Installing mouse guards at hive entrances in the fall is the most effective method to prevent mice from entering beehives for winter shelter. Mouse guards are physical barriers with small openings that allow bees to pass freely but exclude mice. They are typically made of metal or plastic mesh and are attached to the hive entrance in late fall before cold weather sets in. Mouse guards should be removed in the spring to allow for unimpeded bee traffic during warmer months. Using mouse guards is a simple, inexpensive, and highly reliable way to prevent mouse infestations in hives during winter.