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Keenest sense of smell (#ulink_e67d63a9-02a2-5bee-b899-4a4fc8acfe4c)
© Jeff Lepore/Science Photo Library
Many animals rely on their sense of smell to find food or a mate and even to find their way around. Some live in places where other senses are of little use – eyes don’t help much if you spend most of your life in the dark, and ears would be hopeless in a particularly noisy environment – so they rely on smell more than most.
Some animals, such as sharks, are selective in their smelling abilities and are super-sensitive to significant smells that are relevant to activities such as feeding or breeding. In fact, smell is so important to sharks that they have been dubbed ‘swimming noses’. Their smell receptors are fine-tuned to picking up small concentrations of fish extract, blood and other chemicals – but so are the receptors of many other animals. Some catfish have such super-receptors that they can smell compounds at 1 part to 10 billion parts of water.
The likelihood is, though, that moths are the record-holders, especially the males. They use their antennae to home in on the sex pheromones, or chemical allures, released by females and can even detect if these females are on plants suitable for egg-laying. Some females release deviously small amounts of pheromone, to make sure that only those males with the most highly tuned antennae can follow the trails. The likely record-holder for the best known sense of smell is the polyphemus moth: just one pheromone molecule landing on a male’s antennae will trigger a response in his brain.
Most enthusiastic singer (#ulink_e67d63a9-02a2-5bee-b899-4a4fc8acfe4c)
© Flip Nicklin/Minden Pictures/FLPA
Drop a hydrophone into the water in an area where humpback whales are breeding and you may hear a baffling medley of moans, groans, roars, snores, squeaks and whistles. These are the hauntingly beautiful sounds made by male humpbacks, which are famous for singing the longest and most complex of animal songs. Since most singing takes place at the breeding grounds, it is probably used to woo females and to warn away rival males – but the songs may also have more subtle meanings and nuances that we do not yet understand.
A song can last for as long as half an hour, and as soon as the whale has finished, it often goes back to the beginning and sings it all over again. Each song consists of several main components, or phrases, which are always sung in the same order and repeated a number of times, but are forever being refined and improved. All the humpbacks in one area sing broadly the same song, incorporating each other’s improvisations as they go along. This means that the song heard one day is different from the one being heard several months later and, in this way, the entire composition changes over a period of several years.
Meanwhile, humpback whales in other oceans sing very different compositions. They probably all croon about the same trials and tribulations in life, but the differences are so distinctive that experts can tell where a whale was recorded simply by listening to the intricacies of its own special song.
Most gruesome tongue (#ulink_e67d63a9-02a2-5bee-b899-4a4fc8acfe4c)
© Matthew Gilligan
This is probably the world’s most specialised and gruesome isopod – one of a group of crustaceans including woodlice, marine gribbles and slaters. Most isopods lead perfectly normal lives as herbivores, scavengers or carnivores, but some are parasites. Cymothoa exigua has a tendancy to select the mouth of the spotted rose snapper fish for its hangout.
Latching on to the fish’s tongue with its hooked legs (pereopods), it feeds on mucus, blood and tissue, gradually eating away the tongue. Gripping onto the tongue stub, the isopod then effectively becomes the fish’s tongue, growing as its host grows and feeding on particles of meat that float free as the fish eats. The biggest individual isopod recorded was 39mm (1.5in), but presumably it can grow to be as big as the fish needs its tongue to be.
Perhaps the practice is not as gruesome as it looks, as the rose snapper can continue to feed, but no one knows whether a time comes when Cymothoa decides to let go and get a taste of blood in someone else’s mouth. Strangely, the relationship between the fish and its parasite has been observed only in the Gulf of California, or Sea of Cortez, though the fish is found in the eastern Pacific, from Mexico to Peru. It is the only known example of a parasite replacing not just a host’s organ but also its function (to hold prey) – a hard act to swallow.
Most inquisitive bird (#ulink_e67d63a9-02a2-5bee-b899-4a4fc8acfe4c)
© Tui De Roy/Minden Pictures/FLPA
Parrots are highly inquisitive, but even among parrots, keas are exceptional. They’re native to New Zealand’s South Island, a cold, snowy, unparrotlike place where keas have to use all their wits to find a meal. While parrots elsewhere are flying from one conspicuous fruit to another, keas are searching under rocks and bark and in bushes, cones and shells for food such as roots, shoots, berries or insect larvae. This and a mountainous habitat virtually free of predators has, over 2.5 million years of evolution, made them insatiably curious. And they’re especially drawn to things they’ve never seen before. So when humans arrived in New Zealand, the keas were delivered a bonanza of new objects to investigate for food.
Nowadays great sources of fascination are camping grounds and ski-resorts. These parrots are large and have powerful beaks, and they can rip right through a canvas tent for the sheer joy of investigation. A particular favourite is the rubber on cars – windscreen wipers mainly. One gang of keas is said to have ripped out the rubber lining around the windscreen of a tourists’ hire car, causing the glass to fall inwards and opening up the interior. When the tourists returned, they found clothes, food and car parts scattered in the snow, while the keas appeared to be playing a game of football with an empty Coke can. The birds then retreated and watched – with great curiosity, it seemed – to see what the tourists would do about it.
Biggest drug-user (#ulink_e67d63a9-02a2-5bee-b899-4a4fc8acfe4c)
© Steve Robinson/NHPA
Yes, humans are the biggest drug-users. But we are not the only ones who use drugs, and we are only just beginning to discover the pharmaceutical knowledge of other animals. The current top-of-the-list user is the chimpanzee. Like us, chimps get stomach ache from time to time after overeating or consuming toxins. They also get parasites and diseases, and stressed animals usually end up feeling pretty ill.
It’s not surprising that an intelligent primate such as a chimp, which learns by trial and error and example, should have started to use medicinal products, since their forest habitat is full of them. In Tanzania, chimps suffering from diarrhoea have been seen using the leaves of the ‘bitter leaf’ tree that local people know as a medicine for malaria, amoebic dysentery and intestinal worms. Across Africa, chimps have been seen seeking out rough-leafed plants, plucking whole leaves from them, carefully folding the leaves, rolling them around in their mouths and then swallowing them. Excreted whole, the leaves push out parasites such as intestinal worms.
Many other animals also appear to self-medicate. Capuchin monkeys have been seen rubbing their fur with pungent plants that contain healing and insect-repellant properties. Black lemurs rub insect-killing chemicals from millipedes onto their fur. An elephant has been observed seeking out labour-inducing leaves of a tree just before giving birth. Given our increasing need for new antibiotics and remedies, such examples provide a good reason to keep nature’s pharmacy intact by respecting the environment.
Most painful stinger (#ulink_e67d63a9-02a2-5bee-b899-4a4fc8acfe4c)
© Valerie & Ron Taylor/ardea.com
Some say this is the world’s most venomous animal, but this depends what you mean. Is it the venomous creature you are most likely to encounter, does it kill more people than any other, or are the chemicals most toxic? Certainly, a single box jellyfish contains enough venom to kill at least 60 people, and many do die after being stung.
Though the jellyfish has no desire to kill humans, it is a hunter. An adult box jellyfish – as large as a human head, with tentacles up to 4.6m (15ft) long – has a full array of powerful stinging cells, called nematocysts, and hunts mainly fish. It is very active (unlike many other jellyfish) and jet-propels itself through the sea in search of prey. It’s also transparent, ensuring that fish (and humans) don’t spot its deadly tentacles.
There are four bundles of about ten tentacles, most over 2m (6ft 6in) long and each carrying around 3 million nematocysts. The toxin contains chemicals that affect heart muscle and nerves and destroy tissue, the purpose being to kill a fish quickly so it doesn’t get away. But if a box jellyfish encounters a human, it may also sting in self-defence. The pain is excruciating, and without anti-venom, a victim can die from heart failure in just a few minutes. In addition, nematocysts fire not just on command but when stimulated physically or chemically. Strangely, they can’t penetrate women’s tights, and until ‘stinger suits’ became available, lifesavers patrolling beaches would wear tights unashamedly.
Slipperiest plant (#ulink_e67d63a9-02a2-5bee-b899-4a4fc8acfe4c)
© Mark Moffett/Minden Pictures/FLPA
There are many different species of pitcher plant, but all are insect-traps with the slipperiest of sides, providing extra nitrogen (from insect corpses) to help the plants flower and set seed. Among the most sophisticated are the leaves of vine-like Nepenthes. Each of these pitfall traps has an ‘umbrella’ lid and a base partly filled with a soup of digestive enzymes. The lure may be colour (usually red), smell (nectar or, later, rotting corpses) or tasty hairs. When an insect lands on the rim, it slips into the deadly broth, possibly intoxicated by narcotic nectar.
Slipperiness is achieved in two ways, perhaps depending on what insects are likely to be attracted (walking insects if the Nepenthes is on the ground or flying insects if it is up in the tree canopy). The inner walls are usually impossible to climb, being covered with slippery waxy platelets. Others go a stage further and have a surface that attracts a film of water which aquaplanes the insects to their death. Some also use trickery. When their pitchers are dry, ants are lured by the nectar, and don’t slip, and so go and tell more ants about the find. If the surface is wet when they return, they all fall in.
Another of the Nepenthes species is in partnership with an ant that has specialised feet, allowing it to get in and out of the pitcher to retrieve corpses. It eats these and drops the remains and its faeces into the pitcher, so speeding up the release of nitrogen for its predatory host to ingest.
Heaviest drinker (#ulink_e67d63a9-02a2-5bee-b899-4a4fc8acfe4c)
© Mary Plage/Oxford Scientific Films
To say this or any other hummingbird drinks like a fish is to understate how much it drinks. In proportion to its body weight, it drinks a lot more than a fish. (Just to get that cliché straight: freshwater fish don’t drink – they absorb water through their skin. Saltwater fish that drink don’t do so to excess.) In the case of the hummingbird, it’s the fault of the flowers. Hummingbirds have evolved to drink nectar. The flowers they visit have evolved to provide that nectar, and the nectar they provide is typically about 30 per cent sugar and the rest water. To keep their wings going at a rate quicker than the human eye can see – to hover – hummingbirds need a huge amount of sugar, which means that by drinking nectar they take in up to five times their body weight in water every day.
If any other animal, including a human, tried to drink even one times its body weight, it would be dead long before it could do it. So while hummingbirds were evolving beaks to fit into the flowers with their watered-down nectar, they were also having to evolve nature’s heaviest-duty kidneys. Some water just passes through the bird unprocessed, but 80 per cent goes to the kidneys to be expelled as very dilute urine. And why the broad-tailed in particular? It’s simply the most energetic hummingbird, and thus the most supersaturated.
Best mimic (#ulink_e67d63a9-02a2-5bee-b899-4a4fc8acfe4c)
© Roger Steene/imagequest3d.com
If you are a medium-sized predator, the average octopus is one of the most edible animals in the sea. It’s substantial and meaty, and without a shell, bones, spines, poisons or any other unpleasant defence mechanisms. In fact, the best defence most species of octopus have is to stay hidden as much as possible and do their own hunting at night.
So to find one in full view in the shallows in daylight was a surprise for two Australian underwater photographers, swimming off the Indonesian island of Flores in the early 1990s. Actually, what they saw at first was a flounder. It was only when they looked again that they saw a medium-sized octopus, with all eight of its arms folded and its two eyes staring upwards to create the illusion of a fishy body. An octopus has a big brain, excellent eyesight and the ability to change colour and pattern, and this one was using these assets to turn itself into a completely different creature.
Many more of this species have been found since then, and there are now photographs of octopuses that could be said to be morphing into sea snakes (six arms down a hole, and two undulating menacingly), hermit crabs, stingrays, crinoids, holothurians, snake eels, brittlestars, ghost crabs, mantis shrimp, blennies, jawfish, jellyfish, lionfish and sand anemones. And while they mimic, they hunt – producing the spectacle of, say, a flounder suddenly developing an octopodian arm, sticking it down a hole and grabbing whatever’s hiding there.
Most formidable killer (#ulink_e67d63a9-02a2-5bee-b899-4a4fc8acfe4c)
© Mark Carwardine
Anything that can attack and kill the largest animal that ever lived, the blue whale (see (#litres_trial_promo)), has to be the greatest predator ever (apart, of course, from Homo sapiens). But blue whales are peaceable creatures with few defences apart from size, and so maybe the killer whale qualifies better on the grounds that it can kill the great white shark. At a maximum length of 9m (29ft 6in), killer whales are the largest members of the dolphin family and among the largest of all predators, but their real edge is that they’re pack hunters and work together to subdue large prey.
Several distinct forms are known – residents, transients and offshores – each of which differ significantly in appearance, behaviour, group size and diet. The transients are the ones that tend to specialise in larger prey but, perhaps surprisingly, they travel in smaller groups than their fish-eating relatives: fewer than six or seven is fairly typical (fish-eating groups often comprise 15–30 whales). The transients devise different, often ingenious, hunting techniques for different prey. In the Antarctic, for example, they will tip seals and penguins off ice floes and into the mouths of their group-mates; and in Patagonia, they beach themselves to grab sealion pups.
When Basque whalers saw killer whales feeding on the carcasses of dead whales, they called them ‘whale killers’, and the name stuck. Many people prefer to use the more politically correct name, orca, but in Latin, orcus means ‘belonging to the kingdom of the dead’, and so it’s not much better.
Best architect (#ulink_e67d63a9-02a2-5bee-b899-4a4fc8acfe4c)
© John Shaw/NHPA
Some 200 species of ant – most famously leafcutter ants – farm fungus inside their nests as a source of fast food. So do about 3,500 beetles and 330 species of termite. But of all these insects, none seems to cultivate a more difficult crop than the African termite, and no crop requires more elaborate technology to maintain it. The staple fungus of African termites grows only on their faeces and needs a very particular temperature. Anything above or below 30.1°C (86°F) is too hot or too cold, and every aspect of the construction of the termite mound is part of an effort to keep the temperature exactly that.
The termites always build with mud, above a damp pit. They dig at least two long boreholes down to the water table. They also construct a 3m (10ft) diameter cellar, about 1m (3.3ft) deep, with a thick central pillar that supports the main part of the mound. This houses the queen, the nursery and the fungus farms. On the ceiling of the cellar are thin, circular condensation veins, and around the sides of the mound are ventilation ducts. On top are hollow towers – chimneys – that rise 6m (20ft) above ground level. Every dimension is just right for the precise circulation of air and moisture that will keep the fungus at 30.1°C no matter what it’s like outside. What’s more, workers are only a maximum of 2cm (0.8in) in size, and so in relative terms, the mound is taller than any human building – the equivalent of 180 storeys.
Most painful tree (#ulink_e67d63a9-02a2-5bee-b899-4a4fc8acfe4c)
© Bill Bachman/ANTphoto.com
Of course, any tree could fall on you, and plenty of trees are poisonous to eat, but this aside, the trees that cause the most excruciating pain are ones that you just brush against. These are the stinging trees that are found in several parts of the world but are most persistently painful in that land of advanced toxins, Australia. Here are six Dendrocnide species, two of which – the northern shiny-leaf stinging tree and the southern giant stinging tree – are large, tree-like trees, and four of which are more like shrubs. Of the six, the worst agony is said to be inflicted by a shrub, the gympie-gympie, but they all hurt a lot.
What looks at first like a layer of fur on all parts except the roots is really a mass of tiny glass (silicon) fibres containing toxic chemicals. Just a brush against a tree results in the skin being impaled with a scattering of fibres, which act like hypodermic needles and are all but impossible to extract (Australian first-aid kits sometimes include wax hair-removal strips). The poison causes burning, itching, swelling and sometimes blistering that is said to be at its most unbearable soon after contact but can keep causing pain for years. The fibres can penetrate most clothing, and sometimes air-borne ones can be inhaled. Oddly, the stings don’t affect all animals. Insects and even some native mammals actually eat the leaves. The ones that suffer tend to be introductions to Australia, such as dogs, horses and humans.
Loudest bird call (#ulink_e67d63a9-02a2-5bee-b899-4a4fc8acfe4c)
© ANT Photo Library/NHPA
Which bird is loudest depends on who is listening and where. The song of a nightingale overcoming traffic noise is so loud (90 decibels) that prolonged exposure to it could, theoretically, damage your ears. So could the even louder, shrill, 115-decibel cry of a male kiwi or the metallic ‘bonks’ of the Central American bellbird, designed to carry in thick rainforest. But possibly the best long-distance sound to make is a boom.
In Europe, the booming record-holder is the bittern. But the world record-holder is probably the New Zealand kakapo, which is now extinct on the two main islands and, despite great conservation efforts, numbers fewer than 90 individuals. Every three or four years, the normally solitary males gather at traditional kakapo amphitheatres – display grounds with excavated bowls. Here they puff up air sacs in their chest and belly and start booming, an average of 1,000 times an hour for 6–7 hours a night (kakapos are nocturnal, and sound carries best in the colder night air). They do this for 3–4 months to call in likely mates to witness their dance displays and for mating. But since this giant, flightless parrot is now confined to a handful of offshore islands, few people will ever hear its eerie, ‘fog-horn’ boom.
Intriguingly, the booms of Australasian cassowaries are nearly as loud but have an added long-distance element: a low-frequency component below the range of our hearing (though it can be felt). It’s likely that a kakapo boom also contains ultra-low-frequency sound, but its booming is now so rare that it has yet to be completely analysed.
Deadliest drooler (#ulink_e67d63a9-02a2-5bee-b899-4a4fc8acfe4c)
© Mark Carwardine
The Komodo dragon is a renowned giant: the average male is more than 2.2m (7ft 5in) long, and some measure up to 3.1m (10ft 2in). The longest lizard of all, however, is its much slimmer relative, the Salvadori monitor from New Guinea, though two thirds of its 2.7m (8ft 8in) maximum length is made up by its tail.
But the Komodo dragon is the heaviest lizard of all, with an average weight of 60kg (130lb) and a maximum of 80kg (176lb), and it is a fearsome predator. It has large, sharp, serrated teeth for cutting and tearing prey, but its hidden weapon is its bacteria-laden saliva. Once bitten, a victim may escape, but within a few days it will succumb to infection. The dragon then tracks it down with its acute sense of smell – a sense that also makes it a super-efficient scavenger.
Though it is a giant by today’s standards, the Komodo dragon may be a pygmy compared to one of its mainland ancestors (Flores Island supported other ‘pygmies’, including a now-extinct elephant, on which the dragon is believed to have preyed). In Australia there once existed a true giant, the 6.9m (23ft), 617kg (1,370lb) monster monitor Megalania prisca, which became extinct about 40,000 years ago. The Komodo dragon poses relatively little threat to humans and usually only bites when cornered. But Megalania, whether or not it was a deadly drooler, would have been a lizard to be very, very afraid of.
Most sensitive slasher (#ulink_e67d63a9-02a2-5bee-b899-4a4fc8acfe4c)
© Marty Snyderman/imagequest3d.com
A sawfish has external teeth, set around a sensitive, flat snout – the saw, or rostrum (here shown from the underside). Swung from side to side, the saw can be used as a powerful weapon to slash shoaling fish such as mullet and herring, which it then eats off the sea-bottom. Generally speaking, though, the sawfish is a slow and peaceable animal, spending its time in shallow, muddy water, raking the mud with its saw for crustaceans and other prey. The saw-teeth get worn by all this grubbing, but they grow continuously from their bases and so don’t wear out.
Like its close relatives, the rays, it’s perfectly camouflaged against the bottom of the sea, and like its more distant relatives, the sharks, it swims in an undulating way. And like both groups, its hard bits are cartilage, not bone, and its teeth are adapted scales. It has another similarity. Using special cells, the ‘ampullae of Lorenzini’, on its saw and head, it can detect electrical fields generated by prey.
One problem for females is that they give birth to live saw-babies. But a youngster’s saw is covered with a sheath to make birth relatively painless. A much greater problem for all sawfish (possibly seven species) is the fact that their coastal waters are being polluted and developed and that they have been overfished to the point where all are endangered, some critically. A sawfish’s saw is also its downfall. Not only has it been sought after as a trophy, but it also fatally entangles the fish in nets.
Smelliest plant (#ulink_e67d63a9-02a2-5bee-b899-4a4fc8acfe4c)
© Neil Lucas/naturepl.com
What smells bad to us often doesn’t bother other animals. In fact, the scent of the foul-smelling titan arum – the tallest and probably heaviest of flowering structures – is positively attractive to carrion beetles and bees. Whether its smell is the worst, to us, has still to be tested (there are other contenders for this, including the even bigger giant titan, A. gigas). But the titan arum produces a sufficiently awful smell to make people faint.
The ‘flower’, or inflorescence, comprises a vase-shaped spathe (petal-like leaf) at least 1.2m (4ft) tall, which grows rapidly from a gigantic tuber weighing up to 80kg (177lb). Out of this rises a spadix, a spike with thousands of tiny flowers more than 2.4m (8ft) tall, so strange it gives the arum its scientific name: ‘huge deformed penis’. The upper part of the spike produces the smell, and to make it travel further, the spadix generates heat and may steam at night as it pulses its fragrance of ammonia, rotting flesh and bad eggs for up to eight hours at a time.
This attracts pollinating, carrion-loving insects, but few people have observed the pollination, probably because the plant flowers only every 3–10 years and then for just two days. Once the flower dies and hornbills have dispersed its seeds, it’s replaced by a titanic leaf up to 6m (20ft) tall, which makes the food so that, one day, the tuber can grow another stinking flower.
Most impressive comeback (#ulink_e67d63a9-02a2-5bee-b899-4a4fc8acfe4c)
© Don Merton
New Zealand’s Chatham Islands are believed to have been the last Pacific archipelago to be visited by humans. Yet when people finally did visit, they stayed, and they did a pretty thorough job of doing what humans have always done to islands: stripped them of a lot of their native plants and animals. The Polynesians arrived around 700 years ago, the Europeans came along in the 1790s, and between them they caused the extinction of 26 of the islands’ 68 species and subspecies of birds. The main cause was introduced land mammals, and among the sufferers from cats and rats in particular was the 15cm (6in) endemic black robin.
By 1900 it had disappeared from the two main islands and survived only on Little Mangere, a tiny, windswept stack with sheer cliffs that helped keep predators away but didn’t offer the birds much protection from the elements. By 1972 only 18 were left. By 1976, seven.
In the meantime, though, the government had bought nearby Mangere Island and begun to reforest it, and all the birds were moved there. Nevertheless, by 1980, there were just five, with only one breeding pair. But by fostering eggs to other bird species on other islands – which improved the survival chances of the chicks and spurred the breeding female to nest again – conservationists painstakingly cranked the species back to life. Now there are about 250 black robins on Mangere and South East islands, and there are plans to repopulate other islands in the Chathams.
Hottest animal (#ulink_e67d63a9-02a2-5bee-b899-4a4fc8acfe4c)
© Peter Batson/imagequest3d.com
The Pompeii worm thrives in large colonies in one of the darkest, deepest, most hellish places on Earth – close to a geyser of water so hot it could melt the worm in a second. It is also subject to a pressure great enough to crush a person and doused in a soup of toxic sulphur and heavy metals. Communities of Pompeii worms cling to the sides of ‘smokers’ 2–3 km (1.2–1.9 miles) under the sea. These belching chimneys grow over hydrothermal vents on volcanic mountain ranges, created from the chemicals that precipitate out as 300°C (572°F) vent water meets cold seawater.
To survive on a smoker requires super-worm strategies. For its home, the worm makes a paper-like chemical-and-heat-resistant tube. For a thermal blanket, it ‘grows’ a fleece of filamentous bacteria, feeding it with sugar-rich mucus secreted from its back. This blanket may also detoxify the vent fluid in its tube.
Unlike the vent tubeworm Riftia pachyptila, the Pompeii worm has a gut and ‘lips’ which it extends to ‘graze’ on bacteria that grow on the surface of the colony. But no one knows quite how it copes with what are the highest temperatures and temperature gradients experienced by any organism apart from bacteria, for though it angles its head (gills, mainly) away from the hottest water, its tail experiences flushes hotter than 80°C (176°F). Keen to make use of the Pompeii worm’s technology for human endeavours, scientists are now racing against each other to unravel its survival secrets.
Most shocking animal (#ulink_e67d63a9-02a2-5bee-b899-4a4fc8acfe4c)
© Andrea Florence/ardea.com
Think of it as a living battery. The electric eel can grow to be more than 2m (6ft 5in) long, but its organs are packed just behind its head, leaving 80 per cent of its body to electricity generation. It’s stacked with up to 6,000 specially adapted muscle cells, or electrocytes, aligned like cells in a battery. Each electrocyte emits low-voltage impulses that together can add up to 600 volts – enough to render a human unconscious. The positive pole is behind the eel’s head, and the negative pole is at the tip of its tail. It tends to remain straight when swimming, using its long ventral fin for propulsion, and so keeps a uniform electric field around itself.
Electricity affects almost every bit of the eel’s behaviour. As well as stunning or killing with high-voltage pulses, it communicates with other eels electrically and uses electrolocation (a sort of electrical bounce-back system) to detect objects and other creatures in the water. Fish and frogs are its staple prey, and it can detect the minute electric currents these and other living things produce. The eel can’t see well, but this doesn’t matter much, since it is mainly nocturnal and tends to live in murky water.
There are other electrified fish, including the related knifefishes, which generate a weak electric field around themselves that they use to sense objects and fish prey and to communicate. The only other shockers are the torpedo ray and the electric catfish, but neither is as shocking as the electric eel.
Coldest animal (#ulink_e67d63a9-02a2-5bee-b899-4a4fc8acfe4c)
© J M Storey/Carleton University
There’s an African midge so well adapted to drought conditions that, as a sideline, it can withstand being artificially frozen to –270°C (–454°F). Lots of other insects can survive freezing, too, but the creatures that can withstand cold for the longest period are probably bacteria in Antarctica.
The most freeze-tolerant higher animal is the wood frog, which can literally become a ‘frog-sicle’, enabling it to live further north than any other amphibian and to hibernate close to snowmelt ponds, presumably to give it a head start and enable it to reproduce quickly before the ponds dry.
When the temperature drops below freezing, the frog’s liver starts converting glycogen to glucose, which acts as an antifreeze. The blood passes the glucose to the vital cells, which are then protected from freezing on the inside, all the way down to –8°C (18°F). But the rest of the frog’s body fluids, up to 65 per cent of them, turn to ice and the organs, deprived of blood, actually stop working. Even the eyeballs and the brain freeze. It is effectively the living dead. (The painted turtle Chrysemys picta can do this, too, but only briefly.) When a thaw comes, the frog’s heart starts beating and pumps blood containing clotting proteins around the body, which stops bleeding from wounds caused by the jagged ice crystals. The frogsicle quickly comes back to life and, just as miraculously, so do the frozen parasitic worms in its body.
Most talkative animal (#ulink_e67d63a9-02a2-5bee-b899-4a4fc8acfe4c)
© Jenny Pegg
African greys live in huge flocks that sweep through the rainforests foraging for fruit, nuts, seeds and herbs and constantly communicating with each other. In the wild, no one has been able to do more than categorise their calls as, for example, threat or making contact. These calls could, though, be far more meaningful and complex if the language skills of pet grey parrots are anything to go by – for African greys can be taught to understand and speak human language and may some day even be able to read words.
The most famous of these parrots (though several others have been making the news recently) is Alex, protégé of Dr Irene Pepperberg of Brandeis University in Massachusetts. Alex can identify the colours and shapes of objects and what they’re made of. He can, for instance, say, ‘four-corner wood square’ if that’s what he’s been shown. If he wants to be given something or to go somewhere, he only needs to ask. And he can actually make wisecracks and some rudimentary conversation.
