Controlling Those Pesky Mice (Yes, and Rats, Too!)
Text & photo by Neil Soderstrom

For decades, my family and I have more or less lived with mice and rats in a succession of apartments and elderly homes. Until recently, I'd relied almost solely on baited traps to keep rodents in check. But I'd failed to realize the need for a broader strategy recommended by health and rodent-control authorities.

Our First Rat
Our first encounter was as newlyweds, when a rat began visiting the kitchen of our third-floor apartment. Our old brick building sat across the street from a supermarket. One day I watched in horror as an enormous brown rat clumsily bounded from the store's dumpster towards our foundation and vanished.

Soon we discovered rat droppings on the kitchen floor! What to do? We did the time-honored thing. We bought one of those wood-based, spring-activated Victor rattraps and baited it with the Swiss cheese I'd seen in "Tom & Jerry" cartoons. Before bedtime, I placed the baited trap near a rat hole inside the kitchen broom closet. The next morning, when I opened the closet door, I saw that the trap had worked perfectly, as designed.

But instead of snapping on Mr. Rat, it had snapped onto a wad of steel wool, and the cheese was gone. I looked on the broom-closet shelves for the package from which the steel wool must have fallen. No package! No other steel wool anywhere!

Still puzzled that night, I again cheese-baited and reset the trap. By the next morning, the trap had sprung onto a new wad of steel wool, and again the cheese had been stolen. We began to worry that a rat with a high I.Q. had escaped from a research facility.

The third night, I simply placed the cheese-baited trap in the middle of the kitchen floor. The next morning, I found it snapped across the neck of a dead rat. Thus began our trial and error, three-decade-long battle against rats and mice.

Why the Concern?
Mice and rats transmit dozens of serious human diseases and afflictions, including typhus, salmonellosis, dysentery, meningitis, blood poisoning, and bubonic plague (which is still around, though treatable with antibiotics).

Of recent alarm, hantavirus is transmitted to humans by infected native mice. Hantavirus pulmonary syndrome begins with symptoms like a cold or influenza but quickly progresses to extreme respiratory distress that may be rapidly fatal, according to the American Lung Association.

Identified first in the Southwest in 1993, this form of hantavirus has occurred sporadically in the Northeast, with fatalities in Sullivan County and on Long Island. Health officials strongly warn against breathing dust from mouse urine, saliva, feces, fur and nest materials. Of course, rodent "dust" also figures strongly in allergies. Ironically, the hantavirus-infected mice don't become ill themselves. Antiviral drugs remain experimental.

Do rodents bite? In the U.S., rat and mice bites number in the hundreds of thousands annually. Many bites result from attempts at handling them, though many others are unprovoked. Although rats and mice aren't known to transmit rabies, their bites can transmit diseases, including hantavirus.

The compulsive gnawing of rats and mice — they need to constantly "file down" their constantly growing chisel-like front teeth — can prove a hazard to safety as well as to human health. They chew into and sever electrical wiring, often disabling appliances and phone lines, and sometimes causing shorts that start house fires.

Knowing Your Rodents
In rural and surburban areas of our region, the native white-footed mouse (Peromyscus leucopus) is a common houseguest. Weighing less than an ounce, this cute brown mouse has large eyes and ears, long whiskers, and white belly and legs. It often seeks warm shelter as winter approaches and then departs in spring, but it may stay. Some of these mice host the hantavirus, as well as ticks.

Our native Eastern wood rat (Neotoma floridana) sometimes makes house calls. As rats go, this one's about the cutest, resembling a white-footed mouse, albeit a half-pounder. "Cute" aside, one of these wood rats once left amber puddles under our refrigerator after chewing two condenser wires apart and stockpiling all manner of trash, including aluminum foil, fiberglass insulation, shredded fabric, and orange peels — justifying the wood rat's nickname, "pack rat."

Also common in our urban and suburban neighborhoods and throughout the U.S. are two Old World immigrants:

• The Norway — or brown — rat (Rattus norvegicus) is sinister looking, with small eyes and ears. It often prefers to live in ground burrows near water. Though mice weigh less than 1 ounce, Norway rats may weigh up to 1 1/4 pounds, heavier than our eastern gray squirrel.


• The house mouse (Mus musculus) from Europe can be distinguished from our natives by its lack of distinct demarcation between dark upper body and lighter belly.

Because rats and mice are primarily nocturnal, you're more likely to see their sign long before you see them. (If you see mice or rats in your home in daylight, overpopulation may have forced daytime scavenging.) Mouse droppings resemble small dark grains of rice. Rat droppings tend to be dark torpedoes up to 3/4 inch long. Rats also leave telltale urine puddles. Mouse urine may be less visible because mice urinate a fine mist as they travel. Pest-control firms assessing infestations use a UV lamp that makes rodent urine fluoresce.

Mice are more inquisitive about new things in their domain, such as traps, and so are more likely to check them out promptly. They will visit a good food source many times each night for snacks and storage. Rats tend to be more cautious than mice about traps and other new things.

Water needs also vary. Mice can often survive on the moisture in their foods and so depend far less on water sources than rats do. Rats tend to eat heavily when they can, before seeking a drink.

A dead rat behind your walls may stink for weeks; a dead mouse, perhaps just a couple of days. If you've not smelled a decomposing rodent before, you'll know when you do.

Options for Control
Do-it-yourself control options are essentially the same as those performed by pest-control professionals: (1) poisoning; (2) livetrapping; (3) lethal trapping; (4) elimination of food, water, and harborage; (5) exclusion measures; and (6) cleanup.

Although rodent-control professionals and animal-rights activists seem to agree wholeheartedly on removing attractants and preventing house entry, they may strongly disagree on the use of poisons and the options for trapping. People who favor lethal options cite the overriding human health concerns, let alone damage to property and potential for house fires. Those who favor livetrapping sometimes know the risks to themselves and the rodents, sometimes not.

1: Poisoning. In the 1950s a rat poison called warfarin became popular. An anticoagulant, warfarin caused internal bleeding that killed rodents after multiple feedings. Warfarin was hailed as safer than quick-kill poisons if consumed by children and pets because it had an antidote of medically administered doses of vitamin K1. However, genetically resistant rats soon created generations of super-rats in our area that could survive and thrive on warfarin.

Today, anticoagulants vary in formulations but remain available in supermarkets. Some employ an anticoagulant called brodifacoum. According to package cautions, brodifacoum may create blood problems in humans remediable with "oral and intramuscular" doses of vitamin K1 though some patients "may need blood transfusions." It's also toxic to fish, birds, and wildlife.

According to the Washington Post, "Poison-control centers reported last year that more than 15,000 children younger than 6 accidentally ingested rat poison." As a result, some makers have reduced their poison's appeal to children by adding a bittering agent called Bitrex, though these poisons still appeal to dogs, which tend to gulp their meals.

I am embarrassed to admit it, but some years ago I tested poison pellets. Following manufacturer instructions, I partially opened and placed the "bait" boxes in our basement and then watched with daily satisfaction as the blue pellets steadily disappeared. However one day while preparing to don a hiking boot, I was startled to find about a cupful of pellets inside. Where else had those provident little mice stashed pellets?

Soon after, while I was enjoying a televised ballgame, my eye drifted to a movement along a baseboard. There, a pathetically disoriented and perhaps blind mouse attempting to travel was continually bumping and bouncing off the baseboard.

Today, manufacturers optionally offer blocks of paraffinized anticoagulant and recommend placing them inside somewhat tamper-proof housings.

2: Livetrapping. People who oppose poisons as well as lethal traps tend to employ live traps in hopes of releasing rodents to the wild. Although wildlife groups may advertise willingness to "rehabilitate" livetrapped native rodents, they spurn the three alien rodents, which could become threats to natives. Relocation can also mean transmitting diseases and parasites to healthy wild populations.

Are live traps more "humane"? People who've monitored livetrapping and release efforts suggest that livetrapping itself can cause enough stress to kill rodents — certainly to mice, with their high metabolisms. Besides, released rodents tend to die quickly from stress or fall prey to a predator in unfamiliar territory.

In any case, never transport a livetrapped rodent inside your car, which would increase your risk of breathing aerosolized hantavirus. Professional trappers don a special respirator mask, disposable gloves, and clothing, as discussed in the "Cleanup" section at the end of this article.

Besides, our native white-footed mouse has excellent homing instincts for distances of up to a mile. So even though your relocated rodents aren't likely to beat you home, they might reappear in your live trap.

3: Lethal Trapping. The better lethal traps work as effectively on rats as on mice, when sized accordingly. These traps range in complexity from simple spring — tensioned snappers to battery-powered chambers of electrocution that can be programmed to announce a mortality on your pager.

To my mind, snap traps are the most humane of the control options because they dispatch rodents almost instantaneously — without the agonizing punishment of poisons or glue traps and without imposing the stresses of livetrapping that also kill.

Owing especially to hantavirus, I'd guess that legislation will soon require that trap packaging caution consumers on the hazards of handling dead rodents and contaminated traps. The U.S. Centers for Disease Control (CDC) recommends disposing of both trap and rodent inside two sealed plastic bags. As a prior precaution, you can place the baited trap inside an old milk carton or atop newspapers that you can fold over the "catch," thereby allowing you to simultaneously dispose of attendant urine and feces — again, only while wearing disposable latex gloves.

4: Eliminating Food, Water & Harborage
Food. Try to deny rodents the slightest crumb of food. Keep your eating and cooking areas spotless. Protect packaged grains, cereals, and the like inside sealed glass or metal containers. Never leave dirty dishes overnight for rodents to lick clean.

According to Dutchess Public Health Sanitarian Rich Robbins, even the most fastidious people often overlook the obvious. They allow bowls of half-eaten pet food to remain outdoors or indoors. Instead, he advises, "condition pets to eat an entire meal at one time and take the bowls away." Keep pet and livestock food in steel containers with tight-fitting lids.

Dutchess County bans the feeding of wild birds directly on the ground, which would provide seed to rodents. Spillover from birdfeeders, of course, attracts mice and rats.

As to household garbage, Robbins recommends steel cans, rather than plastic that rats can chew through. He also advises placing garbage cans outdoors just before scheduled pickup, rather than allowing dogs and raccoons to tip them and scatter the contents.

Also, rats and mice will dine on pet feces. So it's wise to observe "pooper scooper" laws even if they don't apply where you live and ask your neighbors to observe them too.

Cars often have plastic vent flaps that allow mice to nest in vent channels, like those in the car of a friend who turned his blower on one day and got an unexpected faceful of nest debris.

Water. Indoors, it's important to eliminate sources of water: leaky water pipes and faucets, water bowls, open toilet lids. Also insulate cold-water pipes to prevent condensation drips. Outdoors, some of the same practices that deny water to rodents will deny mosquitoes a chance to breed. Eliminate causes of standing surface water. Keep drain troughs running freely, and seal rain barrels.

Harborage. Rats and mice seek protected places for nesting. Although Norway rats tend to prefer underground burrows from which they make nightly house raids, they'll also nest indoors. Mice like any place they feel safe.

Keep woodpiles far from the house and elevated on masonry tiers.

5: Exclusion Measures. Rodents often enter houses through open doorways not equipped with automatic door closers. Pet doorways remain an open invitation, as do faultily louvered vents, and air spaces around holes for plumbing and power cables.

Mice can enter through dilapidated or poorly installed weatherstripping. They can work their way though holes the size of small coins and infiltrate narrow cracks that may open as a foundation settles.

Sand or talc sprinkled along suspected points of entry indoors and out can reveal tracks. Look for potential entries at all house levels, including the roof.

Try to plug openings in masonry with mortar, or mortar preceded by wads or sheets of quarter-inch galvanized mesh. To plug holes in moist areas, bronze wool and copper gauze serve better than steel wool because they won't rust. Dispensed from a spray can, expanding foam will fill voids that other materials can't, but should be preceded by wire mesh.

Ensure that floor drains have tight-fitting screw-down covers with grate spacing of no more than a 1/4 inch.

Use silicone caulk to seal small openings around incoming pipes and power cables, and around vents.

Check the integrity of door and window screening and the condition of its framing. Ensure that weatherstripping doesn't leave more than 1/4-inch space, even at door bottoms.

Trim trees so they don't reach near the house. Trim shrubs and groundcovers so they're 18 inches from the foundation, allowing you to inspect the ground periodically for evidence of burrows and tracks.

6: Cleanup. Out of concern for airborne hantavirus and other diseases, the Dutchess Health Department's Rich Robbins strongly cautions against attempting to clean up rodent droppings when dry. He instead recommends "wetting them with a dilute bleach solution, which is an effective viricide," and removing the moist material with a dustpan or shovel before bagging it for disposal.

He especially cautions against using a typical wet-dry shop vac, because its filters aren't adequate for the task, and the machine can stir up air. In any case, he suggests wearing disposable gloves, tight-fitting disposable clothing, and a special high-efficiency dust-mist respirator mask, rated N-100. Follow the mask manufacturer's instructions for fit-testing. (Typical disposable dust masks are not adequate against aerosolized hantavirus.)

For cleanup work, you'll probably be safer in hiring licensed pest-control professionals with the knowledge and equipment to minimize health risks. Pestmaster Services, a NY licensed pest-control firm, offers free assessments: (845) 340-9700, www.Pestmaster.com

For Health Dept. phone support, you can call (845) 486-3404.

Neil Soderstrom is a gardening writer and photographer based in Wingdale, NY, also found at www.agpix.com/soderstrom.

Bait For Traps

Virtually all traps depend on a rodent's attraction to a bait, such as peanut butter, chocolate, cheese, seeds, grain, fruit, or meat.

Rats and mice find peanut butter irresistible. It's easy to apply to bait pedals, it doesn't spoil, and its aroma continues to attract rodents for months, even after drying. Yet if left outdoors in the daytime on a bait pedal, peanut butter might disappear without the trap's being sprung. This might trick you into blaming the trap, when instead you should blame ants. Then too, traps tend to require a significant nudge of their bait pedal before springing and so may allow the occasional mouse to gently lick the peanut butter off.

Rich Robbins, a Dutchess County Public Health Sanitarian, cuts American cheese into 1-inch squares and microwaves them a few seconds, just enough to make them gooey before molding them around the trap pedal. The goo would be tough for ants to dice up quickly and resists a rodent's mere licking away. I've tried Rich's recipe and found it deadly — as well as a use for an otherwise irredeemable cheese.