by Ted Dewan
Pet shops would be bereft without fleas: over $1 billion a year are spent on anti-flea products in the USA alone. Pliny the Elder’s solution was cheaper: collect the soil under your right foot when you hear the first cuckoo of spring and sprinkle it over them.
Being unfussy gives fleas an advantage. Our very own species, Pulex irritans, has largely been banished by better hygiene but can still be found on pigs. The fleas on your dog are probably cat fleas, as they are the most common and will live on most mammals or even a passing lizard. In fact, the only consistent requirement for fleas is that an animal sleeps in a den or nest. That’s because fleas’ eggs aren’t attached to their host. They fall off, hatch and feast on the adult fleas’ droppings. This is highly efficient: as a flea sucks its way through fifteen times its own body-weight in blood a day, its other end feeds the blind wormlike larvae. Once they pupate, the cocoons can lie dormant for a year, waiting for our vibrations to hatch them.
Streamlined to move effortlessly through hair, covered in snaggable spines and combs, fleas are hard to remove and even harder to crush. Their legendary jumping skills aren’t even dependent on muscle strength. Wingless, they have turned the wing-hinge structure into a mechanical spring made from a rubbery protein called resilin. This clicks shut as the body plates compress, like a catch on a jack-in-the-box. When released, it pushes down on the leg tendons, achieving an acceleration that is fifteen times that of a space-shuttle launching. The flea uses movement-sensitive hairs to calibrate precisely the distance and direction of its jump, and pumps air into special sacs in its legs to slow down before touchdown.
BUNNY LOVING
Impressive as this is, the real masterpiece of flea engineering is the penis. Proportionately the longest of any insect, it has so many hooks, springs and spines that it’s been compared to a Swiss army knife. Unsurprisingly, it takes a long time to unfold, but then copulation can last for three hours – the equivalent of six weeks for a human. Adult fleas are ready for this marathon as soon as they emerge. No wonder a single pair of fleas can produce another 50,000 in a month, or that Carl Djerassi, the creator of the contraceptive pill for humans, also developed one for fleas.
Fly
Sultan of sperm
Flies are insects with two wings. Mayflies, dragonflies, fireflies and butterflies are not flies. There are 120,000 known species of true fly (almost 7,000 in the UK alone) between them carrying more than a million species of bacteria. The common housefly (Musca domestica) is among the most dangerous animals in the world. It breeds in rubbish, sewage and dung, and spreads tuberculosis, typhoid, cholera, dysentery, anthrax and parasitic worms by excreting, walking and vomiting on food.
Flies are prodigious breeders. In warm weather, the life-cycle from egg through maggot to adult lasts just eight to twelve days. Theoretically, two flies mating in April could produce 191,010,000,000,000,000,000 descendants by August: enough to cover the earth in a blanket of horridness 47 feet deep. But only a small proportion of flies are pests: most are essential for pollination and the recycling of decaying matter.
In Luoyang city in central China the local authority is buying dead flies off residents for 0.06 cents each to promote public hygiene. This is reminiscent of Mao’s 1955 ‘four harms’ campaign against flies, rats, mosquitoes and sparrows. It was stopped when the collapse in the sparrow population led to an explosion of crop-eating insects.
Flies have been much misunderstood throughout history. Arisotle confused the generations that followed him by implying flies had four legs and two ‘arms’, and this was repeated in academic texts for more than a thousand years as no one bothered to look at a fly and check. Only in 1688 did the Italian biologist Francesco Redi disprove what everyone also believed: that maggots spontaneously generate from meat.
Flies land on the ceiling by zooming in close, reaching up with their front legs and flipping their whole body over backwards. They walk around up there thanks to their sticky feet. These are covered in tiny hairs that produce a glue-like substance made of sugars and oils. They are also equipped with a pair of minute claws so they can detach themselves on departure.
MOPMOUTH
Of the flies that are pests, among the most serious are fruit flies: every year they cause billions of dollars of losses in fruit, vegetable and flower crops. Yet they are the most studied and the most fascinating flies of all. Cheap, easy to handle and quickly anaesthetised, it is easy to tell males from females and they breed extremely fast, so that many generations can be studied in a short time. The discovery of chromosomes, which won Thomas Hunt Morgan a Nobel Prize in 1933, stemmed from his work on fruit flies. It turns out that 61 per cent of human diseases have fruit-fly equivalents. Scientists who work on fruit-fly genes (known as drosophilists) like to give appropriate names to their more unusual discoveries. Flies with the ‘Groucho’ gene have more face bristles than normal and ‘Maggies’ have arrested development, like the baby in The Simpsons. Flies with the ‘Ken and Barbie’ gene have no external genitalia. This is a rare fruit-fly indeed. While the human sperm cell is the smallest in the body – it’s only a 500th of an inch long – and a blue whale has sperm only a 5,000th of an inch longer than that – most male fruit-flies are real men. One species has sperm that is 2.3 inches in length – the longest in nature – and its testicles make up a whopping 11 per cent of its body-weight. That’s proportionately larger than our heads. Fruit flies were the first animals in space and are still used by NASA today. They’ve come a long way since their four-legged ancestors of the Middle Ages.
Fossa
Girl becomes boy becomes girl …
The fossa (Cryptoprocta ferox) is only found on Madagascar, where it is the top land carnivore. It’s the size of a spaniel, looks like a cat, but is distantly related to the mongoose. Imagine a cross between a puma and a giant otter that leaps through the branches like a squirrel and you’re close. Its name is a Malagasy word, pronounced ‘FOO-sa’.
Among many odd things about fossa, one remains completely unexplained and unique. The young females start to grow a penis. Actually, it’s a big clitoris, but it has a bone in it and is covered in the same vicious looking backward-facing spines as the male appendage. They leak the bright orange discharge of a sexually mature adult male and develop genital bumps that look like testes. Odder still, when they reach maturity at four years old, all this stops and the clitoris shrinks back to normal size.
Quite why the young fossa females want to look like males baffles zoologists. It isn’t accompanied by a surge in male hormones, or aggression, as in hyenas. Maybe it’s just to keep the boys away until they are ready to mate.
THE DOG-CAT-MONGOOSE THAT LIVES IN A TREE
A brief examination of their mating habits tends to confirm this. A female in heat will climb to the top of a tree, while at its foot a pack of males gather, making threatening calls and getting into ferocious fights. The female will mate with several males over the course of a week, before another female climbs the tree to take her place. Each copulation lasts up to three hours, punctuated by licking, biting and yowling as they somehow manage to stay in the branches. The spiny male penis locks them rear to rear, like dogs.
The fossa’s Latin name, Cryptoprocta ferox, means ‘ferocious hidden anus’ – because a pouch covers the anus and contains glands that it uses to mark its territory.
Genetic evidence suggests that the eight Malagasy carnivores are all descended from a single species of mongoose that ‘blew in’ from African thirty million years ago. That makes fossa a direct relative of the common ancestor of cats and dogs, which is certainly how they look.
They are ferocious hunters, and although they don’t actually attack cattle they will take on large female lemurs, consuming everything: fur, bones, and claws. They will also kill snakes, rodents, fish and birds. Their biggest threat, predictably, is the human destruction of their environment. Since their arrival a mere 1,500 years ago, humans have cleared 95 per cent of the forests that covered the island.
> Madagascan people have a deep fear of fossa, partly owing to the folk memories of a recently extinct fossa relative which was the size of a tiger. Malagasy parents scare their children with tales of them stealing babies, or killing all the chickens in a coop with their terrible flatulence.
Zoologists estimate there are 2,500 fossa left, but can’t be certain. They are masters of concealment: some researchers who have studied lemurs for years have never seen a fossa.
Fox
Clever not cruel
The red fox (Vulpes vulpes) is easily the most widespread and abundant wild carnivore on earth. Foxes are astonishingly adaptable and are found almost everywhere in the world, from deserts to the Arctic Circle. But unlike many of its close relatives, including the wolf, the fox is in no danger of being persecuted out of existence: it is the ultimate opportunist and has learnt to live alongside humans, without sacrificing any of its feral integrity.
In Japan, foxes are sacred to the Shinto religion and ‘fox possession’ is a recognised clinical condition. Symptoms include a craving for rice and an inability to make eye contact.
Despite this, the number of urban foxes isn’t increasing ‘exponentially’; in most Western cities the population reached its maximum supportable size years ago, and the count of surviving cubs each year is almost identical to the number of deaths. The fox population explosion, like almost everything people think they know about urban foxes, is an urban myth. Even the term itself is inaccurate: ‘urban’ foxes are mostly suburban – they don’t like city centres but prefer areas of low-density, semi-detached housing with big gardens, which is why Britain has so many (North American suburbs have raccoons instead).
Urban foxes are just as healthy as country foxes; the town is, if anything, a better environment for them than the countryside. They don’t live ‘mainly’ by scavenging from bins. Foxes will eat literally almost anything: it’s what makes them so successful. Their regular diet includes earthworms, insects, moth larvae, pigeons, rodents, beetles and plenty of fruit and veg. In the autumn, they can practically live on apples, blackberries and rosehips.
They don’t ‘hunt in packs’ or kill cats. Foxes live in small family groups, but always hunt alone. They would never attack a domestic cat or dog unless cornered (although they’ve been known to try their luck with swans). Nor do they massacre chickens ‘for fun’. Foxes are cache-hunters: they will take as many animals as they can, and then bury the carcasses one by one in a ‘larder’ for later. The reason they leave dead chickens behind in the coop is that they are disturbed on one of their many trips to and from the larder.
Most of the nuisance caused by foxes is far outweighed by their indispensable role as rodent-killers. Even the deeply annoying habit of digging up lawns and sports fields is not entirely their fault, as they mistake the smell of blood-and-bone fertiliser on the grass for dead meat, and try to uncover a non-existent corpse. On the other hand, don’t encourage them to nest under your house. At night, the noise of the cubs screaming as they fight and play is indescribable, almost as bad as the smell of carrion, urine and faeces (the latter will be cheerfully deposited as a ‘mark’ on any shoes or children’s toys you leave outside). They also enjoy chewing through electricity and phone wires, and gas and water pipes.
MOUSE DIVING
Urban foxes can easily become tame, even allowing themselves to be fed from the hand and stroked like a pet. This latent tameness was selectively bred in a famous Russian experiment of the 1950s. Within twenty years, the foxes had lost all fear of humans, wagged their tails, developed floppy ears and black and white fur: they had become, in effect, ‘dogs’.
Frog
Toxic paradox
In fairy-tales, frogs are ugly but kind; in real life, they are breathtakingly lovely and deadly dangerous. Such is true, at least, of the brilliantly coloured tree frogs of South America. Their neon reds, shocking oranges, acid greens, purples and blues cover the entire visible spectrum and their eyes are like precious stones.
The world’s deadliest frog is the Golden poison dart frog, Phyllobates terribilis. Sometimes mint-green, sometimes Kodak yellow, it is no larger than a bottle-top but contains enough toxins to kill 20,000 mice or ten men. An amount of its poison weighing less than three grains of salt is sufficient to kill a person and even just to hold one in your hand can be lethal. Poison dart frogs are so called because tribesmen use their venom to tip the missiles of their blowpipes. Captain James Cochrane first discovered this in 1823. He also found out how they extracted the poison: skewering the frog so painfully that it sweated it out. The second most poisonous frog in the world is the Black-legged dart frog (Phyllobates bicolor) of Colombia. It is bright orange or yellow with navy-blue legs. The locals make this one sweat by heating it over a flame.
To vomit, some frog species cough up their whole stomach and then carefully rinse it out with their right hand before pushing it back inside.
FROGGY GOES A-COURTIN’
As a general rule, the more beautiful the frog, the more dangerous it is. This is called aposematism, from the Greek for ‘warning sign’. The tiny, red-and-white-striped Ecuadorean tree frog, Epipedobates tricolor, seems to be wearing a Sunderland FC strip or impersonating a barber’s pole. Comical? Certainly not: it will kill you. Other species aren’t dangerous but have evolved to look as if they are. The Red-eyed tree frog of Costa Rica is green with blue-and-yellow striped sides, orange toes and liquid scarlet eyes. It has a call that sounds like a baby rattlesnake but it is completely harmless. This is called Batesian mimicry after Henry Walter Bates (1825–92) who spent seven years in the Amazon with Alfred Russell Wallace and found 8,000 creatures new to science.
Trinidad’s Paradoxical frog (Pseudis paradoxa) is so called because its tadpoles are three times larger than the adult, but frogs and paradoxes go hand in hand. There are over 5,000 known species and new ones turn up all the time – a hundred in Sri Lanka in 2002 alone. But they’re also dying out at an alarming rate: a third of all frogs are at risk, because frogs breathe through their skin. Though their toxins can occasionally be dangerous to us, the poisons that humans leave lying around are far deadlier to them. This may be a tragedy for both of us. Frog toxins are alkaloids – like cocaine, nicotine, codeine, caffeine and quinine – and scientists are finding that these beautiful paradoxes are living medicine chests, whose deadly poisons can be transformed into drugs that may cure everything from cancer to Alzheimer’s disease. Epipedobates tricolor yields a painkiller 200 times more powerful than morphine; Phyllobates terribilis provides another 600 times as powerful. Both are non-addictive, with no side effects. Inside other frogs may be muscle relaxants and heart stimulants, and cures for strokes, bacterial infections and depression. There is a prince in there, after all.
Giant Tortoise
Large slow larder
In 2006, Adwaitya, the Aldabra giant tortoise (Geochelone gigantes), personal pet of Clive of India, died in Kolkata zoo, aged 255. He was, as far as we know, the planet’s oldest animal inhabitant and it is astonishing to imagine a life that began before Mozart and the French Revolution ending with an announcement on CNN. Tortoise longevity is driven by a slow reproductive hit rate. Giant tortoises are big, cold-blooded herbivores, with a sluggish metabolism. It takes them at least thirty years to reach sexual maturity and although, as adults, they have few natural predators, their young are not so lucky. Even the isolation of an island is no protection: only one egg in ten makes it to adolescence. So, a long life means a much better chance of passing on the genes.
TORTOISE DINGHY
The origins of giant tortoises stretch back fifty million years, to the time when the first turtles hauled themselves on to the land. They were able to exploit the niches left behind by large plant-eating dinosaurs and, predictably, started to grow large. One giant tortoise, Colossochelys atlas, was the size of a small car and spread across the globe, even colonising Antarctica. But the combination of a cooling climate and human ingenuity condemned them (the shell is a
n effective barrier to teeth and claws, but becomes an all-in-one cooking pot on a fire). By 1750, when Adwaitya emerged blinking from his shell, there were no continental giant tortoises left, but 250 species basking happily on their predator-free islands. Today, there are only twelve species, all but one of them endangered.
Giant tortoise oil was considered so delicious that it was the only way of making the flesh of the dodo – called the ‘disgusting bird’ by the Dutch – palatable.
Giant tortoises’ heads gradually grew too big to be withdrawn into their shells – they had survived for so long without attack that even this protection deserted them. They also suffered the misfortune of tasting delicious. Although Darwin – whose theories of natural selection owed so much to the Galápagos species – thought them ‘indifferent’ eating, most early accounts were ecstatic. One giant tortoise would feed several men, and both its meat and its fat were perfectly digestible, the liver was a peerless feast and the bones were rich with gorgeous marrow. Then there were the eggs: the best eggs anyone had ever eaten. Even more useful to sailors, the tortoises could be taken alive on board ship and survive for at least six months without food or water. Stacked helplessly on their backs, they could be killed and eaten as and when necessary. Better still, because they sucked up gallons of water at a time and kept it in a special bladder, a carefully butchered tortoise was also a fountain of cool, perfectly drinkable water.
