from the parental species. These types may co-exist with their parental species in diverse combinations on a body of water and form a common population. There is often a separation of the individual types, as they each exhibit certain differences in their reproductive behaviour. The overall situation is made even more complex by the fact that a crossing with other types of Green Frogs from surrounding areas may be possible.