Mark Carwardine - Extreme Nature

© 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.

© 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.

© 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.

© Robert Suter

The spitting spiders are most closely related to the venomous brown recluse spiders. Like the brown recluses, they have only six eyes (as opposed to eight) and relatively poor vision. But they make up for it with their snaring skills. Their main sense is touch and, as the spiders walk, their two front legs, which are longer than the other six, tap the ground ahead, feeling for something edible.

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