Nick Upton / Tilt shot of a dam constructed by Eurasian beavers (Castor fiber) on a section of the River Otter, Devon, England, UK, June 2018.

Dave Bevan / Beaver (Castor fiber) swimming across a pond, reintoduced by the Welsh Beaver Project, Carmarthenshire, Wales, UK, June.

Nick Upton / Male Eurasian beaver (Castor fiber) at night, feeding on a branch in a pond, Devon Wildlife Trust's Devon Beaver Project, Devon, UK, April.

Nick Upton / Male Eurasian beaver (Castor fiber) at night, feeding on a branch in a pond, Devon Wildlife Trust's Devon Beaver Project, Devon, UK, April.

Nick Upton / Eurasian beaver (Castor fiber) at night, swimming, Devon Wildlife TrustÕs Devon Beaver Project enclosure, Devon, England, UK, March.

Nick Upton / Eurasian beaver (Castor fiber) feeding on grass amongst Meadow buttercups (Ranunculus acris) near a pond in a large enclosure, Devon, England, UK, June. Captive.

Yva Momatiuk & John Eastcott / American Beaver (Castor canadensis) a semi-aquatic rodent swimming across calm pond behind beaver dam on mountain river, fall foliage reflectd in water, evening, Denali National Park, Alaska

Yva Momatiuk & John Eastcott / American Beaver (Castor canadensis) young animal munching on alder branches in glacial kettle pond, Denali National Park and Preserve, Alaska

Gerry Ellis / Taiga vegetation and pond, Chugach National Forest, Alaska

Michael Quinton / American Beaver (Castor canadensis) slapping water with tail in boreal pond, Alaska

Michael Quinton / American Beaver (Castor canadensis) nibbling on leaf from willow branch in boreal pond, Alaska

George Sanker / Muskrat (Ondatra zibethicus) feeding in beaver pond. Acadia National Park, Maine. September.