Why, How and When to Use a Mouseguard 

 

As winter approaches, beekeepers have several important jobs to complete to give their colonies the best possible chance of making it through the colder months.

One small but important task is protecting the hive entrance from rodents. A mouseguard, sometimes called a mouse excluder or mouse entrance guard, can help to prevent mice from getting into the hive while still allowing bees to use the entrance.

Mice are attracted to beehives during cold weather because they provide exactly what mice need: shelter, warmth and protection from the elements. Once inside, however, a mouse can cause considerable damage to a colony at a crucial time of year.

 

Why do mice enter beehives?

During autumn, mice begin to look for sheltered places in which to overwinter. An occupied hive can be particularly attractive because the cluster of bees produce warmth, while the wooden hive provides protection from the elements.

Once inside a hive, mice will build nests from insulation material, debris and pieces of comb. They will also chew through comb and eat stored honey and pollen. 

In addition, the presence of mice can disrupt the colony during these crucial months. A colony that has been well prepared for winter can still be put under unnecessary stress – which can be avoided by fitting a small, simple guard. 

 

What does a mouseguard do?

A mouseguard is fitted over the hive entrance and has openings that are large enough for honeybees to pass through but too small for mice.

There are several designs. Some are perforated metal strips, with a series of slots or holes, while others are castellated, with openings that look like the teeth of a saw blade. There are metal and plastic designs available. The important design element is that the guard should restrict access to mice without preventing honeybees from entering or leaving the hive. Before purchasing, it is also important to ensure that the mouseguard you purchase is appropriate for the hive type and entrance size you have. 

The guard also needs to be securely attached. A determined mouse can exploit a surprisingly small gap, so a loose or poorly fitted guard can provide little protection. Before ordering a mouseguard, ensure that it will fit your hive type. Most guards will fit more than one of the standard hive types but may have to be cut down for certain hives – always check the product description carefully. 

Have you seen the RoBo-Block?

The RoBo-Block offers several features in one handy block. The only entrance block you will ever need? Made for National (405mm), Commercial (405mm), Dadant (425mm), Langstroth (367mm) and Smith (417mm) hives.

Alternatively, the expanding RoBo-Block will expand to fit entrances between 360mm - 425mm.

For those keen to examine pollen, turn the block away from you through 90 degrees and expose a 6mm entrance slot on the left-hand side (this also acts as a mouseguard) plus a bank of 5mm pollen stripping holes on the right-hand side with an alloy slide to expose either feature. Below the stripping holes is a shallow, removable tray which collects the pollen samples. The block will only need to be set to pollen stripping for a matter of minutes as samples will build up rapidly.

In its main position the block is either an entrance ventilator of 3mm holes on the right-hand side or an anti-robbing device of 6mm holes on the left-hand side, with a further row of 6mm holes off-set on the opposite side. Bees in the hive can find their way out and back again. Robbing bees or wasps find it difficult to negotiate both banks of holes. The adjustable alloy slide is used to close the entrance as required, exposing the ventilation holes. Also in this position, the slides can be extended outwards and tacked/screwed to the floor joists; thus the hive will be completely closed and secure if you are planning to move it any distance.

 

When should a mouseguard be fitted?

Timing depends on the local climate and the behaviour of both the honeybees and the mice. In the UK, mouseguards are commonly fitted in autumn, once temperatures begin to fall and mice are actively seeking winter shelter.

You shouldn’t fit a mouseguard too early if the entrance is still heavily congested with honeybees or if the colony is dealing with large numbers of flying bees. You should also check the entrance regularly after fitting the guard to make sure it has not become blocked with dead bees (because the house bees will not be able to clear out dead bees through a mouseguard), leaves or other debris.

As every colony and local climate is different, there is no one-size-fits-all approach. Generally speaking, in the UK, mouseguards are installed in late autumn (typically October) before the bees form a tight winter cluster and stop actively guarding the entrance. 

How to fit a mouseguard

Before fitting a mouseguard, inspect the entrance and remove any debris that is obstructing it. Make sure the colony has an appropriately sized entrance for the time of year.

Position the mouseguard so that its openings line up with the usable part of the entrance. Secure it firmly to the hive (usually using pins).

After installation, watch the entrance for a short period if weather conditions permit. Bees should be able to negotiate the openings without excessive difficulty.

It is particularly important to check the mouseguard after windy weather or other conditions that could cause leaves and debris to accumulate around the entrance.

 

Should you fit a mouseguard over an entrance block?

No, a mouseguard should not be fitted over an entrance block or entrance reducer. Existing wooden entrance blocks or reducers must be removed before attaching your mouseguard. 

Leaving an entrance block or entrance reducer in place behind a mouseguard will restrict ventilation, it can trap moisture inside the hive, and it will block the bees clearing dead bees or debris from the hive. 

Remember that a wooden entrance block or entrance reducer will not be enough to protect from mice, even when reduced to a very small entry, as field mice can easily chew through cedar or other wood to get inside. 

Be careful with ventilation

A mouseguard should not be regarded as a substitute for good winter hive management. The colony still needs adequate ventilation and protection from excessive moisture. At the same time, the entrance should not be so restricted that dead honeybees, snow or debris prevent the remaining honeybees from getting out. The exact approach will depend on the type of hive, its entrance arrangement and the conditions in the apiary.

Don't forget woodpeckers and other winter problems. Rodents are only one of the challenges facing a hive during winter. Strong winds can move hive components, and woodpeckers or other animals may cause damage. A winter inspection should therefore include checking that the hive is stable, the roof is secure and the entrance remains clear. A mouseguard is a relatively simple piece of equipment, but it forms part of a larger winter-management strategy.

 

Remove or adjust the guard in spring

Do not forget your mouseguards once winter is over! As temperatures rise and the colony becomes more active, the entrance may need to be opened up again. A restricted entrance can become a significant bottleneck for a rapidly growing colony, particularly when the bees are beginning to forage heavily.

Inspect the colony and entrance as part of normal spring management and remove or adjust the mouseguard when conditions require it.

 

A small precaution that can prevent a big problem...

A mouseguard is inexpensive, simple to fit, and easy to overlook. However, preventing a mouse from establishing itself inside a hive is a lot easier than dealing with the damage afterwards.

For most beekeepers, the basic principles are straightforward: as autumn arrives, reduce the entrance appropriately, take steps to prevent mice from getting inside, keep the entrance clear of debris, and remember to reassess the entrance when spring arrives.