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 Drafts and withdrawn editions are never mixed into this index.
Harbour porpoises echolocate with narrow-band clicks centred near 130 kilohertz, far above the frequencies killer whales hear well. The leading interpretation is acoustic crypsis: the porpoise navigates by sound its main predator cannot easily detect.
A system of ligaments and tendons called the stay apparatus lets a horse fix its limbs in extension with almost no muscular effort. The animal can doze upright, but it must still lie down to reach the deepest phase of sleep.
Disturbed peacocks snap their wings open to display four eyespots, and the same motion rubs wing bases together to produce a rasping hiss. Experiments with mice and birds show the sound and the spots deter different predators.
To stay under fast ice through the Antarctic winter, a Weddell seal reams and rasps at the ice around its breathing hole with its canines and incisors. The habit wears the teeth down and, in older animals, can shorten their lives.
The Rhesus factor is named for the rhesus macaque, because the antibody that revealed it in 1940 was raised by injecting rabbits with macaque red cells. The human antigen later turned out not to be the same molecule, but the name stayed.
The female lays a single egg and leaves for the sea. The male balances that egg on his feet under a fold of skin for around two months of darkness and storm, eating nothing, and loses a large fraction of his body mass before she returns.
Almost every octopus reproduces once and then dies. Females of Octopus chierchiae, the lesser Pacific striped octopus, have instead been recorded laying successive clutches over many months while continuing to feed, a pattern first reported in 1984 and confirmed in later laboratory culture.
No other snake ranges so far north. The European adder reaches beyond the Arctic Circle in Scandinavia by giving birth to live young rather than laying eggs, which removes the need for warm ground to incubate a clutch.
Holocephalans are the sister group to all sharks and rays, and the two lineages have been separate since the Devonian. Almost everything odd about a chimaera is a consequence of that long independent history.
A mosquito threads a fine stylet into a blood vessel. A horse fly does the opposite: bladed mandibles scissor the skin open, anticoagulant saliva keeps the wound running, and the fly laps from the pool that forms. Only females do it.
A slow loris raises its arms above its head, draws secretion from a gland on the upper arm into its mouth, and mixes it with saliva. The resulting bite can cause severe tissue damage and, in rare human cases, anaphylactic shock.
The shark-shaped body misleads, but the anatomy does not: the gill slits open on the underside and the pectoral fins fuse to the head. Guitarfish sit in the same order as the sawfishes, their closest living relatives.
Instead of gliding on a muscular foot like most snails, the queen conch plants a sharp claw-like operculum in the sand and levers its whole shell forward in a lurching hop. The gait is fast enough to escape some predators.
The long-standing account of constriction as suffocation is incomplete. Measurements in boa constrictors show that coiling drives prey blood pressure into a collapse severe enough to stop the heart, killing far faster than asphyxiation alone would.
Snakes have no external ear and hear airborne sound poorly. A cobra rising to a snake charmer's pungi is tracking the moving instrument as a threat and holding a defensive posture, not swaying in time to a tune.
A flock of tens of thousands turns as one without a leader. Reconstructions of three-dimensional flock positions found that each bird coordinates with a roughly fixed number of nearest neighbours, close to seven, rather than with everything within a set distance.
A black woodpecker cuts a large oval cavity in a mature trunk and rarely reuses it. Those abandoned holes become nest and roost sites for owls, goldeneyes, jackdaws, martens, bats and hornets across European forests.
The tiger shark's tooth is unlike any other shark's: a broad cockscomb blade with a deep notch and coarse serrations on both edges. The shape works as a can opener, letting the shark shear through sea turtle carapace that other predators cannot breach.
Some adult male orangutans grow wide cheek flanges, a throat sac and roughly double the mass of a female. Others stay small and flangeless for years or decades, and both forms father offspring.
Littorina littorea appeared in the Gulf of St Lawrence in the nineteenth century and spread rapidly southward, reshaping New England shores. Whether it arrived with European shipping or was already present has been argued for over a century.
The froth on a summer grass stem is not spit. A froghopper nymph sits head-down inside it, drinking dilute xylem sap and blowing the surplus into bubbles with air from its abdomen, producing a shelter that hides it and keeps it damp.
The passenger pigeon may have numbered in the billions in the early nineteenth century. Within about fifty years of intensive commercial hunting and forest clearance it was gone from the wild, and the last captive bird died in 1914.
The yellow crown and cheek feathers of a budgerigar fluoresce under ultraviolet light, and in an experiment where that glow was masked with sunscreen, the treated bird became measurably less attractive to potential mates.
In Venezuelan caves, Scolopendra gigantea climbs to the ceiling, anchors itself by its rear legs and hangs down to seize bats as they fly past. The behaviour was documented in 2005 and remains one of the few records of an invertebrate hunting flying vertebrates.