What are examples of suitable den sites (holts) that river otters might utilize?

Answer

Abandoned muskrat or beaver lodges

Otters may use abandoned muskrat or beaver lodges, or natural cavities found under tree roots along the bank, as resting places or holts.

What are examples of suitable den sites (holts) that river otters might utilize?
habitatwildlifeUSAdistributionriver otter