Moor Frog (Rana arvalis) lives in temperate wetlands across Northern Europe, Northern Asia. It feeds on insects and invertebrates. Its conservation status is Least Concern.
Hear the Moor Frog
A real field recording of the Moor Frog, made in the wild.
Moor frogs can survive being frozen solid and later thaw without dying. Their bodies produce specialised cryoprotectants that act as antifreeze, lowering the temperature at which internal ice forms and preventing lethal damage, allowing them to endure winter freezes in northern parts of their vast Eurasian range and emerge alive when conditions improve.
During the peak of breeding, male moor frogs turn a vivid blue for only a few days, a change most obvious to human eyes but actually strongest in the ultraviolet spectrum between 350 and 450 nm, which humans cannot see. Males that have already mated tend to appear bluer and have been recorded with higher body temperatures, suggesting the colour may convey information about recent reproductive success and overall fitness.
Moor frogs mainly reproduce via multimale amplexus, where several males clasp a single female at once, creating a polyandrous mating system. Within the female's reproductive tract, the sperm from these competing males race to fertilise the eggs, intensifying sperm competition and influencing which male's genes are passed on to the next generation.
The species inhabits elevations up to 2 kilometres above sea level in the Altai Mountains. Further east in its range it reaches this height, while in western Europe it is found as high as 900 metres. In these high-altitude sites the frogs are usually close to still or very slow-moving water that is surrounded by riparian vegetation. Such water bodies are often strongly acidic, with pH at or below six.
When exposed to acidic water, moor frogs can evolve tolerance within 16-40 generations. This rapid adaptation lessens the harmful impact of low-pH breeding sites on embryos and larvae. Populations originating from acidic ponds show higher survival, greater larval growth but slower development, and larger size at metamorphosis. The degree of embryonic tolerance and metamorphic size is most strongly linked to the pH of the breeding pond.
Sources
Every fact above was checked against these pages, and kept only where one of them states it.
As the first whispers of spring awaken the frozen landscape, the moor frog emerges, its mottled brown skin blending seamlessly with the damp, moss-covered terrain it calls home. With a quiet deliberation, it moves through the world, its webbed feet propelling it silently across the mist-shrouded moors, as if drawn by an unseen thread to the hidden pools and secret waterways that will soon become its breeding grounds. In this fleeting, emerald world, the moor frog is a master of understated elegance, its unassuming nature belied by a remarkable resilience that has allowed it to thrive in even the most unforgiving of environments.
Advertisement
Hear the Moor Frog, and 4,400+ more
Real recorded sounds, 11 nature games and a free Daily 5, 1v1 quiz duels, conservation wins and a safe Kids mode. Free on Feravox.
