A Sting in the Tale (14 page)

All this poses a problem, for finding a nest is enormously time-consuming, and finding the nests of rare species is even worse. Because so few rare ones have ever been found, we know almost nothing about where they might occur, providing a bit of a catch-22. With rare species such as the short-haired bumblebee or the ruderal bumblebee, most of our knowledge comes from the work of Frederick Sladen 100 years ago (they weren't so rare in his day). A detailed understanding of their nesting ecology would be really useful if we wanted to provide them with extra nest sites to help boost their populations. If we could find wild nests, we could study them, and provide a window on aspects of their lives that remain obscure. For example, we could catch the bees coming back to the nest and see what pollen they were carrying, and so learn about where they were collecting their food; or we could study what creatures attack the nests, or count the nests to see how many there are in different parts of the country or in different habitats. All of these things would be valuable to finding out more about the ecology of bumblebees, understanding why they are declining, and working out how best we can help them. So all in all, it would be jolly handy if we could come up with a reliable way of easily finding lots of bumblebee nests.

Bumblebee folk have been pondering this issue for years. One solution is to recruit thousands of people to help. In 2004, Juliet Osborne, the scientist who carried out the bee radar experiments, advertised for members of the public to take part in a national bumblebee nest survey. Her volunteers were then asked to take a deckchair and sit in their garden for twenty minutes. (The deckchair wasn't compulsory but it made the whole exercise much more relaxing – as did a cold gin and tonic.) During this time they were asked to stare at a selected 6-by-6-metre area of their garden, watching for bumblebee nest traffic. Although I have said that such traffic is rather slow and hard to spot, if you stare at a patch of ground for long enough, then if there is a nest entrance you will eventually notice bees coming in and out – and any bumblebee flying out of a hole, or down to ground where there are no flowers, is likely to indicate a nest. The rationale was that twenty minutes would be long enough to spot a nest, though it may seem like an awful long time when nothing is happening (hence the importance of the chair and the gin). If a nest was spotted, the volunteer was then asked to identify the species as far as possible, although most volunteers were only able to classify the bees as belonging to one of five colour groups (e.g. all-brown bees, or bees with two yellow bands and a white bottom, etc.).

Having studied their gardens, these volunteers were asked to repeat the exercise in one countryside habitat, chosen at random from a range of options. Once they had done both, they completed forms describing the places they had watched and any bumblebee nest they had found. Impressively, 719 volunteers from all over the country stepped forward, completed the exercise, and returned their forms to Juliet. Between them, they had managed to find 215 bumblebee nests. Of course this means that over two-thirds of the volunteers had spent forty minutes staring at the ground and found nothing. Disappointment aside, however, thankfully they still returned their data, for in science, the zeros are just as important as the more exciting positive numbers.

One of the more striking results to emerge was that our gardens seem to house more bumblebee nests than the countryside, for Juliet found that, on average, there were thirty-six bumblebee nests per hectare of gardens, with much lower densities in farmland. I find this both encouraging and depressing – encouraging in so far as gardeners such as me who try to make their gardens as wildlife-friendly as possible are clearly doing something right. Our gardens provide lots of good places for bumblebees to nest – old compost heaps, sheds and patios to nest under, rockeries full of cavities and so on – along with a huge variety of flowers; and although individual gardens are very variable in how many good bee-flowers they have, bees are of course no respecters of boundaries and workers from a single nest will range over hundreds of gardens in search of food. At any one time in the spring and summer at least some of those gardens are bound to have some rewarding flowers. By contrast – and here is the depressing bit – farmland has rather fewer places for bumblebees to nest, and very often startlingly few flowers. Arable fields cover much of lowland Britain and they provide no nest sites for bumblebees – being regularly tilled, they have no old rodent burrows. With modern farming techniques, arable fields also tend to be largely free of weeds, so there are no flowers (unless they are sown with a flowering crop such as oilseed rape, which does provide lots of flowers for a couple of weeks but then none for the rest of the year). Juliet's survey did find that hedgerows and fence lines are the best places to find bumblebee nests in farmland, but there are far fewer of these than there used to be because fields have got much bigger.

Following on from Juliet's work, one of my PhD students, Gillian Lye, has also enlisted the public's help in sending her records of the bumblebee nests in their gardens. In this informal study, people are simply asked to fill in a questionnaire if they happen to find a bumblebee nest. This more haphazard approach has so far recorded 519 nests, once again showing that gardens provide a diversity of good sites. Tit boxes appear to be particularly popular, especially for the early and tree bumblebee species. Moreover, some bumblebees seem to like nesting beneath or within certain materials: red-tailed bumblebees, for example, tend to nest under stones or patio slabs.

Gillian and Juliet's surveys have produced some really interesting results, but they are very biased towards what is happening in gardens. They almost never turn up information on nests of rare bumblebees, probably because our rarest species tend to live in such unpopulated corners as the Hebrides or on Salisbury Plain.

An alternative approach to finding bumblebee nests might be to lure them to nest in artificial boxes. Most garden centres sell such boxes and, if these were readily used by bumblebees, they would provide a straightforward way to obtain nests for study. During her PhD, Gillian tested a range of commercial bumblebee nest boxes, and also a selection of home-made designs. Gillian tried out well in excess of 500 nest boxes during her three years, scattering them in different habitats, above and below ground, with or without entrance tunnels, and so on, and then monitoring them regularly to see which ones were occupied. Her prodigious efforts were poorly rewarded: about half a dozen boxes in total were occupied. That is to say, half a dozen were occupied by bumblebees. Almost all housed spiders, slugs, earwigs, woodlice, wasps and so on. If they were rebranded as woodlouse boxes they could be regarded as highly successful, but as bumblebee nest boxes they represent a poor investment.

Over the years, I have hatched various schemes to find bumblebee nests, some more ridiculous than others. I have tried catching queens that were collecting pollen (they do this only once they have established a nest) and tying pieces of silver tinsel to them. My hope was that this would both slow them down and make them more obvious, so that I could run after them back to their nest. It didn't work; the bees either flew far too high and fast to follow or, when I experimented with larger pieces of tinsel, simply flopped down to the ground and devoted themselves to biting it off. I have also tried plotting the direction in which worker bees leave flower patches, in the hope that I could discern a pattern which I could then follow to find their nests, but bees leaving flower patches seem to show no pattern in the directions in which they head off. Another suggestion involves the infrared imaging that the army uses to spot the enemy at night, for as bumblebee nests are warm an above-ground nest should show up even when hidden under leaves. Sadly the equipment involved costs hundreds of thousands of pounds so we have yet to try.

It has long been known that one animal has no trouble in finding bumblebee nests: the badger. Badgers are voracious predators, digging up and consuming everything that they find – bees, grubs, wax, honey, the lot. They must get stung, but they seem not to care, or perhaps the honey makes the pain worthwhile. I once carried out an experiment to see how well bumblebee nests fared on different farm types compared to gardens, in which I placed artificially reared bumblebee nests in various locations. This worked pretty well; the nests in gardens tended to grow much more quickly and become heavier than those on farms, presumably because they have more flowers. The only problem I had was that quite a few of my nests (both in gardens and on farms) were eaten by badgers, leaving nothing but chewed, tattered and very empty boxes.

Salisbury Plain is a magical place, a glimpse of what much of the English countryside may once have looked like – vast tracts of flower-rich downland, supporting all sorts of rare wildlife including perhaps the richest bumblebee fauna in the UK. The Plain escaped agricultural intensification only because the army began buying up the land in 1897 and now owns 38,000 acres – the largest remaining patch of flower-rich chalk grassland in north-west Europe. Of course the peace is occasionally shattered by a barrage of artillery shells or the deafening clatter of a passing tank, but for the most part the wildlife here is free to thrive. The Plain harbours a substantial badger population, and on many fieldwork expeditions I have found signs of recent excavation, holes dug in the ground with a few forlorn bees still hanging around and telltale paw prints in the loose soil. It is said that badgers turn to eating bumblebee nests in dry summers when the worms that they eat for much of the year burrow too deep for them to find. Of course badgers are nocturnal; they have poor eyesight, and clearly find the bumblebee nests by smell. In fact the nests are especially smelly, at least when reared in captivity; I have heard the smell described as like Christmas cake, but if so it is not a type of Christmas cake that I would like to eat. You can create a similar odour by pouring black treacle and sherry over a pair of dirty running socks, sealing them into a Tupperware box and then leaving it in a warm place for a month. Not that I have tried this, of course.

So the solution may well be a pet sniffer badger. Sadly for me, however, badgers do not domesticate well, remaining grumpy and rather dangerous. But if not a sniffer badger, how about a sniffer dog? Dogs are well known for their incredibly sensitive noses; after all, once trained, they can sniff out drugs, explosives and even banknotes. In the USA, dogs have been trained to find termite infestations in houses long before any external signs of damage are visible.
15
Dogs have even been used successfully to detect cancers in humans. If they can manage all that, then surely they could sniff out a highly odoriferous bumblebee nest? I chatted about this idea with Juliet and some of my research group over a number of years, but never quite found time to follow it up. Then, one day in 2004, one of my more go-getting PhD students, Ben Darvill (who subsequently went on to help me found the Bumblebee Conservation Trust), came up with a telephone number for the Defence Animals Centre. Based in Melton Mowbray in Leicestershire, this organisation trains all the army dogs used to detect explosives in Iraq and Afghanistan. They also produce dogs for customs and police use. If anyone could train up a bumblebee sniffer dog, then surely it was them?

I must admit that I felt like a bit of a fool when I rang, fully expected them to laugh, or put the phone down thinking my call was a hoax. Compared to the serious business of sniffing out bombs, asking them to train a dog to sniff out bumblebee nests seemed rather frivolous. To my surprise – and their immense credit – the staff at the Defence Animals Centre were immediately interested. I think perhaps they were a little bit bored of training dogs to do the same thing time after time, and they fancied a challenge. Whatever their reasons, they invited us to visit. So it was that Ben and I and another PhD student named Joe Waters drove up from Southampton on a rainy day in November. I was most disappointed that I didn't see a single pork-pie shop on the way through Melton Mowbray. The Defence Animals Centre's huge site, which also houses the Royal Army Veterinary Corps, has vast stables, along with rows of dog kennels from which a constant howling could be heard, and occasional office blocks scattered across a slightly bleak hillside. As we drove in we passed immaculately groomed and impeccably behaved cavalry horses that were being put through their paces in the damp autumn air, their breath creating clouds of steam.

We met Dutch, a senior dog trainer, who took us for a demonstration. We drove behind his Land Rover along various muddy tracks until we came to a large semi-derelict army building, which might have once been a mess hall and barracks, but clearly hadn't been used for years. There Dutch opened the back of his Land Rover and out bounded a very excited black Labrador called Miffy, eager to get to work. One of us held the dog's lead while Dutch entered the building and hid an object. Then he led us all into the building and gave Miffy the command to start work. She dashed around, her tail wagging crazily, jumping on furniture, crawling under cupboards, poking into every nook and cranny and snorting when she got dust up her nose. After about two minutes her seemingly random searching brought her to a small cupboard set against a wall, at which point she dropped to the ground, her whole body quivering with excitement, nose to the cupboard, her tail a rigid point behind her. Dutch opened the cupboard and there inside was a tiny pea-sized piece of cocaine wrapped in cling film. He threw a tennis ball to Miffy (her reward for success) and she bounded off with it, looking very pleased with herself. All most impressive. If Miffy could be trained to find such a small sample of drugs wrapped in cling film, then surely a dog could be trained to find a bumblebee nest? We had brought with us an old, frozen bumblebee nest in an ice box for Dutch to use as training material. It really was quite smelly and he agreed that it ought to be easy enough to train a dog to find it, but he explained that it might take a few months for them to locate a suitable animal. So we left him with the nest and returned to Southampton.