Young are born in a grass lined nest. When born, the muskrat has short dark fur, closed eyes, and weighs around 22 grams. They are able to swim at 10 days and by 21 days can eat green vegetation. Behavior Muskrats are arranged in large family groups and live in definite territories. If the conditions are overcrowded, the females will kick their offspring out of the group.
Muskrats continue to live in large grous even when fighting and cannibalism occur in high rates.
Muskrats are active at all times of the day but most active from mid-afternoon until just after dusk. Muskrats are good swimmers and can stay underwater for 12 - 17 minutes. Muskrats, however, move relatively slowly on land. Muskrats communicate by musk, which also is used as a warning for intruders. They are capable of vocalizing by squeaks and squeals.