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 Drafts and withdrawn editions are never mixed into this index.
The red admiral was long treated as an annual immigrant to Britain that could not survive the cold season. Records of adults active in midwinter and of overwintering success have accumulated as winters have warmed, changing how the species is classified.
In the Taï Forest of Côte d'Ivoire, chimpanzees crack armoured nuts with stone and wooden hammers. Infants watch and fumble for years before they succeed, and whole populations living beside the same nuts and the same stones never crack them at all.
Newborn emerald tree boas hatch internally and emerge brick red, orange or yellow. They shift to the adult green over their first year or so, a change that appears to track a move to different heights and light in the forest.
An aye-aye drums a branch with a wire-thin middle finger, several taps per second, while swivelling its ears to read the echoes. Where the sound reveals a cavity, it gnaws through with rodent-like incisors and hooks the larva out with that same slender finger.
A gliding Chrysopelea flattens its ribs into a shallow C-shaped cross-section and continues to undulate throughout the flight. Wind-tunnel and motion-capture work shows the undulation is not leftover slither; a snake that stops moving tumbles.
A honey badger's hide is thick and only weakly attached along much of its body. An animal seized by the back of the neck can rotate inside its own skin far enough to bite whatever is holding it.
The size gap between the sexes is among the largest of any bird, with females roughly twice the mass of males. The two hunt different prey as a result, which is thought to widen the range a pair can exploit while breeding.
Behind the walleye's retina sits a reflective layer called the tapetum lucidum, which bounces light back through the light-sensing cells. It gives the fish its glassy shine and a hunting advantage in low light that its prey does not share.
By clearing depressions in the marsh, alligators create pools that persist after the surrounding wetland dries. Fish, turtles, invertebrates and wading birds concentrate around them, which is why the alligator is treated as an ecosystem engineer rather than merely a large predator.
The male fiddler crab's oversized claw is used for waving and fighting, not eating. If he loses it, the small feeding claw on the other side can enlarge to take over the display role, and the regrown limb comes back small.
Trichoplax has no mouth, gut, nerves, muscles or symmetry. It is a flat sheet of a handful of cell types that crawls over surfaces and digests food by pressing its underside against it.
King crabs belong to the hermit crab lineage, not to the true crabs. The evidence is in the count: a king crab walks on three visible pairs of legs, because the fourth pair is reduced and tucked inside the gill chamber.
The famous cackle is not amusement but a group territorial signal, usually given at dawn and dusk by a family party in chorus. Neighbouring groups answer, and the exchange marks boundaries without the birds having to meet.
The Central African slender-snouted crocodile was separated from its West African relative in 2018, using skull measurements from historical museum specimens alongside modern genetics. A name proposed in the nineteenth century was resurrected for it.
Snailfishes have been collected from about 8,000 metres in the Mariana Trench, and since 2022 both filmed and caught deeper still off Japan. Those depths sit close to the point at which fish physiology is predicted to fail.
A woodlouse in a dry garden shed is a marine animal's descendant carrying its ocean anatomy on land. It breathes through gill-like structures on its underside, which is why it dies quickly in dry air and hides under damp wood by day.
Its body is olive, grey or gunmetal brown. The name comes from the inside of the mouth, which the snake gapes open in threat to show a lining so dark it reads as black against the pale gums of other species.
No individual green darner completes the annual round trip. Isotope work on museum and field specimens showed a migratory generation flying north, its offspring flying south, and a third, non-migratory generation overwintering in the south before the cycle restarts.
European sailors called this flightless North Atlantic bird the penguin long before anyone reached Antarctica. When explorers met similar black-and-white divers in the southern ocean they reused the name, even though the two groups are not closely related.
A squirrel monkey's brain is roughly one-fortieth of its body mass, a higher proportion than in humans, whose ratio is nearer one in fifty. The comparison is real but misleading, because small animals routinely carry proportionally larger brains.
A patch of specialised quills on the streaked tenrec's back can be vibrated against one another to produce a high-pitched signal. Stridulation is common in insects; among mammals, this is the only case known.
Analysis of hundreds of indri songs found intervals clustering at ratios of one to one and one to two, the same categorical rhythms that underlie human music. It was the first such pattern reported in a non-human mammal.
Devil facial tumour disease is not caused by a virus. The cancer cells themselves pass from animal to animal through biting, making it one of only a handful of transmissible cancers known in nature.
A female water opossum dives with young aboard. A ring of muscle draws her rear-opening pouch closed and a greasy secretion seals it, keeping the young dry through dives that last well under a minute.