Unfastened-living bees and massive outdated bushes

Synopsis: Historical and veteran bushes come with many giant sufficient to accommodate a colony of free-living honey bees. Right here is a few science and hypothesis at the bushes, the bees and what to search for.

Creation

Why are the copses, coppices and thickets of the United Kingdom (or for that topic Europe or a lot of North The united states) now not full of massive numbers of free-living honey bee nests?

Deja vu? …

Don’t fear, you’re now not dropping your thoughts. That was once precisely the similar sentence I began the publish with final week.

It’s a sound query.

In the event you settle for the numbers I offered final week – remembering it was once a meta-analysis of a rather small collection of experimental research yadda yadda – then there are massive numbers of free-living honey bee colonies someplace available in the market within the surroundings.

Throughout us.

It’s a pleasing idea isn’t it?

What number of?

Neatly, it is dependent just a little on the way you calculate it.

Calculators out!

The density of free-living colonies in Europe was once 0.26/km² and controlled colonies outnumbered them about 4:1. Calculated from the realm (~243,000 km²) this works out at 63,000 free-living colonies in the United Kingdom. The estimated hive quantity here’s 288,000; the use of that as the foundation for the calculation provides a solution of 72,000 free-living colonies scattered round this little island.

Let’s break up the adaptation and make contact with it ~67,000.

And for North The united states (the place the free-living colony density was once 1.4/km²)? The usage of the similar kind of calculations issues aren’t in rather such excellent settlement. The North American continent has a space of ~24.7 million km² and incorporates ~3.4 million controlled colonies. Based totally upon space, it’s predicted that North The united states incorporates ~34.6 million free-living colonies. From controlled colony numbers (which might be outnumbered 7:1) the quantity can be ~24 million.

Once more, let’s break up the adaptation and think it’s 29 million free-living colonies.

Have in mind, there are all forms of assumptions made within the preparation of those numbers however, no matter manner you have a look at them, it’s a heck of numerous bees.

So, the place are they?

Northern climes and adversarial environments

Contemporary proof counsel that Apis mellifera developed in Europe and unfold to southeast Europe and Asia Minor (Carr, 2023), splitting into the more than a few sub-species like carnica, ligustica and others. The honey bee is local to Europe, however was once presented to North The united states (in 1622; Chippie and Harpur, 2021).

Regardless of originating in a northern local weather, honey bees can not naturally live on in one of the maximum northerly spaces of those two continents – the winters are too lengthy and/or the forage to be had is inadequate.

As well as, there are hotter areas in each continents which can be in large part or totally flawed for honey bees; as an example, they’re too dry, have too little forage right through the season or lack any herbal nest websites.

Due to this fact, the herbal distribution of honey bees might be ‘patchy’, upper the place prerequisites are beneficial, low or absent in different places. Within the diagram above, some spaces have prime concentrations of nest websites (blue), others, now not such a lot (inexperienced) and a few, none in any respect (purple).

All that is additional difficult by way of the presence of controlled colonies that proportion the similar surroundings. Misplaced swarms from those controlled colonies grow to be established in herbal nest websites, maximum will perish however some might live on (evolving from controlled to feral to free-living, or a minimum of being outlined as reminiscent of time passes).

All of which is a convoluted manner of claiming that the colony densities of 0.26/km² or 1.4/km² will grow to be much less and no more correct as you have a look at smaller spaces … like throughout a stroll throughout the nation-state on a summer season afternoon.

However which spaces are possibly to have free-living colonies?

Bosky groves

The honey bee developed to nest in cavities. Due to this fact, until most of these free-living colonies are in caves or man-made buildings (e.g. outdated church buildings) they’re possibly to be occupying cavities in bushes.

James Joyce used the time period ‘bosky grove’ in Ulysses …

“of bosky grove and undulating simple and luscious pastureland of vernal inexperienced”

Bosky method ‘stuffed with thickets or brush’, and I intentionally used ‘thickets’ in my opening sentence. I didn’t use bosky as I sought after you to proceed studying the publish 😉

Bosky groves, in addition to “copses, coppices and thickets” (and particularly the final two), indicate immature forest, missing many or probably any really extensive bushes outlined on the subject of their peak or – extra importantly so far as bees are involved – their girth.

Why girth?

As a result of a honey bee nest is rather a big construction and a small tree, or perhaps a medium sized tree, is not likely to have enough girth to deal with it. And the one manner the tree could have bought enough girth is by way of rising for a very long time.

Therefore the ‘giant outdated bushes’ within the identify of this publish.

And it’s those those giant, and subsequently outdated, bushes that I wish to talk about for the rest of this publish following the e-newsletter of a captivating paper at the matter by way of Oliver Visick and Francis Ratnieks from the LASI workforce on the College of Sussex.

Personal tastes

Each observational and experimental research have proven that the honey bee preferentially chooses voids of ~40 litres with a small (~10 cm²), south-facing, front situated over ~5 metres above floor.

The observational research concerned discovering bushes containing bees (‘bee bushes’) and bodily measuring the traits of the hollowed out trunk or department.

The experimental research concerned providing swarms the selection between massive or small voids, or massive or small entrances or north or south going through (OK, you get it) … and figuring out which they like.

For instance, they make a choice 40 litre voids rather than 10 or 100 litres. Those experiments are mentioned in Honeybee Democracy by way of Thomas Seeley who performed nearly all of those research.

Whether or not they’d choose a 75 litre void 7.5 metres above floor with a 12.5 cm² front over one going through north of 37 litres, 2 metres up, with a miles greater front was once now not examined.

Bees can’t be too picky

Nest web page selection is an inexact science.

It needs to be.

Nest web page personal tastes in honey bees developed earlier than hives existed, or for that topic church towers, or our ancestors.

During which I imply Homo erectus, over 2 million years in the past, now not your grandparents.

Herbal voids both exist in caves or in bushes, and there are much more bushes than there are caves. Moreover, bushes are available in all styles and sizes. Due to this fact there should be flexibility within the selection that the bees make.

Something the bees don’t care about is the form of the void.

Round, cylindrical, cuboid, pyramidal … no matter.

This once more is smart. The void (or hole) within the tree effects from herbal harm, reminiscent of a department breaking off following by way of water ingress, or a woodpecker or quite a lot of different reasons that don’t create areas of a selected geometric form.

How giant are bee bushes?

So how giant does a tree need to be to deal with a honey bee nest?

Let’s make some assumptions .

Let’s think that the void is a sphere . As well as, let’s additionally think that the trunk of the tree must be a minimum of 10 cm thick everywhere in the hole to create sufficient structural stress that the tree survives iciness storms.

As an apart, do the bees make a choice higher insulated cavities with thicker partitions? I’m now not certain whether or not the scout bees may assess this (and so they’re those making the selection) however it might be fascinating in the event that they did. Somebody wishes to use for a analysis grant …

You after all know (and I Googled) that the diameter of a sphere will also be calculated from it’s quantity the use of the next equation:

ø = ∛(6 · V / π)

Due to this fact a 40 litre round void has a diameter of 42 cm.

Upload 10 cm on each and every facet (as described above) and you find yourself with a diameter just a little over 60 cm. A tree of this diameter would have a circumference of ~1.8 metres.

Preferably that’s at 5 metres above floor degree.

I’m just a little over 1.85 metres tall and my achieve is nearly precisely the similar as my peak. If my assumptions are proper, I might simply be capable to achieve across the trunk of a tree big enough to deal with this theoretical or modelled honey bee nest web page.

This is, if I may achieve 3 times my peak above the bottom. At chest peak (a lot more uncomplicated to measure) it might be larger nonetheless.

My assumptions most probably aren’t proper .

Cylinders now not spheres

You’ll be able to call to mind the sector as a modelled honey bee nest web page. The biochemist Erwin Chargaff as soon as mentioned:

One of the insidious and nefarious homes of medical fashions is their tendency to take over, and once in a while supplant, truth.

And, as a result of I don’t need you to suppose that honey bee nests are round, let’s evaluate our ideas of the most popular form and measurement of voids in bushes, and the bushes that space them, the use of some actual knowledge i.e. ‘truth’.

At the beginning, tree trunks – at a primary approximation – are cylinders. Due to this fact it’s most probably affordable to think that they may accommodate a cylindrical void extra simply than a round one. This would provide the benefit that, assuming the quantity of the void was once enough (by way of being longer), the flanking wall thickness may well be better, offering extra structural stress.

That’s now not truth … that’s most commonly arm waving.

OK … is that this higher?

Thomas Seeley and Roger Morse (Seeley and Morse, 1978) measured 21 herbal nest websites in bushes. The bulk had been in oaks (Quercus sp.). Listed below are a few related quotes from the paper:

All nest cavities had been vertically elongate and roughly cylindrical .

… and …

The imply hollow space diameter, peak and (peak/diameter) ratio had been 22.7 cm, 156 cm and seven.2, respectively,

And, only for completeness, the use of V = πr2h, a hollow space with the ones dimensions would have a quantity of ~63 litres.

Wall thickness and trunk diameter

Sadly, in regards to the simplest factor that Seeley and Morse seem now not to have recorded is the thickness of the partitions of the tree trunk surrounding the void, or the diameter of the trunk .

A fairly cursory overdue night time seek of the literature grew to become up a Bee Tradition article on thermal potency which said that

… honey bees have thick walled (reasonable 150mm) tree nests.

If you understand of a higher supply please upload a remark under.

So, the place are we? The typical diameter of the void occupied by way of free-living honey bees within the Seeley and Morse find out about was once ~23 cm, and we would be expecting that might be surrounded by way of partitions that had been ~15 cm thick.

Due to this fact, the diameter of the trunk can be ~53 cm, giving a girth (2πr) of one.67 metres.

Right here endeth the geometry lesson .

Large bushes are outdated bushes

Bushes taper. They’re wider closer the bottom. Due to this fact a tree with a girth of ~1.7 m on the peak of the honey bee nest web page would have a bigger circumference at chest peak … which is the standard peak above floor that bushes are usually measured at .

It seems that there are forester’s calculations for how a lot better the diameter is, associated with the Girard shape magnificence and expressed on the subject of tree taper, however let’s think an additional 30 cm.

Bushes develop rather slowly. An oak with a girth of ~2 metres at chest peak is most probably about 80 years outdated (PDF).

And that’s a rather small and younger tree … for an oak.

The superbly named Large Abdominal Oak within the Savernake Woodland has a girth of eleven metres and is considered ~1000 years outdated. There are in a similar way elderly bushes – now not simply oaks – a few of which might be even greater. The Enormous Bushes website online catalogues a few of these behemoths.

Tree-huggers and citizen science

Bosky groves, coppices, copses, thickets and spinneys are not likely to comprise bushes sufficiently old (or, extra particularly, giant sufficient) to deal with a free-living honey bee nest.

Larger is healthier.

Larger bushes imply probably greater cavities or – a lot more necessary – extra alternatives for cavities of the proper measurement. An overly outdated, very massive tree could have misplaced extra limbs, been nested in by way of extra woodpeckers, attacked by way of extra fungi and many others. and so is most probably to supply extra doable nest websites for a homeless swarm.

The Enormous Bushes website online is a citizen science undertaking. You’ll be able to check in and upload notable bushes. There are ~60,000 already indexed (international, I will be able to’t discover a breakdown by way of nation) .

On the other hand, a lot extra fascinating is every other citizen science undertaking, the Historical Tree Stock (ATI; Nolan et al., 2020), as a result of:

• it lists ~190,000 notable – regularly massive and/or outdated – bushes in the United Kingdom
• a cautious survey of 1052 of those notable bushes confirmed that over 4% of those who had cavities had been occupied by way of bees (Visick and Ratnieks, 2023)

The ATI website online is hosted by way of the Wooded area Consider. I couldn’t get the maps to show correctly on my same old browser (Vivaldi), however it labored high-quality with Safari. If to start with you don’t be triumphant … .

Mighty oaks from little acorns develop

Most of the mightiest oaks had been most probably felled within the 18^th and 19^th Centuries throughout the growth in shipbuilding had to construct the Royal Army and for the growth of the British Empire. The lack of those bushes was once additionally dangerous information for barbastelle bats. Replacements planted will simplest now be rising into really extensive bushes.

Most of the bushes that survived the ravages of the shipbuilders had been within the decorative gardens of stately properties or deer parks. Because of this there’s a upper density of those ‘bushes of particular hobby’ (TSI) within the ATI database in those landed estates. TSI’s are outlined as:

… outdated bushes that in most cases showcase veteran traits, reminiscent of a hollowing trunk, crown retrenchment and the presence of saproxylic fungi

The ATI defines bushes as historic or veteran relying upon the volume of those traits which can be provide.

Visick and Ratnieks (2023) surveyed 1052 TSI’s within the south-east of England earlier than the onset of swarming recording proof of cavities and the presence of honey bees.

Via surveying websites early within the yr there was once much less leaf-cover, making the surveys just a little more uncomplicated, and it was once most probably that any bees have been in place of abode overwinter.

Of the 1052 surveyed, 481 (45%) had visual cavities and 21 contained honey bees (i.e. 2% of the whole bushes, or 4.4% of the ones with cavities). Right through the survey an extra 15 ‘bee-containing bushes’ had been situated that had been now not indexed within the ATI. Two bushes contained two colonies.

Traits of the bushes … and the bees

Bees had been present in oak (Quercus), candy chestnut (Castanea), beech (Fagus), ash (Fraxinus), pine (Pinus) and lime (Tilia). Handiest the candy chestnut contained extra colonies than anticipated (7% vs 2% total), probably as a result of those bushes had been one of the greatest surveyed and ~75% of them contained cavities.

Of the 1052 bushes surveyed, 65% had been oak, 8% candy chestnut and seven% beech.

The TSI ‘bee bushes’ had been greater (1.7 m diameter, so a girth of ~5.3 m and subsequently most probably about 350 years outdated ) than the ones now not containing bees (~1.3 m diameter).

The clue was once within the identify of the publish … those are ‘giant outdated bushes’. 

The median hollow space front peak was once 6.8 m (vary 0 to >18 m) however front compass orientation was once it seems that random.

The south east of England is densely populated and there are numerous beekeepers within the space. The landed property with the best density of TSI’s, and the most important quantity surveyed, was once Hatchlands Park, a Nationwide Consider assets close to Guilford in Surrey.

Inside of 10 km of this location the Nationwide Bee Unit’s BeeBase data 412 different apiaries . My back-of-an-envelope calculations counsel that the controlled hive density within the space is 4-6 hives / km².

Those free-living bees are now not an remoted inhabitants. Whether or not they’re in point of fact self-sustaining or – just like the Central Eu inhabitants studied by way of Patrick Kohl et al., (2022) – dependent upon an annual inflow of misplaced swarms, is still decided.

I’ve now not checked the opposite places surveyed however suspect – like different free-living populations – they’re all in spaces containing a large number of controlled colonies.

21 down … 66,979 to move

You probably have a excellent reminiscence you’ll needless to say about 3,000 phrases in the past I estimated there may well be 67,000 free-living honey bee colonies in the United Kingdom.

Visick and Ratnieks have discovered 21 of them. Extra importantly, they have got proven {that a} database of venerable outdated bushes supplies a path wherein important numbers of such colonies will also be situated.

Assuming that 2% of the recognized TSI’s throughout the United Kingdom are ‘bee bushes’ then they are going to house as many as 3,300 free-living colonies.

On the other hand, the ATI database ‘simplest’ lists 190,000 bushes whilst geospatial knowledge suggests there are about 3 billion bushes in the United Kingdom, regardless that maximum are wholly flawed for bees.

We don’t understand how many TSI’s there are in the United Kingdom, regardless that Nolan et al., (2022) means that the ATI database might simplest listing ~10% of the whole in England. Assuming 2% occupancy by way of bees this is able to be ~40,000 free-living colonies.

There are so much extra historic and veteran bushes available in the market to be discovered and recorded … and looked for bees.

After all, for the ones people residing within the faraway, less warm, wetter extra northern places in the United Kingdom (and by way of extrapolation an identical places in Europe and North The united states) don’t suppose that most of these ‘bee bushes’ are within the balmy south. Ann Chilcott (of the very good www.beelistener.co.united kingdom) and Thomas Seeley (PDF) discovered free-living colonies in Cawdor Picket in Scotland.

In the event you pass down within the woods these days … you’ll be in for a pleasing marvel.

In fact, these days there might be no bees about because it’s too rattling chilly.

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Notes

Going again in short to my guesstimates of minimal ‘bee tree’ diameters … it’s value noting that simplest 5% of the TSI’s that had been occupied by way of bees (see the graph above) had a diameter much less than 1 m. On the other hand, those bushes are notable – being massive/outdated – and so most likely now not consultant. I’m certain that smaller bushes will also be occupied by way of bees, however that giant (and subsequently outdated) bushes are a lot more more likely to be ‘bee bushes’. It’s additionally value noting that the odds of darkish gray bars within the graph upload as much as 105% !

There are different efforts being made to catalogue free-living colonies e.g. HoneyBeeWatch, which might be truly out of doors the scope of this publish. I sought after to introduce the concept that of historic and veteran bushes as doable properties for honey bees, to talk about the hot medical proof and, optimistically, inspire you in finding an identical bushes (and bees).

References

Chippie, M.H., and Harpur, B.A. (2021) Genetic previous, provide, and long run of the honey bee (Apis mellifera) in america of The united states. Apidologie 52: 63–79 https://doi.org/10.1007/s13592-020-00836-4.

Carr, S.M. (2023) More than one mitogenomes point out Issues Fall Aside with Out of Africa or Asia hypotheses for the phylogeographic evolution of Honey Bees (Apis mellifera). Sci Rep 13: 9386 https://www.nature.com/articles/s41598-023-35937-4.

Kohl, P.L., Rutschmann, B., and Steffan-Dewenter, I. Inhabitants demography of feral honeybee colonies in central Eu forests. Royal Society Open Science 9: 220565 https://royalsocietypublishing.org/doi/10.1098/rsos.220565.

Nolan, V., Reader, T., Gilbert, F., and Atkinson, N. (2020) The Historical Tree Stock: a abstract of the result of a fifteen yr citizen science undertaking recording historic, veteran and notable bushes throughout the United Kingdom. Biodivers Conserv 29: 3103–3129 https://doi.org/10.1007/s10531-020-02033-2.

Nolan, V., Gilbert, F., Reed, T., and Reader, T. (2022) Distribution fashions calibrated with impartial box knowledge expect two million historic and veteran bushes in England. Ecological Packages 32: e2695 https://onlinelibrary.wiley.com/doi/abs/10.1002/eap.2695.

Seeley, T.D., and Morse, R.A. (1978) Nest web page variety by way of the honey bee,Apis mellifera. Ins Soc 25: 323–337 https://doi.org/10.1007/BF02224297.

Visick, O.D., and Ratnieks, F.L.W. (2023) Historical, veteran and different indexed bushes as nest websites for wild-living honey bee, Apis mellifera, colonies. J Insect Conserv https://doi.org/10.1007/s10841-023-00530-7.