The best method for managing rats is exclusion. Young rats only need a 1/2 inch opening to access an area. When you inspect, listen for scratching, look for droppings, damage, urine (with a black light), and rub marks. Rodents will forage on a variety of items, so sanitation in addition to exclusion is critical. Rodents can cause damage by chewing wood and other items. They have also been known to start fires by gnawing on electrical wires. They carry many different kinds of diseases including food poisoning. Take precaution when removing nest material, droppings, or remains. Rats are active at night. If they are seen during the day there is likely a large population, scarcity of food, or illness within the population. They defecate wherever they go, so droppings will be spread across their foraging area. Note that Norway rats like to hoard food, so may relocate baits.
Both the roof and Norway rat are leery of new things in their environment, so traps should be in place for several days before being set. After being set, they should remain in place for a week before being moved to a new location. Traps should be set along rodent runways to be most effective. The trigger side of the trap should be on the wall side. Because large rodents may move traps, all traps in a school should be secured, even if traps are set on weekends or during holidays.
