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 Drafts and withdrawn editions are never mixed into this index.
Before the dry season, grey mouse lemurs lay down fat in the base of the tail, which can thicken noticeably. They then drop their body temperature and enter daily torpor, cutting energy use during months when insects and fruit are scarce.
Water is drawn in through millions of tiny surface pores and expelled from the central opening. A large individual processes many times its own body volume every minute, stripping bacteria and dissolved organic matter from reef water.
The rufa red knot times its stop in Delaware Bay to the spawning of horseshoe crabs. The eggs are soft and abundant enough for a bird to nearly double its mass in a fortnight, which is why a crab harvest thousands of kilometres from the Arctic affects Arctic breeding.
In cold northern waters a bullfrog larva may overwinter twice or more before metamorphosing, growing to fifteen centimetres. In warm southern ponds the same species transforms within a single season.
Trinidad's guppies gave biologists a rare thing: evolution on a schedule short enough to watch. Moved from high-predation to low-predation streams, male guppy populations became measurably brighter and later-maturing within a few dozen generations.
The gold in the web is not a trick of the light. The silk itself contains yellow pigments, and their concentration varies, which suggests the colour is being adjusted rather than simply produced as a by-product.
Every night a vast layer of small fish and squid rises toward the surface, and every dawn it sinks again. Bigeye tuna go down with it, spending daylight hours in cold, dim water hundreds of metres deep that other tropical tunas avoid.
Nearly every pit viper in the New World gives birth to live young. The bushmaster lays a clutch of eggs and the female coils around them until they hatch, a combination found in no other American viper.
Couch's spadefoot spends most of the year buried in desert soil. Heavy summer rain brings it to the surface almost immediately, and eggs laid that night can hatch within a day or two.
New Zealand had no land mammals apart from bats before humans arrived. In their absence, large flightless insects took up ground-level browsing and shelter-seeking habits, which is why the wetapunga is often described as an ecological stand-in for a mouse.
Guinea worm disease spreads through drinking water because the parasite's larvae live inside Cyclops copepods. Eradication has depended less on medicine than on filtering those millimetre-long crustaceans out of the water.
A chipmunk does not fatten up and sleep through. It fills an underground larder with several thousand seeds and nuts, then alternates bouts of torpor with arousals in which it eats from that store, because its winter fuel is cached food rather than body fat.
Buried in leaf litter with only its head exposed, it twitches a thin, pale tail tip in front of its own snout. Lizards and birds that approach what looks like a grub are struck from a distance of a few centimetres.
A vicuna's fibre measures around twelve micrometres, finer than cashmere and finer than the best merino. Inca law reserved the cloth for royalty, and modern harvesting still depends on catching wild animals, shearing them and letting them go.
The trumpeter's deep resonant call comes from anatomy, not effort. Its trachea loops into a hollow chamber within the sternum before turning back to the lungs, lengthening the air column and lowering the pitch, much as extra tubing does in a brass instrument.
Its hinged front fangs can approach five centimetres, longer than those of any other snake measured. They fold flat against the roof of the mouth when closed and swing forward only as the strike lands.
The arm does not simply snap under strain. Specialised breakage planes in each arm segment let the animal choose where to part company with a predator, and the lost length regrows over weeks to months.
On parts of the British Columbia coast, roughly one black bear in ten carries two copies of a recessive variant that produces a cream-coloured coat. These Kermode or spirit bears are not albinos and not a separate species.
Those long hindwing streamers are not decoration. Their twisted tips return a strong, moving echo that draws attacking bats away from the body, and moths with the tails removed are caught far more often in controlled trials.
Rather than dropping the lower jaw, dusky salamanders raise the upper jaw and skull by levering against a modified neck and jaw joint. The arrangement gives a small streambank salamander an unusually forceful bite.
In a stoop a peregrine can exceed 300 kilometres per hour, fast enough that incoming air would otherwise make breathing difficult. Small bony cones inside each nostril are widely held to break up that airflow, although the mechanism has not been tested directly.
Flying towards an object raises the pitch of the returning echo. Horseshoe bats lower the frequency they emit to cancel that shift, holding the echo steady in a narrow band their inner ear is exquisitely tuned to hear.
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 sable antelope is not born black. Calves are a plain reddish brown, and only mature bulls turn the glossy black that gives the species its name, with cows in many populations staying chestnut for life.