A Sting in the Tale (31 page)

With the help of local New Zealand bumblebee expert Barry Donovan, Nikki had little trouble collecting queens, which she stored in hair curlers
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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.
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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 Sweden 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.

In mid-April 2012 Nikki travelled over to Sweden, armed with her butterfly net and a large box of hair curlers. We all knew that this was really too early for short-haired bumblebees, which don't usually emerge from hibernation until well into May, but Nikki was champing at the bit and didn't want to miss them if it turned out to be an unusual year and the queens emerged early. We had gathered all the necessary permissions to capture the bees in Sweden, but nonetheless a local conservationist somehow got the impression that we had not, and by the power of social media quickly mounted a campaign to prevent the capture going ahead. There was a brief storm of media interest in the Swedish newspapers, in which we were described as ‘typical British imperialists', amongst many other things, but thankfully this quickly died away when it was discovered that we did have both formal permission and the support of local bumblebee experts.

For reasons we do not fully understand, short-haired bumblebees seem to be thriving in southern Sweden, unaffected by the problems that have beset them elsewhere in Europe. Nikki had no trouble catching queens, most of which were feeding on white dead-nettle along the verges of country lanes. By 10 May, eighty-nine of them were safely housed in hair curlers in the camper van and were on their way back to the UK. Nikki handed them over to Mark Brown, who held the queens in quarantine for a fortnight while he carefully examined their faeces to determine if any of the bees were carrying infections. During this period a few of them died, with a parasitoid wasp named
Syntretus
bursting from their bodies. A few more were found to be infected with gut diseases and had to be humanely destroyed. On 28 May, Nikki picked up the remaining fifty-one healthy bees and drove them to Dungeness for their big day.

An excited crowd had gathered at the appointed spot, on the edge of a field full of clover. The respective press offices of Natural England, the RSPB and the Bumblebee Conservation Trust had done a great job and there were swarms of journalists and camera teams, as well as local conservationists, farmers and staff of the various organisations. Nikki had placed a few of the queens in clear plastic boxes, but kept them cool and in the dark until the last moment so that they did not become flustered and bash themselves about trying to escape. When the cameras were ready, and to a hush from the audience, Nikki revealed the first queen bee. Shutters clicked eagerly, and then the lid was opened. The queen buzzed her wings once or twice experimentally, warming her flight muscles while she tasted the air with her antennae. And after a moment or two, she flew away. For the first time in twenty-four years, a short-haired bumblebee was on the wing in England.

The story was much the same with the rest. A few paused to feed on the clover, but then they were off, heading away across the flat fields. And that was the last we saw of them. Of course this was exactly what we might have expected them to do, but nonetheless it seemed rather anticlimactic. Slowly, with nothing left to look at, the crowd of people dispersed and it was all over, at least as far as the media was concerned.

For the rest of the summer, Nikki and her team of volunteers searched for the queens and their offspring, but none were seen. The summer of 2012 was spectacularly wet and awful, which was unfortunate and may have led to the demise of our precious Swedish bees, or it may not. Queen bees are powerful fliers and we have no idea how far they might have gone, or what their fates were. They could have been more or less anywhere in south Kent or east Sussex, and looking for fifty-one bees across several hundred square miles of countryside is a thankless task. It would be easier if the short-haired bumblebee were a distinctive species, but they do look rather similar to several other native species so only an experienced person is likely to notice one, and there aren't many experienced bee spotters. In fact, many members of the public claimed to have seen one having read about the release in the papers, and some sent in photographs of what turned out to be other bumblebee species. None of the sightings could be confirmed.