Among nature's great engineers, beavers and their inventions have long been championed by environmentalists for their ability to protect against flooding, improve water quality and boost wildlife.

Officials had hoped to build a barrier to shield the Klabava River and its population of critically endangered crayfish from sediment and acidic water spilling over from two nearby ponds.

As a bonus it would turn a part of this protected area south of the capital Prague into a nature-rich wetland.

First drafted in 2018, the project had a building permit but was delayed by negotiations over the land, long used by the military as training grounds.

Yet before the excavators got the green light to begin digging, the herbivorous rodents set to work building a dam of their own.