The Book of Animal Ignorance

by Ted Dewan

  Spotted hyenas are Africa’s dominant predator, responsible for a quarter of all game animals killed. Lions are their only rivals and the two species exist in a constant state of war. Both steal food from each other, but contrary to popular belief, lions scavenge more often from hyenas. In many areas, hyena kills are a lion’s main source of food. Hyenas eat fast, and they eat a lot – a third of their own body-weight, or the size of large lamb, in just half an hour. They devour everything: the concentrated hydrochloric acid in their guts digests even the skin and bones, leaving their scat white with calcium.

  For centuries, hyenas have been feared as corpse-eating grave robbers, sexual perverts and cowards. This human dislike of hyenas has ancient roots. The earliest hominid remains in northern Europe from 700,000 years ago are usually found close to hyena-gnawed bones and fossilised droppings. Whether as scavengers or as hunters, our species has evolved in close competition with hyenas.

  Their eerily human-sounding ‘laugh’ is really a signal of submissiveness to clan superiors. Hyenas also whoop, to communicate over long distances. It’s often the laugh or whoop which alerts other animals to come and poach their kill. At least one study has suggested that human music began with the collective hunting chants our ancestors used to ‘outsing’ the ancient enemy.

  LONG-DISTANCE KILLER

  Hyenas aren’t related to dogs: their closest relative is the cat-like civet. All four modern species, including the termite-eating aardwolf, are endangered through habitat loss and persecution by superstitious humans.

  Kangaroo

  Bouncing desert cow

  Imagine what it must have been like being confronted with a kangaroo for the first time. Here’s Captain Cook in 1770: ‘It was of a light mouse colour and the full size of a greyhound … I should have taken it for a wolf or a wild dog but for its walking or running which it jumped like a hare or deer.’ So familiar have kangaroos become that we forget just how different they are from other mammals. A jumping dog with the eyes of a deer, the nose of a hare and the feet of a gerbil. How did it come about?

  The kangaroo’s reproductive organs are worth a detour. The male has his testicles hanging above his penis and the female has three vaginas. It’s perfectly logical. One is for birth, the other two are for sex: they carry the sperm to the two wombs.

  Marsupials or ‘pouched animals’ have ploughed their own furrow for 120 million years, but the large kangaroos (Macropods or ‘big-feet’) are a relatively recent development. The earliest fossils are 15 million years old, from the time Australia’s forests began to recede. Until then, the kangaroos’ ancestors had been non-hopping creatures of the woods – there was even a carnivorous sabre-toothed version. Kangaroos adapted to become grass-grazing ruminants, the marsupial equivalents of bison and antelopes, and, like their placental counterparts, they grew larger to house a digestive system that could handle a tough, fibrous diet. Both their stomachs and their large intestines are fermenting vats full of bacteria and enzymes but, unlike cows, they produce not the greenhouse gas methane but another carbon-hydrogen compound: acetate, which they can recycle as energy. Kangaroo gut bacteria may yet help save the planet by producing wind-free cows.

  Surviving in the hot, dry outback is all about conserving energy. Hopping is not only fast: it uses less energy than any other mode of transport. To avoid the daytime heat, kangaroos feed at night (hence their large eyes) and spend their days lying in the shade and licking their forearms to cool down. Even the remarkable reproductive system helps. Kangaroos, famously, have short pregnancies, with the tiny jellybaby-sized foetus crawling into its mother’s pouch when only a month old. Less well known is the fact that a female kangaroo can store her embryos for many months in one of her two wombs. This not only means she can swiftly replace a joey that dies; she can also time her births to avoid droughts, saving both energy and water.

  This rather undermines the view that marsupial reproduction is ‘less advanced’ than that of placental mammals. The tiny foetus may be underdeveloped but it has what it needs – functioning nostrils to smell the teat and two strong forelimbs to get it there in less than three minutes. (Incidentally, this is why marsupials never developed an aquatic species like whales or dolphins – no gripping arms: no babies.) Once safely in the pouch, the joey latches on, but is too weak to suck: the teat muscle exercises its own portion control, squirting just the right amount of rich milk into its mouth. The mother cleans the pouch, licking up the waste and thereby recycling a third of the milk she produces. When the fully grown joey is kicked out to make way for a new sibling, eight months later, it continues to suckle for several months. Ever mindful of waste, the mother kangaroo’s mammary glands produce full-cream and fat-free milk simultaneously.

  BIG FEET, SMALL CARBON FOOTPRINT

  Koala

  Cuddly bottom-feeder

  Several mammals eat their own droppings, or their offspring’s, but only koalas feed them to their young. The mother produces a soup, known as ‘pap’, which the four month-old joeys slurp up, ingesting important micro-organisms and preparing their delicate digestive tracts for the adult diet, which consists entirely of eucalyptus leaves.

  Most herbivores don’t go near eucalyptus. The leaves are 50 per cent water and contain nasty toxins. But the koala’s guts have adapted to process them and they feed on only thirty of the 600 eucalyptus species that live in Australia; they can even tell the age of the leaves by their smell. To qualify as lunch they have to be between a year and eighteen months old, as young leaves have almost no nutritional value and older leaves contain poisonous prussic acid. On the plus side, koalas hardly ever have to drink – they get all the moisture they need from the leaves – but eucalyptus is so low in energy that they spend twenty hours a day asleep, like sloths. This might also explain why they have, proportionally, one of the smallest mammalian brains. Brains burn energy. The koala’s occupies only half its cranial cavity, floating in fluid like a prune.

  ‘Koala’ means ‘no water’ in the Dharuk language. The Dharuk who lived around Sydney and Botany Bay are all long since extinct. ‘Boomerang’, ‘dingo’, ‘wallaby’ and ‘coo-ee!’ all come from the Dharuk.

  Not even sex distracts them from sleep for long. It’s very straightforward and takes place on a sturdy branch. The male mounts from behind, bites the female’s neck and manages about forty thrusts of his bifurcated penis in twenty seconds. Once thrusting stops, ejaculation (into both vaginas) lasts for thirty seconds.

  This perfunctory attitude might throw some light on the female koala’s enthusiastic, if mysterious, adoption of lesbian behaviour when taken into captivity. Romps involving up to five females are commonplace, and outnumber heterosexual encounters by 3 to 1. They also last twice as long. Unfortunately, wild lesbian sex only helps to spread chlamydia, a sexually transmitted bacterial infection which afflicts three-quarters of all female koalas. Also known as ‘wet bottom’, it makes them smell bad and leaves them sterile.

  THE EUCALYPTUS GUT-BUSTER

  Wild koalas are now officially listed as ‘low risk to near-threatened’. Although aboriginal peoples did occasionally eat them, they didn’t hunt them to near extinction as was once claimed: their population at the time Europeans arrived is estimated at ten million. What nearly did for them was the fur trade. Until it was banned in 1927, millions of skins were exported each year. Now, despite their iconic status, the koala population may be as low as 100,000, bush fires and road traffic having taken a heavy toll. The Australian Koala Foundation estimates that 80 per cent of their natural territory has been destroyed.

  The koala’s scientific name, Phascolarctos cinereus, means ‘ash-grey pouch-bear’ but koalas aren’t bears; they are marsupials, close relatives of the wombat.

  They have fingerprints that are almost indistinguishable from human ones. All primates have ridged finger-ends to help them climb, but marsupials split from the lineage of primates 125 million years ago, before koalas had evolved. The fact that two lineages independently d
eveloped the same trait to do the same job is a good example of ‘convergent evolution’.

  Komodo Dragon

  Big and bad-mouthed

  Ten feet long and weighing up to 20 stone, the komodo dragon (Varanus komodoensis) is already the largest living lizard. Now it holds he distinction of being the largest land animal capable of parthenogenesis (Greek for ‘virgin birth’).

  In 2006, two of the three komodos held in UK zoos gave birth despite having had no access to a male. They managed this by a process called ‘selfing’. In komodos, as in birds (but unlike mammals), it is the female who holds two different sex chromosomes: Z for male and W for female. Each of her ZW eggs has a second mini-egg attached to it, containing a full copy of her genetic information. In the absence of sperm, this gets reabsorbed and ‘fertilizes’ the main egg, producing a set of male (ZZ) non-identical twins.

  This may have evolved as a survival strategy. Komodos are excellent swimmers and are only found on a few small islands in the middle of the Indonesian archipelago. A stranded female could populate a new island by mating with her own offspring.

  The komodo was first discovered by Western scientists in 1910, despite the many local stories of a fierce dragon that lived in the island forests. In 1926, W. Douglas Burden, a wealthy adventurer, led an expedition to capture a live specimen. He failed, but his account of the trip inspired the Hollywood producer Merian C. Cooper to make the film King Kong in 1933.

  Komodos are often called ‘living dinosaurs’, but unlike birds and crocodiles they aren’t direct descendants. Komodos are monitor lizards, closely related to iguanas and snakes. They are fearsome carnivores, with flat serrated teeth (more like a shark’s than a reptile’s) and powerful curved claws. Their bite is fatal and their ‘killer saliva’ is legendary – it contains fifteen virulent strains of harmful bacteria – but recent research has confirmed that komodos are also venomous, with powerful toxins being secreted from glands in the mouth.

  There is only one map that states ‘Here be dragons’ – the tiny copper Lenox Globe of 1507. Hic sunt dracones appears over the eastern coast of Asia, not far from Komodo …

  As the top predator on their islands, their isolation has allowed them to grow huge. They originally evolved to prey on a now extinct breed of pygmy elephant but will cheerfully take down buffalo, deer, goats, or young komodos. To avoid this, the young spend their early life in the treetops, and when joining a communal kill take the precaution of rolling in the prey’s droppings to make themselves as unappetising as possible to their older colleagues.

  Komodos eat once a month, wolfing down three-quarters of their body weight in a single sitting. Afterwards, they lie in the warm sun to stimulate digestion and prevent the food rotting in their stomachs. Sex is predictably violent. Males rear up on their hind legs and wrestle to establish dominance and, having succeeded, restrain the female just long enough to insert one of their two penises in her bottom.

  They are highly intelligent. Captive komodos recognise their keepers and can perform simple tricks. But keep your shoes on, as Phil Bronstein found out. The newspaper editor and sometime husband to Sharon Stone had his foot badly mauled by a ‘tame’ komodo at the Los Angeles zoo in 2001.

  KOMODOS SMELL WITH THEIR TONGUES

  Leech

  A barometer that bites

  There are 650 known species of leech. They are annelids: very close, but more sophisticated, relatives of the earthworm. Although they range in size from tiny to more than 18 inches in length, all leeches have thirty-four segments, each with its own ‘brain’. The head segment contains a simple two-lobed structure, while the others have a clump of neurons called a ganglion (Greek for ‘a swelling’). A single leech survives on a mere 15,000 neurons (honey bees’ brains contain 950,000).

  All leeches are carnivores, but very few species suck blood. The most famous is the European medicinal leech, Hirudo medicinalis. They have three muscular jaws, each of which has a row of tiny teeth. These saw into the skin, severing the capillaries beneath. The jaws sit at the centre of a powerful sucker which creates a vacuum around the wound, funnelling the blood into the leech’s gut. Leeches feed for up to an hour, swelling to between five and ten times their original size and guzzling as much as a tablespoon of blood. When full, they drop off, leaving a Y-shaped puncture wound, rather like the Mercedes badge. They can live for up to six months on a single meal.

  Leech bites do not hurt, but they can bleed for ten hours. This is because leech saliva contains both an anaesthetic and hirudin, an anticoagulant. Without it, the leech would end up resembling a chubby blood sausage.

  Leech gatherers used to stand in lakes and pools, waiting for leeches to attach to their legs.

  Leeches were probably first used in medicine in India around 1000 BC. The practice of bloodletting was used in the ancient Aztec, Babylonian, Egyptian and Greek cultures. Hippocrates taught that it helped restore an imbalance of the ‘four humours’ – blood, phlegm, black bile and yellow bile. By the nineteenth century, the use of leeches in medicine was so widespread that France imported more than forty-two million in 1833 alone. By the end of the century they were collected almost to extinction. Today, they have the same protected status as the white rhino.

  The use of the leech in surgery is back with a vengeance. They are used in burns units and in plastic surgery for their blood-draining and anticoagulant properties. They can also reduce the painful inflammation of osteoarthritis and bruises. British hospitals buy 15,000 farmed leeches every year.

  TEMPEST PROGNOSTICATOR

  Don’t try to remove an attached leech by burning it or pouring on salt. This will make it regurgitate into the wound, causing infection. Use a fingernail to slide under each of the suckers in turn. If you are unlucky enough to have a leech attached inside your mouth, gargle with vodka.

  In 1799, Napoleon’s troops in Sinai drank water contaminated by leeches. These attached themselves to the insides of the soldiers’ noses, mouths and throats, killing hundreds through suffocation.

  Leeches can predict thunderstorms. The change in atmospheric pressure means the water they swim in dissolves less oxygen, encouraging them to move to the surface. George Merryweather’s Tempest Prognosticator, an elaborate leech barometer, was one of the wonders of the Great Exhibition in London in 1851.

  Leech neurons have been used to construct a organic computer called the ‘leech-ulator’. The device asks the neurons to perform simple sums. Unlike silicon processors, the neurons ‘think’ their answer by forming their own connections, one to another.

  Lion

  Sub-Saharan couch potato

  It’s not easy being a male lion. Although they are the only cats to have adopted social organisation over solitary predation, it’s not immediately obvious what benefits it brings. Most of their hunting isn’t co-operative: it only becomes so if the pride is desperate and facing starvation. Even when it is, a single lion has to make the kill, and statistically that’s usually a lioness, because they are faster and more agile. At mealtimes, all social cohesion dissolves; it’s every lion for itself, and while the males hog the carcass, fights break out all round: flailing paws, shredded ears, mewling cubs and lionesses staking their claim by clamping their jaws on the carcass and refusing to budge.

  Lions were widespread in Europe and Asia until relatively recently – the last lion was killed in the Caucasus in the tenth century, in Turkey in the late nineteenth century and in Iran in 1941. The last 300 wild Asiatic lions live in the Gir Forest in Gujarat, northern India.

  Nor does the pride system seem particularly good at protecting the young. Only 10 per cent of cubs make it beyond the age of two; those that survive are lucky to get into double figures: a lion’s life expectancy is much lower than that of the antelopes it chases. It’s just not a healthy way to live, combining a high-fat diet with almost no exercise. The short sprints the lions make when hunting, while being absolutely exhausting, are not the sort of sport which doctors recommend for anything, let a
lone someone suffering from high cholesterol. And then there’s the stress.

  If a male lion isn’t avoiding the hoofs of zebras he’s attempting to kill, or keeping other lions and hyenas off his dinner, he’s either sleeping or servicing the insatiable demands of one of the pride’s lionesses. When a female lion comes on heat, the male is looking at four days of pretty constant shagging – up to fifty times a day. It’s estimated for every cub that survives a year, its parents will have had 3,000 intimate encounters. It’s not immediately obvious why: the female may need lots of spiny penis action to stimulate ovulation, as with domestic cats, or she could be just making sure her old man’s up to the job.

  ROAR POWER

  Each pride consists of closely related females, serviced by a small coalition of unrelated males. These coalitions are regularly tested by outsiders, often younger males who are keen, in the heady flush of youth, to have a pride of their own. Just to be sure, a lioness will occasionally sneak off for some illicit action with one of these rogues. This leads to conflict, which among lions can be very nasty, even fatal. It certainly is for the cubs if the new team wins: the first thing they do is kill, and sometimes eat, the departing coalition’s offspring. No wonder most coalitions last less than three years: it’s too much like hard work.