This sounds like it could hurt a duck population really quick!
FOOD HABITS
Muskrats are vegetarians, but if unable to secure plant foods, they will feed on carcasses of fish, frogs, and other muskrats. Nearly all plants growing in and near their water areas are eaten, but cattails are the backbone of their diet.
Food is not stored for winter use, so they must dig roots and tubers from beneath the ice, returning to their house and burrow to feed. If food sources are too far from the house, a feeding shelter called a "push-up" is built on the ice. A similar feeding platform - a raft consisting of discarded plant food - is constructed for summer use.
A dense winter population feeding on roots and bulbs in a marsh or small lake may consume nearly all the roots. Upper parts decay the following spring, turning the water and soil sour so that few plants will grow in that area. This is called an eat-out, and if little water moves through it, this portion of the marsh may be unproductive for several years.