Pool Frog

Fascinating facts about the Pool Frog

• When Lorenzo Camerano first described this frog in 1882, he called it a variant of the edible frog, yet the tiny 4-7 cm creature he was studying would later earn its own species name after Italian zoologist Michele Lessona. That taxonomic twist shows how a modest pond dweller can reshape scientific categories.
• The pool frog can survive a winter frozen solid in woodland soil, slipping into hibernation from October until March. Emerging from ice-cold sleep each spring, it proves that amphibians can tolerate temperatures that would kill most vertebrates, hinting at hidden biochemical defenses.
• Males sport a pair of white vocal sacs that inflate only during calls, a stark contrast to the grey sacs of the edible frog and the dark sacs of the marsh frog. This visual cue lets females spot the right partner in noisy early-summer breeding ponds, a subtle but vital communication trick.
• Genetic studies reveal two lineages: a northern clade spanning Sweden, Norway, England, Finland and Estonia, and a southern clade covering the rest of Europe. The northern group is now critically endangered in Norway and was once wiped out in the UK, underscoring how geography can drive divergent fates within a single species.
• Fossils dated to the Late Pliocene (3.6–2.58 million years ago) in Russia place the modern pool frog on the continent long before humans arrived, showing that this modest amphibian has weathered dramatic climate shifts and survived for millions of years.

At a glance

About the Pool Frog

The pool frog (Pelophylax lessonae) is a medium-sized, 4–7 cm amphibian whose smooth, glossy skin can flash from light green to deep emerald, while northern clade individuals often wear a brown coat marked by a pale dorsal stripe. Each foot bears a distinctive, semi-circular metatarsal tubercle, and the male’s vocal sacs inflate to a striking white during the night choruses that echo across shallow, stagnant waters from March to October. When the breeding season arrives in early summer, males call from the water’s edge, their bright yellow throats flashing in the sun, while females lay strings of eggs that hatch into herbivorous tadpoles. These tadpoles grow amid fluctuating temperatures, pH, and predator cues, their development accelerating in warm, alkaline pools and slowing when fish or newts loom nearby. As they metamorphose in late summer, the young frogs swap plant matter for a diet of insects, spiders, and other invertebrates, becoming agile predators both day and night. A surprising trait is their ability to survive frozen nights while hibernating in woodland soil, tolerating ice crystal formation in their tissues without fatal damage, a physiological feat that lets them endure harsh European winters.

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