Absconding
Recently, several readers have reported that they’ve discovered that an apparently prosperous (lots of honey) and populous (lots of bees) colony has simply vanished from the hive.
Although some readers were asking if their hives had swarmed, this kind of sudden disappearance—called an absconding—is very different from a swarm. Absconding is believed to be triggered by such a significant threat that the bees are willing to abandon the colony. It can be understood as an act of desperation.
First, however, let’s look at why I am always pretty sure from the reports that the hives haven’t swarmed. When a colony swarms, it leaves behind not only the physical resources (honey and pollen) needed to nourish the parent colony, but there are also always adult bees, brood, and most importantly, developing queen cells. While a late- swarming colony might appear to be markedly smaller than it was a week or two before, it will also show these unmistakable signs, particularly the queen cells. And what readers are reporting are colonies that are completely empty, or nearly so.
But if the bees did abscond, why would they undertake such a low-success project? In Africanized bees, a pollen or nectar dearth is sometimes a cause for absconding. In this case, it is a form of seasonal migration from a poor resource site to a better one. European bees don’t abscond for this reason, and often the reports of absconded hives indicate there are still honey and pollen resources in them.
With European bees, absconding is seen as a response to a severe and sustained threat, such as the smoke from wildfires, repeated nocturnal attacks by mammals like skunks, and even the persistent dripping of water onto the hive top. But the most common threats are the presence in the hive of other noxious insects: ants, yellow jackets, small hive beetles, and of course, the usual suspects in all kinds of bee problems - varroa mites. Keep in mind, the simple presence of any of these issues is unlikely to cause the bees to abscond. The problem needs to be prolonged and severe for the bees to take such drastic action.
For beekeepers, this sudden disappearance of an apparently flourishing hive is very upsetting. It’s still worthwhile trying to understand what factors led up to it, if only so you can try to prevent a recurrence and know whether your hive equipment is safe to use for future bees.
The first thing to do is sit down and work out what you can recall of conditions inside the hive over the previous 6 or 8 weeks. Work out when you last inspected the brood nest, and what was seen. Look up your mite counts and the dates of any treatments you applied. Note any days when a lot of activity was seen outside of the hive, although this could have been either home bees at work and orienting, or a scrum of robbers that had found a weak, undefended colony.
Next, examine the ground around the hive. Are there dead bees visible on the ground? If so, scoop some up and look closely at them to determine their sex (are they drones or workers?) and whether the bees show signs of deformed wing virus, with stunted, misshapen wings. Look at the front entrance for signs of scratching done by skunks to lure bees out at night.
Then open the hive and look for frames with honey. (If you find honey in the frames, the frames will need to be protected to keep them safe from robbing and insect damage.) A hive that has been robbed out will have capped honey cells that have been partly torn open, with lots of loose capping crumbs on the floor of the hive. Finding that the hive has been robbed, however, doesn’t tell you when that happened, nor the reason the hive was vulnerable.
Next, work down to the brood frames. Do you see any capped cells? If you see patches of brood, look for signs of brood disease: pierced or depressed cells, dark dried scales at the bottom of open cells, discolored larvae in twisted or slumpy positions. There are accurate field test kits for brood diseases, but before you order one, why not send us some pictures of what you’re seeing? Because these signs (except for the scale of American foul brood) can also appear in the case of parasitic mite syndrome. This kind of inspection is often done after a winter deadout; read more details about doing that here.
In some parts of the country, ants and yellow jackets can rise to the level of an existential problem for bees, but generally they are just nuisances, or only risky for very weak colonies. Of the two other pests, small hive beetles and varroa mites, it is the mites which are the most common cause of severe trouble for bees.
If you see signs of small hive beetles, keep in mind that they may have moved in after the colony departed. Generally, it takes small hive beetles a while to build up to a crisis level.
Mites, however, are nearly always present and if not previously controlled in summer, they can overwhelm a colony. Perhaps enough so that the bees are prompted to run away from home in order to escape them, no matter how risky that choice may be. But overwhelming mites, and the deadly viruses they spread, can also kill a colony outright, so it may be hard to tell if the colony left or merely died at home.
Turn some of the brood frames upside down so you can see into the roofs of the cells and look for the tell-tale signs of unchecked varroa: little white specks of guanine, or mite poop. A healthy colony’s nurse bees will keep removing the guanine when they clean and polish the cells. A colony under heavy mite stress, however, doesn’t have the resources for that effort.
Of course, it doesn’t really matter whether the bees died in the hive, or left for parts unknown. You’ve still lost a colony. What you need to do at this point is protect the comb resources, especially if you also see small hive beetles or wax moths. Unlike mites which perish or depart with the bees, small hive beetles and moths will continue to scavenge in the combs. Freezing frames is a quick way to kill adults, larvae, and the invisible eggs.
The only reason not to reuse the equipment would be if you see signs of brood diseases which can persist on the combs, in the case of American foul brood, for decades. If you suspect a brood disease, you may wish to request a visit from your local bee inspector to get expert eyes on the frames.
Beekeeping can be thrilling and lots of fun, but when one of your hives absconds, it’s very hard to take. Use your chagrin to try to figure out why, in order to avoid that problem in the future. And honor your departed bees’ by protecting the combs they made so that they can be passed on to new bees next spring.
