Why so few feral colonies?

Synopsis : With so many swarms lost by beekeepers, why are there relatively few feral colonies? Do they die from starvation, depredation or disease? What kills feral colonies?


It can take a long time to understand complex natural phenomena. When you take into account geographic and seasonal variation you often end up with an explanation littered with more caveats than actual answers.

For example … do honey bees compete to the detriment of native solitary bees?

During May in an environment with limitless yellow acres of oil seed rape … probably not, but during early spring in an arable area with limited hedgerows … almost certainly.

OSR and threatening clouds

Sometimes the explanation may seem obvious, but isn’t. Bumble bees restrict themselves to field margins whereas honey bees venture hundred of metres into the middle of a field of OSR. Not only are there huge amounts of pollen and nectar available, but the different species exploit it in different areas of the field.

Not simple and not necessarily obvious 1.

Lost swarms

By many accounts, it’s been a very ‘swarmy’ season. The BBKA’s swarm line was swamped 2. Many beekeepers ran out of equipment (and no doubt patience) hiving swarms lost by beelosers with poor swarm control.

With ~250,000 colonies in the UK I wouldn’t be surprised if there were 50-100,000 lost swarms and casts.

That being the case, why aren’t there more feral honey bees?

By feral I mean honey bees that were once managed and – through mismanagement? – are now no longer managed but are instead free living.

Why isn’t every suitable cavity – in church towers, hollow trees, outbuildings and roof spaces – occupied by ‘lost’ swarms?

Clearly there are some feral colonies, but they are sufficiently rare to be notable.

Those of you interested in feral colonies will also be aware of sites (cavities) that have been occupied by honey bees, but that currently are not.

The obvious explanation is that the pests and diseases – primarily Varroa destructor and the viruses that it transmits – that plague (and can destroy) our managed colonies have precisely the same devastating impact on feral colonies.

By definition, a feral colony is unmanaged. Therefore, any pests or diseases it carries when the swarm leaves the original hive should have an unrestricted opportunity to wreak havoc – and eventual destruction – on the newly established feral colony.

Pathogen loads and colony losses

The statement above is an assumption based upon a couple of observations:

  • the majority of winter colony losses in managed colonies are due to Varroa transmitted deformed wing virus (DWV). This reduces the longevity of winter bees resulting in the colony shrinking to a size below that needed for viability, or – if it survives – incapable of building up in the spring (Dainat et al., 2012).
  • limited studies of feral colony pathogen loads have shown higher levels of DWV than seen in managed colonies, but similar to the levels seen in unmanaged colonies (Thompson et al., 2014).

The relevant figure from the latter paper shows significantly higher DWV levels in feral (F) to managed (M) colonies.

Pathogen levels in feral (F) and managed (M) colonies

In contrast, other pathogen levels tested – black queen cell virus (BQCV) and Nosema – were not significantly different.

The majority of well-read beekeepers are aware of the importance of managing Varroa levels. They also know what happens if the levels are not properly managed – or not managed at all.

Several years ago I presented graphs modelled using BBEHAVE software showing what happens over a 5 year period to colonies that are not treated to minimise Varroa levels.

No treatment

Mite (red) and bee (blue) numbers in untreated colonies over 5 years

I ‘primed’ these calculations with just 10 mites per colony … within two years mite levels exceed ~4000 and were four to five times that within three years (at which point total bee numbers start to fall).

By year four the colonies were managed by a mitekeeper, not a beekeeper, and colonies expired in the fourth or fifth year.

In reality, colonies die within four years because they usually start with many more than 10 mites … 🙁 .


These observations, and those listed above, make it logical to assume that feral colonies do not litter the landscape because the mites and viruses kill ‘em.

In addition to pests and diseases we know that our managed colonies sometimes die for a variety of other reasons.

Queen failures, starvation, natural disasters (e.g. flooding or stampeding cattle) and stupidity 3.

Quiet churchyard

Impervious to stampeding cattle

Other than stupidity I think it’s reasonable to assume that feral colonies probably experience a similar range of ‘threats’, though the stampeding cattle are unlikely to be a problem if they’re in the church tower.


Well, sort of. A lot of the above are assumptions. They’re based upon good observations and a reasonable understanding of the threats to managed honey bees, extrapolated to an unmanaged situation.

To be sure why there are fewer feral colonies than there are swarms lost we really need to observe some feral colonies, record which survive to the following season and look at differences between those that survive and those that do not.

As written, that sounds a pretty straightforward thing to do.

But scientifically it isn’t.

Time and money

For a start you need enough feral colonies to produce statistically compelling results. A handful isn’t enough. That might be enough for an anecdote or two and an article in the local beekeeping association newsletter but it won’t convince a peer reviewer or a journal editor.

You need to repeatedly observe the colonies over a protracted period, recording viability and taking relevant samples for molecular analysis (e.g. which pests and pathogens are present?). In addition, being fieldwork, you need to probably do this for more than one season, and ideally you need to look in a variety of different geographic locations.

And to do this you need to pay for the equipment, travel, staff, reagents, food, hotels etc.


Science is expensive, and not because scientists are particularly well paid 🙁 .

If you work on a global human infectious disease there are (multiple) millions of pounds of funding available from government and industry.

If you work on honey bee biology … not so much 4.

Other than the Thompson et al., study mentioned above there are very few studies of feral colonies, and even fewer of what causes the demise of feral colonies or why feral populations are usually not self-sustaining, but are instead dependent upon an annual influx of lost swarms from beelosers.

Until now

Last October I described an interesting study by Kohl et al., (2022) that investigated the longevity of feral colonies occupying known ‘cavity’ trees. These are trees containing black woodpecker 5 nesting sites. Several hundred mapped ‘cavity’ trees were observed three times a season – May/June, late September, early April – to determine how many became occupied by swarms, and how many remained occupied the following spring.

Temporal population fluctuations of feral honey bee colonies in Germany; A) occupancy rates, B) population density

Of the 112 nest sites occupied, 90% survived from May/June until late September, but only 16% were occupied the following spring.

The annual survival rate was ~10%, and the average lifespan of a feral colony was ~32 weeks.

The populations (in three different old growth German forests) were not self-sustaining. The continued presence of honey bees in the forests was dependent upon the annual loss of swarms by beekeepers in the surrounding environment.

Although perhaps disappointing that the populations were not self-sustaining, these bee trees provide an ideal study cohort to determine why the vast majority of lost swarms do not survive to reproduce (swarm).

Kohl et al., 2023

A the follow-up study discussing the potential and actual causes of feral colony loss has just been published (Kohl et al., 2023) with the snappy title:

Parasites, depredators, and limited resources as potential drivers of winter mortality of feral honeybee colonies in German forests

The results are interesting and a little surprising 6. This is because I’ve always assumed that it’s the double-whammy of Varroa and DWV that quickly kills these feral colonies.

It isn’t.

The study is in the main easy to understand and open access, so you can read about all the details I don’t have the time, energy or intellect to explain.

There’s more to be done. Some of the results lack compelling statistical significance, but – like all interesting science – it provides a good basis for further work and clearly points to areas where additional research is needed.

A working hypothesis

Whilst you can just go out into the field and ‘measure stuff’ (tree height and girth, species, cavity entrance orientation etc.), it’s far better to have a working hypothesis of what might account for the high annual losses of recently established feral colonies and so quantify things that are relevant, so allowing these hypotheses to be tested.

The first, and perhaps most obvious, thing that could account for these losses are the range and levels of pathogens known to be detrimental to honey bees.

Secondly, while studying nest site occupancy in the cavity trees the team had previously found beeswax comb on the forest floor under some trees. Is nest site competition (from a range of other species) or robbing responsible for the demise of feral colonies?

Finally, the environment surrounding the cavity tree would be expected to determine forage availability. Previous studies – and careless beekeepers – have shown that a colony needs sufficient stores to get through the winter. A poor environment offering little forage might be associated with higher levels of feral colony loss.

This provides three testable hypotheses:

  1. Parasites and pathogens limit overwinter colony survival; colonies that perish would be expected to have a wider range or higher levels of honey bee pathogens.
  2. Nest depredation limits overwinter colony survival; colonies that perish would be expected to be visited/robbed by other species and, conversely, nest sites protected from such visits should survive better.
  3. Available forage limits overwinter survival; colonies that survive would be expected to occupy landscapes with greater amounts of flower-rich land within foraging range.

Of course, it might be a combination of these, or these and something unknown or unexpected, but this is a good starting point.

Testing the hypotheses

How were these three things tested and what were the results?

I’m going to be reasonably brief here to keep within 23,000 words. I’ll mention the key tests and what I consider the most important or interesting results 7.

Black woodpecker

The study was conducted between 2017 and 2021. A total of 113 colony winter survival/mortality events were observed, involving 103 unique colonies and 71 cavities. 98% of the cavities were black woodpecker nests in beech trees. Since \~84% of colonies die within a year of occupying a nest site it was inevitable that most testing was conducted on recently established feral colonies – this is particularly relevant when pests/pathogens are considered. There is no distinction made in the paper between feral colonies established for different periods.

Not every feral colony was investigated for pests/pathogens or nest depredation.

Parasites and pathogens

A total of 18 honey bee parasites were quantified – presence and levels – using standard molecular techniques 8 from 20 bees sampled in July from each of 67 feral colonies for which overwintering survival was known.

Perhaps surprisingly the range of pathogens present in colonies that died was not higher. Of the 18 species tested, an average of ~5 were present in colonies that subsequently died and those that survived. Not necessarily the same 5, but there was no consistent differences between the community composition in the ‘dead’ or ‘alive’ colonies.

These feral colonies were not riddled with a wide range of pathogens.

Even more surprising – at least initially – of the 13 pathogens detected (remember, not all were present in every colony), the pathogen levels were not higher 9 in the colonies that subsequently died.

There’s a large table in the paper you can get all the gory details from.

Varroa was not one of the pathogens tested (you cannot meaningfully sample free-living colonies in tree cavities for mites). I was particularly surprised at the prevalence of DWV (no higher than 20-30%) which, using the most sensitive methods, is effectively ubiquitous in managed colonies when tested.

Although at first glance the absence of significant differences in pathogens present, or their levels, is surprising remember that these samples were taken in July and the majority of sampled colonies will have been present at the site for under one year. Whilst there is a relationship between summer pathogen loads and levels at year-end it is not necessarily linear. For example, colonies that experience a long late season brood break (due to poor forage) may have lower levels than one that was not similarly restricted.

Nest depredation

A small number of occupied nests were fitted with camera traps that recorded winter visitors to the tree/nest.

Of the 15 nests observed, 13 bird and 2 mammal species were recorded with 41% of visits involving the nest cavity being entered 10 and so potentially plundered.

Five bird species were observed potentially robbing the honey bee nests; grey-headed, green, great spotted and middle spotted woodpeckers, and great tits. Of these, the latter and green and great spotted woodpeckers are present in the UK.

Pine marten (Martes martes)

In addition to these birds, pine martens were observed reaching into, or entering, nests occupied by feral colonies.

There were no real surprises here. These bird and mammal species were already known or suspected of predating honey bee nests. I’m aware some beekeepers have had problems with pine marten, but they’ve never shown any interest in my colonies.

Nest protection

If nest depredation was an issue, preventing entry by the birds or martens should increase colony survival.

They tested this by stapling 8 mm wire mesh over some nest entrances and compared colony survival of protected or unprotected nests. This was done in two successive winters; in the first, survival of protected nests was twice that of those without mesh (33% vs. 15%) but in the second the same percentage survived (10%), meaning that overall there was no difference in colony survival if potential predators were excluded.

This part of the study was limited by the rather small number of nest sites tested (32 with and 40 without mesh) which, coupled with the low overall survival rate, reduced statistical significance. The authors make a number of suggestions on how this part of the study could be improved in the future.

The surrounding landscape

Feral colonies were observed in three study regions in southern Germany (Swabian Alb, Coburg/Lichtenfels and WeilheimSchongau) located 100-300 km apart. In each region, nest sites were up to 50 km apart. The feral colonies occupying the nest sites had access to potentially different forage types within a radius of 2 km (the forest contains relatively little suitable forage, with the bees visiting neighbouring land).

The proportions of land surrounding each nest sites – classified as either deciduous forest, coniferous forest, grassland, cropland or settlement – was quantified.

When surviving and dying colonies were compared, the former were surrounded by an average of ~6% more cropland (i.e. agricultural land on which crops were grown, together presumably with the field margins and hedgerows that separate areas of monoculture). Although this doesn’t sound much, it was significant.

Why so few feral colonies?

The number of feral colonies in an environment depends upon five things:

  1. Rate at which swarms from managed colonies occupy new sites.
  2. The survival rate of newly established feral colonies – how many survive their first winter?
  3. The successful reproduction (swarming) of established feral colonies.
  4. Survival rate of feral swarms.
  5. Annual survival of feral colonies after their first winter.

For a population to become self-sustaining it must first get established and must then reproduce at a rate sufficient to make up for the annual losses, or at a faster rate to expand population numbers.

The previous study by these authors – discussed in Feral facts and fallacies – addresses the second (and part of the third) of these points.

This new paper looks at why so few (~16%) survive their first winter.

The range and levels of pathogens in these feral colonies (in July) suggests they do not succumb to disease. Instead the results are suggestive that overwinter robbing (or nest disturbance – a subtle but important difference the authors discuss) is probably detrimental and that the availability of sufficient forage is critical.

I was surprised that pathogens weren’t the major culprit, not least because of the higher levels of DWV reported in the 2014 Thompson et al., study of feral colonies.

However, the age of the colonies in the Thompson paper was unclear. Perhaps they were long-established (or at least not just established) feral colonies?

A useful follow-up study would be to investigate pathogen loads in feral colonies in the first and – for the rare survivors – subsequent seasons. My expectation would be that colony losses attributable to disease would significantly increase from the second season.

The environment and feral colonies

The ‘cropland’ designation used by Kohl and colleagues is a rather generic definition. I don’t know the areas of Germany the study was conducted in but, by extrapolation to UK ‘cropland’, imagine it could cover a very wide range of different habitats.

Rather too much arable …

Compare the difference between hundreds of rolling acres of winter wheat dissected by barbed wire fencing and a patchwork of small fields with wide margins, a scattering of small copses and dense hedgerows.

The latter might well be ‘bee-friendly’, the former probably isn’t.

With the intensification of farming the environment our lost swarms try and occupy is increasingly hostile. I would be interested in the comparative survival rates of feral colonies in the prairie-like expanses of Norfolk and somewhere more closely resembling the bucolic scene in Constable’s ‘Hay Wain’.

The Hay Wain

The environment also includes the other species competing for nest sites and food – including the food already stored by the bees. We cannot control woodpecker or pine marten numbers (all are protected species), but an expanded study of the survival of mesh-protected feral colonies would show whether this is a significant cause of feral colony demise.

It’s tough out there … even in established self-sustaining feral populations swarm survival rate is low. Fewer than 1 in 4 swarms of Seeley’s bees in the Arnott Forest survived their first winter. Casts – afterswarms headed by virgin queens – fared even worse.

Although pathogen quantification is time consuming and expensive, simply characterising the environment occupied by feral honey bee nests and protecting some of the nests from depredation, would provide important insights into whether – and how – feral populations (can) become self-sustaining.


The authors have another paper – currently available on BioRxiv (i.e. likely submitted but that has yet to be peer reviewed and published) – entitled Reduced parasite burden in feral honeybee colonies. I have yet to read this in detail but may discuss it in a future post.


Dainat, B., Evans, J.D., Chen, Y.P., Gauthier, L., and Neumann, P. (2012) Dead or alive: deformed wing virus and Varroa destructor reduce the life span of winter honeybees. Appl Environ Microbiol 78: 981–987.

Kohl, P.L., Rutschmann, B., Sikora, L.G., Wimmer, N., Zahner, V., D’Alvise, P., et al. (2023) Parasites, depredators, and limited resources as potential drivers of winter mortality of feral honeybee colonies in German forests. Oecologia https://doi.org/10.1007/s00442-023-05399-6. Accessed July 12, 2023.

Thompson, C.E., Biesmeijer, J.C., Allnutt, T.R., Pietravalle, S., and Budge, G.E. (2014) Parasite Pressures on Feral Honey Bees (Apis mellifera sp.). PLOS ONE 9: e105164 https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0105164. Accessed October 19, 2022.


  1. And what’s written above is a gross oversimplification.
  2. It usually is.
  3. By the beekeeper, not the bees.
  4. Which is why I spent my career working on the replication, evolution and pathogenesis of human viruses, with sideline projects on the biology of honey bee viruses.
  5. A crow-sized bird that excavates ~10 litre cavities for nesting.
  6. To me at least.
  7. You might have different ideas … read the paper!
  8. qPCR of cDNA generated from extracted RNA … bet you’re glad you read the footnote!
  9. i.e. ‘not statistically different’.
  10. Or partially entered – it depends how big the visitor was and how small the entrance was!

18 thoughts on “Why so few feral colonies?

  1. Charlotte Wilson

    I know of 3 feral colonies in my local area.. I’d never considered that they may be repopulated every year.

    There has been honeybees in my neighbours chimney for over 20 years- several swarms out of it have gone to local beekeepers over the years and I suspect there have been many more we haven’t noticed.

    1. David Post author

      Hello Charlotte

      They may be repopulated every season (or every couple of seasons), or they might be a survivor population. However, the best scientific studies appear to show that many populations in temperate regions are not self-sustaining and need regular replenishing (repopulating) from lost swarms.

      There are a lots of anecdotal accounts of ‘bees in the church tower since I was a lad’ (or similar) but very few where the bees, when studied, are shown to be genetically distinct from local managed colonies and where there is compelling evidence that the bees are always present well before any swarming occurred in the region (which might lead to repopulation).

      The ubiquity of Varroa and DWV mean that any truly self-sustaining population must have acquired ways to cope with these parasites/pathogens. There are ways this can occur. Thomas Seeley’s “Lives of Bees” book describes free living self-sustaining populations in the Arnott Forest. He’s published widely on these which show significant behavioural differences that allow mite tolerance.

      Check colony activity in the chimney on the earliest days of the year that your colonies are flying. If they’re not flying from the chimney as well how can you be sure they are there and alive?


  2. simon kellam

    I install tree hives. I started with 5 in the spring of 2019. I now have 80 located, mainly in the southwest of the UK. I have 55 under observation at the moment. I collect data a minimum of twice per year, just before the swarm season and again in September. I do have some under regular observation. 2 of the first 5 tree hives I put up have been constantly occupied. With the 2x per year observations some will argue that colonies could die out and cavities get reoccupied once the swarm season is underway but it gives a very good overview. So far the survival rate for the first winter is 82% and for year 2 is 16%

    1. David Post author

      Hi Simon

      Many thanks for those comments (and your earlier email). Very interesting. I’ve been meaning to follow up your email with some questions.

      The poor survival rate over the second winter is exactly what I would expect from DWV/Varroa-mediated disease. If you assume a strong, healthy colony swarms in the spring of year 1 it’s likely that colony has low mite levels and would therefore survive that first winter without treatment. However, by consequently starting year 2 with elevated mite numbers, the viruses reach devastating levels later in year 2 and the colony dies that winter.

      My expectation would be that Patrick Kohl would see a similar proportion of losses in the second year. The fact that the German study sees much higher losses in the first winter. This may be due to the nest sites under observation are in forage-poor established managed forests. Seeley reports ~75% loss in the first winter, again in old mature forests.

      I would assume your tree hives are located in areas with much better forage … which is one of the questions I was going to put in the email 😉 . I’ll send something in the next week or two …


      1. simon kellam

        Hi David
        Sorry I misled you there. The 2nd year 16% was the fail rate! I meant to put the survival rate at 84% !! I know this goes against many scientific studies but I can only state what I have experienced.

  3. Will Hamilton

    ‘For example … do honey bees compete to the detriment of native solitary bees?

    During May in an environment with limitless yellow acres of oil seed rape … probably not, but during early spring in an arable area with limited hedgerows … almost certainly.’

    Firstly, I’m a fan, thanks for all of the content you’re sending out and have sent out, I regularly share it with our association.

    Secondly, on this, ignoring scientific evidence that different types of bee forage differently (I could find you the research article if you like). According to Prof Dave Goulson (Gardening for Bumblebees) a colony of Honey bees needs on average 1 acre of nectar rich habitat per colony, per year. A Colony’s foraging area (if they’re travelling upto 3 miles in all directions covers over 17,000 acres), of which they are removing 1 acres worth of food per hive.

    There are more beekeepers, but they are small in size on average, the idea that the density of foraging honeybees is depleting the native sources of nectar and pollen is overplayed except in urban areas where there is a concentration of beekeepers and an artificial lack of forage.

    If you were to counter with ‘honeybees forage closer to the hive than 3 miles’ then it still doesn’t work, in this scenario the negative effect of the honeybees is limited to their immediate environment (1 mile in all directions? Still 2000 acres). Beyond this there is plenty of space for solitary bees. I grew up in a large village with no beekeepers, and no honeybees whatsoever.

    I’ll add a couple of other factors to this which haven’t been considered, you see there was a running joke in the social sciences about the willingness of scientists to over generalise their research findings beyond the parameters of their original specific experiments, ignore the human influence/assume it’s consistent and/or rational and assume the homogeneity of sites (what were the specific contexts of the studies you are quoting?). There is of course a fundamental difference between can and does.

    Firstly, in my direct experience, the ability of visually present honey bee colonies to alter farmers behaviour (spraying early morning as an example as is planting crops for the bees because of the heightened interest of the farmers) which helps honey bees but also other pollinators. Successfully pollinated flora also creates additional benefits.

    In Lincolnshire, our Wildlife Trust has banned all honeybee colonies from their reserves and were very underhand in doing this, their justification is a study carried out on one specific small meadow, which isn’t comparable to their other reserves (they only have half a dozen small meadows) and they didn’t specify any key parameters at all ie how many hives, what forage, what time of year, weather, anything….which are key determinants.

    Another human factor being conversationalists take your argument and kick off beekeepers from reserves, what of the lost synergy we would have had if working together?

    Just some thoughts.

    1. David Post author

      Hello Will

      This post is about feral colonies. I used the competition between bees as an oversimplified example of how context can influence the conclusion. This is a subject I intend to return to in a more extensive post at some point in the future.

      A couple of thoughts … there are plenty of ‘farmland-type’ environments that are very forage-poor. By my calculations a 100 acre field of winter wheat flanked by narrow margins and a barbed wire fence is of little to no use by bees. What’s more, the margins (where any forage that does exist) might account for less than 1.5% of the field area. Any flowers in the margins are unlikely to provide nectar/pollen for extended periods. Honey bees in this type of environment are able to forage elsewhere, but will still forage locally and compete with the solitary/bumble bee population that are restricted (because of their limited foraging range) from going elsewhere.

      There are increasing numbers are reasonably compelling studies – wide scale, mixed environments – which demonstrate competition between bees, often detrimental to unmanaged species. I certainly accept that there are indirect benefits (influencing spray times, as you suggest) but I’m not aware that the assumed consequent benefits to ‘wild’ pollinators have been quantified.

      The highest hive densities I’ve seen are in cities. However, there are many regions of the UK with 4-5 hives per square kilometre, and may reach 50-75% the density seen in some cities. Urban environments benefit from elevated temperatures and a considerable diversity of forage. In contrast, a lot of farmland offers a glut of forage at some point in the season, but very little at other times.

      I don’t know a way to work out how to calculate the number of hives an environment can accommodate without having a detrimental impact on native species. We need to work this out … if we (i.e. beekeepers) do not then it’s likely that honey bees will be excluded from certain environments based upon ill-informed arguments.

      Of course, if we determine that we are having a detrimental impact on native species when we exceed the carrying capacity of a particular environment at a certain time of the season, we’ll then need to show restraint and either move hives elsewhere or keep fewer colonies.


  4. Mark Haworth

    It’s been a while since I read the Arnot forest book but wasn’t one of the points that even if mortality was high there were still a heck of a lot of wild colonies. He had more than 2 per square mile I thought, so could the answer be that there ARE a lot of feral colonies in some locales, Germany notwithstanding?

    I’m lucky to own farmland with a lot of woods on the Vermont/New York border 250 miles from Arnot and did similar (albeit amateurish) tests to Seeley and was amazed to find a few completely unexpected colonies in my patch. None of my neighbours have bees, and I don’t keep any there because of bears.

    For example there are 19m acres of woodlands in New York (twice the UK’s woods – there’s more to us than a big city!), or 30,000 square miles so 60-70,000 possible on those numbers. That compares with around 60,000 year round domestic hives.

    1. David Post author

      Hello Mark

      A quick look at one of the Arnott Forest papers suggests there were 8 colonies in an area about 8 square miles, but that’s very approximate as the area of the forest isn’t reported in the paper I looked at and I had to do a back of an envelope miles/kilometres calculation. Don’t trust my maths!

      I’d be surprised if colony densities of feral colonies were routinely that high. Beekeepers are a pretty observant bunch, particularly when it comes to bees (!), and most probably know of a few feral colonies … but perhaps not as many as one or two per square mile. I spend a lot of time in the outdoors and – even before I lived in the howling wilderness – I saw relatively few feral colonies on my regular walks.

      What’s needed is more careful surveying of likely habitat … and there are ways that can be done … which would make a good article for a future post 😉 .


  5. Iain Dewar

    Very interesting post David, and a subject that we, as beekeepers, should think more on. There are certainly more feral colonies around than we might think but as you’ve described, their physical health is their biggest problem, with varroasis the main culprit, and that’s our fault entirely.
    Swarming is an essential element of the honeybee lifecycle, and is a key function in maintaining their genetic health which enables good physical health and as we know strong healthy bees are much more able to cope with a whole range of pests and diseases on their own. They’ve done this successfully in the UK for over 9000 years, it’s only in recent history and with human interference that they have faced unnatural threats which have been species threatening.
    Their plight is man made, we have to put our hands up to that, and do more to raise awareness that the health of honeybees operates at a local level, and is best managed by the bees themselves. If we insist on interfering with their natural mechanisms for genetic selection by carrying out DEFCON 1 swarm control, importing non-indigenous genetics, and moving colonies all over the country, then the already genetically diluted UK honeybee populations will continue to face ever increasing health problems.
    Why so few feral colonies? Lack of nesting opportunities, lack of strong genetics, an upside-down view of swarming, intense factory farming honey, too many chemicals……? There’s a long list but we could start by including in any beekeeping syllabus a section on the honeybee life cycle which views swarming in a very different light. The volume of calls to remove swarms from chimneys, wall cavities, shrubs and trees this year just highlights their need to swarm, and their need for places to nest. Outside beekeeping, land managers and property owners could go a long way to providing honeybees with their natural nesting opportunities by making provision, and by not cutting down standing dead wood.
    ‘Beelosers!’ i think that applies to me! I carry out measures to discourage swarms but I certainly don’t view losing a swarm as a failure or consider others that lose swarms as poor beekeepers. Some colonies will swarm no matter what, and when they do then that’s what they naturally needed to do and the parent colony will recover quickly. Fingers crossed they will find a nest site, and after all, as a conservationist keeper of bees, who am I to stand in their way!
    Iain 🙂

    1. David Post author

      Hi Iain

      I thought twice about using the term beelosers as I didn’t want it to sound too disparaging 😉 . It’s certainly not a disaster, though it will impact the honey crop and might have a negative impact on someone who acquires the swarm in their loft space or chimney.

      I suspect the point you make about a lack of suitable nest sites is a good one. In my walks around Warwickshire and Fife (the climate/forage here on the remote west coast is probably not conducive to feral colony survival, though I’m aware of at least one) I rarely saw feral colonies … but these were agricultural areas in which hedgerows had been grubbed up, copses felled and the only ‘old wood’ was managed woodland, often with serried rows of dull, dark, conifers.

      Presumably, after the swarmtastic late spring we had this year there will be thousands of extra feral colonies going into this winter – for those that found suitable nest sites – though I’d expect the majority of them to succumb to disease (and possibly starvation as suggested above) relatively quickly. The comments made by James and Simon (above somewhere) are interesting and suggest what might be achievable … remembering that behavioural changes associated with Varroa tolerance are not always compatible with practical beekeeping. Is this a problem? Possibly not for those uninterested in honey … in which case why keep bees? For pollination? There are a huge number of other pollinators that are better at it or more deserving of protection!


  6. James McMullon

    Thanks for such an informed article however I believe there are other factors in the mix too.

    I’ve been keeping bees for 5 years on the Llyn Peninsular in North Wales, and have never treated for varroa, I rarely see the results of deformed wing virus (maybe a couple of bees a year) and my winter loses have been around 10% on average (10 colonies 0 to 2 failures maximum each year).

    Our association has about 80 members and the vast majority (if not all) do not treat for varroa, most have not been treating for more than 10 years and do not see losses any higher than I do.

    There is plenty of evidence of established wild colonies in the area, this was one of the reasons local beekeepers stopped treating 10-15 years ago.

    We operate a voluntary conservation area and encourage all beekeepers to source bees locally, rather than importing them. The overall result is that we have a very strong population of local bees which is able to live with and control varroa in their colonies.

    If we take an area where treatment for varroa is necessary to keep colonies going, then these bees, when they swarm, are more likely to surrcumb to varroa without the help of the beekeeper. Unfortunately the situation does not improve over time as the feral bees will mate with kept bees, and if those kept been need help to deal with varroa, then their offspring are likely suffer without help.

    I had a swarm move into our gable end 2 years ago, it did not make it through the winter. A second swarm moved in last summer and that did make it through the winter and has been doing very well over the summer. I know that it is the same colony as bees were flying throughout the winter when the sun was out and the temperature above about 8 degrees C. It’ll be interesting to see if it makes it though the coming winter.

    We do benefit from a wide range of forage over most of the year in this area.

    Perhaps more beekeepers should be sourcing local bees rather than importing bees from other areas/countries which dilutes the local gene pool. Beekeepers might also consider not treating for varroa.

    1. David Post author

      Hello James

      That’s interesting but I’m not sure it is directly relevant to the situation in Southern Germany … we know nothing of the Varroa/DWV status of the original colonies that generated the swarms that populated the woodpecker tree holes. They may have been riddled with pathogens and pests, or they might have been relatively ‘clean’. What’s surprising is that, unmanaged, the primary cause of the demise of the colonies appears to be forage availability and possibly depredation. This suggests that the environment is sub-optimal and, by extrapolation, improved forage – wider field margins, more copses, wildflower meadows etc. – might well improve the survival of colonies that are lost as swarms. Yes … the colonies may be derived from mite-tolerant stocks, but that doesn’t alter the impact on the environment on swarm survival.

      The Lleyn has a relatively low hive density, about 20% of that in many counties in England, which almost certainly contributes to survival.

      I’ve written extensively about the value and importance of local bees. The science demonstrating their benefits is compelling.


      1. James McMullon

        Hi David,

        I think that varroa treatment probably is relevant in Germany, in that beekeepers in Germany were and possibly still are obliged to treat against varroa, this reduces the likelihood that bees will develop the traits to resist varroa.

        I agree that on the Llyn we do have better year round forage than a lot of other areas, especially England, however varroa decimates colonies that are not able to deal with it. Here on the Llyn, as the vast majority of beekeepers do not treat for varroa, bees are able to manage varroa themselves and so swarms do not fail as a result of varroa….one less hazard for them.

        Looking at your blog on the importance of local bees, I see some of this work was carried out in Germany during a time when treatment for varroa was certainly mandatory.

        As you often mention, there are always more questions. It would be nice to run the german study here in the Llyn, I suspect that the local bees would win hands down, not just by a hundred days or so!

        1. David Post author

          Hello James

          At least some of the studies by Ralph Buchler on local bees involved Germany, but lots of other countries across Europe as well.

          With better forage and Varroa tolerance/resistance (the former surely?) then nest site availability should be the rate limiting factor that determines feral bee density. What’s more, based upon the assumption that the area isn’t intensively farmed, feral colony density and survival success should be significantly higher than that seen in other areas of the country.

          Do you know whether this is the case? If it isn’t, then something doesn’t add up.

          If you provide additional nest sites in the environment they should be occupied in due course by ferals (or lost swarms).

          At least some of the Kohl et al., study can easily be recapitulated by a few beekeepers willing to check nest site occupancy at key times during the season. Even easier if the nest sites have been installed (so are visible, accessible etc.). It would certainly be interesting and the comparisons with the Kohl study would be valuable. You would need a statistically meaningful number of colonies to observe – one or two aren’t enough.


  7. Pete Wakeling

    Superb article, many thanks.

    Modern beekeeping involves managing colonies to adjust the reproduction / survival ratio by reducing reproduction (swarming) and increasing survival, in comparison to unmanaged colonies. Some of the reduced swarming may by as a result of selective breeding, therefore an additional factor influencing these results may be that feral bees from previously managed stock are no longer “swarmy” enough to reproduce when faced with all of the other challenges already described.

    1. David Post author

      Hello Pete

      That’s a good point and not one I think the authors touched on. I don’t know enough about German beekeeping but – from my experience in the UK – I think there’s unlikely to be strong selection for ‘unswarmy’ bees in an outbred population from a mixed group of colonies managed by a range of beekeepers. I’d certainly expect individual beekeepers to be able to exert reasonably strong selective pressure, particularly if they’re also controlling the drone population in an area. However, at least in the UK, that’s the exception, rather than the rule.

      After a frantic period of swarming in early June it appears as though there’s a second period of swarming as I heard of two near one of my apiaries this week (neither mine 😉 ).



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