MAMMAL WATCHING
A year after writing a book about the evolution of mammals — and the debt we all owe to our shared mammalianness — Liam Drew surveyed a year’s worth of studies describing the health of wild mammals.
(This essay was originally published as the Afterword to the paperback edition of Liam Drew’s book I, Mammal: The Story of What Makes Us Mammals)
On a bright spring Sunday, six months after my book charting and celebrating the evolution of mammals was published, I took my morning coffee and sat on a bench peering into old English woodland. Before me the sub-seasons were shifting, early spring yielding to late. The bluebells — no longer magical — covered the forest floor still, but now only as yellow-green clumps of leaves apologetically propping up their seed-heads. To watch spring unfurl, that day, one had to peer upward; upward into a canopy shimmering in virginal greens, greens too delicate, too pure to last.
Most of the leaves sprang from bustling hornbeams and birches — these sprightly youngsters hustling for light around and beneath two old oaks only just starting to reawaken, seemingly content to let everything around them get a head start. Elsewhere shrubs, grasses and scrub clamoured into leaf. Everything wanted to grow now — where the sun shone, green raced to be.
The bluebells awaken
Across the gulley where a winter stream occasionally flows, a sagging wire was pinned to flagging wooden posts. There to mark a border — a demarcation of what was ours (my mother-in-law’s) and what was theirs, an offstage Lord to whom great swathes of this forest belong — it seemed that day absurd. I wondered what the wood’s inhabitants made of it. It was too high to trouble a badger and too low to present a deer with a serious hurdle. For birds, it was just another perch. Maybe, they barely minded it at all.
But, still, there it was, a metallic reminder that humans owned this place. Not that Homo sapiens conjured the concept of ownership out of nothing — many species mark and maintain territories and ranges. And wire is undoubtedly preferable to Lord What’s-his-name arriving here weekly to cock his leg against a tree. What felt preposterous was how minimally attached to this land its owner is –does he come here at all? What is this place to him?
Then, on cue, a movement. To my left, just beyond the wire, a ruffle of bluebell remains. I expected to see a squirrel but instead saw a fox. No, a fox cub; no, two fox cubs. Hang on … three! What? No. Let me count these properly — one, two, three, four –no that’s the mother –four, five …Is that? Yes, it is — six! That can’t be right. But it was. I counted again. Six cubs and their mother. Oh my!
By a clump of hornbeam trunks, the six youngsters played in an arc around their mother, who lay on a mound looking out. They pawed at objects, did little jumps and turned brief rolls as if they were enacting an advert broadcasting the importance of playful activities to growing mammals, a topic I’d covered in the book. And as a reminder, too, that play can be a social or individual behaviour, four cubs played solo, while two entertained each other.
Then, watching how the mother’s presence allowed these new animals to develop whatever skills they were developing, I thought once more about how the essential union of successive generations of mammals had emerged as one of my book’s central themes.
Indeed, I thought constantly about how much my young daughters would enjoy seeing this, but was certain that if I got up to leave, the foxes would flee, and that if they didn’t, they most assuredly would when the girls approached. But, no — after I’d tiptoed away, I managed to marshal Isabella and Mariana to the forest’s edge, and with Cristina and her mum behind, a family of five watched a family of seven, elevated by spring and life and all its vitality.
* * *
In 2018, scientists published more than a quarter of a million studies tagged with the keyword ‘mammal’. The interactions between generations of mammals were nicely highlighted in a study that showed how North American moose and bighorn sheep learn their migration routes from their elders. In Germany, researchers showed how, in an apparent bid to reduce running costs, shrews’ brains shrink for the winter then regrow in the spring. Researchers at the University of Cambridge grew something like a placenta in a dish. Meanwhile, sequencing the entire genomes of Himalayan marmots and koalas, respectively, gave insights into how a mammal goes about living at very high altitudes or subsisting entirely on a diet of eucalyptus leaves. Koalas apparently have more taste receptors for detecting plant toxins than other mammals, presumably to allow them to distinguish good eucalyptus from bad.
Also down under, scientists fathomed how wombats defecate cuboid poos — these animals use piles of their turds to signal to each other, and apparently this shape grants the piles more stability while the wombats are stacking. It turns out the last 8 percent of a wombat’s intestines have regions of varying elasticity that cleverly sculpt this shape. On the subject of poo, in Alaska, it was found that fruit-eating bears are a major dispersal mechanism for seeds and that, consequently, many small mammals scramble to gain access to the rich delicacy that is bear scat.
Then, in the category of papers that undermine mammalian uniqueness, researchers in Germany and Italy found that the Somalian blind cavefish — an animal that swims in complete, subterranean darkness — has lost a molecular safety system that protects DNA from UV damage, and it’s the same one that placental mammals lost during their long nocturnal stint. In China, scientists found that certain ant-mimicking jumping spiders — and, seriously, these creatures are dead ringers for ants — do something remarkably akin to lactating, feeding their hatchlings a nutritious secreted solution, albeit from their egg-laying orifices rather than from nipples. Ah, life. But oh, death.
The foxes I watched in May were seven of an estimated 357,000 currently residing on the British Isles according to the UK’s Mammal Society. This summer, the society published a survey that assessed the ‘population size, geographical range, temporal trends and future prospects’ of all 58 species of terrestrial mammals that live wild in the UK. Temporal trends were determined by comparing this year’s population sizes to those that had been estimated at the last such census in 1995.
Water voles, wild cats, black rats and certain bats are all critically endangered on these shores and many other species, including the beloved hedgehog, are in sharp decline. At the launch of the report on the survey’s findings, a journalist asked whether mammals might have an image problem –contrasting the popularity of birdwatching to an apparent paucity of mammal-watchers, the term itself alien. Surely this was untrue, everyone said, but no one could really give a concrete rebuttal. I realised later that the UK’s three most common mammals –field voles, moles and wood mice, all of which are roughly as numerous as people here — are animals I’ve never seen in the wild.
The way that many mammals live their lives out of view — of humans and of as many other animals as possible — contributed to the survey’s other defining feature: its uncertainty. The Mammal Society reckoned that there are 6.3 million pygmy shrews in the UK but, it said, there could be as few as 999,000 or as many as 38.9 million. The population of Daubenton’s bats was estimated at a healthy 1.03 million, but more realistically it is somewhere between a glowing 4.44 million and a distressing 27,000. (The problem with bats is that many people are able to report that a mammal just flew by, but few can say to which species it belonged.)
Part of me liked this mystery and the way it implied that even today, on these most domesticated of islands, mammals can be genuinely wild. But if we’re to truly know the fates of the mammals that live among us, better methods and greater precision are needed.
There was uncertainty, too, in a study out of Israel and California that sought to calculate the mass of all living things on this planet, an endeavour that confirmed my suspicions stood in Darwin’s garden surrounded by thousands of different plants with only a squirrel for warm-blooded company: there really is much more plant than mammal in this world. Globally, for every one gram of wild mammal, there are 65kg of plant, which is to say that for every ton of plant there is, there’s just half an ounce of mammal.
Plants account for 82 per cent of earthly life’s total weight. Next comes bacteria (about 13 per cent), then fungi, followed by the other single-celled groups, archaea and protists, before animals come in second from last, ahead of viruses only. Although, with mammals constituting only 10 per cent of animal life and 0.03 per cent of all life, there’s actually less mammal than there is virus on planet Earth.
If these numbers are surprising, it’s because the reality of ecological balance is surprising. But the way the weight of mammals is distributed these days is startling because humans are quite something.
Homo sapiens — that tiny twig on the mammalian branch of life — now constitute about a third of all mammalian biomass. And, if you throw in our mammalian livestock — mainly cattle and pigs — together we represent 96 percent of all mammalian biomass. All of this world’s five-and-a-half-thousand species of mammal living untamed are outweighed 24-to-one by humans and their domesticates.
Drawing these conclusions is technically challenging, the authors said, and deriving historical trends is harder still, but the researchers cite a study that estimates that since modern humans have been around, the total mass of wild mammals has fallen by about 83 per cent.
According to another 2018 study, when humans are around, it is the largest mammals that are the most vulnerable. Here, authors from a number of US universities used the mammalian fossil record since Homo sapiens and our immediate ancestors have existed to relate a mammal’s body size to its chances of going extinct. The researchers observed that over the last 125,000 years, the bigger a mammal was, the more likely it was to have bitten the dust.
Notably, this wasn’t the case for the preceding 65 million years, and so this change is almost certainly the result of hominin activities. All those giant sloths, giant deer, cow-sized armadillos and mammoths whose spectacular skeletons populate natural history museums — and which make visitors strain to imagine how, when and where such behemoths roamed — were victims of the way feelings of awe and a rallying call to slaughter are conjoined in us. (Another report this year described the discovery of ancient human footprints nested inside those of a giant sloth, a fossilised record of our species stalking its prey.)
Projecting just 200 years into the future, the authors saw nothing in current population trends for elephants and rhinos, hippos, giraffes and other large terrestrial mammals to suggest they’d still be around. By then, they suggested, cows may well be the largest land mammals left alive.
Not only are humans making mammals, on average, smaller, they’re also making them more nocturnal. A survey, by scientists at University of California, Berkeley, of when mammals are active these days showed that mammals living near people try to avoid them by coming out when the humans have retreated to their homes and/or beds.
This observation can be added to the long-known fact that mammals generally try to avoid people by moving away from them in space. The authors said humans are best viewed as “superpredators”, creatures who are abundant and terrifying to many species. Our presence causes wild mammals to always be on guard, constantly pumped full off stress hormones, spending a huge amount of their time in a state of hypervigilance — even when local humans are not bearing arms. Living this way means mammals neglect to undertake basic survival behaviours such as eating and breeding. The study’s authors doubted, too, that moving further into the night was a great fix — naturally diurnal animals, they said, would likely struggle to live amongst the nocturnally adapted animals already active then.
Mammals as small creatures who live by night because the day is occupied by a tyrannical foe… it sounds familiar, doesn’t it? We humans, just one species, are having a global impact on our mammalian cousins that’s akin to the oppressive effect dinosaurs had.
Only we humans operate much quicker than dinosaurs. Damage that accumulated over the course of 125,000 years may be considered short by geological standards, but the effects of what has happened in the last 40–50 years are more like an asteroid crash. In October 2018, the World Wildlife Fund released its biannual Living Planet Report, which stated that across all vertebrates the average species was 60 percent less abundant than it was in 1970.
This followed a German report from the ‘mammals are not unique’ category, published in 2017, showing that in the previous 27 years insect populations — vital components of any ecosystem — had fallen by 75 percent.
Also, in October 2018, Danish researchers asked how long it might take for the mammal species that humans have killed, and are killing, to be replaced by re-evolved types if humans were to be no more — that is, how many years might it take for evolution to craft mammals like those that humans have wiped out from the species that currently remain. They concluded that for mammalian diversity to recover from human interference would take at least 3 to 7 million years.
* * *
I saw the fox cubs again the next time we visited Cristina’s mum, but the visit after that — no matter how often I crept to the forest’s edge — they were gone. Two months later, in the summer, heading out for a walk, Cristina’s mum said absent-mindedly, as she flicked the light switch, ‘Let’s turn this off and help save the planet.’
‘Save the planet!?’ Isabella squawked at me bemused. This remark made absolutely no sense to her six-year-old brain — how could something as big and all-consuming as the entire world need saving? And what did something as trivial as turning off a light have to do with it anyway?
This exchange happened when people, post-David Attenborough’s Blue Planet 2, were being encouraged to use less plastic, and I’d been dismayed that very lunchtime by how much plastic waste I had generated making just one unremarkable meal.
‘Imagine a rabbit, Isabella, ’I began, ‘a rabbit eats the grass and other plants that grow where it lives. And it drinks water from puddles and streams near where it lives too.’
‘Yes…’, she said, clearly unsure about how this related to the whole planet.
‘Well, the rabbit then poos on the ground where it lives. And it wees there too. So, really it takes nothing from the planet. It just borrows water and food, to grow and live. Then, when the rabbit eventually dies, a fox or a crow will eat it, and maggots and other bugs will eat whatever’s left. Slowly, even its skeleton will rot away. It lives its life and leaves no trace.’
I was about to compare this with my trash-strewn wake, but her attention was gone. She’d run off to inspect a hedgerow, leaving me to quietly contemplate how I had that day generated more non-degradable waste than the entire population of wild rabbits that has ever lived.
It was easy to pause the lecture because it felt rather heavy to load all this onto the shoulders of a six-year-old. What had I been building toward anyway? Something like, ‘You see, darling, animals are dying, and the climate is moving toward a state that will be catastrophic for human civilisation as we know it. And your generation’s task — actually mine and yours, because we probably don’t have that much time — is to Save the Planet by being as close to carbon neutral as possible and to desist from constantly destroying natural habitats. This, sweetheart, comes despite the dominant 21st Century narrative and noncapital message that “you deserve to have it all!” Let’s start by not buying that crappy plastic toy you really want because as soon as you were done with it, it would choke a dolphin.’
No child deserves that. But maybe we need them to internalise some of this because these notions don’t seem to run deep enough in us grown-ups. I am writing this — having read the Mammal Society’s survey of UK mammals, the WWF’s assessment of the world’s vertebrates, the study by the meticulous group of German entomologists who directly catalogued insects for 27 years, and all the rest of it — and at some level, I still think surely, it’s not that bad?
Projections, percentages, numbers, news from elsewhere — none of it is fully penetrative. There remains a disjoint between the data that describes the natural world and my gut feeling about life’s resilience — But those fox cubs, I think. And what about the scores of seals we went to see this summer? The green from my window right now; the rabbits, squirrels, magpies, ducks and geese in the park across the road and, hey, I’ve seen rats there too, and, one time, a deer…
Where Blue Planet succeeded was in showing its viewers the turtle trapped in a plastic bag and the dead albatross killed by swallowing a plastic toothpick. We hold those bags in our hands and grasp how they could suffocate or strangle an animal. Maybe this is what every documentary should do. Report on how orangutans are smart, then show the footage of a lone male in a flattened forest trying to push a bulldozer away with his bare hands.
People who spend their lives observing wild animals complain that the mass media is uninterested in reporting on a calamitous 80 percent decrease in population size. They say that the media only come calling when a new extinction is declared — such as the Chinese river dolphin — so that outlet after outlet can run stories asking ‘What have we done?’ only when it is too late.
Biologists and conservationists describe our current time as earth’s sixth mass extinction. But when you think of mass extinctions — like the one that wiped out the dinosaurs 66 million years ago or the Great Dying that occurred 252 million years ago — you picture a world engulfed in poisonous gases or rumbling with spewing volcanoes or smashed by an asteroid; the planet is littered with corpses, the air thick with the stench of death. It looks nothing like this.
There is a failure of comprehension. What does a mass extinction look like? Why, it can look exactly like this: like a feast, a time of absurd plenitude.
One day someone, or something, will write the history of this extinction, just like we try to fathom what happened in the previous five. They will have to reckon with the behaviour of a single unprecedented species, the smartest that’s ever been, whose smarts have seen it spread like an algal bloom. What they will say about us is uncertain — will we keep growing until we’ve smothered and poisoned all about us, like a toxic algal bloom, or will we find ways of living less destructively?
I often think of an online comment below a newspaper report about the above global biomass study and humans ’having ablated 83 per cent of wild mammals’ mass. The comment said, ‘Survival of the fittest. Humans rule and others die out because we adapt better. […] Stop the moaning!’
And I think too about the time this autumn when a friend was on a panel that discussed the effects discarded plastic is having in the oceans. Before the panel, I remarked that, surely, she didn’t have to worry too much about there being a significant pro-plastic presence. But two days later, my friend told me the audience was 50:50 on the idea of trying to control plastic waste. ‘I get REALLY pissed off when people tell me what to do!’, one audience member had barked into the microphone.
And me? Well, I’ve cut down on plastic, compost whatever I can, recycle more diligently and look at my bin’s contents more regretfully. I cry when I watch an orangutan wrestle a bulldozer. I try to eat less meat, but this burger surely won’t hurt too much. I fly less than I used to, but I’m looking forward to returning to New York soon, it’s just one flight, it’s just little me, you gotta live. I buy my children those toys, etc., etc. … I could do so much more.
These conflicts and moral struggles and crises of conscience will be lost to future historians. Anyone watching from any distance could only conclude that Homo sapiens is killing species at a furious rate, knowingly and because it wants to.
* * *
In December, I return to the forest-facing bench with my morning coffee and huddle against a chilly, damp breeze that from time-to-time blows hard. It’s weather that says ‘Go inside!’. Greens are rare now, there are mosses, yes, some brambles and occasional fern fronds, but, no, this is a brown and drawn scene; brown and naked. Now, while the two oaks stand stoic, the birch and hornbeam bend and wave with the wind; their tiny crowns swaying atop long, spindly, sun-chasing trunks –transplanted to a field, these trees would look obscene.
Everything is suspended — the earth’s orbit around the sun is written into the DNA of this place. The wood speaks to how, sometimes, barren times should be simply waited out; endured until favour comes again, ‘Sleep, why don’t you?’, it asks. The hedgehogs sleep, the dormice too, and the bats are tucked up for the winter. Times will be good again, rest, the bluebells will wake you.
I walk to where the fox cubs had played. The leaf-filled mouth of a den is all there is to recall them by. Nothing else says foxes; they’ve left no trace. I hope, really hope, I get to see more of them this coming spring.
Time here feels cyclic — the forest’s gully will soon be a stream again, pools will re-form in the landscape’s depressions, winter will do as winter does, and in January and February, the foxes will, one trusts, find each other, knowing somehow that coupling then will mean their young are born just as the first bluebells bloom…
Because that’s what life does, isn’t it? It comes back, racing to catch the sunshine. Only time isn’t cyclic, it moves only forward, nothing is guaranteed.
December 2018, East Sussex, UK
“I, Mammal: The Story of What Makes Us Mammals” is published by Bloomsbury.