Field notebook
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Field notebook
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Theme trail
This is a live full-text trail through published facts, not a fixed marketing category.
After hatching, ringed caecilian young feed by peeling and eating the outer layer of their mother's skin, which she grows thickened and nutrient-rich for the purpose. They also take a fluid she secretes from the vent.
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 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.
Europe's best-known giant skate was described in 1758 and fished to near extinction under a single name. In 2010 it was shown to be two distinct species that had been lumped together, so the animal on the red list had never been assessed properly.
Satellite tags on Cuvier's beaked whales have logged a dive of 3 hours and 42 minutes off North Carolina, and a separate record depth of 2,992 metres off southern California. Both are the deepest and longest dives recorded for any mammal.
Northern white-cheeked gibbons once sang in the forests of southern Yunnan. Repeated surveys since the late 2000s have failed to find any, and the species is now generally considered extinct in China, surviving only in Laos and Viet Nam.
Male kakapo excavate shallow depressions on ridges and inflate a thoracic air sac to produce a deep boom. The bowl helps project a note low enough to travel kilometres through forest, but so low that females struggle to locate its source.
Crickets and grasshoppers rub one body part against another. Cicadas do something different: a muscle snaps a ribbed plate on each side of the abdomen inwards, rib by rib, and each click of the buckling plate is a pulse of the song.
A robin cocking its head at the lawn is often described as looking, not listening. Aviary experiments point the other way: robins found buried prey with visual, olfactory and vibrational cues removed, and their success fell when white noise masked the sound.
Red touches yellow separates the eastern coral snake from its harmless mimics reliably enough in the southeastern United States. Applied to Central or South American coral snakes, the same rule misidentifies species with dangerous venom.
The three-second goldfish memory is folklore. Laboratory and classroom experiments have shown goldfish learning to press levers, navigate mazes and respond to feeding cues, and retaining those associations for weeks to several months.
A drumming ruffed grouse stands on a log and beats its wings rapidly against the air. The thumping sound comes from momentary vacuums created by the wingbeats, not from the bird striking the log or its own body.
One ear opening is higher than the other, so a sound arriving from above or below reaches them with slightly different intensity and timing. That asymmetry lets a barn owl fix prey in two dimensions and strike accurately in complete darkness.
A marmot family plugs its winter burrow and hibernates together for six to eight months, arousing in loose synchrony. Older non-breeding offspring warm the pups during those arousals, so the young survive winters they could not survive alone.
Losing lungs sounds like a handicap, yet the lungless family Plethodontidae accounts for roughly two-thirds of all salamander species. Breathing through the skin freed the mouth and throat for a projectile tongue instead.
Wild gorilla tool use went undocumented far longer than in chimpanzees or orangutans. The first published record came in 2005, when a female at a forest clearing in the Republic of the Congo picked up a branch and probed the water ahead of her before wading in.
The familiar call is a duet. The sharp kewick comes from one bird, usually the female, and the quavering hoooo from another, usually the male, so a single tawny owl never produces the whole phrase alone.
The name suggests silence, but mute swans hiss, snort and grunt, and their wings produce a loud rhythmic throb in flight that carries far across open water. They are simply quieter than the trumpeting and whooping swans they were named against.
Measured close to the whale, a sperm whale's echolocation click can exceed 230 decibels relative to one micropascal at one metre. The sound is produced not in the throat but by an air-driven clapper at the front of the enormous nose.
A leaping spinner dolphin can complete as many as seven full turns about its long axis before hitting the water. The spin starts underwater, and the animal's tail continues to drive the rotation until the moment it leaves the surface.
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.
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.
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.
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.
Superb lyrebirds are outstanding mimics, but the mechanical sounds that made them famous come almost entirely from captive individuals. Wild lyrebirds overwhelmingly imitate other forest birds, and documented wild chainsaw imitation is vanishingly rare.
Since long-term recordings began accumulating in the 1960s, the tonal calls of blue whales have drifted downward in frequency in every ocean where they have been measured. The shift is small, steady and worldwide, and no explanation has yet been settled on.
Rather than bolting from an ambush hunter that is still at a distance, a golden-rumped sengi slaps the leaf litter loudly. The signal tells the predator it has lost surprise, which for an ambush hunter usually ends the attempt.
Shad detect sound far above the range of most fish, into frequencies used by echolocating dolphins. The ability appears to be an early-warning system, and shad respond to ultrasonic pulses by turning and accelerating away.
Almost all European tits take over existing cavities. The willow tit chisels a fresh chamber into soft, decaying wood each year, which ties the species to dead standing timber that tidy woodland management removes.
During the autumn rut a red deer stag pulls its larynx almost to the breastbone. The move lengthens the vocal tract, drops the resonances of the roar, and makes the caller sound like a larger animal than it is.
Because a cricket's muscles run at ambient temperature, its song speeds up in warm air and slows in cool. Counting chirps over a fixed interval gives a usable estimate of temperature, a relationship first quantified in the 1890s.
The tapping heard in old timber at night was once taken as an omen counted beside the dying. It is a mating signal: the beetle strikes its head against the wood in short bursts and waits for a reply.
Australian magpie swooping is notorious, but it comes from a limited subset of breeding males defending nests for a few weeks, and many individuals never swoop at all. Some birds also appear to target specific people they recognise.
Rather than sweeping the air with loud sonar, the ghost bat hangs from a perch and listens. Rustling footfalls and wingbeats give away mice, small birds and other bats, and the bat drops on them with its wings wrapped around the prey.
Treehoppers make almost no airborne sound. They vibrate the plant stem, and their families communicate along it: a disturbed nymph produces a synchronised group signal, and the guarding mother walks along the branch towards the source and attacks the intruder.
Despite belonging to the genus Panthera, the snow leopard does not roar. Its main long-distance call is a drawn-out, breathy moan, sometimes rendered as a wail or a yowl; chuffing is a separate close-range greeting. Its vocal-fold structure is unlike a lion's.
The young fish is dark blue with concentric white rings, a pattern so unlike the striped adult that the two were once described as separate species. The transformation takes place gradually over roughly two years.
A displaying male skylark climbs to a hundred metres or more and sings without pause while hovering, sometimes for several minutes at a stretch. The song is a near-unbroken stream of trills, sustained by snatched breaths taken in the gaps between phrases.
It locates rodents moving beneath snow by sound alone, then plunges through the crust to seize them. Successful captures have been recorded through snow deep enough to hide the owl completely, sometimes tens of centimetres thick.
A sloth bear is missing its upper central incisors, leaving a permanent gap. It closes its nostrils, digs open a termite mound and sucks the insects through that gap with a noise audible from well over a hundred metres away.
Instead of an open cup in a branch, the ovenbird constructs a domed nest on the forest floor with the entrance at the side, roofed and camouflaged with leaf litter so that it disappears into the surrounding ground.
Homing pigeons combine a sun compass, sensitivity to the Earth's magnetic field, low-frequency sound and, in several experiments, smell. No single sense accounts for the performance, and removing any one of them degrades rather than destroys it.
A paca's zygomatic arches are enlarged and hollowed into chambers unlike anything in another mammal. Air pushed into them appears to amplify a low rumbling call, which makes the paca's skull a rare example of built-in acoustic hardware.
A California sea lion named Ronan was trained to bob her head in time to music and could hold the beat across tempos she had never heard, undermining the idea that rhythmic entrainment requires the vocal-learning brain of a parrot or a human.
The piercing cry played over soaring bald eagles in films and advertisements is almost always a red-tailed hawk. The eagle's own voice is a thin, chattering series of high whistles that sound closer to a gull than to a predator.
A colony of snapping shrimp produces a continuous crackle loud enough to mask sonar returns. During the Second World War, submarines are reported to have sheltered near shrimp beds because the noise degraded the detection equipment hunting them.
The drooping nose of an adult male is not only visual advertising. It acts as a resonating chamber that lowers and amplifies his calls, and nose size correlates with body mass and testis size, so the sound carries honest information about the caller.
A singing male mole cricket excavates a burrow with a bulb-shaped chamber and one or two flared openings. The shape matches the wavelength of his call, and it works as an acoustic horn that couples the sound into the air far more efficiently than his wings alone could.
The claim that a duck's quack produces no echo circulated widely enough that acousticians tested it in a reverberation chamber. It echoes like any other sound; the echo is simply hard to pick out against the call's own fading tail.