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 Drafts and withdrawn editions are never mixed into this index.
Common marmosets have lower incisors as long as their canines and reinforced with enamel on the front face only, forming a chisel. They gouge holes in tree bark, return to the same wounds for weeks, and live on the exudate through the dry season.
Almost no deep-sea animal can see red light, which makes the stoplight loosejaw's red searchlight private. To detect its own beam, the fish uses a retinal pigment derived from chlorophyll it cannot have made itself.
Russian desmans belong to the mole family but live in rivers. They swim with webbed hind feet and a flattened tail, keep burrow entrances below the waterline, and locate prey with a snout that works as a probe rather than with eyes.
Fork-tailed drongos in the Kalahari follow meerkats and babblers, giving genuine warnings of predators. They also give false alarms when a forager finds a large item, and take the food that is dropped as the victim flees.
A male tungara frog calling for a mate broadcasts his location to something else as well. The fringe-lipped bat listens in, distinguishes edible species from toxic ones by call alone, and approaches without needing to see the frog at all.
Archaeological and genetic evidence places dog domestication in the late Pleistocene, thousands of years before any crop or livestock species was tamed. The animals that became dogs joined hunter-gatherers, not farmers, which reorders the usual story of domestication.
The population in Palau's marine lake crosses the basin each day, tracking sunlight eastward in the morning and westward in the afternoon. The journey feeds the algae in their tissues and keeps the jellyfish away from the anemones on the shaded shores.
Juveniles and small males of Tremoctopus tear fragments of stinging tentacle from the Portuguese man o' war and hold them in their suckers, apparently using the borrowed nematocysts for defence and prey capture.
Most fruit-eating monkeys swallow seeds and disperse them. Sakis do the opposite: splayed canines and thick-enamelled molars let them open hard unripe husks and mill the seeds inside, making them seed predators rather than dispersers.
The diabolical ironclad beetle withstands compressive forces around 39,000 times its own body weight. The strength comes not from a thicker shell but from a jigsaw-shaped suture that fails gradually instead of snapping.
American coot chicks hatch with vivid orange plumes on the head and neck that fade after a few weeks. Experiments in which the plumes were trimmed showed parents preferentially fed the brightest chicks, making the colour a signal rather than decoration.
Rather than descending to a pond, the Amazon milk frog breeds in water trapped in canopy cavities. Males call from inside the hole, and the tadpoles develop in a pool that may hold only a few litres.
Given two containers and a shake that revealed food in only one, the African grey parrot Griffin chose the silent container. The result suggested inference by exclusion, a form of reasoning long thought to be rare outside apes and young children.
A velvet worm hunts by squirting adhesive from two nozzles on its head. The jets whip from side to side dozens of times a second, and high-speed filming showed the oscillation is not muscular steering but an elastic instability driven by the flow itself.
Snow goose numbers rose steeply once winter grain fields replaced marshes as their feeding grounds. Fed through winter, the birds returned to the Arctic in numbers the tundra could not sustain, grubbing up salt-marsh vegetation and leaving bare, salt-crusted mud.
On the Mentawai islands, male gibbons begin singing well before first light, sometimes hours before sunrise, while females sing after dawn. The two sexes hold separate slots in the day, and mated pairs never combine their songs.
![Photograph of Acorn Worm: 1. Ptychodera clavigera [currently Balanoglossus clavigerus], von der dorsalen Seite. 1/1. Nach dem Leben. 2. Ptychodera minuta [currently Glossobalanus minutus] q 1 , von der ventralen Seite. 2/1. Na](/_next/image?url=https%3A%2F%2Fupload.wikimedia.org%2Fwikipedia%2Fcommons%2Ff%2Fff%2FEnteropneusta.png%3Futm_source%3Den.wikipedia.org%26utm_campaign%3Dimageinfo%26utm_content%3Dthumbnail_unscaled&w=3840&q=75)
Acorn worms carry rows of pharyngeal slits opening from the throat to the outside, the same structure that appears in fish, and in human embryos as pharyngeal arches. Hemichordates are among the closest invertebrate relatives of vertebrates.
The scatter of dark blotches on a manta's pale underside is fixed for life. Photographs of that pattern let researchers recognise individuals across decades without tagging, and have turned casual diver snapshots into a long-running population record.
The thieving magpie is a folk belief rather than a finding. When shiny and dull objects were placed near food, wild-caught magpies approached the shiny items less often, and often avoided them altogether as unfamiliar.
A sand hopper displaced across a beach heads back toward the correct sea-land axis, and it does so at night using the moon as a compass, correcting for the moon's movement with an internal clock tuned to lunar rather than solar time.
Praya dubia has been recorded at lengths of forty metres and more, exceeding any whale. It is not one animal but a chain of thousands of specialised zooids, and it is so fragile that nets typically return it in pieces.
Silver arowanas take prey out of the air. Watching upward from just under the surface, they launch clear of the water to seize insects, spiders and occasionally small birds resting on branches over flooded forest, a habit that earned them the name water monkey.
The jelly of a spotted salamander egg mass turns green because a single-celled alga lives in it. Unusually for a vertebrate, the alga has also been found inside the embryo's own cells, a partnership with no clear parallel among other vertebrates.
The last stretch of a spider monkey's prehensile tail is hairless underneath and covered in dermal ridges, the same friction skin found on primate fingers. The tail grips well enough to hold the animal's whole weight and can pick up small objects.