How to Kill Rats, Inside and Outside
Rats Circle the Globe
The brown rat (Norway rat) and black rat (roof rat) have followed Europeans in the last couple of centuries to almost every place on earth, including, of course, the Bay Area, where they are both abundant.
Rats seek food, shelter and water. Where these three things exist, you'll find rats.
Our Trouble With Rats
- Rats in the garage, living in the washer and dryer, attracted by dog food
- Rats in the outside barbecue, attracted by the drippings
- Rats inside the house, attracted to food and water under the kitchen sink
- Rats outside, attracted by birdseed in the feeders
Rat in the Barbecue - It Has to Go!
Several shaky YouTube videos show people screaming in terror when they lift the lid of a barbecue and a rat jumps out. On Steven Raichlen’s Barbecue Board, an unfortunate man tells how he lifted his barbecue lid and found “seven or eight rats of varying sizes,” plus plenty of rat turds and an overpowering smell of urine. His wife ordered him to take the new grill to the landfill. Other commenters advised him to clean and rat-proof the grill, not throw it away.
How We Got Rid of Rats
In 2011 we tried poison, traps, and a “Rat Zapper,” a battery-operated device that electrocutes rats. All have their advantages and disadvantages. We are most impressed with the Rat Zapper.
Rat Nest in the Barbecue Area
Our Experience with Rat Poison
Advantages: Rat poison will definitely kill rats. Until recently, in California, you could buy rat poison in large green pellets. We tried it. Rats found the pellets very appetizing; they hauled them to their nests. As they ate the rat poison, it killed them slowly, from internal bleeding. We could tell that they were eating the poison because the poop the rats left behind turned from hard pieces to a runny green liquid.
- Rat poop that contains poison is toxic waste that has to be carefully cleaned up.
- Poisoned rats that are sick or weak could be eaten by cats, dogs and other creatures, who can in turn be poisoned. Small dogs especially are at risk of dying from eating poisoned rats.
- The large green pellets looked like food, which could be tempting to little kids. A small child eating rat poison is a frightening possibility that would require a trip to the emergency room.
Actually, to deal with these latter two disadvantages, EPA banned our green pellets in June 2011. Now the only rat poisons that the general public can buy are slow-acting anticoagulants incorporated into blocks of wax or paste, packaged in disposable bait stations that are designed to keep kids and dogs from getting at the bait directly. The rat excrement will still be toxic, and a dog may still eat poisoned rats, but the slow-acting poison gives its owner a chance to diagnose the problem before the dog eats more.
Rat Poisoning Campaign Leaves a Toxic Mess
Our Experience With Rat Traps
Rat traps work well, inside and outside. Traditional rat traps, like in the video, are spring loaded, with a trigger you attach bait to. I baited one of these with peanut butter and set it under the kitchen sink. In the middle of the night I heard a loud “slap” sound, and knew I had caught a rat. In the morning, I went to the rat trap to see blood all over the inside of our kitchen cabinet, and in the corner, a large mutilated rat. I had to scoop the rat out with a shovel and place it in a bucket.
- Rat traps don’t always kill. Rats can escape maimed from a rat trap and suffer. If you find the rat, then it's up to you to kill it with a shovel or by drowning. I purchased a pellet gun to shoot the injured rats instead of doing it by hand.
- Rat traps may cause a distressing mess. A dying rat may drag the trap around, leaving a trail of blood and guts to be cleaned up.
Video: Rat Trap Demonstration (using pencils and carrots)
Our Experience with the Rat Zapper
My brother introduced me to the Rat Zapper. You put some bait in the reusable trap, and when the rat walks into the trap, electricity--8000 volts, if you believe that--from the batteries electrocutes the rat in a few seconds. Then, all you do is dump the rat out of the trap into the garbage.
My father in-law had a rat problem: rats were getting into his hot tub, and making a new nest in the cabinet of his barbecue every few days. I sent him a Rat Zapper as a gift and he reports that he killed over 50 rats with it. Presumably he replaced the batteries several times: four AA batteries are supposed to be good for 20 kills.
Biconet, which sells the Rat Zapper and other integrated pest management tools, argues that a zapper it is safer to use around children and pets than poison or traps, because its entrance is designed to admit nothing bigger than a rat, and if a dog or child did put a paw or finger inside, the electric shock should trigger a reflex causing the child or dog to pull away from the trap.
I think the Rat Zapper is the way to go. The only disadvantage is that it is not designed for use outdoors, and moisture could short it out. Nevertheless, Biconet says to cover it with a plastic bag or tarp and go ahead and use it outside.
Video: Rat Zapper Demonstration
Buy Rat Zapper
Using Cats or Dogs to Control Rats
For outside rat problems, experts have recommended getting a cat. Cats will hunt rats, and help keep the rat population under control. Still, I wonder if cat predation might make the rat population stronger and smarter, by culling the weakest and slowest rats. And some cats won’t tangle with large Norway rats.
Dogs have been bred for hundreds of years to help humans deal with rats. They catch the rats, bite them and then shake them until they're dead. It's pretty gruesome to watch, but I could see hiring dogs to kill rats if I had a huge rat problem.
Video: Working Dogs Killing Rats
Help From the Government
Your county’s animal control center may help you exterminate rats. We live in San Mateo County on a creek that has been invaded by ivy, which rats hide in. The county has placed and maintained two large rat poison dispensaries in our backyard. We believe our neighborhood would be overflowing with the critters without the county's help.
Increasingly, government agencies are advising us to deal with pests through housekeeping and handyman ideas rather than traps and poison.
Knowing Your Rats
The Norway Rat or Brown Rat is the most successful and widespread mammal on the planet, next to humans. Norway rats tend to stay low, are good diggers and swimmers, and use basements and sewers to invade houses. They seem to be involved in these barbecue incidents (meat is one of their preferred foods); their turds are more rounded than roof-rat turds, and are visible in one of the pictures above. They are ancestors of pet rats (because 19th-century stagers of rat-and-terrier fights used to keep the prettiest rats and tame them) and of laboratory rats.
The Roof Rat or Black Rat is smaller and a good climber. Roof rats tend to stay high, nesting in trees and woodpiles, and using tree limbs and powerlines for travel. They can range 300 feet or more from the nest, living in one backyard and feeding in another. They love backyard fruits and nuts. They may invade attics.
Both kinds are clever at staying out of sight, and at avoiding new things in the environment that might be traps or hazards.
Integrated Pest Management Ideas: Creating Defensible Space
The University of California at Davis Integrated Pest Management Program, our San Mateo County pest control agency, and the Centers for Disease Control all have advice on how to close off openings that rats might use to enter a house. The idea is that, since the Bay Area outdoors, with its ivy, blackberry piles, and fruit and nut trees, is an inexhaustible source of rats, you give up on totally getting rid of the rats in their outdoor space, and you separate the human space from the rat space. If you close off all openings to the basement or crawlspace, around the pipes, and the bottom of the house, and leave none larger than a half dollar, you can theoretically keep the Norway rats out; and if you can do the same for the attic and roof area, and leave no holes bigger than a quarter or so, you can keep the roof rats out. Also, you are supposed to clear vines and shrubbery away from the bottom of the house, so rats can’t hide right next to the house; raise your woodpile up off the ground; and remove tree limbs within three feet of the house so that roof rats can’t use them to leap onto your house. Then if you keep food sources inside the house cleaned up, or secured in chew-proof containers, you can get the rats inside the house to kill themselves with the poison bait, traps, or zappers you set out. End of indoor rat problem—you hope.
Problems arise when the boundaries between the inside and the outside of the house are kind of fuzzy. We humans find it convenient to go in and out of the house with our food, and so do our pets.
Rats will get what they can from our garbage cans, compost piles, barbecues, and bird feeders. Dry dog food must seem ideal to rats; portable, storable, full of protein. In fact it makes a good bait for rat traps. If the dog food is outside, or where rats can reach it, they will get it. Access to a large supply of cat and dog food can create a horrific infestation.
Suggestions for making your barbecue a defensible rat-free space between grills include:
- cleaning it thoroughly;
- burning off residue;
- closing all vents and stopping all holes with aluminum screening, aluminum duct tape, or steel wool (though one writer says a gas grill will melt steel wool);
- covering it with a zippered cover.
Here’s a funny Environmental Protection Agency video advising you to keep your kitchen clean to avoid rats. Of course there’s more to fighting rats than dishwashing. I’m sure the rat shown capering in the dirty dishes is a pet rat, descended from Norway rats but different in behavior.
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