Bottom line is once any animal finds a good food source the will be back for more and more until they are all gone. The key goal is never let them have that first bite. Well keep our muskrats at bay with a biological methods growing another favorite food the cattails. The cattails are grown in the buffer area between the wild streams and the ponds. A further biological method is encouraging the otters to stay on our farm.
Otters eat muskrats and nature is balanced.
As a last resort we have an electric fence that is 4 inches above the ground that is also placed on the buffer zone. This electric fence wouldn't kill a mouse but has effectively kept the muskrats, ducks, and beavers from destroying ponds of lilies. One pond that I installed 2.5 feet deep to 5 feet deep with steep sides has been effective at keeping out all the 28 raccoons that moved in one year. The trick I tried was to make sure the edging rock around the pond was steep enough that they could not perch by the waters edge and slap the water to attract the Koi. A Canadian Company has developed a sprinkler head with a motion detector that goes on for 7 seconds.