Field notebook
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Field notebook
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Permanent editions
Published facts keep their original date, evidence and correction trail. Drafts and withdrawn editions are never mixed into this index.
Hundreds of thousands of Siamese crocodiles live on commercial farms across Southeast Asia, while the wild population is thought to number only a few hundred adults in scattered wetlands. Farm stock cannot simply replace them, because much of it is hybridised.
A breeding male greater rhea scrapes a single nest and courts a succession of females, each of whom lays into it and leaves. He can end up incubating dozens of eggs from several different mothers entirely on his own.
The rolled-up armadillo of cartoons is real, but it is restricted to one genus of two species. Most armadillos have a shell too tightly fitted to the body to close, and they flee down a burrow instead.
The Bramble Cay melomys lived on a single sand cay a few metres above the sea. Repeated storm surges stripped the vegetation it fed on, and in 2019 Australia declared it extinct, the first mammal whose loss was formally attributed to sea level rise.
East African soda lakes are strongly alkaline, with pH values above ten, and run hot from geothermal springs. Lesser flamingos wade and filter-feed in them, protected by tough leg skin and by drinking freshwater from seeps at the shore.
In May 2015 around two hundred thousand saiga died across central Kazakhstan in roughly three weeks, most of a global population. The killer was a bacterium that normally lives harmlessly in the animals' own tonsils.
The hind talon of a large female harpy eagle can reach around twelve centimetres, comparable to the claw of a grizzly bear. Those feet are the whole hunting strategy: this eagle kills by grip, not by speed.
A female echidna develops a pouch only during the breeding season, deposits a single leathery egg directly into it, and carries the egg there for about ten days until it hatches. The pouch then disappears again.
A female fills a nest tube from the far end outwards and controls the sex of each egg. Females go in the protected inner cells and males in the outer ones, so predators and parasites reach the expendable sex first.
Japanese giant salamanders breed in riverbank burrows controlled by one dominant male, known as a den-master. He admits females, fertilises the eggs of several in the same chamber, and then stays to fan and defend the clutch for months.
A guillemot lays one egg on bare rock with no nest at all. The egg is sharply pointed at one end, and the shape has long been explained as an anti-rolling device, though the mechanism behind that has been repeatedly revised.
Female rosy-faced lovebirds strip long pieces of bark and leaf and wedge them among their rump feathers, flying to the nest with a bundle stowed on their back rather than carried in the bill.
A terrapin lives in salt marsh but cannot drink salt water. When rain falls, a thin layer of fresh water sits briefly on top of the denser salt water, and the terrapin surfaces to skim it before the two mix.
Female Osedax have no mouth or gut. They grow root-like tissue into sunken bone, secrete acid to dissolve the mineral matrix, and rely on internal symbiotic bacteria to make use of the bone's collagen and lipids.
A nurse shark rarely chases anything. It places its small mouth against a hole and expands its large throat cavity, generating suction strong enough to pull an octopus, conch or spiny lobster out from cover in a fraction of a second.
An aye-aye runs its skeletal middle finger along a branch at up to eight taps a second, listens to the returning sound with outsized ears, then gnaws through the bark and hooks the larva out with the same finger. No other primate forages this way.
To become nearly transparent while resting, one glass frog packs almost all of its red blood cells into its liver. The trick would normally cause fatal clotting, and how the frog avoids that is unresolved.
Rotating ankle joints let the clouded leopard turn its hind feet backwards, so it can descend a trunk head-down, hang beneath a branch by its hind feet, and move through the canopy in ways most cats cannot.
A gibbon swinging beneath a branch does not twist its shoulder to turn. Its wrist carries a ball-and-socket joint, so the body rotates freely under a stationary hand, which is why brachiation looks so unhurried.
A breeding female great hornbill walls up the entrance to her tree cavity from within, leaving a slit. She moults inside, and the male passes every meal through the gap for months until she breaks out.
Amia is the only surviving genus of the Amiiformes, an order well represented in the fossil record from the Jurassic onward. Since 2022 it has held two living species rather than one, after genetic work split the eyespot bowfin from Amia calva. Everything else in the branch is extinct.
The thick white band running through an Argiope web has been studied for over a century. At least five functions have been proposed, experiments support several of them, and no one explanation accounts for where and when the decoration appears.
Where pine martens have recovered in Ireland and Britain, invasive grey squirrels decline and native red squirrels increase. The predator does not distinguish between them; the two squirrels differ in how well they avoid it.
In green anacondas the female can be several times the mass of a male. Dozens of males may coil around a single female in a breeding ball that lasts for weeks, and the female sometimes eats one of them.