The world’s largest animals have been hiding something. The bodies of the giant rorqual whales—including the blue, fin and humpback—have been regularly displayed in museums, filmed by documentary makers, and harpooned by hunters. Despite this attention, no one noticed the volleyball-sized sense organ at the tips of their lower jaws. Nicholas Pyenson from the Smithsonian Institution is the first, and he thinks that the whales use this structure to coordinate the planet’s biggest mouthfuls.
The Amazonian tree known Hirtella physophora looks rather unassuming, but it is the site of several grisly spectacles. Amid its leaves and branches, an animal, a plant and a fungus conspire to create a nightmarish trap where trespassers become meals, robbers get the death penalty, and assassins are assassinated.
The tree is home to ants called Allomerus decemarticulatus, which defend it from hungry insects. In return, the tree provides the ants with leaf pouches and swollen thorns as shelter, and feeds them with nectar and sugary nodules. These food sources are rich in carbohydrates but low in proteins. To supplement their diets, the ants need flesh, and they get it by shaping the tree into traps.
The ants cut hairs from the plant and weave them together into a hollow gallery, which extends down the side of the tree’s branches. Within the gallery, the ants hide inside small holes, jaws agape. From the outside, nothing can see them. If an insect lands on the trap, hundreds of lurking jaws seize its legs and pull it spread-eagled, as if on a medieval ‘torture rack’. The victim is overpowered and dismembered.
Imagine eating nothing but jelly all your life. It’s hardly the richest source of food, and you might expect an animal with such a menu to be small and feeble. You’d be wrong. The leatherback turtle eats jellyfish and little else, but it grows up to 640 kilograms in weight, and can migrate over thousands of kilometres. How can such a powerful giant subsist on such ethereal meals?
This is not an easy question to answer. Leatherbacks feed well below the ocean surface, and the jellyfish they seek are found in dense but sparse patches. Finding the animals, and studying their eating habits, is very challenging. Mike James from Dalhousie University, Canada, did it by attaching small video cameras to the shells of 19 turtles.
For comparison, the largest fish eye is the 9-centimetre orb of the swordfish. It would fit inside the giant squid’s pupil! Even the blue whale – the largest animal that has ever existed – has measly 11-centimetre-wide eyes.
So why the huge leap in size? Why does the giant squid have a champion eye that’s at least twice the size of the runner-up?
Dan-Eric Nilsson and Eric Warrant from Lund University, Sweden, think that the squid must have evolved its eye to cope with some unique challenge that other animals don’t face. They suggest that the world’s biggest eyes evolved to spot one of the world’s biggest predators – the sperm whale.
“Get off!” “No, YOU get off!” “Okay, we let go on three. One… tw…” “Wait, wait, is that one, two, three and then we let go, or one, two, let go?” “One, two, let go.” “Okay, okay. One… two…” And they both died.
Here is a fatal accident, etched in stone. This fossil comes from Solnhofen in Germany and dates back to the Jurassic period. On the left is Rhamphorhynchus. It’s a pterosaur – one of many flying reptiles that flapped through the skies while the dinosaurs ruled the land. Its arm bones, which supported its leathery wings, stretch out to the left of the image, while its long, stiff tail points downwards. On the right is Aspidorhynchus, a predatory fish with a long, pointed snout.
On first glance, you might think that the fish tried to eat the pterosaur. But Eberhard Frey and Helmut Tischlinger have been studying the fossil in detail, and they think otherwise.
If you ever saw a sawfish, you might wonder if someone had taped a chainsaw to the body of a shark. The seven species of sawfish are some of the wackier results of evolution. They all wield a distinctive saw or ‘rostrum’, lined with two rows of sharp, outward-pointing ‘teeth’. But what’s the saw for?
Barbara Wueringer has an answer: the saws are both trackers and weapons. They’re studded with small pores that allow the sawfish to sense the minute electrical fields produced by living things. Even in murky water, their prey cannot hide. Once the sawfish has found its target, it uses the ‘saw’ like a swordsman. It slashes at its victim with fast sideways swipes, either stunning it or impaling it upon the teeth. Sometimes, the slashes are powerful enough to cut a fish in half. Even less dramatic blows can knock a fish to the sea floor, and the sawfish pins it in place with its saw.
To fans of cheesy pop music, the beat of someone else’s heart is a symbol of romantic connection. To a boa constrictor, those beats are simply a sign that it hasn’t finished killing yet.
A constricting snake like a boa or a python kills its prey by suffocation. It uses the momentum of its strike to throw coils around its victim’s body. Then, it squeezes. Every time the prey exhales, the snake squeezes a little more tightly. Soon, the victim can breathe no more.
We’ve known this for centuries but amazingly, no one has worked out how the snakes can tell when to stop constricting. Scott Boback from Dickinson College has the answer. Through its thick coils, a boa can sense the tiny heartbeats of its prey. When the heart stops, the snake starts to relax.
Philcoxia couldn’t look more unassuming. It’s a small herb that lives in Brazil’s Campos Rupestres region, a sparse plateau of rocky outcrops and white sands. All you’d see of it are a handful of twigs sticking out from the grains, topped with small purple flowers and even smaller leaves. You wouldn’t think that it’s the type of plant that can kill animals.
To find Philcoxia’s grisly secret, Caio Pereira had to look underground. The plant biologist from Unicamp, Brazil, found that the plant traps and digests tiny worms with sticky underground leaves.
A cat-like animal explodes from the long grass and leaps onto an antelope. Its huge bulk drags the target to the ground and its muscled forelegs pin it down. With two long sabre-shaped canine teeth, it stabs its victim in the throat, just the once, severing its blood vessels and windpipe. Death comes quickly.
The hunter could be Smilodon, a sabre-toothed cat that lived throughout North and South America, around one or two million years ago.
Or, it could be a nimravid, another group of hunters that looked like cats, but belonged to a separate, closely-related family. Some of them had sabre-teeth too, and they wielded these weapons between 42 and 7 million years ago, well before Smilodon or its relatives did.
Or, it could be Barbourofelis, a member of yet another group of sabre-toothed not-quite-cats, which lived between 16 and 9 million years ago. Its long sabres slipped into long grooves in its lower jaw, which looked like it was about to melt away.
Many insects are armed with venom, which they can inject into their enemies via a sting. The African ant Crematogaster striatula is no exception, but its arsenal has a disturbing twist – its venom goes airborne. The ant can raise its sting and release its toxins as an aerosol spray. Its targets are termites, whose nests it raids. Even without making any contact, the ants can induce seizures in the termites, eventually paralysing them.
All Crematogaster ants have a mobile sting. The sting sits on the ant’s rear-end, which connects to its torso by a flexible stalk, so the ant can aim it in virtually any direction. Aline Rifflet from the Jean-Francois Champollion University Center saw this ability in action when she watched C.striatula take on termites.