Everyone has felt pain, and many experience it daily. But for such a universal sensation, it is still a mysterious one. We are only starting to understand the molecules that produce a painful sensation. Nature, however, is well ahead of us. Many animals are armed with chemicals that hijack the nervous systems of their targets, producing feelings of intense pain. They are unknowing neuroscientists, and by studying their weapons, we can better understand how pain manifests in our bodies.
Take the Texas coral snake. This brightly coloured serpent, clad in warning hues of red, black and yellow, usually shies away from confrontation. When it’s threatened, it defends itself with venom that can cause excruciating and unremitting pain.
Bumblebees begin their adult lives by eating their sisters’ faeces. After many months as helpless, hungry larvae, they spin a silken cocoon and transform their bodies. When they emerge, ready to face the world, they get mouthfuls of poo. It may not sound like an auspicious start, but it’s essential. The faeces contain special bacteria that act as part of the bee’s immune system, protecting it from an incredibly dangerous parasite.
Gut bacteria are important partners for many animals. We humans have up to 100 trillion microbes in our bowels, and this “microbiota” outnumbers our own cells by ten to one. They act like a hidden, writhing organ. They break down our food. They influence our behaviour. And they safeguard our health by crowding out other bacteria that could cause disease. It seems that gut bacteria play a similar role in bumblebees.
There are two ways of becoming invisible: you can either be transparent so all light passes through your body, or you can blend in by taking on the colours of your surroundings. A truly incredible animal would be able to do both, switching between the two at a whim. And that’s exactly what some squids and octopuses can do.
Sarah Zylinski and Sonke Johnsen from Duke University found that two cephalopods – the octopus Japetella heathi and the squid Onychoteuthis banksii – can switch their camouflage strategy depending on how bright their environment is. When sunlight streams from above, they choose the see-through option. When their world darkens, they go for darker colours that blend in.
The hagfish looks like an easy meal. Its sinuous, eel-like body has no obvious defences, but any predator that moves in for a bite is in for a nasty surprise. The hagfish releases a quick-setting slime that clogs up the predator’s gills, causing it to gag, choke and flee. Scientists have known about this repulsive defence for decades, but Vincent Zintzen has finally filmed it in the wild. His videos also prove that hagfish, generally thought to be scavengers of the abyss, are also active hunters that can drag tiny fish from their burrows.
If you go down to the woods of California today, you might be in for a big surprise. At night, the forests crawl with sinuous shapes that glow with an eerie greenish-blue colour. They are Motyxia millipedes and they shine brightly whenever they’re disturbed. “If you go to the right forest and you let your eyes get adjusted to the night, then you can see them everywhere,” says Paul Marek from the University of Arizona. Some big oak tress can shelter 1 glowing millipede in every square metre. They look like fields of stars.
There are around 12,000 known species of millipedes, and only the eight Motyxia species glow. Marek says, “[They] would definitely be on my top 10 for my imaginary “millipede biodiversity global tour” (along with the shocking pink millipede in Thailand & the longest millipede in Africa).”
But why do the Californian ones glow? Marek knows the answer. With hundreds of millipedes, some clay, and a bit of paint, he has shown that they light up to ward off predators. You might expect that the light shows would make the millipedes easier to find and eat. In fact, it deters hungry mouths.
Some parents give their children a head start in life by lavishing them with money or opportunities. The mother seed beetle (Mimosestes amicus) does so by providing her children with shields to defend them from body-snatchers.
A female seed beetle abandons her eggs after laying them. Until they hatch, they are vulnerable to body-snatching parasites, like the wasp Uscana semifumipennis. It specialises on seed beetle eggs and lays its own eggs inside. Once the wasp grub hatches, it devours its host. The wasp problem is so severe that around 70 percent of the beetles’ eggs can be infested.
But the mother seed beetles have a defence, and it is a unique one. Joseph Deas and Molly Hunter from the University of Arizona have found that they can protect an egg from this grisly fate by laying another one on top. Sometimes, the mothers lay entire stacks of two or three eggs. The tops ones are always flat and unviable. They never hatch into grubs and they completely cover the ones underneath.
The African crested rat is a thief, but its loot only becomes obvious if you take a bite out of it. Doing so would give you a mouthful of ouabain, a poison so strong that it can kill an elephant. The rat doesn’t make the poison itself. Instead, it pilfers it from the local Acokanthera schimperi tree. It gnaws on the roots and bark, chews them up, and slavers a coarse toxic gel onto the special hairs on its flanks. Local people use the same poison to coat their arrowheads. The rat uses it as a chemical shield.
The crested rat is found throughout eastern Africa. It is normally sluggish but when threatened, it puts on a vivid display. It pulls its head back, turns sideways onto its attacker and parts the grey fur on its flanks using special muscles. These actions draw attention to a leaf-shaped crest of brown hairs on its side, which are encircled by a “target” of black and white. It’s almost as if the rat is daring a predator to bite it.
Any animal that takes up the invitation is in for trouble. Domestic dogs do so from time to time, and they end up stumbling about and frothing at the mouth. They often die of rapid heart failure. In two cases where the animals survived, they took weeks to recover. For these reasons, people have long thought that the rat is poisonous; now Jonathan Kingdon from the University of Oxford has proved them right.
A bird of prey flies through the skies of Europe and spots a snake on the ground below. Travelling at high speed and soaring at great height, it has mere seconds to decide if it should attack. If the snake is harmless, it could end up with a nice meal. If the snake is venomous, it could get a fatal bite. How can the bird tell the difference? The shape of the head provides a clue.
All of the dangerously venomous snakes in Europe are vipers, like the adder or the horned viper. And all of them have a triangular head. The shape is so distinctive that you can easily recognise these snakes from a distance. And some harmless species like the grass snake, smooth snake and viperine snake use that to their advantage. When threatened, they flatten their narrow heads into a triangle, mimicking the shape of their more dangerous cousins.
The wasp Dinocampus coccinellae is a body-snatcher, or perhaps a “bodyguard-snatcher”. She’s on the hunt for a spotted ladybird. When she finds one, she stings it and lays an egg inside its body. Her grub hatches and starts eating the ladybird alive. Around three weeks later, it bursts out of its host.
But the ladybird doesn’t die. The grub hasn’t consumed all of its internal organs, and it leaves the ladybird partially paralysed but very much alive. Once out, it spins a silken cocoon between the ladybird’s legs and over the next week, it slowly transforms into an adult. Meanwhile, the ladybird stands guard over its own parasite. Its warning colours of red and black should deter would-be predators, and it twitches erratically if threats draw near. Its tour of duty only ends when the adult wasp eventually emerges from the cocoon and flies away.
In Australia, the penalty for burglary is several years in prison. But that’s for humans. For the small hive beetle, breaking and entering into the hive of stingless bees carries a far harsher sentence – being mummified alive in a sticky tomb of wax, mud and resin.