Many beekeepers become alarmed this time of year when they realize dead bees are covering the bottom board, piled on the landing board, laying on the outer cover, or scattered across the snow. It looks like hundreds! In fact, it probably is hundreds. Many bees die this time of the year and there are many reasons why.
Winter bees are physiologically different than summer bees. Winter bees have more fat bodies and they are designed to live for many months. In contrast, summer bees live only a few weeks. But by late winter, even these winter bees are nearing the end of their lives. More and more will die as spring approaches. By the time brood rearing is well underway, most of these bees will be gone.
In addition to old age, some bees die because of stressful in-hive situations. These include:
- Starvation: Some bees may not have found sufficient food.
- Disease: Any number of diseases may kill winter bees. These diseases include the viruses carried by varroa mites.
- Parasites: The mites themselves can weaken the bees by sucking their fat bodies and hemolymph.
- Cold: Bees on the outside of the cluster may occasionally die of cold. Or bees taking cleaning flights may not make it back into the hive.
- Dysentery: Bees unable to leave the hive for many, many weeks may succumb to the build-up of waste in their bodies. If waste is excreted inside the hive, it promotes unsanitary conditions that may kill other bees.
During the very coldest part of winter these dead bees may not be apparent to the beekeeper. Most die inside the hive and their bodies drop onto the bottom board. The pile can get quite deep without the beekeeper even noticing it. But as the days get warmer, the bees begin to clean the carcasses out of their living quarters. Depending on the temperature they may dump them on the landing board, or fly them out and drop them on the ground or in the snow. Suddenly you see them everywhere, but in truth, they have been collecting all winter long.
If possible, it is a good idea to clear the bottom board of dead bees. You can scrape them out by removing the entrance reducer and running your hive tool or a stick through the hive entrance and dragging it along the bottom board. You don’t have to remove every bee, just make sure the entrance is open. Beekeepers can lose hives to dysentery if the entrance becomes blocked and the bees cannot get out for cleansing flights. Also, if you are using an entrance reducer, it helps to make sure the opening is at the top—not the bottom—of the reducer.
Dead bees on the outside of the hive this time of year are usually a sign that everything is proceeding according to plan. If your cluster is active and has plenty of food, your colony is probably fine.
Honey Bee Suite