Feral: Friend or Foe?
By Andy Collins
This article first appeared in issue 4 of Natural Bee Husbandry
Do ‘wild’ bees still exist in Britain today? What should our attitude be to un-managed honey bees in our environment?
About 8 years ago I began to investigate whether free-living colonies of honey bees existed in my region (Perthshire). My interest had been aroused by the paper ‘Honey bees of the Arnott Forest’ by Thomas Seeley¹ in which he demonstrated that colonies living in trees were able to survive and reproduce in the presence of varroa. Free-living and seemingly varroa-tolerant colonies of honey bees have also been reported in Europe², and in the UK there have been many recent anecdotal reports of apparently long-lived wild colonies, some from experienced beekeepers
It had been assumed until recently that adaptation to the varroa mite must take place over several generations and involve a Darwinian process of selection, with only those colonies able to tolerate the parasite surviving to pass on their adaptive genes. This scenario would require relatively isolated situations to eliminate interbreeding with managed (unadapted) stocks. Several attempts have been made to replicate this ‘live and let die’ approach in managed apiaries to produce so-called ‘Bond’ survivor bees. However, the prospect of losing large numbers of colonies in order, eventually, to produce varroa-resistant bees is not an appealing one to most beekeepers!
In the UK the official position on ‘wild’ colonies is that they are short-lived escapees from managed hives with little intrinsic value. A BBKA-sponsored study³ found free-living colonies that were genetically similar to local managed colonies (i.e. mongrels with genetic contributions from many races of honey bee imported into the UK over the years). High levels of DWV virus were detected in the colonies sampled and it was considered doubtful that they would survive this level of infection in the long term. It is also often stated that these escapees represent a disease risk to local managed colonies (if they are robbed out by the latter after collapsing from varroa-related disease or foulbrood). This helps to explain the official antagonism towards free-living bees.
Some big assumptions?
The presumption that feral bees are necessarily short-lived is based on the experience of conventional beekeepers, especially those with large and intensive operations. Kept under these circumstances colonies untreated for varroa often fare badly and the fate of free-living colonies is usually assumed to be similar. Data on the longevity of free-living colonies in Britain is mainly anecdotal and it is unfortunate that the recent academic study referred to above did not run for long enough to make valid conclusions about their average lifetime.
The twin assumptions: that feral bees must be short-lived and that they are a disease threat are both open to question as we will see.
Finding and monitoring Colonies
Working with two local pest control companies and the local council it didn’t take me long to discover that unmanaged, cavity-dwelling honey bee colonies are, in fact, quite abundant; I found them in abandoned buildings, compost heaps, roof spaces of houses, chimneys, and even long-abandoned, dilapidated hives (though none in trees). As they seemed particularly abundant near apiaries (or former apiaries) it seemed reasonable to assume that many had originated as swarms from managed colonies (this despite the fact that many conventional beekeepers seem to be in denial about ever losing swarms!)
feral colony site F2
feral colony site F4
In observing honey bee activity at a cavity entrance, the key questions are:
is the coming and going from scouts from nearby colonies (or swarms) assessing a potential nest site or is there an established colony in the cavity?
if a colony is present, how viable is it over the long term?
The first question is most reliably settled when pollen collection by foragers is seen. This is a good indicator of the presence of a brood-nest. The longevity question must be settled by regular observations over a long period. In winter when no brood was present, observations were made on mild, sunny days when sporadic flights were often seen. In a strong colony the numbers of individual bees present in these flights increases through February and March, with the first pollen often being seen in March (before any significant nest-site scouting). Regular observations of entrance activity throughout the summer were then required to make sure there has been no dwindling of a colony followed by usurpation by an incoming swarm.
Regular monitoring of several of the 15 free-living colonies I found was impractical due to their inaccessibility. For this reason only the most regularly visited colonies over the period of the study are included in the Table 1 which shows their longevity from the date of first discovery. For two of these colonies there were two periods of about a month when observations were not possible. Otherwise observations were made on at least a monthly basis (usually more often) over the period of the study. Monitoring was more straightforward for a long-abandoned apiary of five hives discovered in the winter of 2013/2014 (colonies F6 – F10).
Table 1 Observations of 10 feral colonies in Perthshire from 2011 – 2017
Solid bars show the period for which these sites were occupied by a viable colony (starting from the time of its discovery). Arrows (→) indicate ongoing viable colonies. Question marks – no observations during this period.
Interpreting the Findings
While a few of these sites appeared to be occupied by colonies continuously over many years (eg F1, F2, F5, F6, F8), other cavities were occupied for shorter periods.
An example of a long-lived colony, F2, has occupied a cavity with a South-facing entrance behind a fascia board continuously for at least five years. A daughter swarm from this colony, F3, moved into a North-facing part of the roof of the same house in 2013, and established a colony which perished in its first winter. The cavity was reoccupied in 2015 by a colony which has survived since and continues to appear vigorous. This makes sense in the light of the studies of wild bees in the Arnot forest where it was reported that most swarms occupying tree cavities do not make it past their first winter.1 Once a large area of comb has been established over a season or two, however, a colony’s long-term prospects were much improved. Incoming swarms are able to make use of existing comb from a defunct colony and indeed actively seek previously occupied cavities. The second colony to occupy the F3 cavity presumably benefited in this way. It may be that some cavities such as F3 and F4 are not big enough to store sufficient winter supplies or are unsuitable in some other way. The fact that colonies in these cavities died out in winter would support the hypothesis of insufficient stores.
1. In winter.
2. In May.
3. In June. Spot the hive! This is F6, a busy colony (in unpromising circumstances).
4. Pollen forager (broom) entering F7 via an improvised entrance in the company of diverse molluscs.
The abandoned apiary hives are a sorry spectacle at first sight. Some of the pallet stands have collapsed and the thin hive walls are rotten in places and have gaps (which the bees seem to prefer to the original entrances). The zinc roofs are sound in each case, however. In high summer wild vegetation completely obscures these hives meaning that the returning foragers have to force their way through to the entrances. (This may actually confer the compensatory benefit of a shady screen in the hottest part of the year, since hives of this type have poor thermal properties and a tendency to overheat quickly in full sun). Three of these hives (F6, F8, F9) have been continuously occupied since their discovery (and possibly well before that), although F9 now appears to be dwindling. The other two have both been occupied by swarms for shorter periods, with F7 reoccupied early in the 2017 season. In general, the occupants are vigorous and are among the first to collect pollen in spring. The unknown original beekeeper has not been seen for over a decade so it is not known whether the occupants are descendants of his/her original bees or whether swarms from other colonies have moved in. I have not disturbed these hives at all - one imagines that they are by now completely propolised and cross-combed internally to the bees liking, rendering them uninspectable in any case. It is not too difficult to imagine many forgotten little apiaries like this dotted around the British countryside!
Although the bees in this study are predominantly dark in colour, some colonies have a variable proportion of individuals with yellow banding. This is probably one indicator of interbreeding with imported races of managed honey bees, of which there are many in the locality.
Even though the data is incomplete it seems clear from these six seasons of observations that some wild colonies are indeed able to survive in the wild in the longer term (more than 5 years). It is significant that this is a region where intensive commercial beekeeping is practised and where varroa treatment is the norm even amongst hobbyists.
That colonies are able to survive for long periods unaided may not surprise apicentric beekeepers, but it runs counter to prevailing conventional opinion and undermines the often-repeated idea that: ‘the honey bees need our help’. Many questions remain: how does the behaviour of these unmanaged colonies differ, if at all, from managed ones? How do they manage to store enough honey to last a Scottish winter? What eventually causes their demise, and are they really a disease risk? How are they coping with varroa-related disease when local managed colonies seem unable to?
What’s in a name?
Before starting to address these questions I would like to clarify some nomenclature. There has been much confusion about how to refer to free-living honey bees, with the terms ‘wild’ ‘feral’ and ‘native’ being used interchangeably without agreed definitions.
In this and the following article the term ‘feral’ will refer to newly establishing colonies of less than two years. The great majority of these will have originated from swarms from managed colonies (simply due to the relative numbers involved – see diagram). Many of these escapees will be short-lived: some will be deliberately eradicated and others will perish in sub-optimal cavities. As we have seen above, a proportion will be able to establish themselves successfully over a period of several years, adapting in the process to environmental pressures, including, presumably, varroa-vectored viruses. The term ‘wild’ therefore seems appropriate for these longer-lived colonies which survive for over two years and reproduce without human assistance.
It is also important to distinguish between ‘wild’ and ‘native’ honey bees. It is doubtful that a genetically pure honey bee corresponding to the Apis mellifera mellifera that may once have been native to the UK still exists anywhere in the wild. Certainly managed colonies of ‘black bees’ are maintained by enthusiasts but the numbers are relatively small and the genetic purity of escapees from these stocks would soon be lost as they subsequently interbred with surrounding populations.
Relative numbers of, and relationships between, managed and unmanaged honey bees in the UK.
Numbers are gross estimates. ‘Feral’: Colonies aged < 2 years. ‘Wild’: Colonies aged > 2 years. Estimates of feral numbers were extrapolated from ad hoc surveys of observations of free-living colonies by beekeepers collated by David Heaf⁴.
A truce with the mite?
The implication of this study is that there is a resident population of free-living honey bee colonies in Perthshire which is tolerant of varroa yet, in all likelihood, freely interbreeds with managed colonies, thereby negating any genetic adaptation assumed to occur in more isolated populations. So how might they cope?
There are, in fact, many behavioural mechanisms by which honey bee colonies are known to be able to adapt to varroa, ranging from increased grooming, early detection and disposal of infected brood, to increased brood-nest temperature (to name a few). Little understood epigenetic factors (induced changes in gene expression in both the bee and the mite) may also have a bearing. It is likely that treatments for varroa inhibit this adaptation process.
There are other factors that favour feral colonies: they are normally further apart than hives in conventional apiaries and the reduced drifting of foragers between hives will allow co-adaptation of bee and mite within individual colonies. Wide colony spacing also favours vertical transmission of disease (from mother to daughter hive), whereas horizontal transmission (between colonies) is favoured by crowded apiaries and by using splits instead of swarms to start new hives. Vertical transmission leads to less harmful variants of pathogens since the host must be fit to reproduce in order to transmit the disease organism. The recent discovery of a less virulent form of the DWV virus prevalent in apiaries where varroa treatments are not used is likely to be significant⁵. The number of varroa in a colony is of secondary importance to its survival if the form of DWV virus present does not cause disease symptoms.
The properties of the cavity adopted by a colony must, to some extent, affect its chances of being able to establish itself. In Northern climates hollow tree cavities offering excellent thermal insulation are the historical favoured choice for honey bee swarms. Yet most of the colonies in this study have adopted cavities with less than ideal dimensions. This presumably reflects the restricted choice available to home-seeking swarms in the modern environment. A typical space behind soffit boards will be much smaller than the 40 litres preferred by the home-seeking scout bees, and will be narrow, giving it poor thermal properties. The abandoned National hives in this study are arguably even worse in this respect, being thin-walled and therefore prone to extreme temperature variations as well as in poor condition with gaps in the rotting wood rendering them draughty. If bees can survive without help in sub-optimal cavities imagine how they might prosper under ideal conditions!
It is hard not to feel admiration for survivor bees. Rather against the odds, most of the ones reported here seem to have thrived compared with the pampered managed colonies in the vicinity which are treated for varroa and copiously fed to avoid starvation. At the same time, it seems improbable that the possible adaptive mechanisms listed above, despite their impressive variety, can explain the long term survival of the bees in this study. After all, these bees are almost certainly very similar genetically to many of the managed populations that surround them. Have we forgotten some other key feature of their environment?
In fact, the environment of the managed colonies might be a better place to look for the key to this conundrum. Managed colonies have to contend with a feature of their environment that none of the colonies in this study are exposed to … ‘an elephant in the broodnest’, so to speak. What sets wild and managed colonies apart is, of course, seclusion … freedom from any form of interference by beekeepers. Unpopular though this assertion is in conventional beekeeping circles, this must be a major factor in the success of wild honey bees. Only when freed of this constant stress can colonies express the full range of adaptive behaviours that allow them to cope with environmental challenges.
‘Wild’ colonies as defined here are a relatively novel and amorphous genetic mongrel: they are, through beekeeper practices of importation over the last 200 years, what we have ended up with and, since they have become established in the wider environment, what we will likely bequeath to future generations of beekeepers. That they can survive and prosper in less than ideal cavities without help in the modern, hostile environment is remarkable. If we can get to know them better they might have more to teach us in our quest for bee-centred beekeeping.
Next time: Taking a Closer Look
In the next article (to be published on The Natural Beekeeping Trust Site soon) I will describe my attempts to monitor what happens when bees are allowed to occupy bee-appropriate cavities (hives, if you must…) without disturbance and free to display all their natural behaviours. Among many surprises, I discovered a surprising clue to their success…
I would like to thank David Heaf for his help in preparing this manuscript as well his untiring support in the search for gentler, more bee-centred approaches to beekeeping. The Trust would also like to thank Natural Bee Husbandry for permission to reproduce this article.
3. Parasite Pressures on Feral Honey Bees (Apis mellifera sp.) Catherine E. Thompson, August 15, 2014, https://doi.org/10.1371/journal.pone.0105164
4. David Heaf, personal communication
5. Superinfection exclusion and the long-term survival of honey bees in Varroa-infested colonies The ISME Journal (2016) 10, 1182–1191; doi:10.1038/ismej.2015.186; published online 27 October 2015 Gideon J Mordecai, Laura E Brettell, Stephen J Martin, David Dixon, Ian M Jones and Declan C Schroeder