The Amazon river dolphin's pink comes from blood vessels near the skin that flush with exertion or excitement, like a blush.

Lionesses do most of the killing. Males often eat first by size and intimidation, then defend the territory.

While a moon jelly's muscle rests, water swirling under its refilling bell pushes it about 30 percent farther per pulse.

Some male garter snakes leave the den smelling like females. The swarm of warm males that mobs them heats them up fast.

A mother cheetah calls her cubs through tall grass with a bird-like chirp that can carry well over a kilometre.

A gland above each eye pulls salt from a penguin's blood and makes brine two to three times saltier than seawater.

Octopus blood is blue because it carries oxygen with copper instead of iron.

Researchers estimated around 17,000 Grauer's gorillas in the 1990s. After two decades of war, fewer than 4,000 remained.

Pectoral muscles can account for around 30% of a raptor’s body weight, the engine of every wingbeat.

At the age a human infant sleeps 16 hours a day, a dolphin calf is swimming, and its mother stays in motion beside it.

A returning emperor finds its mate and chick among thousands by voice alone, with a call built from two tones at once.

Sharks have been around for 450 million years. They were swimming in the ocean before trees existed.

A silverback's chest beat carries a kilometre through the forest. The deeper the thump, the larger the chest behind it.

The last mammoths were still alive around 1650 BCE, when the pyramids of Giza were already a thousand years old.

Blue ringed octopuses carry enough venom to kill a human, yet they are barely larger than a golf ball.

A mother cheetah sometimes frees injured prey for her cubs to chase, a kind of teaching recorded in few other carnivores.

Crows pair for life. A male courts by bowing and offering food, and the bond can last a decade or more.

A male African lion can weigh up to 250 kilograms, roughly four adult humans packed into one animal.

At its peak, one winter crow roost in Auburn, New York, held an estimated one million birds.

Curling its lip loads a second smell organ, so one scent mark tells a tiger the marker's identity, sex and breeding state.

About ten vaquitas survive. They drown in gillnets set illegally for totoaba, a fish whose swim bladder sells for fortunes.

A three-month cub stalking a blowing leaf is rehearsing the moves that, a year and a half later, bring down a sambar stag.

Dogs read hormones and identity with a second smell organ humans lack: the vomeronasal organ.

Each gorilla old enough builds a fresh nest every night, so reliably that researchers census gorillas by counting nests.

All the male humpbacks in one ocean basin sing the same song at any given moment, and it drifts through the season.

A varroa mite the size of a pinhead ferries at least five viruses between bees, one of which leaves wings too stunted to fly.

Fewer than about 350 North Atlantic right whales remain, and deaths from entanglement and ship strikes outrun births.

Leafcutter trails and nest routes often converge on networks as efficient as engineered designs.

Eagle eyes are so large relative to the skull that they barely rotate. Necks turn instead, up to about 270 degrees.

A single great white can produce and shed tens of thousands of teeth in a lifetime, with rows waiting behind the first.

An octopus has about 500 million nerve cells, and most of them live in the arms, not the head.

A narwhal's tusk is its left canine tooth, and millions of nerve endings let it read salinity and temperature.

A moon jelly is 95 percent water. The other 5 percent built a design that has lasted at least 500 million years.

Common dolphins can form schools in the hundreds of thousands, the largest gatherings of any whale, dolphin or porpoise.

A large male bear may kill another male's cubs, because a mother who loses her cubs is ready to mate within weeks.

Where Anatolian shepherd dogs guard the goats, farm killings of cheetahs have fallen by about 80 percent.

Half a million fire ants can solve a flood by linking leg to leg into a living raft.

An elephant calf weighs one hundred kilograms on its first day and stands within twenty minutes of birth.

Blueberry flowers release pollen only to a buzz at one frequency, which bumblebees make with their wings held still.

Inland grizzlies may top out near 250 kilograms. On salmon rivers in coastal Alaska, big males of the same species pass 500.

New Caledonian crows cut tools from pandanus leaves, and the tool designs differ between regions of the island.

Elephant skin runs up to three centimetres thick on the back, yet it can still register the weight of a single fly.

After a fight, one rook may comfort its distressed partner. It was the first such empathy case found outside mammals.

Shark livers can make up to 30% of body weight. The oil provides buoyancy in place of a swim bladder.

Related lionesses form the stable core of the pride, hunting, nursing, and defending territory together.

The last wild Hawaiian crow vanished in 2002. The species survived only because a few dozen birds were already in captivity.

Hammerheads gather in schools of hundreds. That is one of the most social sights in the shark world.

Fine hair-like sensors on a spider's legs can detect the air wake of a flying insect several centimetres away.

At night a tiger sees about six times better than a human, helped by a reflective layer behind the retina.

Dogs can find a human footprint on grass three days after it was left.

A sperm whale can dive to about 3,000 metres and hold its breath for about ninety minutes.

The crystal jelly's green glow lets researchers watch genes switch on. The work earned the 2008 Nobel Prize in Chemistry.

The hallux talon can exceed 130 kilograms per square inch, more than enough to pierce bone.

Cubs spend 1.5 to 2.5 years with their mother, learning her foraging methods, her seasonal timing and which habitats pay.

The paradise tree snake flattens its body to generate lift and glides up to 100 metres, outperforming most flying squirrels.

A dog’s nose holds about 300 million scent receptors. A human nose holds about 6 million.

No ant is in charge. Colony intelligence emerges from millions of simple local rules.

The Gooty sapphire tarantula lives in a small patch of southern Indian forest, and it is critically endangered.

Male coalitions of two to four lions often hold a pride together against rivals.

During musth, a bull elephant's testosterone climbs to sixty times its normal level for weeks or months.

An octopus can pour its entire body through a hole the size of a coin. If the beak fits, the rest follows.

A summer colony of 60,000 to 80,000 honeybees replaces itself at a peak rate of about 1,500 new bees a day.

In 2005 a wild gorilla tested a pool's depth with a long branch, one of the first records of wild gorillas using tools.

A cheetah eats in a hurry because its kill draws stronger animals. Heavy bones and skulls stay for the hyenas.

Spiders were on land at least 380 million years ago, more than 150 million years before the first dinosaur.

A constrictor tightens its coils each time its prey breathes out, until the lungs can no longer inflate.

Males spend around 20 hours a day resting. Their main job is holding territory, not leading every hunt.

Young wolves eventually disperse, sometimes for hundreds of kilometres, to start packs of their own.

Most octopus species live only one to three years, and they learn almost everything alone.

A chinstrap guarding its eggs sleeps four seconds at a time, more than 10,000 times a day.

The only hard part of an octopus is its beak. Everything else is muscle and skin with no fixed shape.

A flying bee builds a static charge, so pollen grains jump the last air gap onto its hairs before it lands.

Some fishing spiders subdue fish up to five times their body weight, then drag the catch to shore to feed.

The Asiatic cheetah survives only in Iran, perhaps 12 to 40 animals, cut off from every African cheetah.

When a dog breathes, part of the air peels into a dedicated smell chamber. Smell and breathing run in parallel.

The diving bell spider is the only spider that lives its entire life underwater, in a silk dome of air.

Wild African elephants have been recorded sleeping near two hours a day, much of it standing up.

Penguins porpoise, leaping clear of the surface, so they can breathe without slowing and scan below for seals.

The extinct penguin Kumimanu fordycei is estimated at 159 kilograms, heavier than two grown men.

Eagles have two foveas in each eye: sharp focus forward and a second patch for tracking prey below.

A tiger cub stays with its mother for two to two and a half years, the longest social bond in a tiger's life.

American crows recognise a researcher years after one bad encounter, and recruit their neighbours to mob that person.

The fuel that powers 200 kilograms of gorilla muscle is made by gut bacteria fermenting salad.

A snake is essentially a very long spine, with 100 to 400 vertebrae depending on the species. A human spine holds 33.

A bear rubs scent onto a chosen tree that tells other bears who it is, its sex, its size and whether it is ready to mate.

An eagle soaring at 300 metres can see a mouse moving in the grass below.

In the Sundarbans the delta ground is sinking while the Bay of Bengal rises faster than the global average.

A single ant brain has about 250,000 neurons, but a colony of thousands can solve floods, farms, and routes.

A wolf can scent prey from up to 2.4 kilometres away and travel 80 kilometres in a single night.

Run a hand from head to tail and shark skin feels smooth. Reverse it and the dermal denticles bite like sandpaper.

The blue whale's heart is the size of a small car, and it beats about eight times a minute.

Wild dolphins create and pass bubble rings, surf boat wakes for the rush, and invent games with no survival payoff.

Japanese honeybees ball around a hornet scout and heat it to about 47 degrees Celsius, a few degrees below what kills them.

When something attacks the crown jelly Atolla, it flashes a spinning wheel of blue light to summon something bigger.

A polar bear finds a seal's breathing hole by smell alone, then may wait hours or days, nearly motionless, for one strike.

A true roar can carry up to eight kilometres in still air, broadcasting across a territory the size of a small city.

The king cobra grows up to 5.5 metres, the longest venomous snake on Earth, and it specialises in eating other snakes.

Serengeti studies recorded 50 to 90 percent of cheetah cubs dying in their first three months.

Mountain gorillas were down to around 250 in the late 1960s. Now they are the only great ape subspecies on the rise.

A big lion's mane spreads its bell over 2 metres and trails tentacles more than 30 metres long, longer than a blue whale.

A male emperor penguin holds one egg on his feet for about 65 days of winter darkness, fasting the whole time.

Sharks navigate open ocean with layered senses. Smell, vibration, and electric fields each work at different ranges.

In the waggle dance, about 75 milliseconds of waggling stands for every 100 metres of flight to the food.

Lions are the only wild cats that live in groups. Every other big cat hunts alone.

A single ant can carry 50 times its own body weight. Scale that up and you are lifting a cement truck.

Urban crows eat huge numbers of crane fly and beetle larvae that damage lawns. The pest control is real, if mostly unthanked.

On Santa Catalina Island, with few large mammals to warn, one rattlesnake population has partially lost its rattle.

Almost every adult sperm whale carries pale ring scars, some as big as a dinner plate, left by giant squid suckers.

In some Congo Basin sites, one forest elephant population's menu has been counted past 500 plant species.

A newborn gorilla weighs about two kilograms and clings to a mother who may weigh 40 to 50 times as much.

A great white can detect one part blood in a million parts seawater, roughly 400 metres away under ideal conditions.

A gaboon viper's pattern copies fallen leaves so closely it is effectively invisible, and it can hold an ambush for days.

Java's extinct Ngandong tiger may have outsized today's largest Amur male by half, and shared its island with early humans.

In parts of Sichuan, farmers climb ladders each spring to pollinate apple and pear trees by hand, blossom after blossom.

Cave bears denned in the same caverns for thousands of years. A single cave can hold the bones of tens of thousands.

An octopus can send two different visual messages at once: one pattern for a rival, another for a mate.

A young horse mackerel can ride among a barrel jellyfish's oral arms, a shelter larger predators hesitate to approach.

Most spiders have six spinnerets, and each one can feed a different silk recipe for a different job.

A leopard seal is three metres long and half a tonne, and it ambushes penguins at the ice edge.