by Dave Goulson
CHAPTER SEVENTEEN
Return of the Queen
The presence of short-haired bumblebees in New Zealand had inspired a plan to bring them back to the UK. Mick and I had learned a fair bit about the sorts of plants that they needed by visiting them in New Zealand. In 2008 I arranged a meeting with the key players at the RSPB’s headquarters in Bedfordshire (a beautiful and vast old stately home strangely known as the Lodge). Natural England’s invertebrate specialist David Sheppard was there, along with Jane Sears from the RSPB, Mike Edwards and Paul Lee from an organisation known as Hymettus (which provides specialist advice on the conservation of bees, wasps and ants), and Brian Banks from Swift Ecology, a consultancy based in Kent. The final stronghold for the short-haired bumblebee had been Dungeness, with the very last British one seen there in 1988, so it made sense for this to be the first release site, should a reintroduction go ahead. It might seem odd that the RSPB was involved, but a substantial chunk of Dungeness is owned and managed by it as a nature reserve. It is perhaps not widely appreciated, but the RSPB makes great efforts to conserve species other than just birds, and had already been busy improving habitats for bumblebees on the reserve. Between us, we discussed what we knew about the short-haired bumblebee, and managed to convince ourselves that there was a realistic chance of success, so long as funding could be secured. It was clear that synchronising the bee with the UK climate was going to be a substantial obstacle, but we came up with a number of possible solutions to this. In the following weeks, David Sheppard pitched the idea to his bosses at Natural England and, to everyone’s delight, they agreed to fund a three-year project, with sufficient money for a dedicated project officer.
We advertised the post and soon after appointed Nikki Gammans, a loquacious freckle-faced redhead from Essex. She had recently finished a PhD on ant biology, and had been involved in translocating rare ants back to sites from which they had died out, so she was well suited to the job; those of us who were on the interview panel had some reservations as to whether she would be able to relate to farmers since she had no farming background or experience, but they turned out to be ill-founded.
The first stage of the project had to be to create enough habitat for short-haired bumblebees to survive. After all, they had died out for a reason, and it would be very depressing and rather pointless to go to the expense of shipping them halfway round the world if they were just going to die out again.
Dungeness is a rather strange place. It has a peculiar, brooding atmosphere, no doubt in part due to the ugly concrete structure of the nuclear power plant that looms above it. Because of the extraordinary flatness of the landscape, the reactor and chimneys are always in view. Ecologically speaking, it is a very unusual habitat, one of the largest expanses of shingle in the world. It has been used for gravel extraction for many years, creating lots of shallow pools that are much loved by wading birds. One might imagine that shingle would be a fairly bleak and inhospitable habitat for bees, but in fact the shingle is swathed in an extraordinary diversity of flowers in spring and early summer. Because there are very few nutrients, legumes, which can fix their own nitrogen via root nodules, thrive, providing lots of the flowers that bumblebees adore. The shifting shingle provides a great habitat for viper’s bugloss, a plant that also thrives on the stony overgrazed sheep pastures and pebble-strewn lake shores of New Zealand where we had found it to be a favourite with short-haired bumblebees. Why then had short-haired bumblebees died out here in the first place? Our best guess was that they had suffered due to changes on Romney Marsh, which encircles Dungeness on the landward side. The Marsh was once filled with flower-rich water meadows and hay meadows, which had been largely destroyed by intensive farming. The area of flower-rich shingle was probably not enough to support a viable short-haired bumblebee population, particularly since in dry years the flowers tend to die off on the shingle before bumblebee nests have completed their annual cycle. Thus the key to success with this reintroduction would be to replace some of this lost habitat on Romney Marsh and the surrounding area.
We could not be sure exactly how much good habitat would be needed, but there was no doubt that the more we could create the better the chances would be that the bees would survive. Thankfully, Brian Banks and local Natural England staff had been working for some years to encourage landowners in the area to improve habitats for bumblebees; although the short-haired bumblebee had died out, there were still other rare species in the area, such as the moss carder and brown-banded carder bumblebees. Together with the work done by the RSPB, there was already a fair bit of flower-rich habitat in the area – certainly more than there had been in 1988 when the short-haired bumblebee disappeared. Nikki set about creating more, working with local landowners, particularly farmers, to encourage them to put in pollen-and-nectar strips, or clover leys, or to sow wild-flower meadows. She organised ‘farm days’, when farmers could meet on a farm and see examples of flower-rich habitat and learn about short-haired bumblebees and the project. Just as the crofters in remote regions of Scotland quickly engaged with the idea of helping great yellows, so many farmers in Kent seemed genuinely excited at being involved in a project to bring back this extinct bee. A local wind-farm company also came on board, agreeing to sow a vast expanse of flowers under their turbines. In no time at all, patches of flowers were springing up all over Romney Marsh and around.
The next phase of the project was to investigate how we might get the bees back from New Zealand and into sync with the UK seasons. Queen bees are fairly easy to find and catch when they emerge from hibernation, since they spend several weeks flying about looking for somewhere to nest. Mick and I had seen short-haired bumblebee queens on our visit. But in New Zealand, these queens emerge from hibernation in December; if we caught them then and brought them back to the UK it would be midwinter and they would quickly freeze to death. Catching young newly mated queen bees at the end of the New Zealand summer (March) would be ideal, as these could be briefly hibernated, brought back and released in the UK three months later in June. The problem with this plan was that queens dive into hibernation underground almost as soon as they have finished mating, so they are seldom seen at the end of the summer. For a rare species such as the short-haired bumblebee in New Zealand, we were not optimistic that we would find enough by that route.
Of course the queens that were used for the original introduction to New Zealand were dug out of the ground while hibernating – if that were possible during the New Zealand autumn, then they could be brought back to the UK while still hibernating and woken up early in June. However, in New Zealand we had seen only small numbers of short-haired bumblebees scattered across a vast area of stony countryside. We had no idea where to dig for the hibernating queens, since there was no obvious equivalent of the ditch sides from which short-haired bumblebee queens were originally dug in Kent. Digging holes randomly to look for queens would be a back-breaking and utterly futile exercise. What then to do?
The ideal solution would be to catch nest-searching queens in the New Zealand spring (December) and persuade them to rear nests in captivity. If a number of nests could be reared then both new queens and males would be produced in March, and these could be mated in cages, the queens put into hibernation and then shipped back to the UK in refrigerated conditions for release in June. This would have been very easy for buff-tailed bumblebees, which breed readily in captivity. Unfortunately many other bumblebee species are extraordinarily hard to breed in captivity, and very little information was available as to how to breed short-haired bumblebees. Nikki did track down a Czech bumblebee enthusiast, Vladimír Ptacek, who had reared one or two short-haired bumblebee nests, and she visited him to find out the details. He had done it by placing young nests in large cages full of flowering clover so that the bees could collect their own food. This was all very well but meant that the rearing would have to be done in New Zealand, for we would not be able to provide stands of flowering clover in the British winter. While investigating the
possibilities we stumbled across contact details for a Rosemary Reid who lived in Christchurch on South Island and who bred bumblebees semi-professionally, selling the nests to farmers. She had apparently bred short-haired bumblebees in the past, and was willing to rear our bees for us, for a price. We agreed that Nikki would go to New Zealand to catch the queens in December 2009, and supply them to Rosemary to set up the captive breeding programme.
With the help of local New Zealand bumblebee expert Barry Donovan, Nikki had little trouble collecting queens, which she stored in hair curlers38 in the fridge in her camper van and transported back to Rosemary’s house in Christchurch. Rosemary gave each queen a supply of nectar to drink and a ball of pollen mixed with nectar in which to lay her eggs. For some she added workers of garden bumblebees, in the hope that they would help the queen rear her brood. Via Nikki, we received regular reports as to the progress of the queens. Some did not take to captivity and soon died. Others seemed to settle down and lay eggs, but then died unexpectedly. Still others successfully reared some offspring, but their nests grew painfully slowly. Part of the problem may have been that Rosemary didn’t have fresh clover pollen, which we think is their favourite, to feed them at the start. Whatever the reasons, the number of queens steadily dwindled until just a handful remained. A few finally produced males and just five new queens, which readily mated. These five queens were put into hibernation prior to being shipped back to the UK. Five wasn’t likely to be enough to establish a new population, but at least we could gain experience in bringing them back, or so we thought. In the meantime their dead nest mates were sent to Mark Brown, a bumblebee disease expert at Royal Holloway in London, to make sure that they didn’t have any unpleasant diseases that we would not want to accidentally bring into the UK. Sadly, a few weeks later Rosemary emailed to say that the five queens had died of unknown causes in hibernation. There would be no reintroduction of short-haired bumblebees in 2010.
Nikki came home from New Zealand and spent her summer encouraging the creation of more flowery habitat in Kent. In December, she went back to New Zealand to try once more. Breeding the bees in captivity had not been a roaring success, and Rosemary was asking for considerably more money this year to repeat a process that had been decidedly fruitless. We couldn’t afford to pay what she was asking, and we were not convinced that she would do any better second time around, so we decided on a different tack. Bumblebee nest boxes are notoriously ineffective in the UK, but in New Zealand they seem to work quite well, and there are old records of them being used by short-haired bumblebees as well as the more common bumblebees found in New Zealand. If the bees could be persuaded to nest in an artificial box outside, then the nests would look after themselves and could be collected in just as they started to produce new queens and males.
With the help of Barry, Nikki set out nest boxes at the sites where she had seen most short-haired bumblebees the previous year. She monitored them every few days, but disappointingly she saw no short-haired queens anywhere near them. After a week or two she started to get a little desperate, and experimented with catching queens and confining them in the boxes with food. This has sometimes been found to work with other species; once they have been trapped in a nest box for a few days they grow used to it so that when the door is opened they do not simply fly away, but adopt the nest as their own. Unfortunately Nikki’s bees had not taken to their boxes, and promptly disappeared when she opened the door. Within a few weeks the time when queens start nesting was over, and we had nothing to show for it. Nikki tried searching for wild nests but it was like looking for a needle in a haystack. Eventually, rather despondent, she returned home.
In the meantime, back in my lab in Stirling, Gillian Lye had been studying the DNA of short-haired bumblebees. I had previously brought back toe samples from my visit to New Zealand with Mick. Gillian had also visited the Hope Entomology Collection in Oxford where she had been allowed to take toe clips from short-haired bumblebee specimens collected before their extinction in the UK. Finally, she had asked a Swedish scientist, Bjorn Cederberg, to send her samples from the only known strong European population of this species, in southern Sweden. Gillian used genetic markers to study the amount of genetic diversity in each population – a measure of their genetic health – and also to compare how similar the three populations were to one another. Her results were somewhat alarming. The New Zealand bees were decidedly weird. They had astonishingly little genetic variation, and were very different from the UK museum specimens. With the help of Olivier Lepais, a French expert in genetic analyses who was briefly based at Stirling at the time, she was able to estimate the probable number of short-haired bumblebees that were introduced from Kent in 1885. You may recall that ninety-seven queen bees survived the journey to New Zealand and flew away when released at the Christchurch Botanic Gardens. No record was kept as to which species were included, but it seems likely that the majority would have been of the more common species such as the buff-tail. Although four species of bumblebee became established in New Zealand, it is very probable that the sample also included other common UK bumblebees such as the white-tail. It would be a fair guess that there were rather few short-haired bumblebees since this was always a relatively uncommon species, but nonetheless Gillian’s results came as a bit of a shock. Her data suggested that the entire New Zealand population of short-haired bumblebees was descended from just two queens.
This is an extreme example of what is known as a genetic bottleneck. If a population crashes to very low numbers – or in this case is founded by very small numbers of individuals – then it loses most of the genetic variation present in the original population. This reduces the potential of the population to adapt, and also leads to very strong inbreeding, since all the individuals are closely related to one another. If the population was started by two queens then within just one generation all bees would be brothers and sisters or at best cousins of one another. As we have seen, inbreeding leads to the expression of rare, recessive and harmful genes, which can result in deformities and generally low survival of individuals. Such populations would normally be expected to die out swiftly, but just occasionally, as here, they do not.39 In New Zealand, there are lots of flowers, and rather fewer competitors than in England. Also, most of the diseases of bumblebees were left behind, so life has probably been fairly easy for bumblebees in New Zealand. It would seem that even bees of low genetic health were able to survive there. But would these bees be able to cope back in England, when faced with more competition and when exposed to diseases that they had not encountered for well over 100 generations?
Further doubts were raised when we examined the patterns of relatedness between the three populations that Gillian had examined. Aside from being inbred, the New Zealand bees were very different from those from the UK. That initial bottleneck and then 126 years of isolation had wrought huge changes in their genetic make-up. Ironically, the Swedish bees were more similar to the original UK bees than were those from New Zealand, despite that fact that the New Zealand bees were direct descendants of the UK population.
Gillian’s work caused us to rethink our plans. Should we continue with our efforts to bring short-haired bumblebees back from New Zealand, or switch to an introduction from Sweden? The genetic data suggested that the New Zealand stock was in pretty poor shape, and that the Swedish bees were actually closer to the original UK bees, but nonetheless there was resistance to the switch. There was a beautiful symmetry to the idea of bringing these bees back to the UK from the other side of the world after a 126-year absence. David Sheppard of Natural England was initially reluctant, correctly arguing that we would probably have not considered doing the reintroduction at all if not for the existence of the New Zealand population. Natural England wanted British bees or bust. However, after long debate, they came around to the new approach. It has significant advantages. The Swedish bees are not out of synchrony with our seasons, making the process much easier since we could simply catch spring queens in Sw
eden and ship them direct to Kent for release. The source population is relatively healthy in genetic terms, and similar to the original UK population. Sweden has the same range of bee diseases as the UK, so the bees would not be exposed to anything new on arrival; this also made it unlikely that we would accidentally import a disease strain that might harm native UK bees. Overall, it seemed much more likely that the reintroduction would succeed if we used Swedish bees.
By the time this decision was made it was too late to organise a release for 2011, but buoyed by the realistic prospect of a release in June 2012, Nikki returned to her spring and summer job of encouraging landowners to create habitat around Dungeness. This work went extraordinarily well. I’m not sure how, but by the end of the summer of 2011 Nikki and the project partners had helped to create over 500 hectares of new flower-rich habitat in south-east Kent. Some farmers had put whole fields into red clover leys, many had sown strips of wild flowers along field margins, and others had undertaken major meadow restoration projects. Brian Banks produced maps of the new habitat, which showed a rash of patches around Dungeness, westwards to Rye and north-west to the edge of the High Weald of Sussex. What is more, we gained strong evidence that this work was benefiting bumblebees. Nikki, Brian and a team of volunteers had been recording bumblebee numbers around Dungeness for the previous few years. Dungeness and Romney Marsh used to have one of the richest bumblebee faunas in Britain, but it wasn’t only the short-haired bumblebee that died out in the area. Shrill carders, red-shanked carders and ruderal bumblebees had also vanished. In 2011, all three of these reappeared of their own accord; several ruderal bumblebees were found in the west around Rye harbour, a single shrill carder turned up at Dungeness, and a red-shanked carder was spotted to the north-east of Rye. What is more, two other endangered species which had clung on in the area in small numbers, the brown-banded carder and the moss carder, had both increased and extended their ranges in the region.
