Extreme Nature

Loudest bird call

NAMEkakapo Strigops habroptilusLOCATIONNew ZealandABILITYproducing a boom that can be heard up to 5km (3 miles) away

© 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

NAMEKomodo dragon Varanus komodoensisLOCATIONislands of Komodo, Rinca, Gili Motang, Gili Dasami and Flores, IndonesiaABILITYproducing dangerous bacteria-laden saliva

© 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

NAMEsawfish Pristis speciesLOCATIONshallow, warm coastal watersABILITYusing its saw for slashing and sifting

© 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

NAMEtitan arum, corpse flower, or devil’s tongue, Amorphophallus titanumLOCATIONwestern Sumatra, IndonesiaABILITYpumping out the smell of decomposing flesh

© 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

NAMEChatham Island black robin Petroica traversiLOCATIONChatham Islands, east of South Island, New ZealandACHIEVEMENTincreasing in numbers from just five to 250 in 18 years

© 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

NAMEPompeii worm Alvinella pompejanaLOCATIONdeep-sea hydrothermal ventsABILITYwithstanding scalding water

© 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

NAMEelectric eel Electrophorus electricusLOCATIONSouth American riversABILITYstunning prey with electrical discharges

© 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

NAMEwood frog Rana sylvaticaLOCATIONCanada and AlaskaABILITYwithstanding being frozen for weeks

© 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

NAMEAfrican grey parrot Psittacus erithacusLOCATIONCentral and West AfricaABILITYcommunicating with humans

© 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.

One story Dr Pepperberg tells about him is how during a demonstration of his ability to identify alphabetic letters on cards, Alex would say ‘sssss’ for S, ‘shhh’ for SH, ‘tuh’ for T and so on and after each correct answer would ask for a nut. Since that would have slowed things down too much, Dr Pepperberg would say each time, ‘Good birdie, but later.’ Finally Alex looked at her, narrowed his eyes and said, ‘Want a nut. Nnn, uh, tuh.’

Most bizarre defence

NAMETexas horned lizard Phrynosoma cornutumLOCATIONsouthern USA and MexicoABILITYblood squirting

© Raymond Mendez/Oxford Scientific Films

Revered by native peoples for thousands of years, the Texas horned lizard has an array of abilities. It eats mainly ants – and lots of them, since much of an ant is indigestible. This necessitates a huge stomach. Eating more than 200 ants a day means exposure in the open for long periods, and being stomach-heavy means a horned lizard finds it difficult to scamper away from predators.

Instead, it relies on an armoury of defences. It has camouflage colouring, with an outline broken by spines and outgrowths, and it will freeze if a predator approaches. Its horns and spines can pierce the throat of a snake or bird, and it can hiss and blow itself up to look even more fearsome. When it comes to coyotes, foxes and dogs, a horned lizard’s most spectacular defence is to squirt foul-tasting blood from sinuses behind its eyes. That usually has the desired effect. But it squirts only when it’s provoked, since it risks losing up to a quarter of its blood.

Such abilities are, however, no defence against human invasion of its land. Its strange shape and colouring has made it attractive to reptile collectors, and its habit of freezing means it is prone to being run over. And with humans have come exotic fire ants, which it can’t eat and which are replacing the native ants on which the lizard depends – a sorry way for such a determined survivor to go.

Smelliest animal

NAMEstriped skunk Mephitis mephitisLOCATIONNorth AmericaABILITYdefending itself with a spray containing the smells that mammals hate most

© T Kitchin/V Hurst/NHPA

Bad smell is all in the nose of the receiver, and we humans have far fewer sensors than most animals. Nonetheless, we can smell a striped skunk up to 3.2km (2 miles) away, if the wind is in the right direction. It’s possible to train our brains to ignore the most disgusting of smells, from vomit and faeces to rotting flesh – but never skunk. Other animals, including African zorillos, Tasmanian devils, wolverines and different species of skunk, produce revolting musk when threatened or attacked, but not of the strength or permanence of striped skunk spray.

The amber oil is made in two muscular glands under the skunk’s tail and can be delivered as a spray or precision jet up to a distance of 3.6m (12ft). The spray contains compounds which are the cause of the vomit-producing smell, like very, very rotten eggs. It can also cause temporary blindness and, if swallowed, unconsciousness. It is virtually impossible to remove from clothes, which are best thrown away after a close encounter.

Other mammals are also revolted by it, and so the skunk’s only serious predator is the great horned owl, which probably has little need of a sense of smell. Skunks prefer not to waste their musk, as the glands take a couple of days to refill, and so they usually raise their black-and-white tail as a warning before spraying. But such warnings go unheeded on roads, which is why cars are now their worst enemy.

Slimiest animal

NAMEhagfish Myxini speciesLOCATIONworldwideABILITYdrenching predators in mucus by the bucketful

© Peter Batson/imagequest3d.com

This is an eel-like animal, 0.5–1m long (20–33 in), without fins, jaws, scales, a backbone or much in the way of eyes. Though not a true fish, it does have gills and excels in a fish-like trait – producing slime. For fish, a thin slime coating is a way of regulating the salt and gas balance between their bodies and the water, repelling parasites and maintaining speed. But for a hagfish, slime is also a weapon.

Its lifestyle is pretty basic, even a little squalid: it lives on the sea-bottom, usually at around 1,200m (4,000ft), where it eats anything it can overcome or scavenge. When it finds a suitable victim, it slithers into it, usually by way of its mouth, and then uses its toothed tongue to rip the animal to pieces from the inside out.

That’s nothing, however, compared to what it does when it’s threatened. Glands all along its sides exude a slime concentrate that reacts with seawater to create a cloud of mucus goo hundreds of times larger than the original secretions. It’s very tough goo, too – reinforced by thousands of long, thin, strong fibres – and the offending predator or unlucky passer-by becomes stuck in it and suffocates. The hagfish itself would suffer a similar fate, except that it has a way of extricating itself: it ties itself into a knot and slips the knot down the length of its body, squeezing free in the process.

Keenest hearing

NAMEgreater horseshoe bat Rhinolophus ferrumequinumLOCATIONEurope and Morocco east to Afghanistan and JapanABILITYtracking and catching insects at speed in total darkness

© David Hosking/FLPA

To hunt and orient oneself in the dark requires an extreme sense. Bats do it by ‘seeing’ with echolocation. They emit high-frequency (ultrasound) pulses from their mouths or noses and analyse the returning echoes to determine the size, shape, texture, location and movements of the smallest of objects. A bat’s nose structure helps focus the sound, and its complex ear folds catch the returning echoes. Echoes from above hit the folds at different points to those from below. And by moving its ears, a bat can hear sound bouncing back from different angles.

The noise is so intense that, to avoid going deaf, most bats ‘shut off’ the sound in their ears as they signal. A bat may ‘shout’ – at 110 decibels, in the case of the little brown bat, which hunts in open spaces; or it may ‘whisper’ at 60 decibels, in the case of the northern long-eared bat, which catches insects around vegetation. Bats using lower frequencies (longer wavelengths), such as the greater horseshoe, tend to glean insects off vegetation or hunt large ones; those using higher frequencies (shorter wavelengths) generally catch flying insects at closer range.

While it is difficult to be certain that the greater horseshoe bat has better hearing than other bats, its echolocation system is one of the few studied in detail and it is undoubtedly impressive. But many other bats have incredibly keen hearing, too, and it is possible that the real record-holder has yet to be discovered.