Category Archives: Biology

Death and the Midden

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Front cover of The Mitchell Beazley Pocket Guide to Mushrooms and Toadstools by David N. PeglerThe Mitchell Beazley Pocket Guide to Mushrooms and Toadstools, David N. Pegler (1982)

A little gem of a book in a consistently excellent natural history series. Rather like its subject, it’s an example of something very rich and rewarding that’s growing quietly in a neglected niche. Representational art, banished from the academies and galleries over the past century, has survived in natural history illustration. When I think of contemporary art that’s moved or delighted me I often think of men like Richard Lewington, illustrator of Field Guide to the Dragonflies of Britain and Europe, and Ralph Thompson, who illustrated Gerald Durrell’s books about animal-collecting in Africa and South America. David N. Pegler’s art is more realistic and detailed than Thompson’s and he may be an even better draughtsman. But if you think he has less scope for quirkiness and humor, with non-animal, let alone non-mammalian, subjects, you’d be wrong. Each of the fungi illustrated here is a finely detailed, delicately tinted portrait in miniature and in situ, often accompanied by the dried leaves or bark or pine-needles of the spot in which Pegler presumably found it. And one of the pleasures of looking through the book is uncovering the unique and often witty touches Pelger has added to some of the portraits. For example, there’s the beetle crawling towards two specimens of Tricholoma portenosum – ‘so good to eat the French call it “Marvellous Tricholoma” (Tricholome merveilleux)’ – and the crumpled sweet-wrapper lying near three Agaricus xanthodermus, the Yellow-staining mushroom found in or on “Parks, roadsides and wasteland”.

But Pegler usually lets the fungi speak for themselves in their bewildering variety of voices from their startlingly wide range of habitats: there are fungi that specialize in sand, marsh, burnt ground, and dung, as well as the more familiar dead wood and leaf-litter. As so often, the English-speaking world still has a lot to learn from the French: where many Brits or Americans are familiar with two or three edible species, the French are familiar with dozens. The Italians, on the other hand, knew a lot about another kind of mushroom during the Renaissance: the poisonous varieties whose symbols – black-skull-on-white-background for “dangerous” and white-skull-on-black-background for “deadly” – add a regular macabre frisson to Pegler’s drawings.

Inner pages of Mushrooms and Toadstools

One of the deadliest fungi, the Destroying Angel (Amanita virosa), is one of the most beautiful too, like an evil young witch out of Grimms’ Fairy Tales: it’s pure white, slender-stemmed, and with lacy clinging veils, but it reveals its true nature by its “heavy soporific smell”. “Do not mistake for Agaricus silvicola”, Pegler warns (the Latin adjective silvicola, meaning “wood-dwelling”, only exists in the feminine form). One of the ways to avoid mistaking the two is that A. silvicola, the Wood mushroom, “smells of aniseed”. Fungi can delight, or revolt, the nose as well as the eye: there’s the Coconut-scented milk-cap (Lactarius glyciosmus) and the Geranium-scented russula (Russula fellea) on the delightful side, and the Nitrous mycena (Mycena leptocephala), “often smell[ing] of nitric acid”, and the Stinking parasol (Lepiota cristata), with its “unpleasant rubbery smell”, on the revolting.

Unless it can assist identification like that, Pegler doesn’t usually say much about any particular fungus, because he’s writing mainly for identification and has to cram hundreds of species into a pocket-sized space. But each species must have its own unique ecological story and Pegler has managed to make his drawings portraits from the wild and not just mycological mug-shots. And each is accompanied by an illustration of its spores, as a further aid to identification and further invitation for the browsing eye. Spores, like fungi themselves, come in many different shapes and sizes. All of which makes this book my favorite in the Mitchell Beazley series. Every book is worth owning or looking at, but the Pocket Guide to Butterflies, for example, has no artistic charm or whimsy. The butterflies are drawn strictly and severely for identification, with nothing accompanying them: no plants, no landscapes, and no jeux d’esprit. And European butterflies don’t come in many varieties or colors: although they often have hidden charms, most of them are frumpish and dowdy when set beside their glittering, gleaming, multi-spectacular cousins from the tropics.

That isn’t true of European fungi, as Pegler demonstrates: both they and their spores come in all shapes, sizes, and patterns. And all colors too. The Hygrocybe genus gleams with reds, yellows, and lilacs, and the species there look much more like magic mushrooms than the genuine article: the unassuming little Liberty Cap, Psilocybe semilanceata, which can open the doors of perception to a world of wonder. Fungi can drive you mad, kill you, or delight your palate, eye, and intellect, and this book captures their richness and variety better than any other I’ve come across. Art, natural history, and culinary guide: it’s all here and The Mitchell Beazley Pocket Guide to Mushrooms and Toadstools is, in its quiet way, a much greater example of European high culture than anything the modern Turner Prize has produced.

Bat’s the Way to Do It!

by in Biology, Book Reviews, Mathematics, Our Lady of the Gutter, Post-Weird, Science and tagged , , , , , , , , , | 2 Comments

I think Britain would be much better off without three things that start with “c”: cars, canines, and coos (sic (i.e., pigeons)). But perhaps I should add another c-word to the list: cats. I like cats, but there’s no doubt that, in terms of issues around negative components/aspects of conservation/bio-diversity issues vis-à-vis the feline community/demographic, they’re buggers for killing wildlife:

A recent survey by the Mammal Society was based on a sample of 1,000 cats, countrywide, over the summer of 1997. The results included only “what the cat brought in” and ignored what it ate or left outside. Leaving aside this substantial hidden kill, it still concluded that cats killed about 230,000 bats a year. This is equivalent to more than the entire population of any species other than the two most common pipistrelles. If these 1,000 cats are typical, and there is no reason to believe that they are not, cats kill many more bats than all natural predators combined. They are one of the biggest causes of bat mortality in Britain, perhaps the biggest. (Op. cit., chapter 6, “Conservation”, pg. 139)

Cover of British Bats by John D. Altringham

That is the unhappy conclusion in John D. Altringham’s very interesting and educative book British Bats (HarperCollins, 2003). Accordingly, I’d rather have fewer cats and more bats. Anyone but a cat-fanatic – and cat-fanatics are found in one or two places – should feel the same, and even the fanatics might reconsider if they read this book. The cat family contains some of the most beautiful and athletic animals on earth; the bat family contains some of the strangest and most interesting. In fact, all bats are strange: they’re mammals capable of sustained powered flight. Little else unites them: in chapter two, Altringham describes the huge variety of bats around the world. They live in many places and live off many things. Some drink nectar, some drink blood; some eat fruit, some eat fish. Some roost in caves, some in trees. Some hibernate, some migrate. Some use echolocation and some don’t. Bats are much more varied than cats and scientifically speaking are much more interesting.

Although echolocation isn’t universal, it is the most interesting aspect of bats’ behaviour and it’s used by all the species found in Britain, from the big ones, like the noctule and greater horseshoe bat, Nyctalus noctula and Rhinolophus ferrumequinum, to the small ones, like the whiskered bat and the pipistrelles, Myotis mystacinum and Pipistrellus spp.[1] Two of the pipistrelles are in fact most easily distinguished by the frequencies they call at: the 45 kHz pipistrelle, Pipistrellus pipistrellus, and the 55 kHz pipistrelle, Pipistrellus pygmaeus. As their English names suggest, one calls at an average of 45 kilo-Herz, or 45,000 cycles a second, and the other at an average of 55. The two species weren’t recognized as separate until recently: they look almost identical, although the 55 kHz is “on average… very slightly smaller”, and they forage for food in the same places, although the 55 kHz is “more closely associated with riparian habitat” (that is, it feeds more over rivers and other bodies of water). But examine their calls on a spectrograph, an electronic instrument for visually representing sounds, and there’s a much more obvious difference. This is a good example of how much the scientific study of bats depends on technology. Human beings didn’t need science to know about and understand the ways a cat uses its senses, because they’re refinements of what we use ourselves. We might marvel at the acuity of a cat’s eyes or ears, as we might marvel at the acuity of a dog’s nose, but we know for ourselves what seeing, hearing, and smelling are like.

Echolocation is something different. Bats don’t just see with their ears, as it were: they illuminate with their mouths, pouring out sound to detect objects around them. And the sound has to be very loud: “The intensity of a pipistrelle’s call, measured 10 centimetres in front of it, is as much as 120 decibels: that is the equivalent of holding a domestic smoke alarm to your ear.”[2] The “inverse square law”, whereby the intensity of sound (or light) falls in ratio to the square of the distance it travels, means that the returning echoes are far, far fainter than the original call. It’s as though Motörhead, playing at full volume, could hear someone at the back of the crowd unwrapping a toffee. How do bats call very loudly and hear very acutely? How do they avoid deafening themselves and drowning their own echoes? These are some of the questions bat-researchers have investigated and Altringham gives a fascinating summary of the answers. For example, they avoid deafening themselves by switching off their ears as they call. They’ve had to solve many other tricky acoustic problems to perfect their powers of echolocation.

Or rather evolution has had to solve the problems. The DNA of bats has changed in many ways as they evolved from the common mammalian ancestor (which also gave rise to you, me, and the author of this book) and those changes in DNA represent changes in their neurology, anatomy, and appearance. It’s easy to see that hearing is important for bats, because their eyes are relatively small and their ears are often large and rigid and come in a great variety of shapes. What isn’t easy to see is what those ears are supplying: the bat-brain and its astonishing ability to process and classify sound-data as though it were light-data. Bats can create sound-pictures of their surroundings in complete darkness. Of course, the feline or human ability to create light-pictures is astonishing too, but we’re too familiar with it to remember that easily. Bats aren’t just marvels in themselves: they should encourage us to marvel at ourselves and what our own brains can do. The digestive system of a bat, cat, or human needs food; the nervous system of a bat, cat, or human needs data. That’s what our sense-organs are there for and in principle it doesn’t matter whether we create a picture of the world with our eyes or with our ears.

Male noctule (Nyctalus noctula) calling from tree-roost to attract mates

Male noctule calling from tree-roost

In practice, there are some very important differences between sound and light. Light works instantly and powerfully on a terrestrial scale; sound takes its time and is much more easily diluted or blocked. A hunting cat can scan an illuminated or unilluminated environment for free, because it doesn’t have to generate the light it sees by or the sound it hears by. Hunting bats have to pay when they scan their environment, because they’re using energy to create sound and induce echoes. Once they’ve got their data, both cats and bats have to pay to process it: it takes energy to run a brain. But bat-brains are solving more complicated problems than cat-brains: Altringham describes the questions a flying bat has to answer when it detects the echo of an insect:

How far away is the insect?… How big is it?… In which direction does it lie?… How fast is it flying and in what direction?… What is it?… (ch. 3, “The Biology of Temperate Bats”, pp. 42-3)

Like insect-eating birds, bats can answer all these questions in mid-flight, but what is relatively easy for birds, using their eyes, is a much greater computational problem for bats, using their ears. “Computational” is the key word: brains are mathematical mechanisms and process sense-data using algorithms that run on chemicals and electricity. Bats were intuitively using mathematical concepts like doppler shift and frequency modulation (as in FM radio) millions of years before man invented mathematics, but man-made mathematics is an essential tool in the study of echolocation. For example, the concept of wavelength, or the distance between one crest of a sound-wave and the next, is very important in understanding how bats perceive objects. Light has very short wavelengths, so humans and other visual animals can easily resolve small objects. Sound has much longer wavelengths, so bats find it hard to resolve small objects. But some find it harder than others: Daubenton’s bat, Myotis daubentonii, and other Myotis spp. “can resolve distances down to about 5 millimetres when given tasks to perform in the laboratory”. But horseshoe bats, Rhinolophus spp., “can do little better than 12 millimetres.”

Why this difference? You have to look at the nature of the sound being produced by the different species: the Myotis spp. use “high frequency FM calls”; the Rhinolophus use “predominantly CF [constant frequency] calls”. The mathematical nature of the call determines the bats’ powers of perception. Calls can also determine how easily a bat can identify an insect: “relatively long calls can have a ‘flutter detector’… If a call is 50 milliseconds long, then within one echo a bat can detect the full wingbeat of insects beating their wings at more than 50 Hz.”[3] So bats can tell one kind of insect from another, something like the way a blindfolded human can tell a bumblebee from a mosquito. But insects aren’t passive as prey and one of the most interesting sections of the book describes how they try to avoid being eaten. Some moths have “ultrasound detectors” and if a moth hears a calling bat, it “will either stop flying and drop toward the ground, or begin a series of rapid and unpredictable manoeuvres involving dives, loops and spirals”.[4] This kind of ecological interaction creates an “evolutionary arms race”: each side evolves to become better at capture or evasion.

The moth/bat air-battle is reminiscent of the air-battles of the Second World War, which involved radar trying to detect bombers and bombers trying to evade radar. One defensive technique was jamming, or attempts to interfere with radar signals or drown them in noise. Some moths may use this technique too. The tiger moths, the Arctiidae, don’t try to escape detection. Instead, they “emit their own, loud clicks”[5], perhaps to interfere with echolocation or startle a predatory bat. Alternatively, Altringham suggests, the clicks may be the aural equivalent of “bright warning colours and patterns”: the moths may be warning bats of their unpalatability. If so, it would be another example of the difference between the costs of sight and the costs of sound. An unpalatable insect in daylight doesn’t have to pay for its warning colours, after the initial investment of creating them, and doesn’t have to know when a predator is watching. An unpalatable insect in the dark, on the other, can’t send out a constant audible warning: it has to select its moment and know when a predator is nearby. Unless, that is, some insects use passive signals of unpalatability, like body modifications that create a distinctive echo.

Bat-researchers don’t know the full story: there is still a lot to learn about bats’ hunting techniques and the ways insects try to defeat them. But “cost” is a word that comes up again and again in this book, which is partly a study in bio-economics. Bats have to pay a lot for echolocation and flight, but flight is a more general phenomenon in the animal kingdom, so the economics of bat flight also illuminates (insonates?) bird and insect flight. Altringham points out a very important but not very obvious fact: that flight is expensive by the unit of time and cheap by the unit of distance. Movement on foot is the opposite: it’s expensive by the unit of distance and cheap by the unit of time. Bats, birds, and insects expend more energy per second in flight, but can travel further and faster in search of food or new habitats. However, bats don’t all fly in the same way: a bat expert can identify different species by their wings alone. The wings vary in “wing loading”, which is “simply the weight of the bat divided by the total area of its wings. Bats with a high wing loading are large and heavy in relation to their wing area, bats with small bodies and large wings have a low wing loading”.[6] Then there’s “aspect ratio”, the “ratio of wingspan to average wing width”, or, because “bats have such an irregular wing shape”, “wingspan squared divided by wing area.”

It’s mathematics again: there are no explicit numbers in a bat’s life, but everything it does, from echolocating to flying, from eating to mating, is subject to mathematical laws of physics, ecology, and economics. Bats have to invest time and energy and make a profit to survive and have offspring. As warm-blooded, fast-moving animals with high energy needs, they’re usually nearer famine than feast, which is one reason they migrate or hibernate to avoid or survive through cold weather and scarcity. They also vary their diet during the year, to take advantage of changes in the abundance of one insect species or another, and seek out specialized feeding niches. Daubenton’s bat, for example, “habitually feeds very low over water”, using echolocation to catch not just flying insects but floating ones too. That is why it needs smooth water to feed over: ponds, lakes, canals and placid streams and rivers. The floating insects are easier to echolocate on a smooth surface, rather like, for humans, a black spider on a white wall. Once spotted, they “are gaffed with the large feet or the tail mechanism and quickly transferred to the mouth as the bat continues its flight”.[7]

Long-eared bat (Plecotus auritus) gleaning harvestman

Long-eared bat gleaning harvestman

One of the photos in the colour section in the middle of the book shows a Daubenton’s bat mirrored in smooth water, having just scooped up prey from the surface. Other photos show other species roosting, perching, or in flight, but the book also has excellent black-and-white illustrations mixed with the text, hand-drawn using a speckled or pointillist technique that suits bats very well. I particularly like the drawings on pages 48, 67 and 101. The first shows a long-eared bat, Plecotus auritus, “gleaning”, or snapping up, a “harvestman” (a long-legged relation of the spiders) from a leaf (ch. 3); the second shows a “male noctule calling from his tree roost to attract mates” (ch. 3); and the third shows a tawny owl trying to catch another long-eared bat (ch. 4).

Owls could be called the avian equivalents of bats: they’re specialized nocturnal hunters with very sharp hearing, but I think they’re both less interesting and more attractive. Bats, with their leathery wings, sometimes huge ears, and oddly shaped noses, are strange rather than attractive and some people find them repulsive. But some people, or peoples, find them divine or lucky: the introduction describes the Mayan bat-god Zotz, with his leaf-shaped nose modelled on that of the phyllostomids, or vampire bats.[8] The Chinese use a ring of five bats to symbolize the “five great happinesses: health, wealth, good luck, long life and tranquillity.”[9] Altringham blames the less positive image of bats in European cultures partly on Bram Stoker’s Dracula, which was first published in 1897. Before then, he says, “bats were not linked with witches, vampires and the evil side of the supernatural in any significant way.”[10] Dracula may have done for bats what the novel Jaws (1974) and its cinematic offspring did for sharks: encouraged human beings to harm the animal fictionally and falsely depicted as villainous.

Daubenton's bats (Myotis daubentonii) in a summer roost

Roosting Daubenton’s bats

If so, British Bats is partly redressing the balance. You can learn a lot from this book about both biology in general and bat-biology in particular. It stimulates the mind, pleases the eye, describes the appearance, ecology, and range of all British species, and points the way to further reading and research. So let’s not hear it for John D. Altringham! Without specialized equipment, that is, but that equipment is getting cheaper and more widely available all the time: you don’t have to be a professional zoologist to record and analyse bat-calls any more. There is still a lot for zoologists, both amateur and professional, to learn about bats. Okay, some of the research – like fitting miniature radio-transmitters to wild bats – seems intrusive and smacks of Weber’s Entzauberung, or “disenchantment”, but the more we know about bats, the more we will be able to help conserve them and their habitats. Bats aren’t villains: cats are. I like both kinds of mammal, but I hope we can find some way in future to help stop the latter preying so heavily on the former. If this book helps publicize the problem, it will be valuable for bat-conservation just as it is already valuable for bat-science. In short, no more brick-bats for Brit-bats: we should control our cats better.

Reviewer’s note: Any scientific mistakes, misinterpretations or misunderstandings in this review are entirely your responsibility.

NOTES

1. sp = species, singular; spp = species, plural.

2. ch. 3, “The Biology of Temperate Bats”, pg. 40

3. Ibid., pg. 45

4. ch. 4, “An Ecological Synthesis”, pg. 98

5. Ibid., pg. 99

6. Ibid., pg. 71

7. ch. 5, “British Bats, Past and Present”, pg. 117

8. ch. 1, “Introduction”, pg. 10. “Phyllostomid” is scientific Greek for “leaf-mouthed clan”.

9. Ibid., pg. 11

10. Ibid., pg. 9

Damsels and Dragons

by in Biology, Book Reviews, Civilization, Clark Ashton Smith, Our Lady of the Gutter, Post-Weird, Science and tagged , , , , , , , | Leave a comment

If I were asked to nominate a great work of 21st-century art, I would not choose anything by the likes of Damien Hirst or the architect Frank Gehry (responsible for the giant metal midden in Bilbao known as the Guggenheim Museum). Instead, I’d put forward something by Klaas-Douwe B. Dijkstra, Richard Lewington, and British Wildlife Publishing of Gillingham in Dorset. They’re not big names like Hirst and Gehry and they’re not earning big money or exercising big influence. And they’re unlike Hirst and Gehry in another way: they’ve created a genuinely beautiful and intellectually stimulating piece of art.

The art-work is called the Field Guide to the Dragonflies of Britain and Europe (2006). Dijkstra oversees the detailed, expert, and fascinating text, Lewington supplies the detailed, accurate, and beautiful drawings, complemented by photographs of dragonflies and damselflies in the wild. Lots of people don’t know the difference between these two suborders of the Odonata, but their common names reflect their appearance: the Zygoptera, or damselflies, are delicate and fold their wings at rest; the Anisoptera, or dragonflies, are robust and always hold their wings at right angles to their bodies. Both come in a huge variety of colours, pure and mixed, as their common names prove: damselflies include the Azure, the Goblet-Marked, the Orange White-legged, the Scarce Blue-Tailed and the Scarce Emerald; dragonflies include the Green and Mosaic Darners, the Banded, Red-Veined, Scarlet, Violet-marked and Yellow-winged Darters, the Orange-spotted Emerald, and the Four-spotted Skimmer. There’s also Somatochlora metallica, the Brilliant Emerald dragonfly, which looks as though it’s made of bright green metal or enamel.

These rich colours, with the complex venation of their wings, have made the Odonata a popular subject for artists and jewellers: for example, the art nouveau master René Lalique (1860-1945) made dragonfly mascots for cars. Unfortunately, the book doesn’t cover the Odonata in art: it’s a scientific text, a microcosm of the macrocosm of biology. Biology depends on accurate description and classification, so odonatology has a rich vocabulary: antehumeral stripes, arculus, carina, clypeus, diapause, discoidal cell, gynomorph, medial supplemental vein, pronotum, pseudopterostigma, siccation, and so on. Even the segments of the abdomen are numbered, from S1, just below the wings, to S9 and S10 at the tip of the tail, where the females have their almost clockwork genitalia. Males have theirs beneath S2, so mating in the Odonata is a complicated, almost tantric, business, as some of the photographs prove. Nomenclature in the Odonata is a complicated, almost incantatory business: Calopteryx splendens, virgo, xanthostoma; Enallagma cyathigerum; Pyrrhosoma nymphula; Anax parthenope, imperator; Ophiogomphus cecilia; Onychogomphus forcipatus; Libellula quadrimaculata; Sympetrum depressiusculum; Zygonyx torridus.

That nomenclature, and that sex-life, are two of the ways that the Odonata are CASean creatures; that is, their complexity, strangeness, and beauty remind me of the work of “the Emperor of Dreams”, the Californian writer Clark Ashton Smith (1893-1961). The obsessive, minutely detailed nature of the book is CASean too, and some of its subjects might literally be emperors in dreams: the common name of the Anax genus is the Emperors. One of these Emperors answered a CASean question I had as I leafed through the book: distribution tides washed back and forth across the little map of Europe that accompanied each specific description, submerging here Britain and Ireland, there France and Spain, here Germany and Scandinavia, there Greece and Turkey, and sometimes all of them at once.

But the strange, isolated island of Iceland, though included on every map, always seemed redundant, like a wall-flower at the Odonatan dance. “Was it a dragon- and damselfly desert?” I wondered. Then I came across Anax epihippiger, or the Vagrant Emperor: “A. epihippiger is the only dragonfly ever recorded on Iceland.” From the magnificent to the minute, from damselflies in the burning deserts of Morocco to dragonflies amid the frosty volcanoes of Iceland, it’s all here in a book that truly does deserve to represent European civilization in the twenty-first century. But doesn’t, alas.