Marin Master Gardeners
University of California
Marin Master Gardeners

Getting rid of rats

Rats are one of the most common pests in Marin County, destroying crops and wreaking serious havoc in the home and garden. They also elicit some of the most visceral reactions from gardeners, who find their beady-eyed presence downright creepy. But make no mistake: Marin is teeming with these unwelcomed critters.

On a brighter note, there are many strategies to both prevent and eradicate rats. The first step is to understand how and why rats show up and what they need to survive. Here’s how to beat them at their own game.

1.  Know your enemy. There are two non-native rats that call Marin home: roof rats and Norway rats. The larger Norway rat (Rattus norvegicus), also known as brown, sewer or wharf rats, are stocky, with a blunt nose and a tail shorter than their body. Moving in an area up to 150 feet in diameter, Norway rats burrow along building foundations, beneath rubbish or woodpiles, and moist areas in and around gardens and fields. Indoors, they usually frequent the ground floor or the basement. Mostly nocturnal, their poor eyesight is offset with keen senses of hearing, smell, taste and touch. They constantly explore and learn about their environment, memorizing pathways, obstacles and locations of food and water.

Roof rat
Roof rat
Roof rats (Rattus rattus), sometimes called black or tree rats, are slightly smaller than Norway rats. With a pointed muzzle, the roof rat has a tail that is longer than its head and body combined. Roof rats are agile climbers and usually live and nest above ground in shrubs, trees (they particularly like palms) and dense vegetation such as ivy, honeysuckle and blackberries. With their excellent sense of balance, they run along overhead utility lines or fence tops at night, traveling up to 300 feet for food. Inside, they can be found in attics, walls, false ceilings and cabinets.

Norway rat
Norway rat
Native wood rats (genus Neotoma) are generally not pests. They are about the size of the Norway rat, have a hairy tail and large ears. They build nests above ground from sticks, twigs, plant materials and man-made debris, hence their common name of pack rats.

 

 

2.  Recognize the signs of infestation. The pitter-patter of tiny but speedy feet across your roof at dusk or dawn, birdseed that seemingly disappears overnight, tomatoes with chunks missing or large comma-shaped droppings all are indicators of rats. And you'll not likely see them, just their damage. They eat nearly any type of food: fruits, nuts, pet and bird food, fresh grain, meat and fish, even slugs and snails. They can gnaw through food containers, electrical wires, doors, walls and insulation. Burrowing types can undermine building foundations and slabs, damage garden crops and ornamental plantings.

3.  Do not create inviting rat habitat. Most living creatures need food, water and shelter to survive. Rats are no different. They often show up in search of one or more of these requirements and end up staying when they find it. This is especially true when they find a food source. Here are some common ways of stopping a potential rat visit:

  • Harvest or pick up fruit, nuts and vegetables as they ripen.
  • Feed your pets during daylight and remove uneaten food right away.
  • Keep garbage and recycling cans covered.
  • Store bulk foods, birdseed and dry pet food in rat-proof, covered metal containers.
  • Use rodent-proof birdfeeders.
  • Remove excess garden debris.
  • Trim trees, shrubs and vines to at least 4 feet away from roofs and utility poles.
  • Thin heavy vegetation from around buildings or fences.
  • Stack wood and household items at least 18 inches above the ground and 12 inches from fences and walls.
  • Seal any opening larger than the size of a dime with rodent-proof material such as metal, hardware cloth, mortar, concrete or copper mesh wool.
  • Weatherstrip front, side and garage doors so they close tightly.
  • Repair damaged ventilation screens.

4.  Get a handle on an infestation quickly. If you need to eliminate rats, trapping is environmentally safe and effective. Large snap traps are inexpensive and can be reused. Location is crucial to their effectiveness: place them in natural travel ways so the rodents will have to pass over them. Put the short side of the trap containing the trigger against the wall or runway. Setting multiple traps 10 to 20 feet apart will improve the chances of catching one. Bait the trap with nuts, dried fruit, pet food or bacon, and secure it to the trigger with light string, fine wire or even glue. Leaving traps unset with unsecured bait until the bait has been taken at least once can improve trapping success. 

There are many readily available poison bait products that kill rats or any other animal that may consume it directly (like a dog or cat). Unfortunately, these products can also inadvertently injure or kill animals that may eat a poisoned rat, and symptoms of poisoning may take hours or days to see. When used indoors, the animal may die within wall or attic spaces resulting in significant odor problems and a swarm of flies.

Rats are potential vectors of disease, so do not touch a dead rat with bare hands and wash hands thoroughly after handling traps. Wearing protective gloves, place a dead rat in a plastic bag, seal it and place it in your garbage can.

Learn more about how to get rid of rats from the University of California Integrated Pest Management online resource. The Marin/Sonoma Mosquito and Victor Control District is another good source of rat control information, including their rat control pamphlet.



Contributors:
Nanette Londeree, Marie Narlock

Webmaster Email: banielsen@ucanr.edu