Today's plan was to create some hibernation habitat for ours (or indeed) any other bumble queens. I certainly succeeded but before I go on to explain what i did, a few words about Bumble bee hiberation are in order.
About Bumblebee Hibernation
The survival of bumblebees depends on hibernation. A bold claim, perhaps, but since colonies are annual and do not survive from year to year, the future "survival" (i.e. development) of a new colony is solely in the hands of the new-born queen and her ability to find a good place to hiberate and survive the winter. The future existence of several hundred bumblebees depends on her success.
I've found very few scientific papers on Bumblebee hibernation (see Bumblebee Links) - one of the foremost appears to be from 1969 with a more recent study analysing that paper and some its weaknesses as well as providing some new data.
Of course, this stands to reason: it is difficult to track bumblebees in the wild and given that both the process of entering a hibernation spot and emerging from it in the Spring are but momentary occasions, it's more or less down to chance to be in the right place at the right time to observe it. Of course, knowing a little about preferences and habitat could lead one to have a better clue of where to look and perhaps to be able to find bees during hiberation, but such a practice is not desirable.
Therefore, we have gleaned what we can to come up with a strategy for possible hibernation in our garden.
What we've learnt so far is that Bumbles prefer a north-facing location (which helps keep the nest coolness required to prevent them emerging too early in spring) and often hibernate in embankments, under tree stumps or roots and sometimes in/under walls. I've not seen an in-depth analysis of the preferences of each species, this may well be an unresearched area. What we do know is that the Queens will tend to burrow down in loose substrate in order to get deep enough not to get frozen during the winter. This is typically 6 - 8 inches, at least for a usual winter.
At first when I discovered this I nearly abandoned my plan altogether - it seemed to me, without getting the bees well underground, I couldn't guarantee their safety in an above-ground nest box, no matter how well insulated. It looked like I could be tricking them into an environment that would prove to be unsuitable for them.
Then, of course, I had my epiphany. Our boxes are equipped with infra-red cameras; basically very small heaters (as we know from how our "indoor" bumbles loved to gather under them) - so we can actually keep the boxes warm. By controlling the on/off times of the cameras we would in fact be able to keep the boxes at pretty much any temperature that is appropriate. I might even be able to automate the process. So, providing I avoid the risk of making Spring seem to come too early, we should be able to keep the bees very safe from a harsh winter - perhaps more so than out in the "wild".
I fully recognise that the chances of getting a queen to choose one of our artifical locations for hibernation is extremely slim, but we have the nestboxes, so there is no harm in trying to put them to good use.
We had two nestboxes to equip for hibernation so I thought I would try two different designs - each may encourage different types of bees or one may provide a better habitat than the other; either way, we will probably learn more by trying two designs rather than one.
For the first box I placed a layer of very small decorative stones about 2 inches thick at one end of the box. Although the bees are reported to burrow 6 to 8 inches down, obviously this design is not going to allow them to do that. However, I thought it was sensible to give them the potential to burrow at least some distance, especially as the route down into the box is a good 8 inches in its own right. I filled with extra moss then used all of the "nesting material" that the boxes were actually supplied with. This is to fill the available space and provide insulation, bearing in mind that the bees usually burrow down below the surface of the ground so would not expect a "big" open space (unlike the spaces they would choose for a nest).
There is tubing to take the bee into the depth of the box and, although not visible in the above picture, it is also equipped with an infra-red camera and a temperature sensor.
I also thought it made sense to try and re-use the "hummock" I had made in Spring as a disguise for the nest box when queens were nest-searching. Not only would this provide extra insulation but would also help with the subterfuge in trying to create a north-facing "embankment". I had the brainwave to actually turn the shelter round so that it was open at the back and could go flush against the wall. I'm not quite sure why I didn't use it like this in the spring; it seems a far more obvious way to improve the disguise of the box.
All that was required was to drill a hole to take the tube to the nestbox entrance and I decided to embed the thermometer neatly in the surface; here's the finished article.
I'm actually rather pleased with it!
Box 2 is our original "master" nestbox, which we brought indoors to care for the disabled bees. Consequently it is actually equipped with two cameras, but we are only connecting up one.
I decided for this box I would try and create something for a bee to really burrow down into if it wanted. So I took the top off an old olive oil bottle, cut it to shape and filled it with more of the small decorative stones. This would lie on its side at and angle, with the stones loose enough for burrowing (well, that's the plan). There's about 3 inches of "burrow length" in this little chamber.
The plan, therefore, was to install this chamber inside the box then pack it tight all round with insulating material. BCW kindly went out and gathered some more moss and I also used a bit of our old hamster bedding to create a nice cosy chamber. The only open space is immediately in front of the lower camera, just to give is something to look at. Again, a tube extends from the entrance towards the back wall of the box. I also placed some aluminium foil down one wall to help with insulation.
This box is going to be less protected from the elements than box 1 because it is going under our hive "shelter" which is not a tight fit - thus the wooden box will be exposed directly to the elements. Insulation is therefore paramount and so another layer of webbing goes across the top and then I topped this off with some more aluminium foil (not shown).
Again, it is equipped with a thermometer in the central chamber. I really don't think a Queen could ask for a better winter residence!
The completed set up
Here's a picture of the completed setup. Both boxes have been mounted in a North facing position, they are very sheltered and shady. So, from an environmental point of view, the main threat is cold/frost as they are not below ground. (Although, that threat still exists for a bee below ground to a degree.)
Over the course of the next few days we will monitor the temperatures in the box and check for thermal stability - i.e. demonstration that they are insulated from conditions outside and maintain a more consistent temperature. We will also check the effect of having the internal cameras (i.e. infra-red) on and off.
If I'm honest, I'm not really expecting anything to use them, but I'd like to think that a bufftail (which loves to go underground) might at least give the fully-covered box a nosey. I'm really pleased with it - ok so the colours are a bit garish - but I think it has the makings of something that could just about convince a bumble to investigate.
We don't quite know when our (or any) Queens will start looking to hibernate - it may be a month or more yet - it may be sooner. But at least we now have something to offer them if they are curious.