In the Maritimes we see a lot of colonies, in the Spring, that have died as a result of obvious shrew predation. For the first 4 years, I struggled with shrew damage before developing a shrew tight entrance system. This entrance system stays in place from December first till the first natural pollen flow begins. The 1/4″ hole causes the pollen to fall off the bees so I turn it up putting the 1/2″ holes down for the spring entrance reducer. This has prevented shrew damage in our hives for 30 years.