By now you’ve probably heard about the newly published study, “Rapid behavioral maturation accelerates failure of stressed honey bee colonies¹.” In my opinion, this is the first paper suggesting a possible cause of colony collapse disorder (CCD) that actually makes sense.
The scientists doing the research used transmitters to learn about the behavior of bee colonies that were under stress. They found that when the foraging force of older workers is rapidly reduced for any reason, young bees quickly replace the missing foragers.
Now this, by itself, isn’t news. Beekeepers have long been aware that worker bees do what is necessary to maintain the colony, and workers will change “jobs” to meet the demand.
But here’s the surprise: they found that young workers who prematurely became foragers made fewer total foraging trips than the older workforce and were more likely to die on their first trip out.
According to the article, in a healthy hive, a worker becomes a forager at 2 to 3 weeks old. But when a colony experiences a situation where more foragers are needed in a hurry, bees that are much younger begin to do the foraging. However, according to the study, these bees are not quite ready for this task and often perish early on. Imagine giving your eight-year-old the car keys and telling him to go buy bread and milk.
So how does this relate to CCD? Well, picture this: you have an active, healthy colony. But for some reason, the foraging force gets in trouble. It could be a pesticide kill, it could be a disease like Nosema, it could be stress from poor nutrition, it could be stress from lack of flowers, or a combination of factors. As a result of the stressors, a large portion of the foraging force dies.
When a large part of the foraging force goes missing, a percentage of the nurses become foragers to take up the slack. But many of these underage or “precocious” foragers don’t make it and they die in the field. As a result, even more of the nurses must become foragers, and many of these die, too.
It doesn’t take long for the colony to go out of balance: there still aren’t enough foragers but now a large part of the nurses are gone as well. Not enough nurses remain to raise a lot of bees, so the brood nest becomes very small and produces very few replacements.
The young foragers die in the field without returning to the hive, and the brood nest is small with just a few bees and a queen remaining. Sound familiar?
The theory isn’t perfect. For example, it doesn’t explain why predators are slow to move into a CCD colony. But overall, it makes sense. It explains why the bees seem to vanish. It explains why the queen is still alive while most bees have disappeared. It explains why the brood nest is so small. It also explains why some collapsed colonies have Nosema and some don’t, why some have many viruses and some don’t, and why some are in heavily infested with mites and some are not.
Like any study, it needs to be replicated and examined. In time perhaps more answers will emerge, but I feel like we are very close to understanding CCD. Now we just have to decide what to do about it.
[line] ¹Clint J. Perry, Eirik Søvik, Mary R. Myerscough, Andrew B. Barron. Rapid behavioral maturation accelerates failure of stressed honey bee colonies. Proceedings of the National Academy of Sciences, 2015; 201422089 DOI: 10.1073/pnas.1422089112
That study provides some very useful information.
Another reason it is important is the fact that a mite will shortens the life of a honey bee by as much as a third. Ordinarily, a worker will spend the final 2 or 3 weeks of her life in the field. Knock a third off her life, and she might get to forage for only a day or two. If that happens to a significant portion of the bees, the colonies’ foraging capacity is severely crippled. The young ‘uns try to make up the difference. But, according to this study, they fail because they aren’t ready.
We beekeepers have a grave responsibility to use effective, approved mite treatments on every colony we manage. Those who think they can keep bees “naturally” will naturally lose their bees to nature within 2-3 years.
Thanks again for your great blog.
An excellent point. When you look at the effect of Varroa-shortened lives in the context of precocious foragers, you realize how quickly a colony can go under.
But if the majority of all bee colonies are treated for mites, how can we explain why these are the colonies suffering most from “CCD”???
Are colonies that are treated for mites most affected by CCD? I’ve never heard that.
Two summer ago I had a colony that was somewhat week, I tried to build it, but the yellowjackets got in to it. What I was left with was similar to what you explained in your post, very little capped brood, too few bees, and a ragged-winged queen. While I have not accredited this to colony collapse, the results of a weak colony and predatory action from wasps was about the same. It probably had to sent young workers to forage who then died and weakened the hive further. The same type scenario, just different causes.
Excellent! I seem to be experiencing this from time to time as well. My problem is that my colonies abandon the lower brood box and try to make it through the winter on just the upper box. It becomes frustrating at times, because if I feed them in the fall or spring, or whenever, they just build up. It’s like they’re constantly moving out of the bottom box, and just leave it empty – open to SHB infestation. But yes, I have had quite a few hives just mysteriously disappear. Some were evident that they had starved, but others, not so obvious.
That is a great article and makes so much sense! While on the topic of varroa, what is your go to treatment for varroa Blaine? I am a newbie and did sugar shake and thymol this fall. When I do choose to feed I put thyme essential oil in the syrup….my bees are looking good so far, been flying about just today and bringing back lots of pollen! Not sure what is blooming here in western NC, but they are finding something!
I feel so lucky that we don’t have Varroa on Maui as of yet–really interesting study, I hope they replicate it soon to verify the thesis.