by Dave Goulson
Each night, I hung up a white sheet in the edge of the forest near the lodge and shone an ultra-violet lamp onto it. To our eyes these lights give out an odd purple glow, but we are unable to see most of the light that they emit. To insects they are enormously bright, for insects’ eyes are able to detect ultra-violet light that is invisible to us. Within seconds of turning on the trap, moths in bewildering variety started to arrive. Some were small and unremarkable, subtly marked in shades of brown, sometimes with scalloped wing margins to give them camouflage when sitting on bark or dead leaves. Some had prominent spots and blotches, in cream, yellow, orange or red, looking very conspicuous on the white sheet but presumably affording them camouflage when perched on forest leaves blotched with fungus or the squiggled marks of leaf-miners. Some were huge: giant silk moths with feathered antennae that they use to sniff out females from miles away; fast-flying hawk moths with powerful, streamlined bodies and long, sharp-pointed wings streaked in green, brown and yellow, which bashed into the other insects as they whirred around the light in excitement or confusion. Other insects came too – noisy cicadas lured in from the trunks of the forest trees where they normally sit to sing; huge chestnut-brown scarab beetles, flying with all the elegance and grace of a particularly clumsy house brick, would come crashing in to the sheet with their wings clattering, and then fall to the ground where they would fold away their wings and sit, apparently exhausted from their journey. Click beetles, wasps, flies, true bugs, and more arrived, some settling down quietly on the sheet, many continuing to zoom around in chaotic circles. It was a fantastic demonstration of nature’s diversity, all displayed on one white bed-sheet. The students loved it, gathering around the sheet in the midst of this storm of insect life, pointing and exclaiming with delight as different weird and wonderful insects arrived, and not minding that the moths landed in their hair and occasionally fell down inside their shirts.
In addition to the animals, the students were also taught how to identify the local plants by Anna, a lovely Ecuadorian lady with an encyclopaedic knowledge of the mountain flora. The plants of Ecuador were all utterly unfamiliar to me, mostly belonging to families that do not occur in Europe, so I tried to pick up some knowledge from her as we went along. Even where the plant families were familiar, the plants themselves looked utterly different – for example in Ecuador, members of the daisy family grow into trees thirty metres tall. It was hard to see any resemblance to the daisies and dandelions in my lawn at home. Anna explained that a great many of the local plants are adapted for pollination by hummingbirds, having deep, tubular, often red flowers that have co-evolved with the elongated bills of the birds. These spectacular birds were everywhere in the forest, the thrum of their wings and their chirping an almost constant companion, though they were often hard to see clearly amongst the dense foliage.
At dawn each day Mauricio, one of the many locals who jointly own the lodge, would lead a birdwatching walk through the misty forest. Dawn is the time of peak bird activity, when they have a brief hour or so of frenzied calling before melting back into the dense canopy. Even then they can be very hard to spot high up in the trees but Mauricio was able to mimic the call of many types with uncanny accuracy, and so he would call back to them. Many were sufficiently intrigued by this new rival or potential mate that they would come down from the treetops to investigate, giving us a great look at them. The evocative names of some of the many species we saw speak for themselves: flame-faced tanagers, golden-headed quetzals, red-billed parrots, masked trogons, toucan barbets, plate-billed mountain toucans, and so on. Among these stunningly beautiful creatures, my favourite was the quetzal. Twenty years or more ago I spent many hours trying to spot them in the forests of Belize without any success, though we heard them in the distance. Here, the quetzals were quite tame, and it was worth the long wait to see them. These are plump, pigeon-sized birds, clothed in emerald green but with a red belly, and in sunlight their green head flashes iridescent gold. The Aztecs and Maya viewed the quetzals as ‘gods of the air’ and as symbols of freedom, goodness and light – their rulers wore headdresses made from the long green tail feathers of the males, which can be up to half a metre long, and were valued more highly than gold. Since the birds were thought to be incarnations of the god Quetzalcoatl and hence were sacred, they were caught live, their tail feathers plucked, and then released (which seems like a pretty undignified treatment for a deity). At Santa Lucia, one male quetzal was particularly bold and would often visit us at the lodge, settling in a tree on the edge of the garden and peering down at us with his gleaming head cocked to one side, as a god might look down curiously at the antics of the mortals below.
When we got back from the early-morning walk we would pause by the hummingbird feeders hung outside the lodge. These were filled with sugar solution, and drew dozens of these tiny birds from the forest for an easy feast. The birds were accustomed to humans, and so we could stand just a few feet away while Mauricio rattled off their names. Hummingbirds are impossible not to love – incessantly active, tiny aerial jewels, glittering in plumage of greens and blues with flashes of red, purple or bronze on the crown of their head, throat or tail, depending on the species. I do not think I will ever fail to smile when I glimpse a hummingbird. The different species were mostly distinctive; the male violet-tailed sylph sported tail streamers longer than the rest of his body. The booted racket-tail had fluffy white leggings and a pair of long wire-thin tail streamers with oval flags at their tips. Some species had stubby beaks, others long, straight tapered beaks, while the tawny-bellied hermits were equipped with scimitar-curved bills. Occasionally a little woodstar would put in an appearance, one of the smallest bird species in the world, little bigger than a bumblebee and flapping its wings at a frantic seventy times per second. This was close-range birdwatching for idiots – contrasting sharply with the peering through binoculars at distant small brown jobs that I was familiar with from birdwatching in the UK.fn5 With Mauricio’s help we quickly learned to identify them all. In total we saw no less than seventeen species of hummingbird on these feeders during our stay, and they fed from dawn to dusk, so whenever I had a spare moment I would pull up a seat and watch them, grinning foolishly to myself.
On the fifth day, the students divided themselves into small groups and set about devising their own original research projects, with a little steering from the staff. I ended up supervising two projects: one a group of three girls who wanted to study the behaviour of the hummingbirds, and the other a pair of girls who were keen on comparing numbers of butterflies and moths in primary forest versus cleared areas or secondary, damaged forests. Once the students were organised and had started collecting their data, I was able to turn my attention back to the bumblebees. I searched all of the forest trails that radiated out from the lodge. It was gruelling walking for the terrain was rugged in the extreme; the trails were all steep, often very narrow paths cut along the side of vertiginous slopes. Slipping off these muddy trails would not have been a good idea. Some trails wound up towards a nearby peak at 2,500 metres altitude, while others plummeted down into gorges at about 1,300 metres, where mountain torrents poured over huge rounded boulders and colourful butterflies fed on salts from the damp sand at the water’s edge. Fortunately by then I was getting over the food poisoning, and my legs had a little more zip in them than before. It was exciting being off on my own in these remote forests, hunting for bumblebees but knowing that I might come face to face with a bear, puma or eyelash viper around the next corner.fn6
I found quite a lot of bumblebees, all male Bombus hortulanus, and all doing more or less the same thing as before: sitting on a leaf, anxiously twitching and pulsing, little balls of energy. Many were in small groups of between two and five, but some seemed to be on their own, fiercely defending their chosen patch of the forest floor even though nobody else seemed to want it. There appeared to be nothing remotely special about the places they chose to sit – they weren’t especially sunny or shady, and there we
re no flowers – so far as I could see there were a million other spots that looked just as good.
The bees were fairly common on the trails uphill, right up to 2,500 metres, which was as high as the mountains within walking distance got, but they petered out quickly when I went downhill; I found none below 1,600 metres. I marked the positions of every one with red ribbon on the stem of their favourite perch so that I could find them easily on the following days.
I went back to watch them whenever I could find time, which was often, as my two groups of students seemed to be getting on well. The hummingbird girls were studying, amongst other things, whether boldness differed between species, and had found that some types of hummingbirds were very bold indeed; they had brown hermits and violet-tailed sylphs actually perching on their hands to feed. My bumblebees were much more flighty, and I had to approach each group of them cautiously. Fortunately their positions didn’t usually change from day to day, so I knew when to slow down and creep forwards to watch them. Sometimes a bee would be missing from his post when I arrived, but if I sat still and waited for a while he would usually return. Occasionally I saw the bees wiping what I guessed to be pheromones onto their perches. Male bees have hairy moustaches, and some species, including those that Darwin observed in his garden all those years ago, use them like paintbrushes to mark leaves and twigs along their race tracks, using a pungent liquid exuded from glands in their head. Presumably the bees were marking their patches, either to attract females or to repel males.
If it rained or became heavily overcast then all the bees vanished – presumably heading into shelter somewhere – but as soon as the sun came out they returned. Occasionally one would disappear for half an hour, perhaps to feed on nectar, though I rarely saw them on flowers – my best guess is that they fed mostly on the flowers of some rainforest tree, far above my head. Presumably this is also the case for the hortulanus worker bees; I didn’t see a single one, but given the number of males there must have been plenty of workers somewhere nearby. One of the great challenges for a biologist working in tropical forests such as this is that much of the action happens in the inaccessible canopy.
On just one occasion I saw a male hortulanus feeding on the flowers of a shrub belonging to the Rubiaceae. This is another plant family whose members are unrecognisable in South America; in Europe, the best known members are low-growing, scrambling plants of meadows and hedgerows such as lady’s bedstraw and cleavers (obscurely known to generations of kids as sticky willy). In South America, once again many of the members of this family are large shrubs or trees, including coffee – making me wonder whether these Andean bumblebees contribute to coffee pollination in Ecuador, though I did not get a chance to check this out.
Where there were groups of males, their aerial battles were fascinating to watch. Sometimes they went on for minutes – two bees often flying headlong at one another like teenage joyriders playing chicken, barely missing one another then arcing round to charge each other again, forming a figure-of-eight pattern in the air. Occasionally a third bee was involved, and then the patterns became chaotic as they frantically zoomed around, occasionally bashing into one another in mid-air. Sometimes they would lock together in a tangle of legs, fur and wings, and fall to the ground for a moment of two before resuming the aerial dogfight. One battle I watched went on for nearly four minutes – I began to feel tired just watching them. Perhaps it was a test of endurance? Inevitably one bee would land first, looking exhausted, and if it returned to its perch it was then attacked by the bee remaining in the air, which would swoop down on top of it, forcing it to return to the fray. The usual outcome was that all the males would eventually retire to their perches, but once in a while one seemed to be driven off, perhaps unable to keep up with the pace, or perhaps needing to top up its energy reserves with some nectar. When this happened his perch was always stolen.
I experimented with catching bees and keeping them in a pot for a while. If they were from a group of bees, it was usually not long before another bee would come along and occupy their spot. It is probably anthropomorphising excessively, but it always looked as if the intruder was particularly pleased with himself but still nervous, expecting to be attacked at any second for its temerity in stealing another’s favourite perch. Some perches seemed to be especially popular – if I removed a second bee then a third would soon turn up and take it over. So what were these bees up to?
Interestingly, there is a direct parallel with another creature that lives in these same forests. The cock-of-the-rock is a bizarre and spectacular bright red and black bird with extraordinary crests resembling those on a Trojan helmet – it is the emblem of the Santa Lucia Reserve. Every September, during the mating season, males come together in the morning in what is known as a lek – a gathering of males to which females come to select their mate. The lek at Santa Lucia is a stiff two-hour walk from the lodge, tucked deep in the forest in a steep-sided valley. The lek takes place just after first light, for about half an hour, so to observe it one must get up at 4 a.m. and do the two-hour walk by torchlight. I couldn’t resist giving it a go, and it was worth the effort to see such a peculiar and fascinating sight: a group of five males performing a head-bobbing dance while fluttering their wings and making hoarse, throaty squawks. Apparently, some days there can be twenty or more birds there, so I caught it on a quiet day. The idea is that a female looking for a mate just has to come along and watch – all the males from roundabout are gathered here, strutting their stuff, and she can pick the most attractive as her mate. By doing so, her sons will hopefully inherit the same sexy characteristics and be desirable mates, so furthering the family line. The males don’t contribute anything to looking after the offspring, however, for after a quick copulation the chosen male returns to the lek. If he is particularly desirable, he may get to mate many times, while his less impressive rivals may not mate at all. While I was there I didn’t see any females visit the lek; I guess that they turn up very rarely, so that most mornings the antics of the males are to no avail.
It isn’t just cock-of-the-rocks that lek, for in the UK black grouse do it, and the great bustards on Salisbury Plain. The clouds of black flies that one often sees in summer, dancing together in sheltered places near streams, are probably doing something similar. A few species of antelope, wasp and fish also lek. It is easy to see the benefits for the females, for they get to select the pick of the crop, and the system is great for the most handsome males, but it must be a frustrating business for the less fortunate males who are forced into a competition that they cannot win.
Presumably my bumblebees were doing something similar, but in a less aggregated and more aggressive way than the cock-ofthe-rocks – instead of dozens of males at one hotspot they were in small clusters, sometimes on their own, and instead of just displaying, the males indulged in aerial combat. So far as we know, male bumblebees only really have one function in life – mating – so their behaviour ought to relate to finding a mate in some way. It is very hard to conceive what else it might be for. I guess that females must come along occasionally, like female cock-of-the-rocks (which perhaps should be called hen-of-the-rocks?), possibly attracted by the pheromone, or perhaps attracted by the same mysterious qualities that the males see in their perching locations. If she finds a single male guarding his lonely post, would she mate with him, or reject him as a sad loser who can’t manage to obtain a perch at one of the prime locations where several males gather? Would she travel on, looking for a group of males so that she can compare them and choose the sexiest? If so, then the lone males are wasting their time, and they should try to join a larger group, like a male cock-of-the-rock. Over time, perhaps that will happen. Maybe these are incipient leks, and in a few thousand years the males will be gathered in even larger groups. Or maybe the females aren’t so fussy, or don’t need to make a side-by-side comparison before choosing a mate, so that solitary males occasionally get lucky?
We don’t know the answer to any of these questio
ns. If I can, I want to go back, to try to understand them better. I never saw a single queen, but presumably virgin queens do turn up occasionally. Perhaps I could film the male aggregations, and so stand a better chance of catching a visit by a queen. I could try pasting lots of pheromones onto leaves to see whether they attract queens, but that would involve getting the pheromone out of the heads of the males, which they almost certainly wouldn’t enjoy. I could measure the males, to see if those that occupy the clusters are bigger or stronger than those perched on their own. I could DNA fingerprint the males, to see if the clusters consist of brothers or unrelated males, and I could see if the aggregations of males tend to be in the same place each year. There are so many possibilities.
They may all seem rather trivial – why does it matter what these bees are doing? But then Darwin’s studies could have been dismissed as trivial, were it not for the fact that ultimately he came up with perhaps the most important theory that science has yet devised. While his contemporaries were engaged in obviously practical endeavours such as developing new types of steam engine and building the foundations of industrial chemistry, Darwin spent decades watching worms, scrutinising barnacles, getting his children to chase bees, and comparing the shape of the beaks of finches from the Galapagos. How fantastically esoteric! Who could possibly have predicted that this would lead to something as devastatingly profound as the theory of evolution by natural selection? Of course I’m sure I’ll never discover anything one-trillionth as important, but we should not dismiss the value of trying to understand the world around us, for who knows what it might reveal?
