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 Drafts and withdrawn editions are never mixed into this index.
A scout hornet that enters an Apis cerana japonica hive is engulfed by hundreds of workers that vibrate their flight muscles. The ball reaches around 46 degrees Celsius, which the bees survive and the hornet does not.
At the Spencer Gulf spawning aggregation, large male cuttlefish guard individual females directly and fight off rivals. Smaller males instead adopt female colouration and posture, hide their fourth arm pair, and are admitted past the guard to mate.
During breeding, female and nestling hoopoes secrete a dark, strong-smelling preen oil carrying symbiotic bacteria. Those bacteria produce antimicrobial compounds that appear to protect eggs and feathers from spoilage organisms.
In dark or muddy water an otter tracks fish by feel. Its stiff facial whiskers detect the hydrodynamic wake a swimming fish leaves behind, allowing pursuit with little or no visual information.
Caecilians are usually described as underground animals, and most are. A small number, including Kaup's caecilian of the Amazon and Orinoco, live instead in rivers, with laterally flattened bodies and a fin along the tail.
Handled roughly, a ladybird leaves a yellow drop on the skin. That fluid is haemolymph forced out through pores at the leg joints, carrying bitter alkaloids, and the beetle's red-and-black pattern advertises it in advance.
Most perching birds put three toes forward and one back; parrots and woodpeckers use two and two. Trogons also use two and two, but it is the second toe that turns backward, an arrangement called heterodactyly unique to the order.
Once a year, in the days around the last quarter moon of October or November, the rear half of the palolo worm breaks off and rises to the surface to release gametes. Islanders time the harvest years in advance.
After mating on land, the male wraps the string of eggs around his hind limbs and carries it for weeks, moistening it when needed, then wades into water only when the larvae are ready to hatch.
Chameleons do not shift colour by moving pigment alone. Panther chameleons have a layer of skin cells containing a lattice of guanine nanocrystals, and by changing the spacing of that lattice they retune which wavelengths of light it reflects.
The shifting rainbow sheen across this snake's scales contains no coloured pigment at all. Microscopic ridges in the outer scale layer split white light into its components, so the colour changes with the angle of view.
Chitons cap the teeth on their rasping tongue with magnetite, a hard iron oxide, mineralised from scratch by the animal. It is one of the very few cases of an animal making a magnetic mineral into a working tool.
Demodex folliculorum lives head-down in human hair follicles and is present on the great majority of adults. It is inherited from close contact in early life, and its genome shows the reduction typical of an animal that has become wholly dependent on one host.
Described in 1866 and then not reliably recorded for over a century, the crested gecko was widely assumed lost. A cyclone-following expedition to New Caledonia found it again in 1994, and captive breeding has since made it one of the commonest pet lizards on earth.
Most marine mammals insulate with fat. The sea otter has almost none, relying on the densest fur known, and pays for it with a metabolic rate two to three times that expected for its size and a near-constant need to eat.
An animal with one of the strongest measured bites among living vertebrates lifts newly hatched young into the pouch at the floor of its mouth and ferries them to water. The same jaws that crush bone close on hatchlings without injuring them.
Until 2018 the slender-snouted crocodile was treated as one species spanning West and Central Africa. Splitting it in two left the western form with a far smaller population and range, and it was assessed as Critically Endangered.
Instead of forcing air through the throat, it throws its body into overlapping C-shaped coils and rubs serrated flank scales against one another, producing a dry rasping sound that carries across open ground.
For decades the mound was described as a chimney driven by nest heat. Measurements in the field showed something else: the outer walls heat and cool through the day, driving air back and forth like a slow lung.
In grass too tall to see through, a serval stands still with its outsized ears rotating, locates a rodent by sound, and pounces onto a spot it has never seen. Its hunting success rate is among the highest recorded for any cat.
Beneath a thin keratin shell, a toucan's bill is a lattice of bony struts and air. The result is a structure roughly a third of the bird's length that adds only a small percentage of its mass.
Dried Lytta vesicatoria was sold for centuries as an aphrodisiac. The active compound, cantharidin, is a caustic toxin, and the effect it produced was urinary tract irritation, with a narrow margin before organ failure.
Nearly every skate seals a single embryo inside each horny capsule. The big skate is an exception: its unusually large cases routinely contain three or four young, and as many as seven have been recorded in one.
Ctenocephalides canis exists, but in most of the world the flea taken from a dog is Ctenocephalides felis. The cat flea is a poor specialist and an excellent generalist, feeding on cats, dogs, humans, ferrets and a long list of wild mammals.