One mouse can easily kill a colony. This is one of those awkward facts.
Had a very interesting conversation this week with a Bee Farmer with many years of experience running hundreds of colonies. He says an I have no reason to disbelieve him that he has never had a mouse problem with his hives. The odd one in the honey store house but not the bees. When asked about his floors he does not use mouse excluders but has all of them made with an 8mm slot entrance. In other words he has designed/engineered out the problem.
Some of our manufacturers could pay attention to this issue or is it not done as mouse excluders would no longer be needed and of course year on year that amounts to quite a lot of sales.
Are we being mugged by the vendors? Just a thought.
So before you buy that poly hive measure the entrance as it too should be no more than 8mm deep. There is no need for more in my experience.