Forested riverbanks usually do not support muskrat populations. Typically, if levels are too low, food availability will also be low. Stream gradients and velocities were studied in Massachusetts to determine habitat selection by muskrats. Islands and coves can usually provide additional shoreline and more vegetation for food and cover than bodies of water without these features. They rarely use submergent vegetation.
Muskrats eat the basal parts, rhizomes, and leaves of aquatic emergent vegetation.
Muskrats will kill the young of other muskrats when populations are too dense. Low water levels may encourage undesirable species to take over. This usually occurs in pure Olney bulrush stands, and can have a detrimental impact on stands. Regeneration can occur through sprouting from rhizome fragments in the substrate.