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 Drafts and withdrawn editions are never mixed into this index.
Rather than confining scent to a few glands, a takin secretes an oily substance across its whole skin. The coat it soaks into sheds the constant rain and fog of eastern Himalayan slopes and gives the animal a strong, bitter smell.
A sifaka's legs are built for launching from vertical trunks, not for walking. On the ground it holds its arms up and bounds sideways in a series of two-footed hops, a gait that looks like dancing and is a compromise rather than a display.
A threatened hognose writhes, gapes, everts its tongue and rolls belly-up, sometimes voiding musk and faeces. The performance is undone by two things: it will roll back over if righted, and it peeks at the threat while supposedly dead.
The two kinds of tree sloth look alike and live the same upside-down life, but their lineages parted around 28 million years ago. Their shared body plan is convergent evolution from different branches of the extinct ground sloths.
When water rises, a colony links workers into a buoyant raft that carries the queen and brood on top. The mass behaves like a viscoelastic material and can stay afloat for days or weeks.
It no longer feeds by pumping and straining water. Tiny hooked spicules covering its branches snag passing crustaceans like burrs, and the sponge then grows a membrane over the trapped animal and digests it where it hangs.
Push a live sponge through a fine mesh and it becomes a suspension of individual cells. Left in seawater, those cells find each other, sort themselves by type, and rebuild a working sponge, an experiment first done in 1907.
Pseudaspis cana pursues golden moles and rats through their own tunnel systems, where its prey has no room to flee. Its narrow, hard-edged head and heavy neck muscles are built for digging and for constricting in a confined space.
It is an elongated left canine that spirals counterclockwise and grows through the upper lip. Unlike ordinary teeth it has a porous outer surface with nerve pathways reaching the pulp, so a hard tissue built to be insensitive is instead richly innervated.
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.
Cedar waxwings normally end the tail in a yellow band. Since the 1960s, birds with orange tail bands have appeared in the northeast, traced to nestlings eating the fruit of introduced honeysuckles containing a different carotenoid pigment.
Common carp are listed as Vulnerable on the IUCN Red List while simultaneously ranking among the world's most damaging invasive fishes. The assessment applies to genuinely wild native populations, not to the farmed and feral fish that dominate elsewhere.
Caught in the open, the armadillo girdled lizard curls onto its back, takes its tail in its mouth and holds. The result is a spined ring presenting no soft surface, which is also the origin of its genus name, Ouroborus.
Instead of laying a clutch, female fire salamanders retain the eggs internally and deposit live larvae into a stream. In some mountain populations the young skip the water stage entirely and emerge as miniature land salamanders.
No scorpion lays eggs. Striped bark scorpions give birth to live, pale, soft-bodied young that immediately climb onto the mother's back and stay there until their first moult, a period of roughly one to three weeks.
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.
Great blue herons carry patches of special feathers that never moult but fray continuously into a fine powder. The bird works this powder into its plumage with a comb-like claw, using it to absorb fish slime and oils.
The largest embryo in each of the sand tiger's two uteri consumes its smaller siblings and then the unfertilised eggs the mother keeps supplying. Only two pups are born per litter, each already about a metre long.
Brushtail possums were released in New Zealand from 1837 to start a fur trade. With no native predators and abundant palatable foliage, they multiplied into the tens of millions and now strip native forest canopy and raid the nests of native birds.
The image of lemmings hurling themselves off cliffs comes largely from a 1958 Disney documentary in which the animals were driven off a bank for the camera. Real lemmings disperse when crowded, and some drown attempting water crossings.
Megaloceros giganteus ranged from Ireland to Siberia, and its closest living relative is the fallow deer, not the elk or moose. The name stuck because so many superb skeletons were dug out of Irish peat bogs by nineteenth-century collectors.
The colours running along a ctenophore in daylight are ambient light scattered by beating rows of fused cilia. Many comb jellies do also produce real bioluminescence, but that is blue-green, faint, and only visible in the dark.
Wartime sonar operators found an echo layer that seemed to be the sea bed, except that it rose towards the surface each night and sank again by day. The layer turned out to be living animals, lanternfishes prominent among them.
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.