Sometimes, rainforest creatures come to you…

My first night of a 4 month field season, I settled down to sleep listening to the buzzes and squawks of the jungle night, mosquito net carefully tucked in all around my mattress. After a while, in the pitch dark, I felt the net trembling, as an animal climbed down the cord that held it up. Then it climbed down the net itself, and then – I’m not sure if it was the first night or later on once this had become routine – it ran across my toes. Welcome to the rainforest, where the creatures come to you.

A few minutes later I heard it knock over all the things I’d unpacked onto my shelves in an attempt to settle in to my new home. It turned out to be an opossum, a large mousey marsupial, which was encouraged on its nightly forays by a long-term resident at the field station who lived in the room next to mine, who left apple cores out for it to find.

Earlier in the evening I’d discovered a very effective (for someone who isn’t good with spiders) energy saving device above the lightswitch. spider lightswitch

It was a good introduction, as various animals were frequently found in the station buildings, from the boa that settled in a couple of metres beyond my desk in the library, to the (absolutely massive) tarantula that appeared in my bedroom (some may wonder why an arachnophobe would live in the jungle), the frogs and geckos that patrolled the bedroom walls, the curly centipedes that would drop from the palm thatched dorm roof, the cockroaches that could be found snacking on soap in the middle of the night, and once a tiny black scoprion in the middle of my bedroom floor.

I became quite attached to one particular creature that I shared a cabin with for a while, although the first time I saw it – a black frog appearing in the toilet bowl when I flushed it – it made me jump. He would appear as the flush was pressed, swim hard against the current to avoid being swept away, and disappear again under the rim afterwards. It took me ages to figure out he wasn’t living just out of sight in the bowl, but up in the cistern. What the toilet offered over the forest I don’t know, but he was always there, swimming away. Until one day I was devastated to see him swim not quite hard enough, and disappear down the pipe. I was happy to see him again a few days later, or if not the same frog, another who shared its taste in cisterns.

My field assistant once encountered a jaguar a few metres away when he made a night-time trip from the dorm building to the bathroom cabin, at CICRA’s satellite station CM1. The two buildings are separated by a short stretch of grass. As he was about to return to the dorm, he spotted huge eye-shine in the beam of his headtorch, and could even make out the markings on the jaguar’s face. The eyes moved down to the ground, and back up again, as if sizing up prey. The following morning dawned grey and rainy, meaning no mist-netting could be done, and I wondered why he was up and wide awake so early. He hadn’t been able to get back to sleep.

CM1 bathrooms are evidently treacherous places, as this photo from good friend and fellow CICRA resident,  Brian Phillips, shows. Might make you re-think how badly you need to go.

snake chain

The Road to Cocha Cashu

Cocha Cashu is one of the most renowned rainforest research stations in the world. It is in Manu National Park, Peru, one of the most biodiverse places on earth, where the Andes give way to the Amazon lowlands. A lot of hugely influential work has been carried out at Cocha Cashu, and it is on my wish list of destinations to visit. This lovely video by primatologist and conservationist Mark Bowler gives an insight into the journey into the jungle from the mountain city of Cusco. Getting to the rainforest can be half the fun, and if this doesn’t make you want to run away to the jungle then nothing will.

The invisible moth: a beautiful illustration of natural selection

Moth camouflage Ecuador cloudforest Bellavista

This moth, found in the cloudforest in Ecuador (at Bellavista, which I have written more about here), blends in perfectly with its background, even down to the lichen spot mimics on the tips of its wings. The purpose of colour patterns such as these is to make the outline of the moth hard to detect, thus making it difficult for predatory birds to distinguish it against the bark of the tree. The success of the camouflage is a question of life or death for the moth. A moth that is a poor match is more likely to get eaten, and one that is a good match is more likely to live. Therefore the next generation will be dominated by descendents of moths that were successful at blending in. This is natural selection, famously stated (and often misunderstood) as ‘survival of the fittest’, with the most camouflaged moths in this example being the most fit. The predatory birds provide the ‘selection pressure’ on the moth population, which has evolved in response to this pressure to be so well camouflaged.

However, the process is dynamic: the birds are also responding to the moths. A bird who is better able to pick out a camouflaged moth against the tree will be better fed, and better able to raise a brood. So again those most successful (the fittest) will contribute more to the next generation than those less fit. Greater visual acuity will in turn select for better camouflaged moths, and so on, resulting in an ongoing coevolutionary relationship. In evolutionary biology, the ‘Red Queen hypothesis’ relates to cases such as these. The name refers to Alice in Through the Looking Glass, by Lewis Carroll, where Alice is told by the Red Queen that ‘here, you see, it takes all the running you can do, to keep in the same place’.

The best commute in the world, and searching for a subflava in a gold mine

One of the main questions we were investigating was the importance of rivers in structuring populations of our chosen antbird species (the Peruvian warbling antbird Hypocnemis peruviana, yellow-breasted warbling antbird H. subflava, and the chestnut-tailed antbird Myrmeciza hemimelaena). In other words, how connected are individuals on one side of a river with those on the other? Are they equally likely to mate with those on near and far sides of a river? And if there are river effects, do these differ between species, depending on their ecology and behaviour? (These are questions at a local scale, that form part of broader questions relating to the diversification of Amazonian birds; more background information about the project is given in an earlier post.)

It is possible to look at population connectedness by using genetic analysis of blood samples. In a technique analogous to DNA fingerprinting, individual patterns of genetic markers can be described for each bird. Instead of using these to work out the relationship between two birds, the distribution of markers within a whole population can be assessed. Clusters in the data reflect groups of individuals that are more closely related to each other than to other groups. These clusters can then be matched with their geographical location, and if they fall on opposite sides of a river, then this would suggest that the river is a barrier to gene-flow (interbreeding) between populations.

Our analyses are still not complete, so the final part of the story is not yet known, but all this meant that we needed to cross the river to collect samples. Instead of setting off into the forest in the morning, we would descend the 250 stairs from the high upland terra firme, down to the riverbank. We’d scramble into a boat, and if the engine started quickly, we’d be on our way in the dawn twilight, watching the sky change colour, and the mist rise from the river. It was only a short journey down river, either 10 minutes to the village of Boca Amigos, or 20 minutes to a satellite station belonging to CICRA, known as CM1. But it was a beautiful way to travel to ‘work’, one that I never failed to appreciate, and one that was always different depending on the weather and light.

Boca Amigos is a small village, home to a handful of families, with most houses also seeming to double as a shop or bar. There’s a small school, and a football pitch, as can be found in every Peruvian community no matter how small. We’d arrive before many people were up, and would quietly walk between the houses to reach the trails into the forest beyond.

The journey to Boca, and our exploration of the surrounding forest, also brought home one of the less beautiful aspects of life in the Amazon: gold mining. We would pass mining dredges on our way downriver (in fact we could hear them, generators running late into the night, from CICRA).

The price of gold keeps on rising, and the opportunity to make a decent living in the jungle by mining gold continues to attract migrants, particularly from the Andes. The work is tough and relentless, but profitable. It results in huge mounds of gravel, deforestation, and leaves behind desolate expanses of bare ground, and pits filled with polluted water.

The cheapest and easiest way to extract gold is to use mercury. Mercury is therefore being constantly washed into the river, entering the forest ecosystem and food chain, and is likely to be having a terrible effect not only on the forest species but also on human health. The whole issue of mining is complex and controversial: the needs of people and the protection and conservation of the rainforest requires a careful balance, which has not yet been reached. It is an issue right across Amazonia. Although the blue-tarpaulin covered mining camps that we walked through behind Boca were small-scale, some mining operations have an impact on a much greater scale, and anyone who has flown between Cusco and Puerto Maldonado will have seen a huge scar in the otherwise mostly unbroken rainforest canopy.

Mist-netting around a gold mine was not something I had expected when I set off for Peru. It was shocking to see the devastation of the mines. We would climb over huge felled trees, and navigate around the pits, trying to hear our species singing above the noise of the generators.

We found birds adjacent to the mines, and were defecated on from a great height by a group of howler monkeys who objected to our presence, so jungle life continues in the adjacent forest. This gave some hope that once abandoned, the mines could be reclaimed by the forest. But I have no idea how long it will take for all traces of the mines to be gone, as the ground has not simply been cleared, but excavated, and the effects of mercury – invisible and far-reaching – are likely to persist for much longer. Working there also gave us a more personal perspective on the whole situation. We exchanged buenos dias with miners as they were preparing their breakfast, bemused at the site of us with our microphones and mist-netting gear, and they came to our rescue when our boat engine wouldn’t start. It is easy to say that the mining should be stopped – and heartbreaking to learn about the extent of the destruction across Peru and beyond – but is not easy to achieve, especially whilst also ensuring the livelihoods of those who currently depend on it. A much more in-depth and eloquent report on gold mining can be found on the Smithsonian magazine website, and an award-winning new film, Amazon Gold, documents the destruction of the Peruvian rainforest for gold. The trailer below is well worth a look.

Zen and the art of outwitting a small bird

A working day started soon after 4am, so we could be at our chosen spot by sunrise. In the dark, I would scan the floor for dangerous creatures, shake any more from my clothes, and tip my boots upside down just to make sure before putting them on. Despite my fears of spiders, snakes, scorpions, cockroaches, centipedes…I think I only ever found a frog, in a boot, once.

I’d meet my field assistant in the comedor, and we’d quietly go through our morning routine, filling water bottles, stocking up on breakfast snacks, and then assembling the various bits and pieces we needed in the field: a toolbox full of needles, tubes of ethanol, capillary tubes, bird rings, rulers, and scales, speakers, mp3 players, mistnets, bird bags, bamboo poles, machetes, microphone and sound recorder.

Setting off into the forest, the low light – if any at all – would turn to almost complete darkness as we entered the trail system and walked under the canopy. It took a while for the light to reach us through the trees, so we made our way by the light of our headtorches, which would catch the blue shine of spiders’ eyes on the forest floor.

It felt exciting to head off into the forest while many were still asleep at the station, seeing the first of the new jungle day, and enjoying the sound of the nightshift merge into the dayshift. It also meant we got to walk face first into all the spiders’ webs that had been constructed across the trails over night. We’d walk waving a stick or machete in front of us to catch the webs first.

Rainforest sunrise

We were out to find three particular species of bird. All three are antbirds, small, insectivorous birds that lives in the understorey of the forest. One species, the chestnut-tailed antbird (Myrmeciza hemimelaena) barely gets above the ground, zipping between dense tangles of vegetation half a metre off the forest floor. The other two are usually found between 1–4 metres off the ground; one, the yellow-breasted warbling antbird (Hypocnemis subflava) has a tendency to be found in bamboo patches, while the other, the Peruvian warbling antbird (Hypocnemis peruviana) is usually in the broad-leaf forest matrix. Finding them was easy, because they are all highly territorial, defending their patch of forest against intruders. We could mimic an intruder, by playing the song of each species on our speakers, prompting an angry, defensive bird to head in our direction. Generally, this would bring both male and female birds towards us, as they defend their territories together as a pair, and sing duets to do so. The challenge once we knew where they were was to work out where to put a mist-net with the highest chance of them flying into it.

A mist-net between two bamboo poles, supported by orange cord

The trick was to anticipate which branches or tangles of vegetation would be most appealing to the birds, and the route they might take from one to another, and to put the net between them. Sometimes the trail itself was suitable, other times we’d need to clear enough space to fit the 12 metre long net. We’d loop it onto two bamboo poles, pull it taught, and tie the poles to suitable trees nearby. The net extended from the ground up to almost 4 metres, and consisted of 4 parallel pockets running the length of the net. It was hard to see, and if positioned out of the light would be almost invisible, to us as well as the birds (and on one occasion a furious large Amazonian squirrel that thrashed about until it thrashed itself free). The speakers would be placed on the ground in the middle of the net, with the appropriate song playing on a loop. When a bird flew into the net, it would fall into the pocket just beneath it, unhurt but slightly tangled. We’d keep a close eye on the net and quickly extract a bird once it was caught. It would be put into a small cloth bag until we were ready to process it a few minutes later.

Bird bags on our machetes

So that we would know if we saw, or caught, the same bird again, we put small rings on their legs – one metal ring with a unique number, and then three coloured rings in a unique combination. I’d measure the length of the wing, tarsus, beak, and weigh the bird, as well as take a couple of drops of blood from the vein under the wing for genetic analysis. Within a few minutes the birds would be released back into its territory.

Taking a blood sample from a chestnut-tailed antbird. Photo credit: Frances Buerkens

But it wasn’t always so simple, and we must have spent many hours watching birds come towards the net, fly over it, stay just next to it, and not fly into it. There was nothing we could do but watch, and will the bird to fly where we wanted it to. Sometimes we’d re-position the net and try again, sometimes it would be so close for so long that we couldn’t give up, but sometimes the birds were just not going to fall for our tricks. Add to that a swarm of ants, a nest of tiny ticks, bamboo spikes or wasps and a day in the field was often a lesson in patience and calm. We’d head back for lunch in the heat of the day, brandishing hard-won blood samples, the forest quite different to how it had felt at dawn, anticipating cold showers, ‘clean’ clothes, and tasty food.

Ants all over my binoculars