Small Mammal Pests

Small mammals such as mice, rats and shrews mostly enter hives in autumn and winter, when the bees are clustered and cannot defend the entrance. The damage is usually noticed in spring: chewed combs, droppings and a foul-smelling nest. A mouse guard fitted in good time in autumn prevents the problem almost completely.

Which animals, and when?

When the weather turns cold and the bees form a cluster, the lower and outer parts of the hive are left unprotected. A warm, dry hive full of honey and pollen is ideal for rodents looking for winter shelter.

• Mice (house mouse, wood mouse): The most common winter pest. They build their nests in the outer frames, away from the cluster.
• Rats: Being larger, they cause heavier damage to woodwork and frames; they get into neglected, cracked hives.
• Shrews: Small insectivorous mammals; they can slip in through narrow gaps and eat bees in winter. They do less damage to comb than mice.
• Larger mammals such as badgers: They do not enter the hive, but in some regions they scratch at hives, knock them over or force the bottom open to get at brood and honey.

Signs: what to look for at the hive

There is no need to open the hive in mid-winter; most signs can be seen from outside and on the floorboard.

• Wax crumbs and pieces of comb in front of the entrance: These show that there is chewing going on inside.
• Nesting material on the floorboard: Dry grass, leaves, paper and shavings.
• Rodent droppings and a sharp smell of urine: Bees dislike the smell and are reluctant to use soiled frames.
• Chewed frames and combs: Hollows, especially in the lower parts of the outer frames away from the cluster.
• Dead bees in front of the hive or on the floor with their heads or thoraxes eaten.
• A restless, scattered cluster: A colony that is constantly disturbed consumes more stores and weakens; weak colonies may not survive the winter.

Prevention: mouse guards and entrance reducers

The lasting solution is to physically prevent the animal from entering the hive. A perforated metal strip fitted across the entrance (mouse guard) lets bees through but stops mice.

1. Timing: Fit the guard in autumn, before the nights turn cold and the cluster starts to form. In regions with mild winters it is also safe to fit it in autumn.
2. Check inside first: Before fitting the guard, make sure there is no mouse in the hive; otherwise you will trap the animal inside.
3. The right size: The holes in commonly used guards are about 9.5 mm. The height of the entrance gap must also be narrow enough to keep mice out; a gap left open beside or under the guard makes the whole measure useless.
4. Blockage by dead bees: Throughout the winter, especially after cold spells, check from outside whether the entrance is blocked with dead bees; if it is, clear it with a thin stick.
5. Remove it in spring: Once the colony expands and starts bringing in a lot of pollen, take the guard off; the metal edges can scrape off the pollen loads.

Also repair cracks in the hive body, loose floorboards and gaps around the roof. Keeping the hive on a stand both reduces humidity and makes it harder for rodents to get in.

What to do if a mouse has got in

1. On a suitable, windless and mild day, open the hive briefly; remove the mouse and the nesting material.
2. Take out chewed combs soiled with droppings; set heavily soiled frames aside for rendering.
3. Rearrange the colony with clean frames of honey and pollen next to the cluster; do not leave the hive unnecessarily large.
4. Clean the floorboard and fit a mouse guard.
5. Check the colony in spring; if it is weak, consider uniting it with a strong colony.

Protect the comb store

Empty combs in storage also attract rodents; the damage is often greater than in the beehive. Store combs off the ground in rodent-proof closed cupboards or tightly closing hive boxes. Seal gaps under store-room doors.

Common mistakes

• Fitting the guard in mid-winter, after the mouse has already moved in.
• Reducing the entrance but leaving the gap between the floorboard and the hive body open.
• Leaving the hive too large for the colony to fill before winter; empty outer frames are a mouse's favourite spot.
• Forgetting the guard in spring and restricting pollen collection and ventilation.

Many small mammals are useful in the ecosystem, and some are protected. The aim is not to exterminate the animals but to cut off their access to the hive and the store.