Extreme Nature. Mark Carwardine
reason to keep nature’s pharmacy intact by respecting the environment.
| NAME | box jellyfish Chironex fleckeri |
| LOCATION | near-shore waters of parts of Australia and South-east Asia |
| ABILITY | causing excruciating pain and possible death |
© 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.
| NAME | pitcher plants Nepenthes species |
| LOCATION | South-east Asia |
| ABILITY | catching prey in slippery, deadly pitchers |
© 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.
| NAME | broad-tailed hummingbird Selasphorus platycercus |
| LOCATION | North America |
| ABILITY | can drink up to five times its body weight in a day |
© 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.
| NAME | Indo-Malayan mimic octopus |
| LOCATION | Indonesian-Malaysian archipelago |
| ABILITY | pretending to be anything but an octopus |
© 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.
| NAME | killer whale, or orca, Orcinus orca |
| LOCATION | oceans worldwide |
| ABILITY | preying on the |