They are the cock roaches of rodentia. While they may be beneficial In their natural environs, such as high meadows, they are about as welcome in an alfalfa field as roaches are in your kitchen.
In their native areas, they exist in normal populations according to the carrying capacity of the land. When they migrate down into the fertile valleys and farmlands, their populations explode in the presence of the unnaturally dense food supplies created by agriculture. In other words, they INFEST the land, like rats in the sewers of our cities.
Also, just like roaches, they are cannibals. As an instinctive survival mechanism, they eat the carcasses of their dead. This is a trait shared by most infestuous species. It allows their gross population booms to linger after the high-density food supply has been cut off. This one reason why, again like roaches, they never quite seem to go away. They are a very stubborn problem and they deserve my culling skills.
