I had eight honey bee colonies going into winter last year (2014) and all but two of them were destroyed by shrews. The shrews squeezed through the half-inch mesh I’d been using since 2010 to keep mice out. But no one ever told me about shrews. The little buggers easily squeeze through half-inch mesh. They slip inside and pluck one bee at a time from the edge of the cluster. They eat the bee’s innards, toss away the bits of legs and other desiccated body parts, then climb towards the cluster for more… until they eat approximately 125% of their body weight in bees every day, gradually reducing the size of the cluster until the colony is dead.
That’s how I lost six colonies last year. With only one mated queen and no extra brood, I performed a miracle and managed to expand my remaining two colonies into five colonies last summer. They may not be the strongest colonies I’ve ever seen, but they’re hanging in there (so far). All of my hives have quarter-inch mesh covering every entrance now. Shrews will never get anywhere near my bees again.
Looking back on my notes from last year, along with photos and videos I shot and the memory of the experience burnt in my brain, the first sign of a shrew inside one of my hives seems obvious. It’s in this photo from January 5th, 2015:
It might not look like much, but here’s the deal: The photo was taken on a cold day when the bees in all of my other hives were huddled inside trying to stay warm. But the bees in this colony were flying frantically around the bottom entrance and there were more dead bees in the snow in front of this hive than any of the others, probably from the bees flying out and instantly freezing to death. More dead bees in front of one hive isn’t great, but it’s not necessarily the end of the world. The telltale sign for me was the fact that a large number of bees were flying in and out of the bottom entrance on a freezing cold windy day when they’d normally stay inside. Something had them spooked. I realized afterwards, that was the day a shrew got inside the hive.
And there was nothing I could do about it because it was too cold to open the hive (or so I thought at the time). I came back a few days later and found even more dead bees outside the hive and knew for sure something was absolutely not right. This particular colony was small because it was started from a late-season swarm. It was dead about three weeks later. I saw other signs of a shrew inside the hive over those three weeks (shrew droppings along with pieces of bees everywhere), but I didn’t know what I was looking at. I brought the dead hive home to do a postmortem and found the shrew, alive and well, between two frames where the brood nest used to be.
Today, if I discovered any sign of a shrew inside a hive, I’d tear the hive apart and scare away the shrew, or I’d remove the frames of the brood nest and place them in a new, clean, shrew-proof hive box. Exposing the bees to cold winter air is normally not a great idea, but if I have to choose between that and allowing a colony to be literally eaten to death by a damn shrew, I’ll take my chances and tear the hive apart any day.
A large number of agitated bees pouring out of the bottom entrance on a freezing cold day is not a definitive sign of a shrew inside a hive. But when you’ve got seven other hives showing no signs of activity on the same freezing cold day, I think it’s fair to suspect something’s up. Likewise, a large number of dead bees in the snow in front of a hive is an even less definitive sign of a shrew inside a hive. But when you’ve got seven other colonies with barely a spec of dead bees in front of their hives, I think it’s fair to suspect something’s up.
My experience with shrews is well-documented on Honey Bee Suite as well.