Though some of us have been known to keep rats or mice as pets, rats and mice are notorious urban pests.  They eat and contaminate food, garden produce and fruit, and transmit diseases to humans and pets.  They also cause structural damages to property with their gnawing activity.  The best way to manage the problem once you know you have one is to clean up debris where they can hide, remove food and shelter resources, eliminate entryways into buildings (exclusion), and/or use traps or baits.

Common signs of rodent infestation include:

  • visual sightings on fences, trees, bushes, patios, roofs, etc.
  • nibbled or damaged fruit and vegetables
  • droppings 
  • smudge marks from their greasy coats rubbing along walls, rafters, pipes
  • noise in the attic and walls
  • gnawing sounds and gnaw marks
  • damage to plastics and coverings on electrical wires or pipes
  • unsettled pets and/or pets bringing home rodent carcasses

Is it rats or is it mice?  

2 species of rats are prevalent in California:  Roof rats & Norway rats

ROOF Rats:  

  • brown to black in color
  • slender with large, nearly hairless ears and a pointed snout
  • tail longer than head and body
  • agile climbers
  • favor above ground nests in shrubs, trees or dense vegetation
  • indoors they favor attics, walls, false ceilings and cabinets


  • known as the Brown rat or Sewer rat
  • stockier than roof rats and have a shorter tail not longer than head and body
  • small ears and a blunt snout
  • builds burrows along building foundations, beneath rubbish, or in woodpiles
  • indoors they favor basements or the ground floor for nesting
  • nests are commonly lined with shredded paper, cloth, or other fibrous material
  • found in 48 contiguous states - will live wherever people live 


  • dusty gray with cream-white belly
  • round body
  • large ears and large dark eyes
  • small, not exceeding 4" in length
  • long, mostly hairless tail with obvious scale marks growing to about the length of head and body
  • musky odor indicating their presence



  1. Make sure garbage and garden debris are kept covered with tight-fitting lids.
  2. Seal all cracks and openings that are larger than ¼ inch around the building/house.
  3. Trim trees and keep dense vegetation at least 3 feet away from housing structures.
  4. Make sure doors, windows, and screens fit tightly.
  5. Regulate pet food - distribute only the amount of food they will eat in a single feeding session and store pet food in sealed containers.


T-Rex (jawed) rat trap

T-Rex (jawed) rat trap

Snap traps (jaw traps) are the safest, most effective, and most economical way to trap rats and mice. They are meant to trap and kill rats or mice quickly and in one movement. Bait traps with food attractants such as peanut butter or jerky bits (your discretion). 

  • For Roof rats, place traps in off-the-ground locations such as ledges, shelves, branches, fences, pipes, or overhead beams.
  • For Norway rats, place traps close to walls, behind objects, in dark corners, and in places where you have found rat droppings.  Always make sure the trap is facing a wall or structure in the rats path. Grease marks from their fur should give you an idea of their transportation routes. 
  • For mice use similar placement to the Norway rat.  

Some offer glue boards as an effective way to trap rodents, but there is controversy over the humane aspect of this method.  Animals remaining stuck in the boards suffer a slow, agonizing death; and some animals that free themselves lose skin, fur or limbs in the process.


Example of a bait station with bait loaded

Example of a bait station with bait loaded

  1. Seal buildings before baiting outside to prevent poisoned rats from coming inside to die.
  2. Avoid using baits indoors - dead rats create bad odors and could be a potential danger to pets and residents.
  3. Place baits in tamper-proof bait stations and secure them from children and pets


For more information on rodent identification, life cycle, biology and management check out Pest Notes from UC IPM Online provided by UC ANR.

If you have questions about infestation or need help with eradication, call and mention the website for a free inspection!

Cam Gray