Everything You Know About Animals is Wrong E-Book

Matt Brown

• Herausgeber: Batsford
• Kategorie: Geisteswissenschaft
• Sprache: Englisch
• Veröffentlichungsjahr: 2020

Seitenzahl: 188

Beschreibung

A humorous and informative book, debunking a range of commonly held myths about animals. Camels store water in their humps and magpies love to steal shiny objects. Or do they? A must-read in the Everything you Know series, this book debunks a range of old-cod stories about animals in author Matt Brown's inimitable humorous and fascinating style. Covering everything from the myth that lemmings throw themselves off cliffs in suicide (they don't, but on occasion some just fall off) to the one about bats being blind (they're not, and they can see but use the more sophisticated echolocation for certain hunting). From head in the sand ostriches to cats landing on their feet, a wealth of information on our beloved pets to creepy crawlies and wild giants, this book will set the marvel of the animal word straight. Plus, there are special features on the odd diets of animals and how wrongly they are portrayed in the movies. All the old stories and myths about animals we've had since childhood are gleefully debunked in a hugely entertaining book.

Leseprobe

EverythingYou KnowAbout Animalsis Wrong

EverythingYou KnowAbout Animalsis Wrong

Matt Brown

Contents

Introduction

Beastly basics

Animals must move, breathe and possess a head

Animals must have sex to reproduce

Two different species cannot interbreed

Complex animals have more genes

Fish were the first animals to leave the oceans

The first animal to leave the Earth was a dog

We’ve got animals well catalogued

Humans didn’t invent it

A muddle of mammals

All mammals are warm-blooded

Bulls are enraged by the colour red

Camels store water in their humps

Bats are blind

Lemmings commit suicide by leaping from cliffs

Humans evolved from chimps

Elephants use their trunks like straws

The lion is King of the Jungle

You’re always within 6ft of a rat

Porcupines can shoot their quills

Marsupials are found only in Australia

Curious diets

Pets’ corner

Dogs see only in black and white

One dog year is equivalent to seven human years

Dogs say woof

Rabbits should be fed carrots

A cat can survive any fall

Goldfish have seven-second memories

Feathered fallacies

Ostriches bury their heads in the sand

Penguins hang out with polar bears

A duck’s quack does not make an echo

Owls can turn their heads through 360 degrees

Turkeys come from Turkey

Magpies love to steal shiny objects

Touching a baby bird will cause the parents to abandon it

Pigeons are just flying rats

Bread is bad for birds

London’s parakeets were released by Jimi Hendrix

Just how wrong are the movies?

Reptiles and amphibians

You can get warts from toads

Chameleons change colour purely for camouflage

Boa constrictors suffocate their prey

T-Rex was the largest upright dinosaur, and other dodgy dino myths

Life aquatic

All sharks are merciless killing machines

Watch out for piranhas! They kill

The blue whale is the world’s largest living species

Whales and dolphins are fish

Octopi have eight tentacles

All eels are born in the Sargasso Sea

The horseshoe crab is a living fossil

Don’t mix them up

Creepy crawlies and minibeasts

Daddy longlegs are the most poisonous spiders

Earwigs burrow into human ears

Centipedes have 100 legs

Bees always die after a sting

All spiders have eight eyes

A praying mantis female will always eat the male following sex

An earthworm cut in two becomes two new worms

Other myths and misnomers

Are you pronouncing it wrong?

Let’s start a new wave of fake facts

Index

Acknowledgments

Introduction

Animals are a new thing. Let your time machine take you back to a random moment in Earth’s history, and you would be lucky to find anything that sniffs, scuttles, breathes or wriggles. Simple life first arose some 3.5 billion years in the past, but our animal ancestors only got going 600 million years ago. Five-sixths of the history of life on Earth lacks animal forms or, indeed, anything more exciting than pond scum. Our kind have flourished somewhat since. The sheer variety of animal life is so overwhelming that no human mind could ever appreciate its full beauty. Beetles alone come in 400,000 flavours, and those are just the ones we know about. If Noah really did construct an ark of all the animals, he must have spent several lifetimes merely taking the register.

Even so, animals represent the merest aliquot from the soup of life. Compared to the unfathomable numbers of bacteria and other microscopic forms, the sum of animal species is vanishingly small. Eight million animal species call this planet home (by outrageously uninformed estimate), of which only 1.5 million have been described. The number is dwarfed by the supposed trillion species of bacteria. Animals might even be considered footnotes in the story of life. We were preceded by microorganisms, we are vastly outnumbered by them now and, in that far-off time when an expanding Sun makes conditions tough for multicellular life, we shall one day cede the planet to their sole possession. You could call it an underdog story.

This is, essentially, a book of animal trivia. But, as with the other books in this series, it is my conceit to turn the usual ‘fact file’ format on its head by looking at the stuff we all get wrong. Each section starts with a well-known ‘fact’, which is then debunked. If you thought that a camel stores water in its hump; that a daddy longlegs is highly poisonous; that goldfish have tiny memories; or that lemmings routinely throw themselves off cliffs, then read on.

Throughout the centuries, people have entertained many unlikely beliefs about animals. Salamanders live in fires. Single magpies bring bad luck. Cats will do what you tell them. Literature ancient and modern roars with invented beasts: unicorns, manticores, griffins, jackalopes, sphinxes, harpies, gruffalos, basilisks and dragons*, to draw just a few from an ongoing Western tradition. Then we have the ‘cryptids’ – animals whose existence is assumed by anecdote, if not by science – such as the yeti, the chupacabra and the Loch Ness Monster. This ‘unnatural history’ is beyond the scope of this book, although I may make reference here and there.

We have no need to invoke fantastic beasts. The natural world throws up its own unbelievable concoctions, from moths that live off the tears of birds, to animals that make musical instruments. The tasselled wobbegong, the bone-eating snot-flower worm and the monkeyface prickleback sound every bit as fanciful as a creature of myth. The natural world contains universes within universes, and much remains unexplored.

Sadly, no book about animals can shy away from the growing and widespread threat to the planet’s fauna. Everywhere we look, habitats are under threat and populations are in decline. Year by year, the advancement of global warming brings new casualties. We are living through the early stages of a new mass-extinction event, like the one that killed off the dinosaurs (and many other animal groups). Only, this time it is human industry and not an asteroid that is reaping havoc. I’ve chosen to make this book a celebration of the wonders still bountiful in the natural world, rather than a 150-page lament on what might be lost, but a tone of impending calamity must creep in here and there.

Finally, there’s one well-known animal whose biology doesn’t feature much in this book. For the myths and misconceptions concerning our own species, Homo sapiens, see the previous volume Everything You Know About the Human Body is Wrong (2018).

Let the nitpicking begin!

* FOOTNOTE: Just to confuse matters, those last two are also the names of real, less fearsome animals.

Animals must move, breathe and possess a head

‘Are insects really animals?’ I hear that a lot. Creepy crawlies are often perceived as something apart from the animals. It’s our mammalian bias in action. For many of us, the word ‘animal’ conjures up images of hairy, four-legged creatures, like dogs, cats, sheep and horses. We’ll agree that frogs, birds, snakes and the like are also animals, though somehow on a second tier of animal-ness. Fish occupy a murky place, both physically and in our reasoning. Most of us will allow that fish are animals if we think about it, but there’s a temptation to put them in some other, ‘inferior’ category*.

Insects are even more alien to our sensibilities. They look nothing like us. Six writhing legs, antennae, compound eyes, larval stages, to say nothing of their tiny dimensions. Small wonder that we don’t, in the everyday sense, regard them as animals at all. Yet the merest mite is a subject of the animal kingdom just as surely as the most walloping whale. Indeed, insects make up about two-thirds of all animal species. It is us mammals who are the outliers. Of the 1.5 million animal species known to science, only 69,000 have some form of backbone, of which just 5,450 are mammals. The ‘proper animals’ that lick or bark or prance around on four paws represent just 0.4 per cent of the known animal kingdom, and a still smaller percentage if we estimate the number of as-yet unknown species. To a close approximation, mammals don’t exist.

Insects and their friends are bona fide animals. What’s more, when we explore the wider kingdom of animals, insects begin to look like close cousins. At least they have heads (in the adult stage – boundaries blur with grubs). Many familiar creatures, including jellyfish, starfish and sea cucumbers, lack anything that might convincingly resemble that body part.

Spread the net wider and we find still stranger beasts. Sponges and coral look like exotic forms of plant. They have no heads, no limbs, no brain. They lack even symmetry. Our instinct is to lump them in with the decidedly asymmetric plants. But they are animals, albeit very peculiar animals. Pass a sponge through a fine sieve and it will disintegrate into its constituent cells. Leave these cells alone for a while and they will reassemble back into a sponge. Try doing that with a monkey*.

Bryozoans look still less like animals. Many grow into branching, frond-like clusters, easily mistaken for seaweed or other types of plant. The greater horn wrack (Flustra foliacea), commonly found on North Atlantic beaches, not only looks like seaweed, it even smells of lemon. It is an animal – or rather a colony of animals, since bryozoans typically club together in their thousands to form larger structures. Weirder still is the Iridogorgia sea fan. This deep-sea coral looks like a stretched-out slinky toy, whose unanchored end is covered in orange fronds. Caspar Henderson, in his aptly titled The Book of Barely Imagined Beings, likens this riot of arcs to a mathematical theorem.

What do all of these fantastic beasts have in common? What makes them definitively animal? How does one get the keys to the Kingdom Animalia? There are, you will be delighted to hear, no easy answers to these questions.

The term ‘animal’ comes from the Latin animalis, which translates as ‘having the breath of life’. We might conclude from this that all animals breathe. By and large, they do. From the tiniest bryozoan to the mightiest elephant, the animals’ branch of life is one that must take in oxygen to survive. It’s not, though, the best definition of what makes an animal. Plants and fungi need oxygen too, as do many forms of bacteria*. Then we have the (so-far) unique case of the Loricifera.

These recently discovered animals live among the sediment at the bottom of the sea, and grow to no more than 1mm in any dimension. They come in many species, but all have a vase-like abdomen known as a lorica, out of which spill dozens of spines known as scalids. The ensemble reminds me of a bowl of wilted flowers. At least three species of Loricifera, found 3km (nearly 2 miles) down in the Mediterranean near Greece, do something distinctly weird: they live their entire lives without oxygen. The discovery, made in 2010, was a complete surprise. This was a trick that only bacteria were supposed to pull. But here we have animals, large enough to be seen without a microscope, that do not breathe.

Another common characteristic of an animal is that it will move around. Most plants and fungi and some bacteria live out their lives wherever they were first deposited. They only get to travel if an outside force disturbs them. Animals have legs, tails, wings, muscles and (in the case of squids) jet funnels. We have the locomotive freedom to find food, seek a mate and avoid danger. But you only have to track back a few paragraphs to find counterexamples. Corals and sponges are pretty motionless. Barnacles and mussels don’t get about much either. Limpets are famous for their tenacious grip, not for a dynamic social life. Yet even these sedentary animals are mobile during their immature stages. It must be so, otherwise how would the barnacle attach to the ship’s hull in the first place? The best we can say, then, is that all animals move, but some do so very slowly or for only a small part of their life cycle.

The one trait that does connect all animals is a multicellular existence. Bacteria and their cousins are always single-celled, while animals are aggregates of many cells. The multicellular animal is a recent invention. Single-celled life pootled along happily for about three billion years. Then, a mere 600 million years ago, some of these singletons came together to form the first multicellular life. Nobody knows what these avant-garde organisms looked like – small, soft bodies from the distant edges of time do not make for good fossils – but the best guess is some kind of simple sponge. This was the dawn of the animals.

Today, any species formed of multiple cells (that isn’t a plant or fungus) is deemed an animal, while those that embody just one cell are never considered to be such. This was not always the case. The protozoa, of whom some 50,000 species have been described, are a form of life that long caused headaches for taxonomists. These microscopic life forms are single-celled but possess many animal-like charms. Their cells have nuclei and lack cell walls, just like animal cells. Protozoa also move around and ingest food. Even the name means ‘original animal’ or ‘primitive animal’. And so they were classed until well into the 20th century. Nowadays, they are usually classified to their own kingdom of Protista, which you’ll note has dropped the animal-riffing suffix of ‘zoa’.

Everywhere you look in nature, you will find species that do not neatly fit into the artificial pigeonholes we humans have constructed. We’ve seen animals that are more like bacteria, and single-celled organisms that might pass for animals. Even the distinction between animal and plant is not always clear cut. One of the key hallmarks of a plant is its ability to photosynthesize*. Plants contain small molecules called chlorophylls that enable them to harness the Sun’s energy, and thereby convert carbon dioxide and water into sugars. They build their own food.

No animal can produce its own equivalent of chlorophyll. One or two creatures have, however, found ways to steal somebody else’s. These include the rather beautiful sea slug Elysia chlorotica, which looks for all the world like a leaf. The sea slug gets its vibrant green colour from munching on algae. Somehow, the algal photosynthetic cells survive intact and find their way to the slug’s skin. The pimped invertebrate is then able to draw energy from the Sun using its purloined chlorophyll. It can go without food for at least nine months. Researchers still don’t understand how the slug can do this. It’s unclear why the chlorophyll cells are not destroyed in the gut. And how the slug integrates the chlorophyll into its biochemistry, so very different to that of the algae, is a complete mystery. Sadly for researchers, the solar-powered sea slug is difficult to find. It is also among the countless marine species at risk from global warming and habitat loss.

So there we have it. Animals don’t have to have a head. They need not move around (at least in the adult stage) or even find oxygen. Some animals look remarkably like plants, while some plants have taken on forms that resemble animals. We even have a whole kingdom of life, the Protista, whose members act like animals reduced to one cell. As we will see throughout this book (and the others in the series), misunderstandings often stem from the human need to classify and categorize. The simple word ‘animal’ is trickier to pin down than a squid in lotion.

* FOOTNOTE: Hence the number of ‘vegetarians’ who will happily devour a tasty bit of cod, or even lobster. They’re not really animals, are they? I should also add, while I’m here, that fish don’t technically exist as a class of animals. A trout may be more closely related to a goat than it is to a hagfish. We tend to bundle everything in the water together and call them ‘fish’, but the term is fairly meaningless at the genetic level. This fishy titbit is celebrated in the podcast No Such Thing As A Fish, a spin-off from the BBC’s panel show QI.

* FOOTNOTE: Do not try doing that with a monkey.

* FOOTNOTE: The teeming forms of life on Earth are traditionally divided up into high-level categories called domains and kingdoms. We, for example, inhabit the Kingdom Animalia in the Domain Eukaryota. Other kingdoms include the bacteria, plantae (plants), fungi, archaea, chromista and protozoa. These designations can be confusing to the non-specialist, and are prone to change. Because this is a book about animals, and not Everything You Know About the Classification of Life is Wrong, I’m sticking to everyday terms and familiar kingdoms.

* FOOTNOTE: Even this isn’t universal or definitive. Dozens of plant species entirely lack chlorophyll. These plants, which include species of orchid and lily, instead act as parasites, and derive their energy from fungus.

Animals must have sex to reproduce

Take a cutting from a plant, stick it in some soil and, with a bit of luck, you’ll have a brand new, thriving plant. Leave a bacterium alone in your lunchtime gravy, and you’ll have two million by supper. The natural world is rife with asexual reproduction. Most plants and all single-celled organisms – which is to say, the overwhelming majority of life forms on the planet – can create the next generation without partnering up. There are many ways to do this, but all result in new individuals with almost identical DNA to the parent.

Animals, by contrast, like to couple. They engage in sexual reproduction. Genetic material from Animal A and Animal B comes together to create a little Animal C that is genetically different from either parent. Scientists still argue about the point of all this. Why go to the bother of finding a compatible partner? Why take the (often considerable) effort of bringing egg and sperm together? Could we not just bud off, and be done with it? After all, the Earth is home to an estimated 5,000,000,000,000,000,000,000,000,000,000 bacteria that get along fine without sex. You have 100 trillion of the blighters on your person right now. If life is all about passing on genes, then they’re doing just handsomely.

Sexual reproduction does have its advantages. It creates a diverse population with resilience against the slings and arrows of selective pressure, and helps its proponents to shrug off unhelpful mutations. But is it obligatory? Can any animals make like bacteria and spontaneously reproduce without finding a mate? The answer is an emphatic YES.

In the land of the small, asexual reproduction isn’t just a lifestyle choice, it’s sometimes the only way. Bdelloid rotifers – microscopic, slug-like animals that dwell in fresh water – have non-existent sex lives. No male bdelloid has ever been observed. This is an animal that reproduces entirely by asexual means. Embryos develop without the need for (or possibility of) fertilization in a one-parent process known as parthenogenesis. Millions of years ago, the bdelloids did form couples. They still put out chemical signals to attract mates, but no one ever picks up the call. And so the creatures must draw on their own resources. As a result, whenever a bdelloid reproduces, her daughters are clones, all genetically identical to the mother and to each other.

Bdelloid rotifers are a rarity. They abandoned sex millions of years ago, and now have no choice but to reproduce alone. Plenty of other animals, though, dabble with self-cloning when it suits them. Insects are the keenest adherents. Species of midge, stick insect, wasp, ant and bee, to name but a few, are capable of parthenogenesis under certain conditions. Any keen gardener will know how quickly aphids can ruin a plant. These tiny insects spread so rapidly thanks to asexual reproduction. The mother aphid can push out a clone daughter every 20 minutes, and each of these already has a small granddaughter inside. This rapid reproduction, typically in the spring, is crucial, as so many larger insects will make a meal of the newborns. Even so, most species will switch to sexual reproduction later in the year.

‘Yes, but what about “proper” animals?’, we might ask, with our usual bias for larger creatures, more like us. Here, too, asexual reproduction is well-established, if rare. Something like 0.1 per cent of vertebrate species are able to undergo parthenogenesis. Whiptail lizards are the undisputed champs. Like the bdelloids, these reptiles have entirely jettisoned males and sperm in favour of self-cloning. It’s another all-female species.

In 2001, a hammerhead shark was born in a Nebraska aquarium. This was an immaculate conception. The tank contained only female sharks, all of whom had dwelt there for three years without so much as a whiff of male shark. Genetic tests confirmed that the youngster had identical DNA to one of the adult sharks. The hammerhead had reproduced asexually. Something similar happened to the only two sexually mature female Komodo dragons in Europe (both in English zoos). Each had a litter of offspring, despite never encountering a male. DNA analysis again confirmed parthenogenesis. All the hatchlings were male, thanks to a quirk of reptilian genetics.

Like so many things in life, the distinction between sexual and asexual reproduction can be a little blurry. Nature enjoys variations on a theme. There are many ways to reproduce asexually, and even more ways to make a sexual coupling. Sometimes the two are not so far apart. While humans cannot (yet) produce babies through a solo effort (thank goodness), we do occasionally dabble on the shores of asexual reproduction. Identical twins arise when an already fertilized egg splits in two, leading to separate embryos. The process would be impossible without an initial shot of sperm, but the subsequent split might be considered a form of cloning.

Two different species cannot interbreed

Try though you might, you will never have a child with a weasel. Nor a leopard, baboon or muskrat. As you’ve probably noticed, we belong to a different species. We inhabit different genetic islands. Almost by definition, it is biologically impossible for two different species to interbreed. Plus, it would be gross.

Actually, animals that we consider as separate species can sometimes get it together. A lion and a tiger will occasionally breed, producing a hybrid animal known as a liger or tigon, depending on who mounts whom. A donkey and horse can spawn a mule. A sheep and a goat may forge a geep or a shoat. I could produce further examples until the cows come home – preferably in the company of a yak who might father a herd of yattle.

In most cases, viz. the mule, the offspring are infertile. The genetic mashup is too much of a stretch to allow a second generation. But not always. Sometimes two separate species can produce young who are themselves able to bear young. Such couplings call into question the very definition of a species.