Even then, if the new object appears to be food, only a small amount is taken. If the food contains an acute poison causing symptoms after a short while, rats may not touch the bait again. This is commonly called bait shyness. R. rattus behaves similarly but not to the same extent, while M. musculus tends to explore rather than avoid new objects. The New Object Reaction wears off in time, but has to be taken into account when a rodent control programme is planned.
Many rodent pests are characteristically mobile and able to disperse rapidly.
However once individuals have established a territory or home range, they will not move very far, as long as conditions remain favourable. It is often believed that rodent pests invade areas from several kilometres away. This is not exactly true. If large numbers of rodents suddenly appear in an area, it is probably because environmental conditions have become favourable for them, and indigenous populations are able to increase at several places in the area at about the same time. This then gives the impression that the animals are on the move.