The common brown frog

The European brown frog is the most common frog in Denmark.

The common frog (Rana temporaria) is undoubtedly Denmarks’s most well-known amphibian, also known as the European brown frog. It is the most common of the 3 species of brown frogs in Denmark.
The species is found throughout much of Europe and is the most common frog in Denmark.
They are typically brown in colour, but some individuals may have green, yellow or even reddish variation of colours.

Outside the breeding season (March-April), common frogs live a solitary life in damp places near ponds or marshes or in long grass. They are normally active for much of the year, only hibernating in the coldest months.

Sources: Wikipedia, arkive.org, NaturGuide.dk.