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 Drafts and withdrawn editions are never mixed into this index.
An osprey's outer toe rotates to the rear, letting it hold a fish with two toes in front and two behind. Spiny scales called spicules on the underside of the feet add friction against a slippery, struggling body.
Approaching a crab, the broadclub cuttlefish sends dark bands sweeping forward across its body and arms. Experiments indicate the moving pattern interferes with the crab's ability to detect the approach.
Sulcata hatchlings fit in a hand and are sold cheaply. Adults reach seventy to a hundred kilograms and can live longer than the person who bought them, which is why rescue centres across warm countries are full of tortoises nobody planned for.
Male common wall lizards carry white, yellow or orange throats, and the morph is largely genetic rather than a passing mood. The colours correlate with differences in body size, immune measures and behaviour, though the pattern varies between populations.
Roe deer mate in high summer, but the fertilised egg stops developing and drifts free in the uterus until midwinter. It is the only deer known to use this delay, which lines birth up with spring growth after a summer rut.
The red-eared slider is native to a slice of the American south. It now breeds in Europe, Asia, Africa, Australia and South America, established almost entirely by owners releasing hatchlings that grew larger and longer-lived than expected.
Males repeat a loud two-part bark, usually rendered as to-kay, several times in succession from a perch. The name is onomatopoeic across languages in its range, and the call functions in territorial advertisement rather than as an alarm.
The purse-web spider never leaves its silk sock to hunt. When an insect walks over the buried tube, the spider drives its long fangs straight through the silk from the inside, then cuts the wall open and drags the prey in.
What was long treated as a single wide-ranging giant has turned out to be a cluster of genetically distinct lineages. Decades of moving farmed animals between river systems mixed those lineages before anyone recognised they were separate.
By the standard laboratory measure the inland taipan's venom outranks every other snake tested. No human death has been recorded from its bite, because the snake lives where almost nobody does and retreats rather than confronts.
A startled pademelon strikes the ground hard with its hind feet, producing a low thump that carries through dense forest where sight lines are short. Others nearby respond by freezing or bolting for cover.
The animal best known for hunting penguins spends much of the year filtering small crustaceans. Its cheek teeth interlock into a coarse sieve, and krill can make up a large share of its diet in some seasons and regions.
Temperate bats must line up birth with the summer insect peak despite mating in autumn. Bent-wing bats do it by fertilising the egg immediately and then holding the embryo's development almost still through hibernation.
The blades along a sawfish rostrum are not teeth from a jaw. They are modified dermal denticles, rooted in the cartilage of the snout, and unlike jaw teeth they are not replaced if one is broken off.
A gorgonian fan is a plane, and that plane sits perpendicular to the water flow. The orientation is not aesthetic. It puts the maximum number of feeding polyps into moving water carrying plankton, and a fan facing the wrong way feeds poorly.
Its African and South American relatives burrow through drought inside mucus cocoons. The Queensland lungfish cannot. It has one lung rather than two, functional gills it still depends on, and no estivation behaviour, so a dried pool kills it.
The last wild Arabian oryx were shot around 1972. Animals held in captivity were bred and released, and in 2011 the species became the first to be moved from Extinct in the Wild back to Vulnerable on the IUCN Red List.
Hovering costs more energy per second than almost any other vertebrate activity. Pallas's long-tongued bat meets the bill by routing sugar from a flower straight into working muscle, rather than storing it first, within a few minutes of the sip.
Two reef rays carry blue spots and are routinely swapped in captions, so images labelled ribbontail often show a maskray instead. The giveaway is the tail: only Taeniura lymma has blue stripes running down each side of it.
A living sand dollar is dark purple-brown and covered in a moving felt of short spines. The smooth pale disc that beachcombers collect is its bleached internal test, exposed only after the animal has died and the spines have fallen away.
A singing tui often appears to stop mid-phrase, throat working but no sound emerging. The long-standing explanation is that some notes fall outside human hearing, though recordings have not yet captured them, and very quiet notes would look the same to a watcher.
A single fertilised egg splits into four, so a nine-banded armadillo litter is normally four genetically identical young of the same sex. Obligate polyembryony of this kind is known only in armadillos of the genus Dasypus.
Christmas Island red crabs leave the forest at the start of the wet season and walk to the sea, but the release of eggs is fixed by the moon: females spawn before dawn on a turning high tide in the last quarter, so the water is briefly still.
Grind a blue jay's feather to powder and the blue vanishes, leaving dull brown. The colour is not a dye at all but an optical effect produced by nanoscale air pockets inside the feather barb scattering short wavelengths back to the eye.