Managing rodent pests
Because rats and mice are prolific breeders, ignoring a problem can result in a much more damaging infestation. They can chew on materials including insulation, siding and wallboard; gnaw on wiring and start an electrical fire; consume and contaminate stored food and transmit diseases.
Identify the problem
You may have a rodent problem if you notice any of the following conditions:
- Rodent droppings – check the size to determine if they belong to mice or rats
- Chew marks on wood or food and around pipes
- Dirty rub marks along frequently used routes
- Noises in walls
Rodent species in B.C.
- Leaves dark, oval pellet droppings, 15-20 mm long with rounded heads
- Weighs up to 0.5 kg (about 1 lb)
- Has a blunt nose and ears that are relatively small for the size of its head
- Has a tail that is shorter than the length of its body (including its head)
- Prefers moist conditions and generally live at ground level, in crawl spaces and burrows around building perimeters
- Leaves droppings that are 10-15 mm with pointed ends
- Is slimmer than the Norway rat
- Has larger ears
- Has a tail that is longer than its body and head put together
- Nests in ceilings and attics
- Leaves dark brown pellet droppings, about 6mm long with pointed ends
- Weighs less than 30g
- Has a pointed nose, relatively large ears and a nearly hairless tail
- Nests in hidden, enclosed spaces using shredded paper, insulation, string or other soft materials
- Prefers grains and seeds, but will nibble on almost anything
- Gnaws through wood, asphalt shingles and soft mortar
- Squeezes through cracks little more than 1 cm wide
Keep them out
Make sure that buildings are in good repair and that access to food and water are restricted. Take some extra precaution to make sure that conditions are inhospitable to your unwanted guests:
- Block all openings with durable materials or use heavy wire mesh to cover openings that cannot be blocked
- Regularly inspect and repair entry points
- Remove hiding places near buildings like firewood, equipment or dense vegetation
- Prune back branches that hang over eaves and roof areas
- Remove any sources of food and water:
- Store cereals and dry food in glass or metal containers
- Keep pet food and birdseed in sturdy, covered bins
- Store produce in a refrigerator or a secure room that has heavy wire screens on vents open to the outdoors
- Compost kitchen waste in sturdy, closed bins – don’t put meat scraps or bones in the compost bin
- Store outdoor garbage in tightly-closed containers
- Make sure bird feeders are away from buildings and seeds don’t spill on the ground
- Repair any leaky plumbing
Ensure that native species are not harmed by control methods. If in doubt, use a live trap to catch the animal so you can identify it.
Use a professional pest control operator to help with a serious rodent problem. They will know the behavioural differences between different rodents which will help effectively manage the pest.
Once the infestation is under control, repair or seal any access points to prevent new infestations from starting.
When baited and set properly, snap traps are effective at killing rodents quickly and humanely:
- Set traps at right angles along walls where rodents travel, with the bait side of the trap toward the wall
- Use bait like dried fruit, peanut butter (mixed with oats), cheese, marshmallows, onions or any other food they've already been nibbling on
- Rats are cautious about new things so leave the baited traps out for several nights before setting them
- Wear gloves to handle the trap and all dead rodents
- Wrap the dead animal in plastic and put it in the garbage
- Used traps are more attractive to mice than new traps
Live traps are also effective. They do not need to be reset to continue catching rodents. Rodents die of stress and exposure if they're held without food or water so check the trap daily. If choosing a live trap for humane reasons, consider what to do with live rodents that are caught.
Some cats can catch mice or rats – especially if they have access to where rodents are living like an attic or crawl space. A few things to note about cats catching rodents:
- A cornered adult rat can seriously injure a cat
- Cats may bring live rodents into living spaces
- Rodents often carry parasites that can be passed onto cats
Poison baits should only be used as a last resort. They risk poisoning children, pets and wild animals either directly or indirectly (for example, when a pet or wild animal catches a dying rodent after it has eaten the bait). They also can cause a rodent to die and decompose in an inaccessible place which leads to a terrible smell and insect infestations.
Poison must be placed in areas inaccessible to children, pets or other animals, in tamper-proof bait stations. Never scatter poison baits over the ground or inside a building (this is dangerous and illegal). When using any bait, always read the label and follow the directions.
Cellulose (from powdered corn cobs)
Available as a pelleted bait. Cellulose from powdered corn cobs appears to interfere with the digestive system by causing blockages in the intestine, resulting in dehydration and death. Bait can be used indoors for rats and mice. Use in commercially available bait stations and protect from children and non-target animals. These products pose a negligible risk to avian and mammalian predators and scavengers that may feed on dead or dying rodents
These baits cause death by internal bleeding. They present a moderate to high risk of secondary poisoning to other animals that might eat the poisoned rat.
Once the pests have been eliminated, dispose of the bait properly.
Repellers are expensive and seem to be effective only over small areas for a limited time. They may initially work but eventually rodents get used to the sound and learn there's no harm associated with it.