Besides good water quality and abundant food, what is the third essential requirement for a thriving river otter population?

Answer

Suitable den sites, called holts

The text specifies that otters require three main things: good water quality, abundant food, and suitable den sites, which are referred to as holts.

Besides good water quality and abundant food, what is the third essential requirement for a thriving river otter population?
habitatwildlifeUSAdistributionriver otter