Some thoughts about disease and herbivores

Some thoughts I had about how disease might affect the behaviour of wild animals and their ecological effects, after seeing people social distancing in March 2020.

I went to Sainsbury’s to buy food and everyone in the street was walking quite a large distance apart from eachother, because of the coronavirus. People were also spreading out into side streets which are normally not used so much. This made me wonder whether a similar thing might happen in wild animal populations. I think it’s a lot like those simulations in behavioural ecology when you have a model of each individual with a zone of repulsion, a zone of alignment, and a zone of attraction in concentric circles, and by adjusting the sizes of the zones you can get groups of “animals” to behave in different ways, e.g. swarming randomly, moving in a circle, or all moving in straight lines. These models can help to understand things like starling murmurations. Anyway, I think basically what has happened with the coronavirus social distancing advice is that we have increased the zone of repulsion.

Perhaps in wild animal populations diseases could have a similar effect: when there are more diseases, animals might spread out evenly over the landscape, but when there are fewer diseases they could form tighter herds. Also, like the people walking down side streets, perhaps individual animals would choose to go into less optimal habitat in order to get away from others who might have a disease.

This could have a knock on impact on how they affect the ecosystem. When herbivores are spread out, they would have a low impact over a wide area, probably leading to fairly homogenous vegetation (e.g deer in Scotland). But when they’re in tight groups moving around the landscape, they would have intense impacts on small areas at once, probably creating a more heterogenous mix of vegetation (e.g. wildebeest in Serengeti). They might also disperse nutrients around the landscape better when they’re in roaming herds, and create patches of high nutrients (e.g. when they die and enrich the ground in phosphorus with their bones) which would affect plant communities, and maybe influence fires by creating areas of short vegetation which act as fire breaks / suppressing vegetation more evenly over a larger area.

A recent study found that wild boar populations in Spain tend to be less disease-ridden in areas where wolves are present. So perhaps predators might have a double effect on how herbivores group themselves: not only is it safer for them to be in tighter herds when predators are around (more eyes to spot danger) but also because the manky diseased ones get eaten the risk of transmitting diseases by being in tight herds is reduced. Also, maybe in Scotland the fact that people shoot the biggest and healthiest deer means that the manky diseased ones will survive, and so they tend to spread themselves out over the landscape to avoid catching the diseases, which could be a reason why the vegetation is basically all the same, rather than some grazed areas and some patches of trees.

It would be interesting to investigate these things in somewhere like the Serengeti. Perhaps you could compare different species and see if their disease load correlates with how spread out they are. Also, maybe when there is a big outbreak they might distance themselves from each other. People have done similar research comparing the mating systems of different herbivores in the savannahs with their ecology. Small things like duikers tend to be monogamous, live at low densities and selectively browse on high quality leaves; some medium sized antelope have leks which they graze very short; and big things like cape buffalo and wildebeest just go around in massive herds munching through relatively bad quality vegetation, because their massive guts enable them to digest it. Interestingly, the fact that really big herbivores (e.g. elephants) can eat really bad quality vegetation is probably a reason why the ecological functions of extinct megafauna can’t be replicated by extant smaller herbivores.

So anyway, I might be wrong about some of these things but it is very interesting to think about and I would be interested to hear any of your ideas.

The Limits of Science

This is a slightly edited version of an article which I wrote for Varsity, the student newspaper in Cambridge.

Courtesy of innovations in science and technology, famines, plagues, wars, and infant mortality are now so low that most people living in economically developed countries expect to survive to old age, something which is unprecedented in the history of our species. Our modern society is able to avoid or survive diseases and wars far better than previous civilisations, but the final problem facing any civilisation is running out of food.

Some farming practices may be able to reduce nutrient losses on a per hectare basis, but this does not solve the problem if lower yields necessitate using more land for agriculture. In order to entirely eliminate nutrient losses from the food system, we would need to fertilise crops with our own faeces and dead bodies. Applying artificial fertilisers mined from rocks can help, but these will inevitably run out.

Yet now, it seems as if even food production, the ultimate constraint on our survival, could be solved by technology. Bacterial cultures could produce food from thin air (or, rather, water), and be processed into substitutes for much of what we eat. We would still need to grow fruit and vegetables, but the amount of land required for this is tiny compared to what is required to produce animal products.

Is there any limit to what technology can solve? Thinking about the evolution of technology throughout history helps us address this question. Technology is a part of our cumulative culture, and there is a compelling argument that culture evolves by natural selection acting on memes, analogous to how organisms’ physiology evolves by natural selection acting on genes. In this sense, technological advances and scientific breakthroughs have little to do with individual people, but are to a large extent a product of the culture which these individuals experience. In support of this idea, there are many examples of convergent evolution. Agriculture arose at least 10 times independently. Calculus was formulated by Isaac Newton and Gottfried Leibniz around the same time. Big religions with just one or a few gods tend to evolve from animism and the worship of various spirits, wherever agricultural societies emerged from hunter gathering.

The various developments which eventually led to the iPhone may have been reliant on chance events. But if one of the inventors of Morse code, circuit boards, or miniature batteries had been run over by a bus before their big breakthrough, it seems highly likely that someone else would have made it in their stead, and the iPhone would still ultimately result. If Charles Darwin had never gone on the voyage of the Beagle, it is highly likely that someone else would have discovered evolution by natural selection. In fact, Alfred Russell Wallace did.

Physiological evolution has in some cases come close to the limits of what is physically possible. Some trees have reached their maximum possible size. Our eyes can detect single photons. Dogs’ noses can detect single molecules. Similarly, there surely must be limits to technology and scientific discoveries. There is surely a finite amount which can be known about the world, and, like distantly related groups of animals under similar environmental conditions converge on the same ecotypes, we will eventually arrive at a given set of explanations for how things work. Evolution, or the laws of physics, exist, and were just waiting to be discovered. To a certain extent, the way in which we think about things is influenced by our language and our culture, but the principles of formal logic and mathematics upon which science is ultimately based are the same regardless of the language which we use to express our internal thoughts and the cultural biases which impact hypotheses.

If evolution, culture and even ideas always converge to common ground, we might reasonably ask: do our individual choices matter, or is everything predetermined? Arguably, our actions are strongly influenced by our values and general worldview, which is shaped by the culture in which we live, which is to some extent a product of biogeography. The general direction of society is modelled by the struggle for survival between different memes which infect our minds and propagate themselves as we transmit ideas to others. In this sense, perhaps we are not in any way “special” compared to other creatures: we are all governed deterministically by evolutionary processes.

However, what sets us apart from other evolved species is our ability to predict and manipulate the world. For example, physicists could predict that if you dropped a hammer and a feather on the moon, they would hit the ground at the same time, and when people went to the moon, they showed that this was indeed true. Hypotheses in complicated systems like ecology can never be proved definitively, but we can use statistics to discriminate the better theories from worse.

So, whilst our beliefs and values are just human constructs, humans have the remarkable ability of predicting phenomena which occur regardless of the cultural frames through which we perceive them. To quote the astrophysicist Neil deGrasse Tyson, “The good thing about science is that it’s true, whether or not you believe in it”. And, although recognising that our actions are to some extent predetermined can make life feel meaningless, I think it’s impossible to imagine a better existence than to be a conscious being in a world full of fascinating things.

Living rivers

This is a modified, referenced version of an article which I originally wrote for Beaver Trust and was published on The Ecologist.

Rivers are interesting things. They flow inexorably towards the sea, carrying what was once billions of raindrops, in huge web like networks fanning out across the landscape. They braid and meander, changing their course imperceptibly slowly. But how have rivers changed over time, and how did this affect the species living within them?

In the Cambrian and early Ordovician periods (before around 450 million years ago), the continents were bare. Plants had not yet colonised the land, and without the weathering caused by their roots, there was no soil, only loose rock, gravel, and sand. Sedimentary records tell us that the rivers at this time were braided: split into smaller streams rapidly shifting across the riverbed, leaving behind diagnostic alternating layers of fine grained and coarse grained sediments. Today, these kinds of rivers are found in the Arctic and high mountains – places where there is no vegetation to stabilise the riverbanks – as well as on beaches. When there is heavy rainfall, the whole channel is submerged and a new pattern of streams appears when the waters subside.

When plants gained a foothold on the land, things began to change. Even the liverworts, diminutive slimy things which you might find on a damp boulder, had an impact on the structure of rivers. By weathering the top layer of rocks, they created clay. This cohesive mud resulted in more stable riverbanks, which slowed down the sideways migration of the channels. The clay and decaying organic matter created soils, which allowed more sophisticated plants to colonise. Their root systems further stabilised the floodplains, forcing braided rivers into more defined and slowly meandering channels.

The next big change came with the origin of trees, which by the Carboniferous period were covering vast areas of river deltas (and, as they fell into the anoxic swamps, forming much of the world’s coal). Rivers would have often become blocked by fallen trees and piles of debris, which force the current sideways, carving out new channels into the floodplain. The result would have been a complex shifting mosaic of channels, oxbow lakes, and swamps in various stages of vegetation succession. It was in similar shallow swamps (although slightly earlier, in the Devonian period), that Acanthostega, thought to resemble the ancestor of terrestrial vertebrates, would have clambered through the waterweed in shallow pools. Today, rivers of a similar kind can still be found in undisturbed parts of the Amazon.

It’s not just plants that have influenced the changing patterns of rivers, but also animals, and none has had more impact than the beaver (apart from, of course, humans). The first beavers evolved in the Eocene period, around 45 million years ago.

Beavers are herbivores and mostly eat the young shoots of trees, leaves, bark, and aquatic vegetation. In small streams, they build dams to raise the water level and so enable easy access to their food without leaving the water. Flooding the surrounding land encourages the growth of willow trees, one of their favourite foods, and by coppicing these trees the beavers maintain a supply of new shoots. Their ponds also serve as a food store: in summer, they cache branches at the bottom of the pond to eat in the winter. Because the engineering of their environment is so crucial to the beavers’ own survival and reproduction, it is even argued that beaver dams are part of the beaver’s extended phenotype.

Not only are beavers’ engineering works fascinating in their own right, but they create huge benefits to other species. Sequences of dams create deep, slow flowing sections interspersed with faster riffles. Dams force water sideways onto the floodplain, creating braided multi channel systems, and this is sometimes helped by the beavers digging canals to get to nearby trees. Some trees behind the dams are killed by the rising water levels, whilst other species regrow after being coppiced by the beavers. The huge diversity of physical environments at different spatial scales – speed of flow, shape of channels, sizes of sediment grains, water temperature, air temperature, sunlight penetration, density of vegetation – creates myriad different niches which can support a huge number of species.

Ponds are perfect for frogs and fish larvae; riffles and gravel banks for dippers; swampy areas for water rails and moorhens; dead trees for woodpeckers, owls, and bats; and lush coppiced vegetation for songbirds. In fact, many of these species may have evolved to exploit the habitats created by beavers, so it is no surprise that wetlands with beavers support more life than those without.

More generally, we tend to overlook the effects that living organisms have on their world because most of the ecosystems around us have been “downgraded”, and we perceive what we know as the norm. In many places, most of the highly influential species, which are often the largest, have been lost. Now, physical processes and simple food chains are the main factors at play, but in systems which retain a huge diversity and abundance of lifeforms, and species which engineer their environment, living organisms have profound effects on other species, the flows of energy and nutrients, and even the physical geography. Intriguingly, even some scientists use almost poetic phrases like “ecosystem metabolism” to talk about the functioning of the biosphere.

Through studying the effects that reintroduced beavers have on streams, the sedimentary record in floodplains, and old maps, it has become clear that the river structure which we perceive as the norm – a single channel and dry floodplain – is in fact a recent anthropogenic feature. Before we hunted beavers to extinction for their fur and scent glands and canalised rivers to protect agriculture and enable navigation, river systems would have filled the bottoms of valleys, with snaking channels, ponds, wet meadows, and willow scrub.

By bringing back beavers and setting aside un-farmed corridors along rivers, we could revive these incredible ecosystems. Beaver ecosystems could fan out into every valley in an interconnected network, like blood vessels pumping life back into the landscape. So many other species could flourish in the habitats that beavers create: otters, water voles, marsh tits, spotted flycatchers, frogs, water rails, egrets. Long forgotten species could return, like black storks, which thrive on the abundance of amphibians in beaver wetlands.

Although seriously conserving biodiversity will ultimately require a reduction of the land area that we use for food production, reintroducing beavers could have huge ecological benefits with relatively little impact on farming, if an appropriate management system is in place. Furthermore, their wetlands can filter out some of the runoff from agriculture, and attenuate flash flooding which damages both farmland and people’s homes.

Beaver wetlands could also rekindle our sense of wonder at the natural world. Squelching through a beaver wetland in Devon, I found it humbling that this entire ecosystem had been created by another species. Experiencing these living systems would create hope and optimism at a time when the state of the natural world is continually in decline.

For thousands of years, humans have been untangling the complex web of life, yet now, equipped with an unprecedented understanding of the living world, we can start to put things back together. Reintroducing beavers could weave back together the biological and physical processes in our rivers, and create wonderful living landscapes. They are like a fully automated tool for ecological restoration, and we only have to release them and let them do their work.


Walking / running from Bath to Cambridge

I recently walked and ran from my house near Bath, to Cambridge (to start my final year at university), a distance of around 160 miles over 4 days.

Before starting, I did not feel in top form because I had just got back from a month away in Singapore and Malaysia, where I didn’t do any exercise. However, I had decided that I definitely wanted to run to Cambridge at some point in my degree, and the only other opportunity would be at the start of the summer term (the start of the spring term would be too dark and miserable). Therefore, if I left it until the summer and ended up being injured at that time, there would be no other opportunities. (edit: the cancellation of the summer term due to coronavirus would have prevented me from doing it then, so it was lucky I decided to do it at the start of the year).

Although I had wanted to run to Cambridge anyway, I thought it would be good to raise money for a charity. I have been obsessed with beavers after first reading about their ecological impacts, and in the Easter holiday visiting a beaver swamp in Devon which was probably the most amazing wildlife site I have ever been to. About a week before the start of the run, I found out about the Beaver Trust, and decided that, since they were a brand new charity specifically about beavers, this was too good an opportunity to miss. I set up a fund-raising page, packed my stuff for the term in Cambridge (my dad drove it there after I had arrived), and left at fairly short notice after deciding to commit to the idea.

The kit I took with me: sleeping bag, sleeping mat, bivvy bag, jumper, waterproof, water bottles, head torch, compass, chlorine tablets (never actually required), battery pack, cable, first aid kit (also never used), wallet, snacks.

The route was broken into 3 convenient sections. Firstly, the Kennet and Avon canal could take me all the way from Bath to Newbury, a distance of about 57 miles. After that, there would be about 15 miles of roads and footpaths to connect to the Ridgeway, a long distance trail. This would take me about 45 miles to within a few miles of Luton and from there it was another 38 miles to Cambridge, again along a mixture of roads and footpaths. My ambitious plan was to complete this in 3 days: day 1 along the canal, day 2 the connecting bit and most of the ridgeway section, and day 3 the last few miles of the ridgeway and the final section from Luton to Cambridge. More realistically, I was confident that if I could complete the canal on day 1, then I could definitely finish it in 4 days.

The first part of the route – (almost) the length of the Kennet and Avon canal

The first half of day 1 was pretty nice. I was running at about 6-7 miles per hour, stopping about every 2 hours to have a drink or eat a cereal bar. After lunchtime (which didn’t actually involve a significant meal because I was just snacking on cereal bars), I alternated between walking and jogging. At around 6pm, I asked someone how far it was to Newbury, and he said 6 miles. This made me feel great, so I speeded up and decided to push on and wait to get some proper food once I arrived. However, this must have been a mistake, because after a few hours I had still not arrived. Looking at google maps, I think he must have meant 16 miles. By the time I arrived I was only walking, with huge blisters around the base of my toes, and very hungry and tired. I also realised that I had only sat down once all day. I found a pub in Newbury that had a special meal deal to share between 2 people, and ordered one just for myself. Unfortunately, I was so tired that I couldn’t eat most of it, so packed it into a box and left to find somewhere to sleep. It was around 11pm by the time I fell asleep in some bushes in a park next to a road, and I didn’t sleep well due to the noise of the traffic.

A massive meal on the first night, after only eating a few cereal bars all day.

The next morning, it was painful to move my legs to get out of the sleeping bag, and walking through Newbury I was overtaken by an old granny. I decided to ditch any idea of going on nice footpaths and take the most direct route along the road to Goring, a town where I would pick up the ridgeway trail. This was only about 15 miles, but took me around 6 hours. The blisters were a big problem. With blisters around the front of your foot, you automatically put your weight on the outside edge of your foot, however, walking in this abnormal way can shift the problem to the muscles in your leg and ankle. The solution is to pop the blisters so that the fluid can drain out and focus on pressing the blisters into the ground and feeling the pain every time you step, so that you are pushing off the ground normally with your forefoot and toes. In the short term this is more painful but compared to hurting your legs and ankles (which could actually prevent you from completing the challenge) the blister pain is less of a problem.

Good advice for covering long distances

After getting some cheese toasties for lunch and buying some mars bars and energy drinks, I spent the afternoon navigating quite inefficiently to join the Ridgeway path. Having finally reached it at around 6:30, I was feeling pretty tired, but I still had at least 2 hours left to fill my allocated time of at least 12 hours a day on the move (it seems excessive to spend 12 hours not moving when there is basically nothing else to do apart from move, eat, and sleep, and you only need about 8 hours of sleep). I set a timer on my phone for 3 hours, put my head torch on, and jogged and power walked along the trail. The terrain was gently undulating and it was more peaceful and easier to focus in the dark. I think that, although sticking to main roads might seem like the quickest option, running along trails can actually be quicker, because the variation in topography, scenery, and surface underfoot can keep you motivated (and also make it easier on the blisters). Although the scenery was quite picturesque, one thing I didn’t like was the absolutely vast numbers of pheasants in this area.

After a few hours of jogging and power walking through the dark my hands and mouth felt weirdly fuzzy and I couldn’t always walk in a straight line, so I kept a look out for any dry places to sleep. When I reached the M40 motorway, the track passed under it through a tunnel, which was perfectly dry. Compared to the previous night’s accommodation, this was luxury! It was calming to feel like I was far away from other humans (in reality I was only about 2 miles from the nearest town and there people driving above me), but the downside of this was that I didn’t find anywhere to eat, so only had some peanuts and a mars bar for tea.

Luxury accommodation under the motorway

The next morning I drank an energy drink and, after my blisters had numbed down, managed to jog for about 2 hours (in which I covered about 10 miles). At around 11am I ate 2 cheese toasties and bought a few more mars bars and energy drinks, then continued running. Cruising along the trail through woodlands and chalk grasslands, and up and down gentle hills, it was, for the first time in this journey, actually enjoyable. For a couple of hours I tagged along with 2 other runners who looked like they were training for an ultramarathon. However, after they went home, I realised that we had left the main path that I was supposed to be on. I then spent about 2 hours walking through the woods trying to rejoin it, and, when there were only a few hours of daylight left, I decided to ditch finding the trail and take the most direct route along a main road to Luton, the next significant point on the journey. Fuelled by another energy drink, I managed to properly run about 6 miles. However, the tendons on the front of my ankles seized up, so I had to walk and limp the last 7-8 miles into Luton. I bought some bread, milk, nuts, and fruit, and went to sleep in an overgrown area of a park. Nestled in some long grass, looking up at the stars, and further from the noise of traffic than I had been on the past two nights, it was very peaceful. Today had been the best day of the journey.

The next morning the tendons on the front of my ankles were incredibly painful whenever I moved my feet, and it was a struggle to get out of my sleeping bag and start walking. I decided that, in order to not do any serious damage, I would not try running today, and would stick to the shortest possible route along the main roads. It was only 38 miles to Cambridge, so I was confident that I could walk this in a day. Taking an extra day would make the overall finishing time of 5 days sound pretty rubbish, so I was determined to simply continue walking until I got there. In the end, it took 16 hours, the last 4 of them in the dark and the rain. For most of the time I was limping because of the pain in my ankles. Taking ibuprofens did make a big difference (or maybe its just the placebo effect), so at some points I could walk fairly normally. I walked past some huge fields covered with solar panels. Because solar panels are very inefficient, this made me wonder whether restoring woodland on this land, rather than covering fields in solar panels, could actually sequester more carbon than the reduction in emissions from using solar panels instead of burning fossil fuels (I’ve tried some rough calculations but am not sure what the answer would be). The last 10 miles seemed to take forever. My pace slowed down as I got closer to Cambridge, as if I would get infinitely closer but never actually reach it. Reaching the edge of the city, I felt like I was almost there, but it still took an hour or more to walk into the centre. Even when I could actually see the end a few hundred metres away, I couldn’t celebrate, because it would still take a few minutes in the cold and rain to cover that distance. I arrived at 11pm, had an amazing shower, ate some porridge, and went to sleep feeling incredibly happy. 

Here is a breakdown of how far I covered on each day, according to google maps. Estimates for days 2 and 3 are very approximate, because google maps cannot recognise the Ridgeway trail, so I had to drag the route to the nearest roads. I didn’t do any proper training for this challenge, so I’m sure someone else could do it much faster.

Day 1 – 57 miles, 14 hrs

Day 2 – 30 miles, 12 hrs

Day 3 – 36 miles, 11 hrs

Day 4 – 38 miles, 16 hrs

Lundy Memories

This summer I was a long term conservation volunteer on Lundy island. I spent most of my free time photographing and filming the wildlife, mostly underwater, and exploring the coastline. It was an absolutely awesome 3 months, with some truly mind boggling experiences. Here are some of the most memorable (in no particular order):

Swimming as fast as I could along the east side of Lundy, feeling the water rushing past and looking down at the amazing patterns of many different seaweeds. Sleeping out near the north end of the island amongst a cacophony of manx shearwaters flying in to feed their chicks. Listening to the screaming of peregrines as I woke up in my bivvy bag. Watching storm petrels flitting across the sky just above my head in the dark. A seal hugging my leg for about a minute. Snorkelling through spectacular sea caves with seals. Peering over the cliff edge to see 2 female seals with pups on a secluded beach below. Walking past a seal pup about 2 metres away when it hauled out on the road near the jetty. Swimming far out from the west side of the island to photograph seabirds underwater. Swimming the length of the island. Meeting an angry seal in a remote cave. Sneaking up on turnstones, oystercatchers, and common sandpipers to within a few metres by kayak. Attempting to climb up a bramble covered cliff, wearing only shorts. Trying to kayak through the narrow gap between 2 rocks as the tide rushed through in the opposite direction. Getting heat stroke during the 14 mile Lundy race. Walking up the island at 3:30am the next morning, with just a bit of orange light in the sky. Swimming in complete darkness with bioluminescent plankton lighting up silver as I disturbed the water. Walking around in the dark, and in the moonlight. Sleeping behind a rock at the top of a cliff, and waking up with no memory of where I was. Watching the sun go down over the horizon countless times. Watching the sun go down over the horizon with puffins silhouetted in front just a few metres away, swimming around in the reflection of the sunset. Fulmars flying past my head closer than 1 metre whilst I was swimming. Fulmars flying past me when I was sitting on the cliff edge, close enough that I could have touched them. Watching and photographing shags just a few metres away at the bottom of the cliffs at the north end as the sun went down over the horizon. Glimpsing deer running like ghosts silhouetted against the blue glow after a cloudy sunset, as I was walking up the island to sleep. Looking into the eyes of guillemots underwater as close as 1 metre. Swimming with puffins and guillemots for up to 5 hours a day for several weeks. Being surrounded by the bubble trails produced by guillemots and puffins underwater. Seeing the most awesome stars. Putting on a wet wetsuit at 4:30am. Snorkelling with 3 incredibly inquisitive seals at sunrise in absolutely unreal visibility and the most epic light. Being smashed around by big waves whilst photographing guillemots underwater, and also when trying to get out onto the rocks. Swimming around in the bay beneath a seabird colony at sunset, with all the birds wheeling around overhead. Watching a peregrine hunt kittiwake chicks inside a cave. Listening to kittiwakes calling in the dark as I fell asleep.