Rainforest Animals

The Assassin Bug glues the drained corpses of its victims onto its own back, building a tower of bodies taller than itself.

Why it works: When an assassin bug stabs prey with its sharp beak, it injects saliva loaded with venom and digestive enzymes -- special chemicals that break body tissue down into mush. This is digestion happening OUTSIDE the body: the prey's insides turn to soup so the bug can suck them up through its strawlike beak, leaving an empty shell. Scientists think the bug saves those shells and glues them on its back because the messy pile breaks up its outline, so a hunting spider can't tell it's a tasty bug -- though exactly why the trick fools predators is still being studied.

The Bowerbird builds an entire decorated gallery out of sticks just to win a mate.

Why it works: A male bowerbird is not really making "art" the way a person does. He does all this because females will only mate with a male whose display passes a tough test, so the fanciest, most patient builders win. The size trick is real physics: things look smaller the farther away they are, so by putting small objects near the female and big objects far back, everything looks about the same size. This "forced perspective" makes the court look tidy and may make the male himself look bigger and more impressive. Scientists think the long hours of work are an honest signal that he is healthy, sharp-eyed, and good with detail.

The Cassowary has a dagger-shaped claw up to five inches long on each foot, and can slash with a single kick.

Why it works: A cassowary's kick is dangerous mostly because of physics. Its big, muscly legs are built for sprinting through thick forest, so they can swing with a lot of force. That force gets focused onto one sharp, dagger-shaped claw on the inner toe, made of keratin (the same stuff your fingernails are made of). Pushing a big force through one narrow, pointed claw is what lets it slice, the same way a pencil tip pokes harder than your flat hand.

The Chameleon fires a sticky tongue twice the length of its whole body in about a hundredth of a second.

Why it works: A chameleon's tongue works like a tiny bow and arrow. First, a muscle slowly stretches stretchy tissue (made of a protein called collagen) wrapped around a bone in the tongue, squeezing energy into it like a pulled-back rubber band. When the chameleon lets go, that stored energy snaps free all at once and flings the sticky tip forward way faster than any muscle could push on its own. That stretch-and-release trick is what makes the tongue blast out in about a hundredth of a second to grab a bug.

The Electric Eel can generate up to 860 volts — enough to stun a horse.

Why it works: An electric eel's body is packed with thousands of special cells called electrocytes, lined up like the cells inside a battery. Each one is a flat, modified muscle cell that makes only a tiny voltage (about 0.15 volts), but when the eel's brain sends a signal, it releases a chemical that opens tiny gates in the cells so sodium particles rush in and flip each cell's charge. Because all the cells fire at the exact same instant and are stacked in a long line, their tiny voltages add up into one huge jolt of up to 860 volts. The eel also has organs that send out gentle electric pulses, and it senses how those pulses bend around hidden fish, which is how it 'sees' prey in muddy water.

The Glass Frog has see-through skin, so you can watch its heart beat through its body.

Why it works: A glass frog looks see-through because of what its blood is doing. Red blood cells soak up green light and shine back red, so flowing blood is the easiest part of the frog to spot against a green leaf. When the frog sleeps, it pulls almost 90% of those red cells out of its blood and tucks them into its liver, which is lined with tiny mirror-like crystals that hide their color. With the red cells stashed away, light passes through the frog's muscles and skin instead of bouncing off, so its outline blurs into the leaf and predators looking up from below can't tell where the frog ends and the leaf begins.

The Goliath Birdeater flicks a cloud of tiny barbed hairs off its belly that lodge in eyes and skin and burn for hours.

Why it works: Those itchy hairs aren't really hairs at all. They are tiny, stiff bristles called urticating hairs, and under a microscope each one is covered in backward-pointing barbs, like a miniature harpoon. When the spider feels threatened, it rubs its back legs over its belly and flings a cloud of these bristles into the air; the barbs snag in soft wet places like eyes and skin, and because they point backward they are hard to brush out, so they keep poking and irritating for hours. The 'hiss' is a trick called stridulation: the spider scrapes rough, hooked hairs on its legs against each other, making a buzzing sound the same way running your finger over a comb does.

The Leaf Sheep runs on sunlight like a living solar panel.

Why it works: A chloroplast is a tiny green machine inside plant and algae cells that uses sunlight to make sugar. The leaf sheep eats green algae but does not destroy these machines. Instead it stores the still-working chloroplasts in the leafy parts on its back, where they keep catching sunlight and making food the slug can use. Scientists are still puzzling out exactly how the slug keeps these stolen machines alive for so long, since it does not carry the algae's repair instructions.

The Lyrebird can perfectly imitate a chainsaw, a car alarm and a camera shutter.

Why it works: Birds don't sing with a throat box like ours. They use a special organ called a syrinx, deep in the chest where the windpipe splits toward the lungs. Tiny muscles squeeze and stretch this organ while air rushes through, changing the pitch and shape of the sound, and a songbird can control its two sides separately to make two sounds at once. The lyrebird has an unusually specialized syrinx plus a great memory for sounds, which lets it copy almost anything; but scientists are honest that they don't fully understand exactly why this bird is such a perfect mimic when other birds aren't.

The Mantis Shrimp throws the fastest punch on Earth, at the speed of a bullet.

Why it works: The shrimp's club isn't powered by muscle alone. Muscles slowly bend a tiny springy, saddle-shaped piece of its shell, storing energy like a loaded bow, while a little latch holds it in place. When the latch lets go, all that energy releases at once, so the club shoots out at the speed of a bullet. It moves so fast the water behind it can't keep up and briefly turns to vapor, making bubbles that collapse with a flash of light and a burst of heat, adding a second hit. (Its eyes really do have up to 16 color receptors, but scientists found it doesn't see colors more finely than we do; it uses the extra receptors to recognize colors super-fast instead.)

The Orchid Mantis lures bees better than a real flower does, so pollinators fly toward it instead.

Why it works: A flower lures bees with its color and with the way it soaks up ultraviolet (UV) light, which bees can see but people cannot. The orchid mantis fakes both: its petal-shaped legs and body match the color and UV pattern of nearby flowers so closely that, to a bee's eyes, the mantis looks just like a blossom. The bee flies in expecting nectar, and the mantis's strong, spring-loaded front legs snap shut on it. Its shade can slowly shift between whiter and pinker as it grows, but scientists are still working out exactly what controls that change.

The Pistol Shrimp snaps its claw fast enough to create a bubble nearly as hot as the surface of the sun.

Why it works: Here's the surprise: it's not the claw smacking shut that makes the bang. When the claw snaps closed, it squirts out a jet of water so fast that the water pressure inside the jet drops, and the water boils into a tiny vapor 'bubble' even though it's cold. A heartbeat later that bubble collapses and crushes the vapor inside so hard and so fast that it briefly heats to almost 5,000 degrees, flashes a speck of light, and bangs out a shockwave. So the heat, light, and loud crack all come from the bubble popping, not from the claw itself.

The Sloth only poops about once a week.

Why it works: A sloth eats only tough leaves that give very little energy, so its whole body runs in slow motion to save fuel. Digesting one leafy meal can take weeks, so waste builds up slowly until a big pouch in its gut is full, which is why it only goes about once a week. Why it then risks the dangerous climb to the ground instead of dropping waste from the trees is still debated: some scientists think the poop feeds tiny moths and algae that live in its fur, while others think the buried waste leaves a smell message to help sloths find a mate.

The Tarsier can rotate its head almost a full half-circle in each direction, just like an owl.

Why it works: A tarsier's eyeballs are so gigantic that each one fills its eye socket completely, leaving no room for the tiny muscles that would normally swivel an eye around. So instead of moving its eyes, the tarsier moves its whole head, using a super-bendy neck to swing it almost halfway around in each direction, just like an owl. The eyes grew this huge because tarsiers hunt in the dark and, unlike many night animals, their eyes have no mirror-like layer to bounce light around, so they have to be enormous to soak up every bit of dim light.

The Wood Frog can freeze into a solid lump of ice every winter and thaw back to life in spring.

Why it works: When ice starts touching a wood frog's skin, its liver gets a signal and quickly turns its stored sugar (glycogen) into lots of glucose, pumping this sugary 'antifreeze' into the blood and all its cells. The trick is WHERE the ice forms: water gets pulled out of the cells and freezes in the spaces between them, so the delicate insides of cells stay liquid. The glucose keeps too much water from leaving each cell, stops the cells from shrinking too far, and blocks sharp ice from forming inside them. With its blood frozen in place the heart has nothing to pump, so it simply stops until spring thaws everything out.