3 Steps to Banish Rats and Mice from Your Shed, Barn, and Farm
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How to keep rodents from contaminating animal feed and chewing wires
November 15, 2021
Raise your hands! Who’s had rat or mouse problems? These rodents will gnaw through car and tractor wires, leave droppings that contaminate animal feed, spread disease, and cause expensive repairs. Do NOT wait until cold weather arrives to tackle an infestation! See 3 steps to control rodents now in sheds, barns, and farms to avoid such headaches—and save a lot of money in the long run.
Here at The Old Farmer’s Almanac, many of us live on small farms; have horses, cows, sheep, or goats; or raise chickens! And, yes, we have all dealt with rodent problems. In this article, we’ll share our experiences and advice so that you can avoid some of the most common rodent issues.
The simple reality is: If you have a shed, a barn, and/or livestock shelters, the chances are excellent that you’re going to have rats and mice. Food and nesting sites are plentiful in these warm spaces, especially as colder weather approaches. However, the critical thing is that you need to address rodent control BEFORE the rodents show up. An ounce of prevention is worth a pound of cure.
The Many Costs of Rats and Mice
Although they spend most of their time hidden away, rodents are not a minor issue and are certainly not the sort of problem to be kept “out of sight, out of mind”! According to the United States Department of Agriculture (USDA), rodents destroy more than $2 billion in animal feed every year. That’s not all they can do, though:
As any farmer knows, rodents will chew through the electrical wires of tractors, trucks, cars, and other equipment, necessitating expensive repairs.
Rats and mice also chew on structural support in buildings. Their teeth never stop growing, so they have to constantly chew—on anything! Damage to live wiring in structures can spell F-I-R-E, something to be avoided at all cost.
Rat and mouse urine and feces will contaminate horse, chicken, goat, or other animal feed, which not only wastes feed and is an expensive problem, but also spreads disease from animal to animal through contamination.
Both mice and rats are messy eaters and spoil far more food than they ever consume. Even if just two mice are active inside a barn for six months, they can devour as much as four pounds of grain and leave up to 18,000 droppings.
Let’s not forget that vermin can also carry pathogens harmful to the humans who spend time around these sheds, barns, and farms. They are prolific carriers of diseases, including bubonic plague, leptospirosis, rabies, and bacterial food poisoning.
Image credit: Purdue Extension
Identifying the Problem
You’re not often going to see rodents during the day; they begin foraging soon after dark, and most of their food gathering occurs before midnight. Use a powerful flashlight to search for signs of their presence in dark places and to spot the animals after dark.
Droppings are one obvious sign of rodents. Rat droppings are black and bean-size (about 3/4-inch); mice droppings are black or dark brown and about the size of a rice kernel (about 1/8-inch). Most droppings are found where the rodents rest or stop to feed. Fresh droppings are black or nearly black, look wet, and have the consistency of putty. After a few days, droppings become dry and hard and have a dull appearance.
You may also see rodent footprints in the form of narrow, worn trails through dust and dirt. Rats tend to travel the same route—along walls, along fences, under bushes—nightly. Rats may also leave a tail dragline in the middle of their tracks. Try spreading talcum powder around suspected rodent hideouts, then check back a couple days later for footprints and tail swishing in the powder. To spot, shine a flashlight at a low angle, causing the tracks to cast distinct shadows.
Rats’ teeth keep growing and growing, so they have to keep their incisors worn down by gnawing on hard surfaces. Look for evidence of chewing around pipes in floors and walls and on door corners, siding, floor or ceiling joists, boxes, on wires, and tack.
If you do see rats or mice during the day, this indicates that you have an established population. The rule of thumb is: There are 25 to 50 mice or rats for every one seen around barns, sheds, or poultry houses.
Fortunately, rats do not usually travel more than 100 feet from their home base, and mice do not venture more than 10 to 30 feet.
Don’t wait to address a rodent problem! Both rats and mice reproduce incredibly quickly. A single female mouse can produce up to 56 offspring per year. Norway rats average four to eight offspring per litter and have four to six litters per year.
Photo: A mouse chewing wires and leaving droppings in shed. Source: Tenra/Shutterstock
3 Steps to Banish Rats and Mice
1. Rodentproof your shed, barn, and farm.
Rodentproofing is a challenge, but an absolute must-do. House mice can fit in spaces as small as a dime, while rats can flatten themselves to squeeze through cracks the size of a nickel.
Prevent access to shelter
Assess all of the walls, especially where pipes, wires, cables, and power lines enter or leave the structure. Look for holes or cracks.
Seal all openings in walls, the foundation, and roof joints with concrete, sheet metal, or 1/4-inch hardware cloth. Copper wool is also a temporary solution (avoid using steel wool; it quickly corrodes after getting wet).
If you have corrugated metal walls, check that the seams are sealed tightly.
Check the condition of attic and foundation vents; cover these—as well as dryer vents—with 1/4-inch wire screen mesh or install commercially-available vent guards. Basement drains should be screened. If the drain is no longer used, seal it.
Cover the chimney top with spark arrester screening.
Put a sealing gasket on the bottom of a garage door; check each end for gaps and then seal.
Keep barn and shed doors closed at night. Cover door bottoms that are subject to gnawing with metal flashing or hardware cloth, and keep the openings no larger than 1/4 inch.
Ornamental shrubs next to the house should be pruned up at least 18 inches from the ground.
Cut back any overgrown vines, such as English ivy, which rats will use to climb up and hide in.
Prune tree limbs that overhang onto the roof. Trim tree branches at least 4 feet away from utility lines that lead into structures (or contact the utility company).
Photo: Rodents contaminate animal feed and grains. Source: Bachkova Natalia/Shutterstock
2. Sanitize the area.
Part of an effective rodent control strategy involves preventing access to food and water and keeping your structures neat and clean to avoid providing easy shelter.
Keep ALL food—especially horse, chicken, pet, and animal feed—in rat-proof buildings, rooms, or containers. Metal cans are best; they will chew right through plastic.
Keep garbage in cans in tight-fitting bins and do not allow larger critters like raccoons, opossums, and skunks to make a mess of the garbage.
Water attracts rodents, too. The main constraint of rats is that they cannot live long without water if their diet doesn’t contain adequate amounts of liquids. Make sure that none of your water pipes, faucets, or hoses are leaking water. Also check for wet spots on the floor, which probably indicate a roof leak. Do not leave buckets or troughs with standing water. Eliminate access to other sources of ground water as well.
Avoid leaving hay bales, feed bags, building materials, or anything that could make a good hiding place for rodents lying around. Stack wood or other materials at least a foot from walls or fences and a minimum of 12 inches off the ground (use pallets). Try to use containers and/or designate storage shelves and hooks for materials such as feed, tack, and tools.
Clean up any food spillage, debris, dirt, and trash inside and around structures.
Have fruit trees? Harvest when ripe and clean up any fallen fruit as soon as possible.
Keep food scraps out of compost piles unless you can cover the compost with a mesh-screened lid.
Feed pets both water and food indoors. Also, clean up outside pet droppings, which rats will eat.
Use rodentproof bird feeders with baffles, just as you would use with squirrels. Birdseed attracts the most rats around buildings. Also be sure to clean up any spilled seed on the ground.
Routinely check for dead rodents and remove them as soon as possible. Use gloves to pick them up, double-bag the carcass, and dispose of them in a secure outside trash container
Photo: Rodents nest and chew on electrical wires in vehicles. Source: Bachkova Natalia/Shutterstock
3. Safely reduce the population of rodents.
If rat problems persist, some form of population reduction, such as trapping or baiting, is almost always necessary. Unfortunately, ultrasonic sounds or other uses of sound or motion do not deter rats. No repellent is truly effective long-term either. Below are several solutions. (Keep in mind that no method will be effective if you do NOT rodentproof and sanitize as described above!)
Cats: It’s always a good idea to have a barn cat to help limit rats and mice, but only if the rodent problem is a very limited one. Cats often bring rats and mice INTO barns from fields, which introduces disease. Also, bear in mind that cats allowed to roam outdoors may kill songbirds, chipmunks, snakes, lizards, and young rabbits and squirrels in addition to your rodent pests. For some cats, after a tussel with one adult male rat, they prefer easier prey!
Traps: Snaptraps are thought to be more humane than other traps (such as glue traps) because they kill the mouse instantly. Live traps are not recommended because trapped rats must either be killed or released elsewhere (which may be illegal in your area). If snaptraps are used, the placement is very important and you may need to experiment. Rats and mice prefer a stationary object on at least one side of them as they travel. So, move objects around to create narrow runways along walls leading to traps or force rats through a narrow tunnel or opening. Rats and mice will also avoid a trap after it’s triggered, so you need to set up many traps to keep the trapping time short and decisive. Note that traps are NOT recommended for outdoors, as chipmunks, raccoons, songbirds, pets, or other animals could easily spring the trap, killing or injuring the animal. Also, traps do NOT work well in areas where there’s a lot of dust, so this can make them ineffective in barns.
Rodenticides: The most effective way to reduce the rodent population is through rodenticides, though we consider this a last resort given their potent toxicity. Unlike older, first-generation baits—which often took multiple days to take effect—there are baits today that are fast-acting and only take one dose. This means that they can be used in targeted and more limited ways. In addition, with the leading second-generation baits, most of the active ingredients are excreted, limiting the possibility of a pet or wildlife being affected by eating a poisoned rat. (Norway rats are now resistant to the first-generation rodenticides such as warfarin.)
If poison bait is used outdoors, it must be registered for such use, applied according to label directions, and sit inside a bait box. Bait boxes are designed so that children, pets, and non-target wildlife cannot access the bait, but a rat or mouse can. They can be purchased from a farm supply store (such as Tractor Supply Company), hardware stores and tack shops and through the Internet.
When using baits, safety must always be the first consideration:
Carefully follow all label directions.
For both safety and ease of application, choose ready-to-use commercial baits that are no-touch pellets or bars. Do not make your own bait.
Do not use baits near livestock or poultry.
Only use in areas where rodents are unlikely to be preyed upon by wildlife.
Always place poison baits so that they cannot be accessed by children, pets, or other nontargeted animals.
We hope the three steps described above give you the information you need to make a plan! Rodent control is always on the to-do list for those with farms, barns, and animals, but you can certainly manage the costs by simply being proactive!