The most common rats found around Fresno County homes and neighborhoods are Norway rats and roof rats. They are similar, but key differences can help determine the best strategies for management. The Norway rat – which, despite its name, is thought to be originally from China – builds burrows along building foundations, beneath trash or in woodpiles. Indoors they tend to remain in basements or the ground floor. Roof rats are great climbers and usually nest in shrubs and trees, while inside they favor attic spaces, walls and false ceilings. The Norway rat is the stockier of the two, with small ears and a blunt nose. The roof rat – likely from South Asia – has a longer tail than body, larger ears and pointed nose.
Removing food, water and shelter is the first line of defense against rats. Since they love cat and dog food, put out only enough for pets and bring it inside at night, if possible. Keep food waste and garden trimmings and leaves in the green waste collection container with the lid closed. Thin dense plantings and remove climbing plants, trees and shrubs within three feet of the home.
Trapping the animals in a snap trap is the safest, most effective and most economical way to control rats, according to the UC IPM Program. Toxic baits are a commonly used alternative, however they pose a risk of poisoning non-target species, pets and humans.
Rats, she said, have a persistent sense of neophobia, the fear of new things. They are naturally very wary of new traps that may be placed on their stomping grounds. Quinn suggests pre-baiting the trap to overcome this tendency. In other words, before setting the trap, place it in the area where rats roam and add a helping of peanut butter, nuts, dried fruit or dry pet food, then wait for the rats to eat. After they have taken the pre-bait, set the trap with a very small piece of bait, which they then will be more likely to approach.
To increase success, place several traps in trees and shrubs for roof rats, or at ground-level in areas frequented by Norway rats.
“You have to remember that traps also impact non-target wildlife,” Quinn said. “You can try putting the trap under a milk crate to keep out songbirds, but you have to remember if you have wildlife like raccoons, they can stick their hands through there. You have to be very, very considerate if you have wildlife in your yard.”
Resources:
UC IPM Urban and Community Webinars (YouTube)