Mouse Guard for Beehives: Why You Need One, When to Fit It, Pros and Cons
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A mouse guard for a beehive is a strip of metal with rows of holes about 3/8 inch across, fitted over the hive entrance. The holes are big enough for worker bees to walk through but too small for a mouse. Fit one in fall, before the first cold nights send mice looking for shelter, and take it off in spring once the colony is flying strongly. In most cold and temperate climates it is one of the cheapest ways to protect a colony over winter.
Below: why mice move into hives, how a guard works, when to fit and remove it, the honest downsides, how to make one from hardware cloth, and what to look for if you buy one.
Why mice move into beehives
As nights turn cold in fall, field mice look for a dry, sheltered spot to nest. A beehive is ideal: it is warm, it smells of food, and once the bees pull into a tight winter cluster at the top of the hive, the bottom box is left largely unguarded. Clustered bees do not leave the cluster to defend the far corners, so a mouse can move in, chew out a nest cavity in the lower combs and settle down for the winter.
The damage is real:
- Destroyed comb. Mice chew through drawn comb and frames to make room, then line the nest with grass, leaves and shredded wax.
- Eaten stores. They eat honey, pollen and sometimes the bees themselves.
- Contamination. Urine and droppings foul the comb. Bees may refuse to use it in spring, and it usually needs replacing.
- Stress and loss. A disturbed winter cluster burns more of its stores, and a colony already weakened by mites or low stores may not survive.
Many beekeepers only discover the problem in spring when they open a dead colony and find a nest in the bottom box. If that happens to you, our guide to deadout inspections will help you work out what went wrong. For other hive raiders, see beehive pests from mice to bears.
How a mouse guard works
It comes down to size. A young mouse can squeeze through a gap about 1/4 inch high, which is less than the height of a standard Langstroth entrance or even the notch of a wooden entrance reducer. Mice can also chew a wooden reducer to widen it. A metal guard with round holes about 3/8 inch across solves both problems: bees fit through easily, and the round shape and hard metal leave a mouse nothing to squeeze into or gnaw.
Most commercial guards are a strip of stainless or galvanized steel the width of the hive, pinned or screwed across the entrance. Some are sliding designs that double as an entrance reducer, with a row of bee holes on one side and smaller ventilation holes on the other.
When to fit and remove a mouse guard
Fitting it in fall
Put guards on before the first frosts, when night temperatures start dropping toward freezing. In much of the northern US that means September or October; in milder areas it may be November. The key is to beat the mice. A guard fitted after a mouse has moved in simply locks it inside.
- Check the bottom box first. On a mild day, look for chewed comb, nest material or droppings on the bottom board. Evict any mouse before fitting the guard.
- Fit it when bees are home. Early morning, evening or a cool, rainy day, so you are not shutting foragers out.
- Close every gap. Check the upper entrance, gaps under the outer cover and any holes in old boxes. A mouse will find the one you missed.
Fitting mouse guards sits naturally alongside the other jobs on our fall beekeeping checklist and our guide to preparing hives for winter.
Removing it in spring
Take the guard off once nights stay above freezing and the colony is building up, with plenty of foragers bringing in pollen. That is usually around the time the fruit trees and dandelions bloom. By then mice have moved outdoors, and a strong spring colony can defend a full entrance. Leaving the guard on into late spring slows traffic when the colony needs it least.
The downsides: pollen and dead bees
Mouse guards are not perfect, and it is worth knowing the two common complaints.
Pollen scraping. Some beekeepers report that foragers squeezing through 3/8-inch holes knock pollen loads off their legs, and you may see pollen pellets on the landing board. This matters most in early spring when the colony needs pollen for brood. It is a good reason not to leave guards on longer than necessary, and a point in favor of guards with slightly larger holes or 1/2-inch mesh.
Dead bees clogging the holes. Over winter, bees die naturally and the undertakers drag them to the entrance. In cold weather they cannot always get the bodies out through the small holes, and a pile can build up and block the guard. Check entrances after cold spells and clear them with a bent wire or stick. A guard fitted slightly above the bottom board, or a hive with an upper entrance, reduces the risk.
Mouse guard pros and cons
| Pros | Cons |
|---|---|
| Keeps mice out while bees come and go | Can knock pollen off returning foragers |
| Metal cannot be chewed, unlike a wooden reducer | Dead bees can block the holes in cold weather |
| Cheap and quick to fit | Slows traffic if left on into spring |
| Also narrows the entrance against robbers and cold drafts | Useless if a mouse is already inside when fitted |
| Lasts for many seasons | Needs a quick check after each cold spell |
For most beekeepers in areas with real winters, the pros win easily. The downsides are managed by fitting and removing the guard at the right time and glancing at the entrance now and then.
DIY mouse guard from hardware cloth
You can make a perfectly good guard from 1/2-inch hardware cloth, the galvanized wire mesh sold at hardware stores. The 1/2-inch squares let bees pass freely and keep mice out.
- Cut a strip the width of your hive front (about 16 1/4 inches for a 10-frame Langstroth) and 3 to 4 inches tall. Wear gloves; the cut edges are sharp.
- Either fold it lengthwise into a long “V” and press it into the entrance, or lay it flat over the entrance and staple or tack it to the front of the bottom board.
- Make sure there are no gaps at the ends or along the bottom.
Do not use smaller 1/4-inch mesh. Bees struggle to get through it, drones cannot pass, and it strips even more pollen. Check the mesh size on the label; 1/2-inch and 1/4-inch hardware cloth sit side by side in most stores.
Our mouse guard picks
When buying, look for stainless steel (it will not rust), a width that matches your hives, and screws or pins included. Adjustable sliding guards are handy if you run a mix of 8- and 10-frame Langstroth hives.
1. BeeCastle Stainless Sliding Mouse Guard and Entrance Reducer, 4-Piece (best all-season guard)
This stainless steel guard does two jobs. One side has round holes for the bees, so it works as a mouse guard all winter; the other side has small holes that let air in while closing the entrance to bees, which is useful when you move a hive. The sliding design adjusts from 7-7/8 to 16 inches, so it fits both 8- and 10-frame hives, and the set includes 16 screws for fitting the four pieces.
- Good: Mouse guard and entrance reducer in one; adjustable for 8- and 10-frame hives; screws included
- Watch for: Screws into the hive front, so it takes a few minutes longer to fit than a push-in guard
2. Stainless Steel Sliding Mouse Guard, 4-Piece (best for mixed hive types)
This four-piece stainless sliding guard adjusts from 11.81 to 15.75 inches wide. The listing says it fits 8- and 10-frame Langstroth hives as well as Flow, Layens and Warre hives, which makes it a practical choice if your apiary has a mix of hive styles and you want one guard that covers them all. Stainless steel will not rust or be chewed through, so one set should last many winters.
- Good: Wide adjustment range; listed for Langstroth, Flow, Layens and Warre hives
- Watch for: Minimum width is 11.81 inches, so measure narrow entrances before buying
Frequently asked questions
Do I really need a mouse guard on my beehive?
If you get freezing winters and have fields, woods or outbuildings nearby, yes. Mice are one of the most common causes of winter comb damage. In warm climates where colonies never cluster tightly, many beekeepers skip them.
What size holes should a mouse guard have?
About 3/8 inch for round holes, or 1/2-inch square hardware cloth. Both let worker bees through and keep mice out. Smaller openings make it hard for bees to get in and out.
When should I put a mouse guard on?
In fall, before the first frosts, typically September or October in northern areas. Check that no mouse is already in the hive before you fit it.
Can I use an entrance reducer instead of a mouse guard?
A wooden reducer on its smallest setting helps, but it is not reliable. Young mice can squeeze through the notch, and mice can chew wood to widen it. A metal guard is the safer choice.
How do I know if a mouse is in my hive?
Look for chewed wax, grass or leaves and droppings on the bottom board or at the entrance, and a musty smell. Bees that are unusually agitated in cold weather can be another clue.
A mouse guard costs little and takes minutes to fit, and it can save a winter’s worth of comb. For more cold-season advice, see our bee care guides.
