History and origin
The Edible frog was first described by Linnaeus in 1758, the scientific name of this hybrid is Pelophylax kl. esculentus. Pelophylax is from Greek and is composed of two words, the first is 'mud' and the second is 'guardian' name given because these frogs never move far away from the water and they often stay immobile on the waters edge as if they were guarding the mud. kl. means klepton and comes from Latin and means 'stolen' 'conceal' because stolen is reference to the chromosomes which are stolen in order to form a different frog when P.ridibundus and P.lessonae interbreed. Esculentus is from Latin and means 'edible'.

Characteristics
This species has intermediate characteristics between Pelophylax lessonae and Pelophylax ridibundus.

Description
=Size=
- Eggs: The eggs measure about 6 to 8 mm in diameter.
- Tadpoles: The tadpoles measure about 5 to 8 mm long when they first hatch, reaching a size of about 50 to 75 mm long before metamorphose.
- Juveniles: The juveniles measure 20 to 30 mm long at least when they exit the water.
- Adults: Males measure up to 90 mm long where as females measure between up to 110 mm long (max. 120 mm long).
=Morphology=
- Eggs: They are laid in separate balls in a single cluster of only about 3000 to 10000 eggs.
- Tadpoles: They do not have a very tall tail, it ends in a rounded manor. Their tail does not come up onto the back.
- Adults: This species has intermediate characteristics between Pelophylax lessonae and Pelophylax ridibundus.
=Patterns & colours=
- Eggs: They are brownish on top and creamy or white on the underside.
- Tadpoles: They are greyish, brownish... their bellies are light creamy.
- Adults: They are usually green with fading irregular brown blotches on the back, they sometimes have a light line running down the middle of the back. Sometimes they may be brownish with only their head and flanks green. Their eyes are golden, their belly is whitish with dark irregular speckles.

Geographical range
This hybrid occurs where P.ridibundus and P.lessonae both occur. Found all over central Europe and generally in the northern parts, found from France to Russia, their southern limits are the lower third of France, northern Italy, northern Croatia, extreme north Bulgaria, their northern limits are northern Germany, and Estonia. Found in a very small area in Sweden on the eastern coast, possibly introduced from Estonia.

Subspecies
None described.

Sexual differences
Males have nuptial pads on their hands which are greyish in colour. Males can be completely green during the breeding season being rarely brown. Males have a pair of external vocal sacs. Females are larger then the males but have slimmer limbs.

Seasonal variations
Males nuptial pads cary in colour being darker during the breeding season. Males become lighter during the breeding season (green/yellow).

Diet
They feed on ground invertebrate, spiders, insects, water insects, moths, flies... fish, newts, sometimes the same species, small birds... Tadpoles eat mainly vegetation but also ants and micro-organisms.

Defensive habits
They will emit a defensive call if caught, otherwise they will jump into the water and hide.

Reproduction
The breeding season can last up to 1 to 2 months (starts in March). Reproduction sites are still water holes, in ponds, lakes or in swamps... Males are seen sitting on an algae rock singing at each other as if they are running a singing competition. When a female comes within eye distance of our singing males, the singing stops and the most impatient males immediately swim over to her, they then take the female to an area in the water with many plants, sticks and in general a lot of vegetation. Then there is another competition between the males, but this time there's a judge, the female. They sing at each other an the one who has the most piercing sound should normally win the females wishes to breed. the winning male will climb onto the females back and hold her behind her front legs, the male wraps his arms around her and sometimes the males thumbs will come into contact. The female will then eject a small clutch of eggs which the male fertilizes on their way out of the female. After a short pause, the same happens again. If they are disturbed they will dive and separate, often swimming in the opposite direction, if the female comes to the surface and can't see the male she was just with, she will take another male and this procedure will reproduce until the female is empty.

Sexual maturity, life span
The average life span for Pelophylax kl. esculentus is about 14 years, they reach their sexual maturity in their second year.

Habits
They are active by day but are, in contrast to other water frogs, they can be seen far from water whilst hunting or migrating, sometimes being observed to up to 500 m from water. They hibernate on land.

Call
A rapid laughing like call 're...re...re...' up to 30 notes a second, each croak lasts for up to a 1.5 seconds, sound (p)www.oreilleverte.com:

Habitat
They live all year round in or around the water, they are the most common in calm parts of rivers, but also found in isolated ponds ad other wet areas. They are very common in slow flowing waterways. They seem to prefer more open areas. They hibernate on land.

Predators
They are hunted by both Natrix species, the owl and many aquatic birds.