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apisanitas.HONEY BEE HEALTH
Predators

Mice and rodents

Severity : Moderate Autumn and winter; stored combs all year roundReview in progress
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Key points

  • Wood mice and house mice move in during autumn, when the cluster contracts and no longer guards the outer combs.
  • Shrews are insectivores: they do not chew wax, they eat cold, sluggish bees.
  • A mouse guard fitted before the first cold spell, on a hive with no intruder inside, solves most of the problem.
  • Stored combs must be kept in a room or stacks that rodents cannot get into.
  • No poison baits in the apiary: they also kill birds of prey, foxes and pets.

In winter, a hive offers a small mammal everything it wants: a dry shelter, some warmth, wax for a nest, honey, pollen and bees to eat. While the colony is active, guard bees drive most intruders away. But once the cluster contracts in the middle of the brood box, the outer combs and the floor are no longer defended2.

Mice are not a disease, and they rarely kill a strong colony on their own. Yet the damage they do is real and easy to prevent: chewed combs, fouled stores, a cluster disturbed in the depth of the cold.

The animals involved

Rodents: wood mice and house mice

In Europe, the wood mouse (Apodemus sylvaticus) is a frequent visitor to apiaries in the countryside, along woodland edges or near hedges. The house mouse (Mus musculus) prefers buildings: it is found mostly in honey houses, barns and rooms where supers and combs are stored. These small rodents get through surprisingly small holes: a technical fact sheet on rodents states that the house mouse squeezes through openings more than 6 mm in diameter3.

Once inside, the rodent builds a nest of chewed wax, grass and leaves, usually in a corner of the floor, away from the cluster.

Shrews: insectivores, not rodents

Shrews (genera Sorex, Crocidura…) look like small mice with a pointed snout, but they are insectivores. They do not chew combs: they eat bees. In Canada, the New Brunswick apiary inspection service describes the pygmy shrew (Sorex minutus) as an underestimated threat to overwintering colonies: the animal, which weighs about 3 g and eats more than its own weight every day, grabs a sluggish bee from the edge of the cluster, carries it away and hollows it out, removing the head or opening the thorax4. The same source recommends a winter entrance of about 6 mm against them. How significant the problem is in Europe is less well documented, so caution is needed about its scale.

When and why they get in

Intrusions begin in autumn, as temperatures drop, and continue all winter. The critical moment is when the colony forms its cluster: bees no longer patrol the floor, and a rodent can move in without being stung. Wide entrances, damaged floors, ill-fitting crown boards and nucs with large entrances all make it easier7.

Damage

  • Destroyed combs. Rodents cut into combs, often on the outer frames and the bottom of frames, to build their nest. Woodwork may be gnawed too2.
  • Fouled stores. Urine and droppings contaminate wax, honey and pollen; affected combs must be cleaned or rendered1.
  • Disturbed cluster. Constant comings and goings make the colony eat more. A US extension publication links the presence of mice to more dysentery and mortality2.
  • Lost colonies. A British beekeeper reports the complete loss of a strong nuc occupied by a family of mice for a few winter weeks7.
  • Bees eaten. With shrews, it is the cluster population itself that shrinks4.

Recognising their presence

  • Coarse chewed wax debris, mixed with twigs, grass or leaves, on the floor or in front of the entrance.
  • A compact nest in a corner of the floor.
  • A strong smell of urine when the hive is opened7, black droppings.
  • Combs cut away, especially on the outer frames.
  • Small piles of wings, legs and bits of abdomen, bees without heads or with an opened thorax: the signature of shrews4.
Photo needed — Hive floor at the end of winter with chewed wax debris, dry grass and a mouse nest in a corner.

Do not confuse

Observation Rodent Other possible cause
Wax debris on the floor Coarse pieces mixed with plant material, nest Fine “sawdust” from normal winter uncapping
Destroyed combs Clean cuts, droppings Silken tunnels and cocoons: wax moth
Piles of dead bees Heads or thoraxes missing Whole bees: winter losses
Hole in the hive wall Hive gnawed from inside Hole drilled from outside: woodpecker

Woodpeckers, the other winter predator

Some woodpeckers attack hives, mainly in hard frosts. In Britain, the green woodpecker (Picus viridis) is known to drill through the walls of brood boxes, level with the frame lugs, when temperatures stay below freezing for long periods; the behaviour appears to be learned and varies from one area to another6. In a German study of wild colonies living in tree cavities, several woodpecker species (grey-headed, green, great spotted and middle spotted) were filmed pecking at the combs5.

Common protections are chicken wire stretched on canes around the hive, or a plastic sheet fixed to the sides of the box, which stops the bird from getting a grip6.

Photo needed — Brood box drilled by a green woodpecker level with the frame lugs, after a cold spell.

Diagnosis

Diagnosis is visual. In winter, look at the front of the hive and, if the floor is open mesh with a tray, at what lies on the tray. At the first spring inspection, lift the outer frames and examine the floor. A dead hive should be examined properly before blaming rodents: their presence is often a consequence of the colony’s death, not its cause.

Regulation

Rodent damage is not subject to any health notification in France. Rodenticides are biocidal products whose use is regulated; rules on access and use vary between countries.

Prevention

  1. Fit a mouse guard or entrance block before the first cold spell. Regional bee health bulletins in France repeat this every autumn9. An opening about 7 mm high is often quoted; commercial entrance blocks in France offer passages of that order (up to 8.5 mm depending on the model), while North American guides recommend openings of about 9.5 mm (3/8 inch)11. Since mice get through holes over 6 mm3, there is no universal figure. The lower the opening, the better it also keeps out young mice and shrews, but the more likely it is to clog with dead bees.
  2. Check the hive has no intruder before closing it: a guard fitted too late shuts the rodent inside8.
  3. Close other gaps: damaged floor, ill-fitting crown board, feeder holes, gnawed corners.
  4. Raise hives off the ground and cut the grass around them to reduce cover.
  5. Use the hive’s entrance reducer if it is well designed; some reversible floors have a winter position that lets only bees through8.

Protecting stored combs

Out of season, supers and drawn combs attract rodents as much as hives do. It is common to stack them on a solid board with a well-fitting lid, or to keep them in a room whose doors and cable openings are sealed. This must remain compatible with wax moth control and with the rules for disinfecting equipment.

Why avoid poison baits

The anticoagulants used as rodenticides also poison non-target animals: birds of prey, carnivorous mammals, dogs and cats, either by eating the bait or by eating a poisoned rodent. A global review documents such secondary poisoning in many mammals and birds10. A well-fitted physical barrier makes poison unnecessary.

In practice: what beekeepers actually do

The rodent problem is solved mostly by organisation: fitting the right protection at the right time, and removing it in time.

The calendar

  • Late summer or early autumn: most beekeepers fit guards while preparing hives for winter, before the first frosts.
  • In winter: a quick look at each apiary visit to check that guards are in place and not clogged with dead bees.
  • In spring: guards are removed or opened up once foraging clearly picks up again, so as not to hinder pollen loads.

The end-of-winter check

  • Look at the floor: coarse wax debris, plant material, droppings.
  • Lift the outer frames and notice the smell when opening.
  • Remove the nest and fouled combs; clean or replace the floor if needed.
  • Note which hives were affected, to review how they are closed next autumn.

The kit

  • Metal mouse guards or entrance blocks, with nails or drawing pins to fix them.
  • Entrance reducers and floors in good condition.
  • Chicken wire or plastic sheeting for apiaries exposed to woodpeckers.
  • Lids and solid boards for stacks of stored combs.

The checklist

  1. Hive inspected, no intruder before fitting.
  2. Guard fixed, no other way in.
  3. Grass cut around the hives.
  4. Stored combs in closed stacks.
  5. Floor checked at the first spring inspection.

The most common mistakes

  • Fitting the guard too late, with a mouse already inside.
  • Forgetting nucs, often the most vulnerable with their large entrances.
  • Leaving guards clogged with dead bees at the end of winter.
  • Leaving guards on too long in spring.
  • Storing supers open in a room used by mice.
  • Putting down poison in the apiary or honey house without weighing the risk to wildlife.

Frequently asked questions

Can a mouse kill a colony? A strong, well-closed colony usually gets away with damaged combs. But a family of mice settled in for several weeks can destroy a colony, especially in a nuc7.

Can chewed combs be saved? A lightly damaged, unsoiled comb can be repaired by the bees. If it is soaked with urine or droppings, it is better to render it.

Do mouse guards stop shrews? Not always: shrews are smaller than mice. Where they are a problem, a lower winter entrance of about 6 mm is recommended4.

References

  1. FAO, IZSLT, Apimondia, CAAS (2021). Good beekeeping practices for sustainable apiculture. FAO Animal Production and Health Guidelines No. 25.
  2. Brummel C., Kittle S., Lynch-O'Brien L., Weller S., Wu-Smart J. (2024). How to Build an All-Season Mouse Guard for Langstroth Honey Bee Hives. NebGuide G2361, Nebraska Extension, University of Nebraska-Lincoln. extensionpubs.unl.edu
  3. English Heritage. Pest Fact File No 15: Rodents. english-heritage.org.uk
  4. Vita Bee Health. News of the shrews (account by F. Colpitts, Chief Apiary Inspector, New Brunswick). vita-europe.com
  5. Kohl P.L., Rutschmann B., Sikora L., Wimmer N., Zahner V., D'Alvise P., Hasselmann M., Steffan-Dewenter I. (2023). Parasites, depredators, and limited resources as potential drivers of winter mortality of feral honeybee colonies in German forests. Oecologia 202: 465-480. doi.org
  6. The Apiarist (2014, updated 2024). Woodpeckers. theapiarist.org
  7. The Apiarist (2016). Mouseguard. theapiarist.org
  8. Fert G. (2022). Visite de contrôle d'un rucher en automne. Abeilles & Fleurs No. 852. apiservices.biz
  9. Bulletin régional de la santé de l'abeille, Bretagne, No. 7 (October 2025). DRAAF Bretagne and partners. draaf.bretagne.agriculture.gouv.fr
  10. Nakayama S.M.M., Morita A., Ikenaka Y., Mizukawa H., Ishizuka M. (2019). A review: poisoning by anticoagulant rodenticides in non-target animals globally. Journal of Veterinary Medical Science 81(2): 298-313. doi.org
  11. Carolina Honeybees. Why do beekeepers need mouse guards? carolinahoneybees.com

Updated : October 8, 2026
Written by : Apisanitas editorial team
Reviewed by : Review in progress