Bees in the cold
Guest post written by Dean Haley
Stingless bees are widely regarded as being unable to control nest temperature like honey bees do. For the vast majority of stingless bees this is very true. Some species however, such as our T.carbonaria and A.australis extend into temperate areas with colder Winters and frosts.
I decided to study the effect of cold on some bees. I put australis, carbonaria and hockingsi in the dairy section of my fridge. I have a digital thermometer that can give me max and min temps since last reset.
BEES IN THE FRIDGE
My fridge ran at 4.1 to 14.8 degrees. Often when I observed the bees the temp was about 7.
Hockingsi fell over straight away and curled up on the floor. At day three I warmed them up and one third revived. By day 5 they were all dead.
Carbonaria were better than hockingsi. They did not fall over and could walk above 12 degrees. All were still alive on day 2 but by day three, 46% had died. There was one left alive on day 5.
Australis were better. At these temperatures they did not fall over at all. They could walk above 12 degrees. 80% were still alive on day 3, 50% alive on day 9 and the last one died day 14.
I also looked at carbonaria brood. 1 day in the fridge did not hurt it. Brood kept in the fridge for either 3 or 6 days was similar in that about 30% of the brood died, usually as a group along one edge.
By the way, carbonaria brood kept at room temperature (range 24 to 29.6 degrees) for 1, 3 or 6 days was unaffected by being out of the colony. All this brood hatched.
I am as you know interested in stingless bees ability to survive in colder parts of Australia. Explorer journals show that stingless bees were once distributed further south than they are today.
BEEHIVE IN THE FRIDGE
Armed with the above data I got really excited. What would happen if I put an entire carbonaria bee colony in the fridge? As long as I took it out before 3 days I shouldn’t kill bees, right?
I talked to my bee buddy, Bob Luttrell to see if there was any data out there. Not too much he said, and he loaned me some Hoboware temperature data loggers (www.onsetcomp.com) and wished me good luck. Thanks Bob, very much appreciated.
I started with a well established T.carbonaria hive in a OATH box. The colony weight was 7kg (bathroom scales) and brood, internal structures and honey pots very well developed. I drilled a hole in the side of the box close to the mid line for my wires. I placed the brood probe between two layers of relatively young brood. The honeypot probe was at the same level in the box, about 2.5 cm from the front of the box.
UNINSULATED BOX
Have a look at the hoboware graph recording 12 days of temperature data. Red line is brood, blue line honey pots and the black line is ambient temperature. There are three sessions where I put the box in the fridge.
The first session is an uninsulated box for 17 hours and watch that blue honey pot temperature crash to 12 degrees. What worries me about this, is that the brood temperature is ok but the honey pots are cold. If bees leave the warmth of the brood area to eat some honey they might get cold an unable to return to the brood area.
SOME INSULATION
The second session in the fridge lasted for 24 hours. The average temperature was about 6 degrees with the odd cold spot as low as negative 3 degrees. My lettuce froze..
I let the box get a bit cold by keeping it without insulation for 5.5 hours and then I enclosed it in foam insulation. This is pretty good insulation covering every surface of the box and without a significant air gap. There were double thicknesses of 25mm insulation at the base and the roof of the box. For me this was a really interesting session because the brood started warming up hours before I took the box out of the fridge. The bees have control of that brood temperature! It is ranging 27 to 30 degrees. It is Superb.
FULL INSULATION
I went for one last session in the fridge. I fully insulated the box in my super foam cover and placed in the fridge for 12 hours. At six the next morning I had the box (fully insulated) outside to catch the morning sun and left the insulated box there for the next two days. I love how the insulation has smoothed out the peaks and troughs of the ambient temperature. I just love it.
IN CONCLUSION
I showed a few friends pictures of my beehive in the fridge and they all asked how is this possible, why don’t they die? The reality is that I had the fridge thermostat set on mild and freezing night temperatures can be common in carbonaria country with day time maximums sometimes less than 10 degrees, so I see the refrigerator experiment as completely relevant. This article really is aimed at country that is generally considered too cold, or marginal for the survival of carbonaria. Now this means cold Winters only, not cold all year around, sorry Melbourne and Canberra!
In southern areas with cold Winters you want some serious insulation on your box. Standard boxes are ok for sunny QLD but not so for the temperate south where a cold snap of 3 or 4 days might kill your bees. That being said there are arguments for thicker walled boxes rather than foam insulated boxes. They look better, last longer and are not prone to get water, pests, ants etc caught between the foam and the inner box.
Feed your bees, please! Looking at these brood temperatures convinces me that they are burning lots of energy (honey) to maintain things. Don’t let them run out of food.
Put them in the sun. Winter sun in southern regions.
When you get those southern cold snaps, when it’s snowing on the tablelands and the pipes in your house are freezing each morning… bring your bees inside for a week. Cover the entrance with flyscreen or whatever and bring them inside. Don’t spray them with the flyspray though.
AUSTRALIS HIVE IN THE FRIDGE
The thermal characteristics of A.australis have been studied by previous authors. Megan Halcroft monitored hive temperatures for 12 months and reported that australis had some ability to warm their brood area. This is especially so in Spring, but the temperature of the brood is not raised much in Autumn and Winter. Megans works is very well presented and set out. I fully encourage you to check out her studies here:
My current study involved a medium strength australis colony in a 2L internal volume box constructed from 40mm thick western red cedar. I inserted a Hoboware temperature probe in the centre of the brood mass (Red Line), and the second probe in the honey pots (Blue Line). Another probe measured Ambient temperature (Black line).
I put them in my fridge a total of three times in this 9 day study. The first time was with an uninsulated box and honeypot and brood temperature followed ambient. A brood temperature of 7 degrees was observed after just 9 hours in the fridge.
A Styrofoam box was used for extra insulation immediately before the second session in the fridge and the styrofoam was left on until the end of the study. The extra insulation has provided some slight advantages. Thermal lag is increased and the minimum temperature experienced inside the nest has not fallen to ambient (refrigerator) temperature even after 12 hours.
CONCLUSION
My study does not show a great ability for australis to control nest temperature. On the other hand the individual australis bees were more tolerant of cold temperature than either carbonaria or hockingsi bees. Based on both bees and hive data, I’d start to worry about your australis hive after one week of extremely cold weather.
There is a real difference in the way that australis and carbonaria react to the cold, and what we can do to help them survive. In truly cold areas I would recommend insulation or thicker boxes for both types of bees. When you get really cold snaps that last for more than a week, consider bringing bees inside, both australis and carbonaria.
SOME FINAL THOUGHTS
What about a beehive that sits inside your house on your windowsill? They won’t get cold.
Dean,
What a great practical experiment you have done .I’m sure this will surprise and help a lot people understand what is required to keep these little guys going in some of the colder parts of their habitat range .Bee’s local to these cold conditions probably do a little better.
What do you think about cooling a hive prior to doing a split? You could then do it indoors with no loss of workers or risk of exposure to natural enemies.
It would be possible I guess, BUT its a lot of mucking about I guess, and it would take a day to cool down the hive.
I do my splits and access to the hives real early in the morning, before sunrise. Bees are dosile and I get no ” flyers”, and very little bees leaving the hive at all. That would be the better go.
Hi Dean
Great to see the dataloggers put to such good use. Certainly there is a lot of food for thought in there, and perhaps in that data is an explanation for the 30% loss rate of Qld bees that are sold south.. Peter Clarke with his styrofoam covers (not without their issues) has found they work, and others are copying. Even up here the covers are coming into use for the other end of the scale, high temperatures. Same issues at play. My historical data shows that styrofoam covers work, both in winter, and in summer. As you say, a thicker box wall achieves much the same result in a neater format. I was amused by the good shifted out of the way in the refridge. I have a spare one, and will be testing boxes to give a cold rating, at the same time as I am getting a heat rating. Perhaps one day I will have a scale to descibe the effectiveness of a box in its environment. It is not far away.
.Great work with these demonstrations. I think of the carbonaria right across Warwick, they would have to experience close to those conditions in a cold spell.
>>>>>> I think of the carbonaria right across Warwick, they would have to experience close to those conditions in a cold spell.<<<<<
As a kid we would hunt down caronaria on the family farm near Oakey. So they do survive up on the Downs. We only found them on the high ground by the way, not in the hollows, BUT yes temps down to below zero for very short periods.
Graham
You have the monopoly on useful inn’ematiof-arrnot monopolies illegal? 😉
Thank you all for your positive comments and certainly Bob, Warwick is a good example of a carbonaria area with cold Winters (frosts and negative temperatures) and warm to hot Summers. Of course it’s not just carbonaria that live in Warwick, australis live there too.
I am particularly interested in hearing peoples experiences with foam insulation in colder areas, and would love to hear from anyone keeping australis in Sydney, or south or west of Sydney.
Dean
OK I did some number crunching, and its looks like the bees don’t actively maintain the internal temperature of the hive, its more a passive control Looks to me you would be right, overnight is ok, BUT if the bees are forced to leave the ball and source honey for energy, they wound get back, and that starts the death spiral.
From the data, the key thing to look for is not how cold the nights, its more how warm the day will get.
Hi Graham,
Thanks for your comment but I do not agree.
There are a number of things to look at in the data. Most of the data is taken with a 25mm thickness hoop pine box without insulation and only some data is taken with the insulation in place. It’s a bit like concluding my heater doesn’t work when I have all my doors and windows open.
Dean
ok to disagree, that what makes life go around.
The data is very clear on a number of things, with clear statistical correlations. The main thing I draw out of it are.
1. Passive Heating – It is clear the native bees do rely on passive heating, ie reactive changes. Unlike honey bees, that have dedicated “heaterbees”, who sole job is to generate heat and distribute it within the hive to maintain a very even hive temperature, native bee from your data obvious don’t have these. They rely to probably balling on the brood. There is clear correlation between brood temp and honey pot temp that demonstrates no real increase in metabolic activity of the bees.
2. Outside warming up. – Its also clear they don’t warm the hive up from inside out. While that does occur, they rely far more on external heat to get the warmth up.
And yes one set of data doesn’t make a thesis, nor prove a theory. BUT it does give direction where to follow up. For me its a curiousity factor only, I don’t suffer cold here (well that aint true, got to 22C last night, had to throw a blanket on, got very chilly)
Graham
Hi Graham,
It’s true there is a passive heat input into the hive. When the outside air temperature is warm the bees can suck it into the hive. I have also seen carbonaria place dark resin outside their door and this heats up in the Winter sun. Bees come outside and sunbake on this heated resin and then go back inside.
The control of brood temperature I am referring to is in the second session in the fridge where the brood temperature heats up 4 hours before the box comes out of the fridge. This was an insulated box.
The honey pots are not heated as far as I can see. Any heating here is passive, from outside air when its warm, or a little leakage from the brood maybe. In the end, the rate at which the honeypots lose heat to the external cold environment becomes important. In the third fridge session, with a fully insulated box they lost 7.39 degrees in 12 hours which is a cooling rate of 0.616 degrees per hour.
Dean
Eve wrote
>>>>You have the monopoly on useful inn’ematiof-arrnot monopolies illegal? <<<
OK, I normally get most cryptic messages, BUT this one totally escapes me. Best I can work out, I have an illegal wing strut, and trying to corner the market..
Anyone care to help me understand what is being said.
Graham L Sanders
There is now a major new piece of T.carbonaria temperature work completed by Jenny Shanks of Western Sydney University. In her PhD thesis she devotes a chapter to in hive temperature. This 13 months of observations for multiple hives is a major resource and well worth reading. Her paper can be found at Dr Megan Halcrofts website http://www.beebusiness.com.au
Dean