Beyond Barn Cats: How to Keep Mice and Rats from Feeling at Home in Your Barn

If all rodents were as harmless as Mickey Mouse, you might not mind sharing your barn with them. Unfortunately, that's not the case.

Rodent droppings contain bacteria that carry disease.  Rats and mice are also hosts of fleas, ticks and mites that are associated with a number of diseases.  In some cases, a disease can cycle through the rodent population and then affect dogs, horses and humans in the area. 

Among the diseases connected to rats and mice are salmonella, leptospirosis, plague, rickettsialpox, murine typhus, hantavirus (more common in dry, Southwestern areas), sin agua virus, Lyme disease (the deer mouse is a host), tularemia, and Rocky Mountain spotted fever.

Rats and mice will eat grain and feed, but even what they don't consume can be contaminated with their urine and feces. Because their front teeth grow continually, they'll chew on a variety of surfaces, including wood and wires. All that gnawing can damage equipment and even cause a fire hazard if chewed electric wire causes a "short."

Creature Comforts

You might think that installing a couple of cats in the barn is the answer. While this may provide some deterrent, a feline patrol posse isn't enough to eradicate a rodent population. That's because the typical barn offers exactly what rats and mice are looking for: food, water and shelter.

Since rodents are nocturnal, they aren't typically spotted during the day. (If you are seeing them during daylight hours, this is a sure sign of a large population and you'll want to take immediate steps to control it.)

It doesn't take long for a few rodents to become many. Mice start reproducing at just four to five weeks of age. A single female 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.

Both rats and mice reproduce year-round with their reproductive cycle and number of offspring increasing when they have adequate food, water and safe shelter.

Rodents poop. A lot. One mouse typically produces 50 to 75 droppings per day, so you can imagine the mess that a large number of rodents will leave behind. Droppings are usually the first sign you have rodents in the area. Other evidence includes:

• Holes chewed in feed bags, plastic containers
• Damage from chewing to blankets, pads, leg wraps, etc.
• Gnawed wires
• Chew marks on wood (stall ledges, doors, window frames, etc.)
• Smudge marks along walls, pipes, rafters (dark marks left by the oils and dirt in rodents' coats)

Unfortunately, if you don't control rodents in the barn, they're likely to end up invading nearby structures--including your house.

Take Action

"An integrative pest management system uses sanitation, exclusion and rodenticides to control rodents," says Doug VanGundy, Vice President of research and development with Central Life Sciences, in Dallas, Texas. "There's not one silver bullet, so you have to use all three methods to keep the rodent population down."

While it's not possible to eliminate every single rodent, because more will come in from outside your property, with the right program in place, you can drastically reduce populations--and their exposure to horses and humans.

An effective management program includes; Sanitation, physical barriers (exclusion), traps, and bait stations/rodenticides.

Start with Sanitation

Rodents love dark, damp areas, so keeping your barn clean, dry and well-lighted makes it less inviting to them. Tall grass and vegetation offer shelter, so keep the area around your barn tidy and mowed. Don't stack fence boards or lumber near the barn.

Make food sources hard to access. Rats and mice will quickly chew through plastic or paper bags, and plastic and wooden containers.

"Wooden feed bins aren't going to keep them out; you have to use metal bins or cans with tight-fitting lids," adds VanGundy. "Clean feed tubs after every meal and sweep up any spilled grain because that's a 'dinner bell' for rodents."

Dispose of it in a tightly-sealed metal trash container; don't just toss old grain outside the barn.

Use Exclusion Methods

Create physical barriers so rodents can't get in. Rodents can squeeze through incredibly small openings, so you'll need to do more than just shut the door to your feed room. Blankets, leg wraps and saddle pads can become a source of nesting material, so you'll want to keep rodents out of the tack room, too.

"Steel wool is a great deterrent," says VanGundy. Look for any gaps around windows and door frames, under sinks, around plumbing and electric lines, in hot water heater closets, etc. Pack small openings with steel wool; use caulking to hold it in place.

Traps and Bait Stations/Rodenticides

If you are still seeing signs of rodents, utilize traps and bait stations/rodenticides. "Rodents like the dare and they prefer to travel with one side of their body along a wall, so take advantage of this natural behavior when placing traps and bait stations." advises VanGundy.

Place "snap" traps along walls with the baited end of the trap facing the wall. “Tunnel” traps work best when placed lengthwise along walls, making it inviting for mice to enter the tunnel. Peanut butter, bacon, butter, chocolate candy or marshmallows have proven to be inviting bait. (Use gloves when emptying traps and when re-setting used traps.)

For best results, place bait stations/rodenticides strategically along walls where rodents are known to travel. Whether you use ready-filled stations or ones that are refillable, replace bait periodically so the rodenticide remains fresh. Place the stations where barn cats, dogs, or children can’t access them.

There are two basic types of rodenticide: anti-coagulants cause internal bleeding and nervous system toxicants attack the nervous system. (While there has been some research with using sterilization products for rodent control in the future, this option is not currently available.)

"With both anti-coagulant and nervous system toxicants, the animal typically has to eat the bait only one time for the product to work," VanGundy explains. "The rodents tend to die in their burrows, so you usually won't see dead animals." If you do happen to find a dead rodent in or near the barn, pick it up with a shovel or by hand wearing a glove and dispose of it in a sealed trash container.

"Follow label directions carefully and use rodenticides appropriately so domestic animals and children can't get a hold of them," says VanGundy.

"Rodents are more likely to look for warm shelter during the colder months, but your rodent control strategy should be a year-round program," he notes, adding that an ongoing management program will be most successful in keeping rodents out of your barn.