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 Drafts and withdrawn editions are never mixed into this index.
Each guard hair is unpigmented and hollow-cored, and the skin beneath is black. The animal looks white because the hairs scatter light in every direction, not because any pigment in the coat is white.
Wombat faeces come out with flat faces and squared edges, a shape produced nowhere else in the animal kingdom. The corners are formed inside the intestine by regions of wall that stiffen and stretch at different rates.
The Cuban tree frog's head skin is co-ossified, grown directly onto the skull bones. The arrangement reduces water loss and gives the head a hard surface, and it is why the skin will not slide over the crown.
Western science described the red panda in 1825, decades before the giant panda became known outside China. The name panda belonged to this animal first, and the two are not close relatives.
For most of the twentieth century the North American elk was filed as a race of the European red deer. Genetic work split the group, and the elk now stands as Cervus canadensis, an eastern lineage with its own history.
Little skates push themselves along the seabed on a pair of slender pelvic fin lobes, alternating left and right. Work published in 2018 found the neurons controlling that gait use the same genetic programme that drives limbed walking in land vertebrates.
A male raises a coloured abdominal fan, waves his third pair of legs and drums vibrations through the leaf litter. A female who does not accept the display may treat the performer as food rather than as a mate.
Radar and radio-tracking place foraging Mexican free-tailed bats well over a kilometre above the ground, intercepting migrating moths in high-altitude airflows. The behaviour explains both their long narrow wings and their unusual speed.
Spiders have no extensor muscles at some leg joints. Pressure in the circulating haemolymph straightens the limb instead, which is part of how a jumping spider launches several body lengths onto prey it has already measured by eye.
After the female lays her clutch and leaves, the male emu sits on the nest for roughly eight weeks. Through most of that period he does not eat, drink or defecate, living off body fat and losing a substantial share of his weight.
For most of the twentieth century the beaded lizard and the Gila monster were held to be the world's only venomous lizards. Discoveries of venom glands in monitors and iguanians since 2005 have made that textbook line obsolete, though helodermatids remain the clearest cases.
Desert scorpions run on an extraordinarily low metabolism. Several species, including large burrowing scorpions, have been kept alive for six to twelve months without food, an endurance that comes from spending almost the entire year motionless underground.
The domestic turkey is too heavy to get airborne, which has given the whole species a flightless reputation. Wild turkeys fly strongly over short distances and spend every night roosting in the branches of tall trees.
Pigs have sweat glands but almost no functional ones for cooling, so they cannot lose heat by sweating. Wallowing in mud is thermoregulation, and the mud outperforms plain water because it evaporates more slowly.
The black swallower's stomach stretches into a translucent sac below its body, letting a fish of about twenty centimetres engulf prey several times its own mass, sometimes with fatal results.
Harriers carry a stiff ruff of feathers around the face that funnels sound toward the ears, much as an owl's disc does. They fly slowly and low over vegetation, and experiments show they use hearing as well as sight to detect concealed prey.
The thick-billed parrot feeds on pine seeds in the mountains of northern Mexico at elevations where snow lies in winter. It once ranged into Arizona, and a 1980s reintroduction there failed.
Most Pacific salmon juveniles spend a year or more in fresh water. Chum fry generally do not: they emerge from the gravel and migrate downstream to the estuary almost at once, which frees the species from needing productive nursery rivers.
A tapir swallows large fruit whole, walks for hours, and deposits intact seeds far from the parent tree. Few other animals in Central American forest are big enough to move seeds of that size, which makes the tapir hard to replace.
An adult pygmy marmoset weighs roughly the same as a deck of cards and has a head and body about the length of a human finger, with a longer tail behind it. Mouse lemurs are smaller, but they are not monkeys.
Juvenile green tree pythons twitch the pale tip of the tail near the head so that it resembles a moving grub or worm. Small lizards and frogs approach the decoy and are taken by the strike waiting above it.
The dusky farmerfish weeds unwanted seaweeds out of its territory until a preferred red alga dominates. In some populations the crop, Polysiphonia, is scarcely found outside these territories at all, an unusually complete case of animal cultivation.
Larger than the African buffalo and than any wild bison, a bull gaur can stand around two metres at the shoulder and exceed a tonne. Its most visible feature is a muscular ridge running along the back.
Cultures of Carausius morosus have been maintained for generations with no males present. Unfertilised eggs develop into female offspring by parthenogenesis, and males are so rare in captivity that most keepers never see one.