Pool frog Pelophylax lessonae

Description

The pool frog is smaller and shorter than the lake frog and the edible frog. Adult individuals reach a length of 4-7 cm, rarely 8 cm (SVL). The hind limbs are proportionally shorter than those of the lake and the edible frogs - the heels of the hind limbs, when outstretched straight forward, only extend up to the eyes while in the edible frog they usually extend as far as to the snout and in the lake frog past the tip of the snout. On the back of the thighs of the pool frog, there is an intense yellow and black pattern and the vocal sacs on male frogs are white. In Continental Europe, pool frogs are typically bright green or grass green in colour, and at the time of spawning, males often show up lemon-yellow colouring in the head and front lobes. Usually, there is no patterning on the abdominal side. The metatarsal tubercle of a pool frog is larger and more protruding than that of a lake and an edible frog, almost symmetrical and semicircular. A good rule of thumb is that the tubercle of a pool frog is more than half of the length of the innermost toe of the hind foot, but of a lake frog and an edible frog usually less than half of the length.

The croaking of the pool frog is more subdued than of the lake frogs and the edible frogs. Its sound is smoother and more purring than that of lake frog and edible frog, and the cackle characteristic of the lake frog is missing. The pool frogs in Sweden and Norway belong to the so-called northern population, which is genetically and morphologically different from the Central European stock. Individuals of the northern type are mostly brown in color, with a yellow, white or green streak running along the back. Sometimes there is also a bit of green on the head and sides. Often, there is dark pattern on the pale abdomen side. In the northern population, females are darker and their colour is more contrasting than of males. Sometimes, the dorsal side of females is nearly black. The extinct original pool frog population in England was also included in this northern stock.

Also, pool frogs found in Finland are brown in color, like the pool frogs in Sweden and Norway. By appearance, it can be concluded that also the pool frogs in Finland belong to the northern stock, but it has not been genetically verified yet. In Finnish conditions, usually it is relatively easy to distinguish a pool frog from an edible frog on basis of external characters. However, it is possible to mix up the pool frog with the common frog (Rana temporaria) and, especially, with the moor frog (Rana arvalis). In this case, a clear charasteristic of the pool frog is the white, yellowish or green line running along its back.

Source: FinBIF species descriptions
Description text authors:

Translation: Luke 2023.

CC BY 4.0

The map represents observations of this taxon, but it may not be used as a distribution map.

squares
Observations
  • Total squares
Checklist
FinBIF master checklist
Scientific name
Pelophylax lessonae
Author
(Camerano, 1882)
Vernacular names
  • pikkuvihersammakko (Finnish)
  • gölgroda (Swedish)
  • Pool frog (English)
Identifier
http://tun.fi/MX.201018
Taxon rank
species
Occurrence in Finland
Published from Finland
Status in Finland
  • Anthropogenic
  • Regular vagrant
This species is invasive
EstablishmentUnknown
Regulatory Status
  • Government Decree on Invasive Alien Species of National Concern (1725/2015) ?
  • Government Decree on Managing the Risk Caused by Alien Species (704/2019, VN 912/2023) ?
Finnish Regional Red List Category
  • 2019 NA – Not Applicable
Expert
  • Markus Piha
DNA barcode sequences
Informal groups
  • Reptiles and amphibians
  • Amphibians