Exclusion is an important rodent control technique. It will get rid of the rats by making it difficult for them to enter the home or structure. Rats are easier to exclude than mice because rats a typically larger. Mice can enter an opening as small as 3/8″ wide. All openings greater that 1/4″ should be sealed to exclude mice. For rats, all openings greater that 1/2″ should be sealed. Rats (especially Roof rats) are wary of new objects, new foods or changed in environment. They are constantly exploring surroundings and notice changes and are suspious by nature.. This is why traps and bait stations may be avoided for a day or two. They approach new food or object with caution. Within a rat colony, they may be a few rats that are extra cautious and manage to avoid traps or eating rodent baits.