Pest-proof your barn for winter

Follow three simple steps to keep wildlife from wintering in your barn.
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Follow three simple steps to keep wildlife from wintering in your barn.

Last fall I fell into a fierce dispute over territory. It started innocently enough---a darting shadow along the floor of my barn aisle. A mouse? Maybe, but even though I caught only a glimpse of brown fur, it looked too big to be a mouse. I set about doing a little detective work---inspecting both the inside and the outside of my barn’s foundation for entry holes or rodent droppings. The more I looked, the more the evidence mounted.

barn aisle

A colony of Norway rats, better known to horse owners as the “barn rat,” had set up camp beneath my barn’s dirt foundation. These rodents had not only established an elaborate series of cleverly hidden entry and exit holes, but they’d obviously been gnawing on one or two supporting barn timbers. I was familiar enough with rat behavior to know that they’d be most active after I shut off the lights for the night.

My skin crawled just thinking about it.

Aside from the structural damage rats inflict, they ruin feed, chew through electrical wires and spread salmonella, hantavirus and a host of other diseases. The typical female barn rat has four to six litters per year with breeding cycles peaking in the spring and fall.

This wasn’t a dispute I could put off, even for a week or two.

Most of us have waged similar battles at some point over the years against all sorts of unwelcome visitors. The situation is often worse in the fall when animals like rats, mice, bees, venomous spiders and---believe it or not---some species of mosquitoes look for shelter from the harsher weather to come. Of course, these animals aren’t deliberately making your life difficult. They’re just looking for a place to wait out the cold months.

“Animals just do what they need to do to survive,” says Laura Simon, president of the Connecticut Wildlife Rehabilitators Association and wildlife ecologist with the Humane Society of the United States. “They survive by following their instincts, which means that many animals in the fall will search for a steady source of food and shelter. Horse barns are perfect environments for them, offering a supply of grain or pet food and lots of nooks and crannies to hide in.”

For the most part, you probably don’t mind sharing your farm with wildlife. In fact, it’s part of the appeal of keeping horses---with one stipulation: They can’t bunk in your barn. And as with so many things in life, it’s much easier to bar entrance than to evict them later.

“That’s why prevention is so important,” says Simon. “Rather than wait until we have a problem and then feel we have to pluck every last one of them from our horse’s environment, we need to make our barns as unappealing as we can.”

When devising your prevention strategy, says Simon, remember that the best way to change their behavior is to adjust yours. “We have to be diligent in making sure we don’t offer wildlife a source of food and shelter in our barns. In many barns I’ve visited there’s a bowl of food left out for the resident barn cat 24-7. That’s like putting out a blinking neon buffet sign to wildlife.”

Simple measures, like keeping feed in metal containers and sweeping up bits of grain that fall on the floor, go a long way toward deterring animals from moving into your barn, but further action might be necessary depending on how determined the critters are in your neck of the woods. Whatever your situation, here’s a three-step process for winter-proofing your barn that will get you started.

1. Make a clean sweep

A daily sweep of the barn, especially the feed room, is a good way to keep out rodents, raccoons and opossums---all of them love clutter and stray bits of feed. The trick to controlling wild animals is to control the food source. “If you have a barn cat,” says Simon, “instead of leaving a bowl of food down all the time, try putting the bowl out once a day in the middle of the day. Cats are smart, and they’ll adapt to this new schedule in no time.”

Also tidy up your barn aisle and tack room. Animals, especially mice, love to hide and nest in old blankets, leg wraps and saddle pads that have been left on the floor.

As you organize your barn spaces, avoid placing items against the exterior walls. The spaces beneath or beside garbage bins and tarps, as well as within stacks of lumber, all make great nesting places for snakes, rodents, spiders and carpenter ants.

Also be mindful of wildlife lures like bird feeders, suet cakes, vegetable compost heaps and open garbage bins. You can still feed the songbirds, but place feeders well away from the barn and consider using seed that doesn’t create as much waste, such as sunflower kernels instead of sunflower seeds in the shell. Place bird feeders on poles with stovepipe baffles positioned at least four feet off the ground to deter squirrels and mice. Sweep up uneaten seeds that drop to the ground.

Mice love compost heaps, especially in winter, so place kitchen and manure composts well away from the barn and your home. Compost provides a relatively dry home, and if it’s from the kitchen, a constant source of fresh food. Keep the compost damp and turn it frequently to discourage visitors from settling in. Elevated and fully contained barrels or tumblers work great for kitchen composts and rarely attract rodents. 

2. Batten down the hatches

You can’t seal off every opening, but patching any holes and crevices you find will reduce the opportunity for wildlife to enter your barn. Take an inventory of trouble spots, paying close attention to the foundation exterior, under siding or near the roof soffits.
If you have a prefabricated building, make sure all gaps at joints are protected by metal flashing.

If you see signs of wildlife while doing your inventory, you’ll want to find out if the creatures are still in residence before blocking entry. The last thing you want to do is barricade a colony of rats or other animals inside the barn. “If you do see a hole and you’re not sure whether the space it leads to is occupied, stuff a crumpled ball of newspaper into the hole and wait 48 hours,” advises Simon. “If the newspaper stays in place, the hole is probably unoccupied and it’s safe to close it off.”

Keep in mind that mice can squeeze through an opening smaller than the size of a penny. Seal off entry points with a quarter-inch woven/welded hardware cloth or caulk with a patching plaster. Pay special attention to plumbing. If you can see light, mice can probably gain entry. Caulk holes or pack them with a stainless steel/polyfiber product. Steel wool is sometimes used to fill in holes, but it will rust and stain your walls. One similar alternative is copper scouring pads, which are made of copper-coated wire.

Scrutinize your hay storage areas. “Hay sheds and lofts offer ideal hiding places for raccoons and opossums,” says Simon. “Mice and rats may make homes under pallets. Even though it may seem like a lot of trouble initially, I recommend blocking entry to pallets by stapling galvanized hardware cloth all around the perimeter and across the top. You’ll keep the ventilation you need, but it will go a long way to deterring wildlife from nesting under there.”

3. Control populations

If you follow Steps 1 and 2, you’ll avoid most pest problems before they start. And that’s a good thing. “We must be responsible when it comes to controlling wildlife conflicts,”
says Simon. “If we make our barns inhospitable, they’ll find another place to spend the winter.” But what if you already have a problem? Here are three common methods for ridding your barn of unwanted visitors:

• Mechanical traps. If you already have mice or rats, you might be tempted to try trapping them, but be forewarned---it’s a loathsome job. What’s more, says Simon, it is generally futile: “The more you trap, the more animals you end up with. That’s because if the source of the problem isn’t removed [food or nest site attractants] then more animals from the surrounding area will replace any removed. The Humane Society of the United States does not consider trapping to be an effective method for resolving nuisance wildlife problems.”

Glue traps are considered by most wildlife experts to be extremely inhumane because the stuck animal tries frantically to get away and can’t, and it undergoes extreme stress, trauma, dehydration and physiological exhaustion before succumbing to death by starvation. The nature of traps---even those deemed humane---underscores why prevention is the backbone of the best pest control programs. “Despite their bad reputation,” says Simon, “rats are highly intelligent creatures.” They’re smart and often very suspicious of anything new so they tend to not go into traps.

• Chemicals. Poisons or rodenticides are risky in the barn or farm setting. Rodenticides contain chemicals that act as anticoagulants, aggressively thinning the blood to the point of death. Toxic if inhaled or on contact, most anticoagulants are formulated as pellets or block baits that may prove appealing to cats, dogs or even horses. Because of that risk, never place baits in a horse’s stall, and, no matter where they are used, enclose them in bait boxes (store-bought or homemade) that will keep out the curious (and hungry) cat, dog and random wildlife.

Another drawback of rodenticides is the risk of secondary poisoning.

“When beneficial predators like owls and hawks eat rodents that have ingested poison, they can become very weak and die,” says Alex Godbe, director of The Hungry Owl Project in Marin County, California. “Secondary poisoning is devastating to raptor populations as well as other animals like coyotes, bobcats and mountain lions, all of which help to keep rodent populations down. As their numbers decline, we only increase our pest problems.” In addition, the killing of protected species is a violation of state and federal law.

• Integrated pest management. IPM is a system of control that incorporates prevention and environmentally friendly control to keep wildlife out of structures or from damaging crops. Vineyard owners in California, Oregon and Washington State have been using barn owls for rodent control for decades. Horse owners can use similar strategies by installing barn owl nesting boxes facing outward, away from the barn, to discourage owls from entering. While research shows that owls can transmit sal-monella through their feces, the advantage of their presence far outweighs the risk. In fact, according to Godbe, it’s a proven, safe and highly effective method of keeping rodent populations down. “The average barn owl family consists of four to five chicks, and those chicks have enormous appetites, eating up to six or more rodents per night. We have a lot of success stories from farmers, homeowners, orchards and stable owners who have installed owl nesting boxes.” For information on height, placement, and best locations for nesting boxes, visit The Hungry Owl Project at www.hungryowl.org.

The onset of cold weather is a powerful motivation for mice and other pests to seek safe shelter. “Animals will search for food and shelter in the fall,” says Simon, “but if you follow a good prevention program, they’ll look elsewhere for shelter---and stay out of your barn.”

This article first appeared in EQUUS issue #457, October 2015.