I had a report recently from a mason bee enthusiast telling me that his mason bee colony had been attacked by rats and most of the cocoons had been taken. These images show what happened. One thing I note in the pictures is that the house wqas on a fence with a platform in front of the bank of tubes. It is best to have nothing that birds or rodents can stand on, and that might have prevented this type of predation. If one is concerned at this time of year, it would be a good idea to gently fasten a fine mesh wire screen to the opening of the box, or since the activity of the bees is probably finished, moe the house to a cooler safe location — gently because you want to be sure that the bee eggs have been secured into the food matrix.