Bee Quest

by Dave Goulson

  The ruderal bumblebees may also offer a clue as to what is going on. Ruderal bumblebees in Argentina appear to have been almost as badly affected by the arrival of the buff-tails as have dahlbomii. This is intriguing since the ruderals also originate from Europe, so one might expect them to be resistant to European diseases. On the other hand, those in Chile and Argentina were brought from New Zealand, where they had been living for about a hundred years since their original introduction from England. If they had not been exposed to a particular disease for a hundred generations in New Zealand they might well have lost their resistance to it. Thus the cause of the problems, if indeed it is a disease at all, must be something which occurs in Europe but was not transferred to New Zealand when bumblebees were introduced there. As luck would have it, I had collected samples of ruderal bumblebees from New Zealand some years earlier so it would be easy enough to check what diseases they have there – I just need a little funding from somewhere to cover the costs.

  With a little more detective work, I hope that we can diagnose the cause of the demise of dahlbomii, but what then? We cannot vaccinate the remaining bees in Tierra del Fuego before they are wiped out. It might conceivably be possible to set up a captive breeding programme, but this would be extremely tricky, for they have never been bred in captivity before, and in any case we would probably never be able to release them back into the wild unless future technology can provide some permanent solution to the problem. One of the more innovative suggestions that has been put to me is that we should evacuate some dahlbomii from Tierra del Fuego to the Falkland Isles, which have no native bumblebees at all. The climate there is probably quite similar, though I have no idea whether there are suitable flowers, or whether dahlbomii would survive. Perhaps an Anglo-Argentinian project to save a bumblebee could help to repair the poor political relations between our two countries? On the other hand, might we do more harm than good by going down this route? There are no doubt native pollinators of some sort in the Falklands, and they might suffer from competition with a new bumblebee, or even be infected by diseases that naturally occur in dahlbomii. All things considered, and appealing though this idea is, I suspect that we should learn our lesson and not meddle even more with things we do not well understand, for fear of making things even worse.

  Potentially, there are more dire consequences of the introduction of buff-tailed bumblebees than the demise of dahlbomii. We have no idea how the other South American bumblebees will respond when faced with this new invader. If the disease hypothesis is correct, then it seems probable that the other native species will also be susceptible. The lovely opifex were just a short hop north of the advance wave of buff-tails heading for Mendoza in 2012, and at the time of writing this in 2015 it seems highly likely that the populations Jess and I found have been overrun. Will they too disappear? Further north still, there are many more bumblebees. South America has twenty-four in total, many living in the Andes of Peru and Colombia. How far can the buff-tails go? We do not know. It should be possible to predict this from their known climatic tolerances – in Europe they range from Scotland to the south of Spain, and also to Morocco, Tenerife and eastwards into the arid lands of the Middle East. They are clearly highly robust and adaptable creatures, perhaps more so than any other bumblebee, and with the cool mountain chain of the Andes to follow northwards, they may be able to penetrate much of South America. Only time will tell.

  It is not entirely without hope. Tierra del Fuego may prove to be too cold for buff-tails, although I doubt it, but if this were so then it could remain as a refuge for dahlbomii. There may be undiscovered, remote mountain populations of dahlbomii in parts of the Andes where buff-tails cannot penetrate. The occasional sightings of dahlbomii near Bariloche, eight years after buff-tails arrived there, provide perhaps the brightest prospect. Just as a small proportion of the Native Americans survived the onslaught of disease, so it may be that these surviving dahlbomii possess a degree of resistance. If enough have survived, perhaps their population may slowly recover, for the habitat in which they once thrived is mostly still there, waiting for them.

  After Bariloche, we headed east. I would have loved to continue southwards far enough to finally see some dahlbomii, but we didn’t have time, and we knew what we would find in that direction, for Marina already knew how far buff-tails had spread south from Bariloche. Instead, we turned east, away from the Andes, to complete the picture of how far buff-tails had spread, and to find out whether there were any native bumblebees between Bariloche and the Atlantic coast. We soon left the verdant forests behind and were once more in an arid, inhospitable, rocky landscape. We drove past fantastic folds of limestone, layers of rock once laid down in a seabed perhaps 100 million years ago, now tilted on their side and buckled by volcanic activity. To make a change from bee-hunting, we spent a while clattering around amongst the rocks looking for fossils. They teemed with ammonites, long-extinct molluscs from the ancient sea. There have been some remarkable fossil finds in Patagonia, including several new species of dinosaur, but we didn’t find anything quite so dramatic.

  Although we didn’t find any dinosaur fossils, the following day we did round a corner to see a real dinosaur eating a man, or so it at first seemed. For reasons that remain obscure, someone had constructed a life-sized fibreglass replica of one of the larger predatory dinosaurs and placed it in the middle of nowhere. A passer-by had chosen to park his car under the gaping jaws, climb onto the roof and then jump up to hang from the teeth, just as we came into view.

  As we travelled towards the distant east coast, we searched every good patch of flowers for bumblebees, but we were not to find a single one of any type on the rest of our trip. We saw many other wonderful sights – including rheas, giant flightless birds first described in detail by Charles Darwin in his travels on the Beagle. Most were family groups trailing a dozen or more youngsters. There were guanacos and llamas, trotting in small groups across the dry plains, but no matter how hard we looked we could find no bumblebees. Buff-tails seem not to have penetrated far to the east, which is peculiar given the extent of their spread north and south, and also that the prevailing wind would carry them eastwards. There is an extensive area of near-desert immediately east of Bariloche, but no worse than those they must have crossed to move north. Three hundred kilometres to the east we found well-watered, flower-rich areas where I would guess that they could thrive, and I suspect they will arrive there eventually.

  Further east we crossed the Pampas, a vast area of grassland dotted with acacia trees, which in spring has many flowers. It seemed as if it ought to be a good place for bumblebees of some sort or other, but we found none. Here the gauchos did have more impressive beasts to herd, for this region supports fifty million head of cattle. We had already eaten plenty of beef, but that evening we carelessly ordered a ‘mixed barbecue’, expecting more delicious steak cuts. This was perhaps naive, for we were served an interesting selection of body parts which we struggled to identify, but which almost certainly included slices of barbecued penis and an awful lot of tripe. Eventually, after covering nearly 6,000 kilometres of bumpy and dusty roads, we emerged on the coast near the city of Bahia Blanca. There was a pleasant sandy beach so we rushed in for a refreshing dip, but I was almost immediately stung by a jellyfish, which rather took the fun out of it. The tentacles stuck to the flesh of my feet, causing red weals to rise up as if I had been whipped.

  The introduction to South America of European bumblebees is yet another cock-up in a long history of predictable catastrophes orchestrated by man. It occurred long after we should have known better. Presumably a few farmers thought they might benefit financially from having buff-tailed bumblebees in their fields in Chile, and the wildlife of an entire continent is now paying the price. It is conceivable that twenty-four species of bumblebee could be wiped from existence by this one thoughtless act. There does not appear to be any solution to the problem, no way of undoing what has happened. We can hopefully identify the agent behind th
e decline of dahlbomii, and perhaps this will be useful for informing any future debates as to the advisability of introducing non-native bumblebees elsewhere. Perhaps the native bumblebees in northern South America have some bumblebee equivalent of syphilis which might halt the spread of buff-tails.

  The latest news from South America, as of January 2016, is that the buff-tails have reached the northern shores of the Strait of Magellan. At the narrowest point, the Strait is only about ten kilometres across, so this is unlikely to hold them up for long. A Chilean entomologist named Jose Montalva has successfully launched a campaign to raise the profile of dahlbomii, and to encourage people to send in records of sightings of both the native and invading species. A few dahlbomii continue to be seen in the invaded area, giving hope that these may be individuals with resistance to the European diseases. It will be fascinating to see what happens, and all we can really do now is cross our fingers and hope for the best. I also hope that one day I will get to see a giant golden bumblebee, alive and well in its native forests, but unless I can find a pressing need to go to Tierra del Fuego sometime very soon, the odds are probably against me.

  CHAPTER FIVE

  California and Franklin’s Bumblebee

  Biological diversity is messy. It walks, it crawls, it swims, it swoops, it buzzes. But extinction is silent, and it has no voice other than our own.

  Paul Hawken

  In spring 2013 I was invited to Davis, part of the University of California, to give a couple of talks on my research on bumblebees and to meet with the research group of Neal Williams. Neal is a bee biologist, a gangly, laid-back and exceedingly likeable guy whom I had met a couple of times at conferences, and whom I knew to be doing some exciting work on how best to boost pollinator populations in farmland in California, so I was keen to go and learn more about what they were up to. I also had an ulterior motive, for Davis is within striking distance of the last known haunts of Franklin’s bumblebee.

  The tale of Franklin’s bumblebee is a sad one. Were it not for the work of one man, Robbin Thorp, we would know almost nothing about this species. Robbin is also based at Davis, where he worked for all of his long career. For many years he was mainly focused on honeybees and crop pollination, but in his later years he became particularly interested in wild bees, including both bumblebees and the numerous solitary bee species to be found in California. When he retired, now twenty years ago, he had the freedom to do whatever he liked and he focused his interests more on bumblebees, conducting regular field trips all over the USA and elsewhere to study them. It was Robbin who discovered most of what we now know about Franklin’s bumblebee.

  Franklin’s is an attractive, medium-sized bumblebee, almost entirely velvet black with a smart, broad yellow collar, a little military in appearance. It was named in 1921 after Henry J. Franklin, who wrote the first monograph of the bumblebees of North and South America in 1913 and was the first to describe the species. So far as we know from Franklin’s work and museum records, Franklin’s bumblebee was always restricted to quite a small geographic area, on the border between California and Oregon, the smallest known natural range of any bumblebee. As is so often the case, we have no idea why it was restricted to this particular area – it wasn’t extraordinarily fussy in any way that we are aware of, but something kept it tied to this region. It fed on common enough plants, including lupins, Californian poppy and horsemint, amongst many others. We don’t know much about where it nested, but it probably used old rodent burrows like many other bumblebees. Until about 1994 it was quite common if you knew where to look, which Robbin did.

  Tragically, in the mid-1990s something awful unfolded in North America. A whole group of bumblebees very rapidly disappeared from almost the entire continent, in just a couple of seasons. The bees that went were all close relatives, belonging to the subgenus Bombus (to clarify, all bumblebees belong to the genus Bombus, but this is divided up into lots of subgenera of which one is also, confusingly, called Bombus). This group included some of the commonest bumblebees in North America: the rusty patched bumblebee, the yellow-banded bumblebee, and the western bumblebee. Suddenly, these species went from plentiful to scarce or absent. They disappeared entirely from vast tracts of their range. Luckily, most of them have hung on somewhere; for example, the rusty patched bumblebee can still be found at a few sites in Illinois and Iowa, in the north-west of its originally very large range, which once stretched across eastern North America. The yellow-banded bumblebee seems to be doing okay in parts of Maine and Vermont, while the western bumblebee is still reasonably common in Alaska, though it has vanished from perhaps three-quarters of its range. Sadly, Franklin’s bumblebee is the exception. Franklin’s also belongs to this subgenus, but unlike the others it was already a local bee, with a relatively tiny range spanning an area of perhaps 300 by 100 kilometres. In 1995 Robbin noticed that there were fewer than usual, and year on year the population plummeted. By 2006 they were gone. Ever since, Robbin has returned to their former haunts near the California–Oregon border to hunt for them, but without luck.

  So what happened? Our best guess is something similar to the tragedy that is unfolding in South America, although this time there was no deliberate introduction of foreign bumblebees. The cause of the demise of this whole group of bees may have its roots in Belgium in the 1980s, with the commercialisation of bumblebee rearing. A veterinarian and amateur bee enthusiast named Dr Roland De Jonghe discovered that bumblebees provided superbly effective pollination for tomatoes, something that honeybees are pretty hopeless at, and he began rearing buff-tailed bumblebee nests for sale. Prior to this, scientists had reared small numbers of nests for research purposes, but nobody had tried to gear the process up for mass production. Demand for De Jonghe’s nests was huge,fn1 not just within the Netherlands but also from abroad, and by 1990 several factories had sprung up in Belgium and Holland with rival companies vying to satisfy the global thirst for bumblebee nests.

  North American tomato growers wanted access to this new technology, but unlike in Chile, their regulations prevented importation of alien species. Techniques for mass-rearing North American species had not been developed at the time; exactly how the European bumblebee breeders do this is shrouded in secrecy. I was once lucky enough to be shown round the three biggest European factories, but each company insisted that I sign a non-disclosure agreement so that I couldn’t reveal their secrets. What was intriguing was that each factory has developed quite different rearing techniques, but because they will not share knowledge with their competitors they are unable to optimise the process. Sadly I cannot tell you any more or I might find myself in court.

  Clearly in this climate of secrecy folk in North America could not simply ask how to set up their own bumblebee-rearing factories. The story as to exactly what happened next is hazy, but legend has it that queens of some North American species were sent to the European factories to see if they could persuade them to found nests, and that these nests were then returned to North America. It sounds like an entirely plausible scenario, but it is hard to find documented evidence, and the bee-rearing companies are not keen to admit involvement for reasons that will become apparent.

  Unfortunately, it seems to have thus far proved impossible to mass-rear bumblebee nests that can be guaranteed to be free from diseases. Bumblebees naturally suffer from a range of diseases, including viruses, bacteria and fungi, and these are inevitably brought in to the factories when they are starting up new cultures with wild-caught queens. The bumblebee nests also have to be reared on pollen that is taken from honeybee hives, for there is no other cost-effective way of gathering the thousands of kilos of pollen needed (try collecting pollen from flowers yourself, and you’ll soon realise that bees are much better at this than people). Many of the diseases of honeybees and bumblebees are shared, so this pollen provides another route for accidental introduction of bee diseases into the factories. The factories do their best to stamp out diseases as they are clearly not good for business, but the
nests leaving the factories are still commonly infected. A recent study published in 2012 by an Irish research group showed that nests from all of the main European factories are routinely infected with a whole range of unpleasant pathogens.fn2

  It seems very likely that the North American bumblebee nests that were returned from Europe had picked up one or more European diseases, and that these then escaped into the wild bumblebee populations in North America. Unlike the situation in Patagonia, the disease is not being spread by an invading bee species, but presumably spread through the native species. Robbin thinks it was probably a virulent strain of a fungal disease called Nosema bombi, causing a sort of bee diarrhoea. Whatever it was, if indeed it was a disease, we have no idea why the impact was so great on one subgenus and not on the other North American species, although it may be significant that the main species reared in the European factories, the buff-tailed bumblebee, also belongs to the subgenus Bombus bombus. Perhaps, also, the bumblebee species that have not been affected sometimes carry the disease without showing symptoms.

  Conclusive proof for this explanation is conspicuously absent. Just as with dahlbomii, the collapse of these North American bumblebee populations was so fast that it caught scientists napping, and by the time anyone realised what was happening it was largely all over. Nobody could find the bodies and identify what had killed them. Those populations that hung on were presumably those that had a little natural resistance, so even if the pathogen were identified and they were experimentally exposed to it they would perhaps not die.