A Sting in the Tale (13 page)

The spiders aside, our bee-counting revealed something we hadn't anticipated. Just over half of all the bees we counted were honeybees. Honeybees are the anorexic cousins of bumblebees, smaller, slimmer and much less furry; they are usually fawn or tan in colour with vague darkish stripes. Now honeybees are also not native to Tasmania. They come from Europe and the Middle East, but they have been domesticated by man since prehistory (ancient Egyptian hieroglyphs contain carvings of bee hives). Because they have always been highly valued both for crop pollination and for their honey, we have imported honeybees to every country in the world except Antarctica. They were introduced to Australia in 1821, and there is now a very big honey industry. Tasmanian leatherwood honey is particularly delicious, and fetches a premium price.
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When we analysed our data, which contained many thousands of records of insects at over 120 sites, we found no measurable effect of bumblebees whatsoever. Places where bumblebees had recently invaded had just as many native bees (both in terms of numbers of different species and numbers of individual bees) as places where bumblebees had not yet arrived. By contrast, the honeybees were having a major effect. Wherever we found honeybees, there were on average only one-third as many native bees. With hindsight, this result is perhaps not surprising. Honeybees were much more numerous than bumblebees, and as they also live in much larger colonies, if any non-native species was going to be competing with native bees by using up lots of pollen and nectar then honeybees were always going to be the more likely candidate. They also have quite short tongues, as do all the native bee species, so they tend to feed on the same flowers, whereas bumblebees have longer tongues and so tend to choose different flowers (although there is lots of overlap). So if bumblebees were impacting on native species, they were far more likely to be doing so on birds such as honeyeaters, who favour deeper flowers.

Discovering that honeybees seemed to be having a harmful effect on native species put us in a rather delicate position. Bumblebees had recently arrived in Tasmania, and had we found that they were causing harm to native bee numbers nobody would have been too upset or surprised. On the other hand, honeybees are highly valued and make a significant contribution to the economy. Many people make their livelihoods from keeping them, and they no doubt contribute to pollination of many crops. Understandably, these folk would not appreciate a bunch of Poms swanning over for a few weeks and then declaring their beloved honeybees to be undesirable aliens. But on the other hand, there is no doubt that honeybees are a non-native species. It also seems to me common sense that flowers can produce only so much nectar, and that there can therefore be only so many bees in a particular habitat. Something has to give, and that thing is likely to be the local flower-visiting insects. This is just as true elsewhere in the world as it is in Tasmania. There are huge honey industries in New Zealand, mainland Australia (I've always thought eucalyptus honey tasted rather medicinal but it is very popular), and throughout the Americas, and in all these places honeybees are non-native.

Let me bore you with a few figures. A single honeybee hive contains 50,000 workers or more, and it is common for beekeepers to put twenty hives in a single place – 1 million bees. A single honeybee nest harvests up to 60 kilograms of pollen and 150 kilograms of nectar per year. At high hive densities, honeybees can harvest up to 22,500 kilograms of honey per square kilometre. The New Zealand honey industry produces 8,000 tonnes of honey per year from 227,000 managed hives, or thereabouts. Some of these vast quantities of honey are obtained by the bees foraging on crops which are in turn pollinated, but a large proportion comes from the bees visiting wild flowers. With this much honey being taken by honeybees, it seems obvious that there is likely to be an impact on other creatures that need nectar.

Even in places where honeybees naturally occur such as the UK, beekeepers often create unnaturally high densities. A student of mine, Kate Sparrow, recently found that bumblebees in Scotland tend to be smaller in places where there are lots of honeybees, presumably because of competition for food.

I do not want to pick a fight with beekeepers. Most are very fond of bumblebees and other insects. They are invariably aware of the shortage of flowers in the countryside and keen to support efforts to make it more bee-friendly. In short, in many ways beekeepers are the natural allies of a bumblebee conservationist such as me. But there is no denying the potential conflict and I am sometimes saddened by the strong reaction of some beekeepers to the merest hint that their bees might occasionally do harm. It is the simple truth. In fact, there are rather few places where there is likely to be any major conflict between conservationists and beekeepers. In most of the farmed countryside, be it in Tasmania, New Zealand or the UK, the benefits that honeybees provide through pollinating crops and producing honey greatly outweigh any small impact they might have on other insects. But in a few special places, it might be wise not to station honeybee hives. Imagine a small nature reserve in Tasmania, for instance, supporting the last-known surviving population of the striated dongle bee (a hypothetical creature, in case you were wondering). Would this be a sensible place to put twenty honeybee hives? Similarly, imagine a small Hebridean island called Oronsay, supporting a population of the endangered moss carder bee. Would this be a sensible place to put another twenty honeybee hives? In both cases (one theoretical, one real), the obvious answer would be no. But it is surprising how much hot water I have got into for saying so.

I have digressed. Jane, Andrea and I set out to discover whether bumblebees in Tasmania were doing any harm. So far as native bees were concerned, the answer seemed to be no. We also looked at the seeds of the introduced tree lupins to see whether the arrival of bumblebees had awakened a new sleeper weed. In this respect, bumblebees appeared to be having a strong effect. Lupins are related to peas, and their seeds form in rather similar pods. Each yellow spike has lots of individual flowers attached to a central stem, and if all goes well then each flower produces a pod full of seeds. In places where there were no bumblebees, roughly 60 per cent of flowers fell off without setting any seed, and where they did set seed there were only about two seeds per pod. In contrast, in sites where bumblebees had become common, only 30 per cent of flowers set no seed and on average there were about six seeds per pod. Overall, bumblebees were allowing each lupin plant to produce more than four times as many seeds. It seemed likely that the arrival of bumblebees might well lead to tree lupins becoming as big a weed in Tasmania as they are in New Zealand.

Eleven years later I wanted to find out what had happened. By that time I was based at Stirling University, and an excuse to escape the Scottish winter for some Antipodean sun was even harder to resist than ever. So it was that in December 2010 I found myself reprising our whistle-stop tour of Tasmania, this time with a PhD student named Ellie Rotheray, who was moonlighting from her studies of the UK's rarest fly, the pine hoverfly.
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On our first morning, with lashings of coffee inside us to counteract the effects of jet lag and a thirty-eight-hour journey, we tried to find some of our former lupin populations just south of Hobart. We hadn't had the benefit of a GPS back in 1999 so we had no precise coordinates to go to, but I did have scribbled notes on a very tatty map and I thought that I remembered the sites fairly well. The first lupin patch on the edge of the pretty seaside town of Kingston was still there, just, but had largely been destroyed by diggers creating what appeared to be a rough car park. Only a couple of bedraggled plants survived, half-buried under the rubble. The second patch, a little further south along the side of a main road, seemed to have disappeared entirely. We drove up and down looking for it, as I scratched my head and mumbled apologetically, ‘I'm sure it was round here somewhere…' I was starting to fear that we had flown 11,000 miles on a wild goose chase. We headed south, and as we failed to find a couple more lupin populations, I felt increasingly foolish. It wasn't until we reaching the sleepy fishing village of Dover, near Tasmania's southern tip, that we saw our first decent patch of yellow lupins. Dover is a tiny place, a cluster of fibreboard houses strung around a beautiful sandy bay, the sand strewn with abalone shells from the local fishery. At the back of the beaches the lupins had been spreading in the dunes, forming a dense strip for half a mile along the bay. They looked stunning, framing the icy blue sea, surf and sand with a crescent of vivid yellow, but they had been steadily strangling the native flora, forming a dense, impenetrable thicket.

The pattern was similar elsewhere: coastal populations tended to have expanded, while the inland populations tended to be small and ephemeral. Many of the inland populations we had found in 1999 had gone, wiped out by herbicides or development, but other populations had popped up here and there. The worst infestation was on Bruny Island, a gorgeously remote and sparsely populated twist of land off the east coast of southern Tasmania, home to more echidnas and fairy penguins than people. Here, the lupins were running amok, spreading along the sandy coast and in dense swathes into the gum forests inland. We dutifully counted every plant in all the lupin patches we could find around Tasmania; as ways to earn a living go, I can think of many worse for it is one of my favourite places on earth, paradise for a naturalist. In our twelve-day tour, as well as lots of lupins we saw pods of dolphins frolicking just feet from the shore, sea eagles, flocks of black cockatoos, penguins, duck-billed platypus, wombats, more echidnas than you could shake a stick at, and even a beer-drinking pig named Priscilla.
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The bumblebees seemed to have taken very well to Tasmania, having now spread throughout the island from the wild and windswept west coast to the sunny north-east. This despite recent genetic evidence suggesting that they were all the descendants of a very small number of queens that made it here in 1992 – perhaps just one or two – and hence all horribly inbred.

What we didn't see this time was Tasmanian devils. Whilst the roads were still as littered with corpses as they were in 1999, where previously the devils had comprised perhaps a quarter of the body count, now there were none. The poor brutes have been afflicted by a grotesque plague, a deadly facial cancer which is infectious and spreads when they bite each other – which being rather bad-tempered beasts they are prone to do. No one knows where it came from, but it is most likely a disease accidentally introduced by man. It has all but wiped them out, so perhaps I will never now see one in the wild.

Once back in a frightfully cold Scotland (the temperature in December 2010 regularly fell to -20°C), I set about analysing the data. Overall, we found 76 per cent more plants in 2010 than in 1999, with many coastal populations having doubled or tripled in size. The conclusion is that it does look as if lupins in Tasmania are spreading and likely to become a major problem in the future.

In recent years the Australian horticultural industry has also been making applications to allow the release of bumblebees on the mainland. No doubt the Australian tomato growers are desperate to put down their vibrating wands and let bumblebees do the work, and it is hard to blame them for this. It would certainly save them money, and maybe they would get bigger, sweeter tomatoes too. But my guess is that the cost to other farmers through worsening weed problems could vastly outweigh the benefits to the tomato industry. Thankfully and wisely, the Australian government have turned down the applications so far. The country doesn't need any more non-native species. Nonetheless I worry that bumblebees may one day soon mysteriously appear there, much as they did in Tasmania. After all, the distance from Tasmania to Victoria, the neighbouring state on the mainland, is much smaller than that from New Zealand to Tasmania, and regular passenger ferries cross between the two.

I love bumblebees. Beekeepers love their honeybees. Both are enormously valuable and important creatures. But mankind has wrought enormous harm on our ecosystems by shifting species around the globe. In New Zealand, I enjoyed watching rare UK bumblebees and honeybees happily feeding upon and pollinating huge, colourful stands of viper's bugloss, lupins, foxgloves and clover. Yet as I stood there contentedly chewing upon a pie made of venison (another non-native), I knew that I was watching an ecological travesty. The truth is that in New Zealand we have patched together a Frankenstein ecosystem on the wrong side of the world, and that in so doing we have annihilated the native creatures that used to live here. We all have to accept that, in the wrong place, both bumblebees and honeybees can do harm, and that very great care should go into considering the risks before any more bees are released outside their native ranges.

CHAPTER EIGHT

Quinn and Toby the Bumblebee Sniffer Dogs

The music of the busy bee

Is drowsy, and it comforts me
;

But, ah! 'tis quite another thing
,

When that same bee concludes to sting!

Andrew Downing (nineteenth-century American horticulturalist)

One of the great difficulties in studying bumblebees is finding their nests. They can be in all sorts of odd places, many of them tucked underground in old rodent burrows, in hedge bottoms or amongst the roots of a tree. Others prefer compost heaps, bramble thickets, lofts, rockeries, holes in trees or tit boxes. All that these sites have in common is that they tend to be tucked away out of view.

A honeybee or wasp nest can contain tens of thousands of workers, and the traffic passing to and fro becomes pretty obvious if the nest is in a garden or other place frequented by people. All you have to do is look for streams of flying insects and follow them back to their nest. The number of bees in a bumblebee nest increases through the spring, and the size to which such nests grow varies between species, but even the largest ones rarely reach as many as 300 or 400 workers. For most of the year, the traffic amounts to no more than one or two bees a minute, so even garden nests are easily overlooked. In my experience most gardens have several bumblebee nests each year – at the time of writing my quarter of an acre in Dunblane has at least two: a small buff-tailed nest in an old compost heap, and a very large white-tailed nest under a piece of old wood beneath the children's trampoline. Indeed my eldest two boys, Finn and Jedd, had been happily bouncing about just above the nest for several weeks before I pointed it out to them. The bees themselves seemed not the slightest bit perturbed by their trampolining.