Beekeepers in many areas of the country, including Southeastern Missouri, struggle with controlling mice in the apiary.  The hive is a nice, sheltered, relatively warm area for them to seek refuge from the cold and wet during the winter months.  While in the hive, mice can wreak havoc, destroying comb and foundation as well as leaving behind nasty bedding, food remnants, and potentially disease-laden feces and urine.  A well-prepared beekeeper will take reasonable precautions to reduce the possibility of mice gaining entrance into the hive in cold months when the bees are clustering, unable to defend their hive.

How do we keep the mice out?  Well, there are quite a few commercial mouse guards that can be purchased, from suppliers such as Mann Lake, Kelley, Amazon, as well as Isabee’s.  Or, those with even a slight amount of DIYer in them can devise something, even as basic as hardware cloth affixed to the front of the hive covering the bottom board.  Some say they must be made from metal because mice can chew through wood, plastic, and other materials.  Some even suggest hardware cloth is child’s play for a determined mouse.  So, what to do?

I recently came across some YouTube videos and associated web pages from Matthias Wandel (I learned about Matthias from Frederick Dunn, a beekeeper in PA) in which he experiments first with how small a hole a mouse (and shrew) can get through, followed by how small a gap a mouse can fit through.  Since most of us use an entrance reducer and essentially use a rectangular entrance, the gap experiment is probably most applicable to us.

Check out Matthias’s videos and associated web pages here:

How small a hole can a mouse get through? –,

Smallest gap for a mouse experiment lego machine –,

The long and short of it?  11 mm (0.43″) seems to be too small for an adult mouse’s skull to get through.  So, be safe and go 10 mm (0.39″) if you are not convinced.  In fact, if we made our entrance reducer height to be just at or above bee space (3/8″ = 0.375″), we should be fine.  Whatever width should be OK (your preference) …

Contributed by Terry Romanko

Posted 11/1/2020