The Book of Animal Ignorance (20 page)

Leech

A barometer that bites

T
here 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.

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

I
t'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.

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 alone 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.

Even the lion's mane – that universal symbol of virility – means something different to a lioness. Sporting a big, dark mane doesn't make you a breeding hero; in fact, as a fifty-a-day beast, you're probably history – manes are the leonine equivalent of nostril hair. But the absolute sign of a lion having given up trying to cut it as an apex predator or the King of the Jungle is when he turns man-eater. Slow, weak and always hanging around, we are easy prey: the lion's equivalent of a night in front of the TV with beer and a pizza.

Lizard

Pleasantly reptilian

W
hen the remains of the giant reptiles of the Mesozoic era were first discovered, Sir Richard Owen dubbed them ‘dinosaurs' from the Greek
deinos
sauros
, ‘terrible lizard'. Encountering crocodilians in the New World, the Spanish called them
el lagarto de Indias
, ‘the lizard of the Indies'. This became ‘alligator' in English. But though there are more than 4,675 species of lizard, dinosaurs and alligators are not among them. Lizards are the reptile equivalent of rodents, found all over the world. They have a ‘third eye' in the centre of their heads beneath the skin; they smell using their tongues and the cracks in their bottoms go sideways. Some are legless and distinguishable from snakes only by their movable eyelids, which snakes do not have.

AUTOTOMATIC PILOT
(Autotomy = ‘self-cut')

The biggest group of lizards are skinks. They have tails with special fracture points. If a predator grabs them, their tails snap off and wriggle convulsively for several minutes, distracting the predator and giving the skink time to escape. The legless Glass lizards are even more dramatic: their tails shatter like glass if they're assaulted. Armadillo lizards (
Cordylus cataphractus
) roll into balls; blue-tongued skinks stick their tongues out; horned lizards squirt blood from their eyes. Australian frilled lizards
(
Chlamydosaurus kingii
) have a pleat of skin around their necks. When they are threatened, this opens out like a golf umbrella, making them seem much larger than they are. The flying dragons (
Draco
volans
) of South-East Asia leap from trees, gliding to safety on brightly coloured parachutes. And lizards also escape by running – though none quite so stylishly as the basilisk, or Jesus Christ lizard (
Basiliscus basiliscus
), which has large webbed hind feet, enabling it to stand up and walk on water. The fastest lizards are six-lined racerunners (
Cnemidophorus sexlineatus
): at 18 mph they are the fastest reptiles on earth. Only one lizard lives in the sea: the Galápagos marine iguana (
Amblyrhynchus
cristatus
), which dives 30 feet under water to nibble algae on the rocks. Some lizards are venomous but, luckily for humans, they secrete poison by chewing and need a good old gnaw to cause anything more than a mild swelling. The heaviest lizard is the 20-stone Komodo dragon; the lightest is a dwarf gecko so tiny it would fit on your fingertip.

Geckos are popular house guests in hot countries because they eat insects at night. Brook's half-toed gecko of West Africa (
Hemidactylus brookii
) even has a transparent belly to advertise to its hosts how many flies it has caught. Geckos can walk vertically up glass and scientists have recently discovered how. Their feet are covered in half a million tiny hairs, each of which splits into hundreds more with diameters less than the wavelength of light. This creates a powerful bond between the electrons in the two surfaces. Half a square inch of adhesive tape based on this principle has already been manufactured. If enough can be made to cover a human hand, you could hang by it from the ceiling. In China, lizard soup is used as medicine for asthma, colds, lungs and the heart. In Antigua, lizard soup is also said to be good for asthma. Provided the patient isn't told what's in it. Apparently. that just makes it worse.