Marsh FrogPelophylax ridibundusWhere and when to see them

The Marsh Frog is a large, strongly aquatic frog belonging to the European water frog group. It is native to much of central and eastern Europe and parts of western Asia, including the Danube basin. In France, including the wider Saône region, introduced populations occur alongside other closely related water frogs. Its loud breeding calls are often more noticeable than the animal itself, especially around warm, sheltered wetlands.

Size

Adults usually measure 6–15 cm from snout to vent, with females generally larger than males.

Weight

Varies considerably with size and sex; large females can exceed 100 g.

Lifespan

Can live for around 10 years in the wild.

Status

Least Concern (IUCN).

Marsh Frogs spend much of their time in or immediately beside water. They bask on banks, floating vegetation and other sunny resting places, diving quickly when disturbed. They can be active by day and at night, depending on temperature and local conditions. During the breeding season, males gather in calling groups and use paired vocal sacs to amplify their calls. Males compete for calling positions and access to females. Females lay eggs in clusters in the water, and the tadpoles develop there before metamorphosing into froglets. In cold weather, Marsh Frogs become inactive and usually overwinter underwater.

• The scientific name ridibundus means laughing, referring to its distinctive calls.
• Males have two vocal sacs rather than a single throat sac.
• Marsh Frogs are among the largest frogs native to Europe.
• They can hybridise with Pool Frogs, forming part of the edible frog complex.

Wildlife opportunities depend on the river reach, water levels and species. River-specific viewing months have not been confirmed; general species seasons are not a local sighting forecast.

This species favours permanent water bodies with sunny margins and plentiful aquatic vegetation. Typical habitats include ponds, lakes, marshes, canals and slow-flowing stretches of rivers. Along the Danube, sheltered side channels, backwaters and floodplain wetlands can provide suitable conditions. In the Saône region, ponds, quiet channels and vegetated river margins may support populations. Exposed banks and fast-flowing main channels are generally less suitable than sheltered shallows.

Adult Marsh Frogs are opportunistic predators that take a wide variety of invertebrates, particularly insects. They also eat spiders, worms and other small animals encountered around the water's edge. Larger individuals occasionally consume small fish, amphibians and other vertebrate prey, including smaller frogs. Tadpoles feed largely on algae, detritus and associated microorganisms, with their diet changing as they develop.

Common name

Marsh Frog

Scientific name

Pelophylax ridibundus

Animal group

Amphibians

Size

Adults usually measure 6–15 cm from snout to vent, with females generally larger than males.

Weight

Varies considerably with size and sex; large females can exceed 100 g.

Lifespan

Can live for around 10 years in the wild.

Status

Least Concern (IUCN).

Identification

Marsh Frogs are robust water frogs with relatively long hind legs and eyes set high on the head. Their upperparts range from green to brown or greyish, usually with dark spots and sometimes a pale stripe down the centre of the back. Calling males inflate two greyish vocal sacs, one on each side of the mouth. Colour and size alone are not reliable for separating them from related water frogs and hybrids, so confident identification may require calls, expert examination or genetic evidence.