Field notebook
Opening the requested public page…
Field notebook
Opening the requested public page…
Theme trail
This is a live full-text trail through published facts, not a fixed marketing category.
Before reaching sexual maturity, female fossas grow an enlarged, spine-covered pseudo-penis and rust-orange fur matching adult males, a disguise thought to reduce harassment, then lose both traits within a couple of years.
Aplysia californica has around twenty thousand central neurons, some nearly a millimetre across and individually identifiable from animal to animal. That combination made it the organism in which the cellular basis of simple learning was first worked out.
Newborn emerald tree boas hatch internally and emerge brick red, orange or yellow. They shift to the adult green over their first year or so, a change that appears to track a move to different heights and light in the forest.
Its body is olive, grey or gunmetal brown. The name comes from the inside of the mouth, which the snake gapes open in threat to show a lining so dark it reads as black against the pale gums of other species.
A squirrel monkey's brain is roughly one-fortieth of its body mass, a higher proportion than in humans, whose ratio is nearer one in fifty. The comparison is real but misleading, because small animals routinely carry proportionally larger brains.
The shoulder hump that identifies a grizzly is not fat or bone but a mass of muscle anchoring the forelimbs. It powers the digging that supplies much of the bear's food, and it distinguishes grizzlies from black bears at a glance.
Botos are born grey and many adults turn pink, but the colour is not evenly distributed. Males are pinker than females, and the pinkest males are those carrying the most bite marks from fights with other males.
The white-tailed eagle was shot out of Britain by the early twentieth century: the last known breeding was on Skye in 1916, and the last bird was killed on Shetland in 1918. Norwegian birds released on Rum from 1975 rebuilt the population.
In the 1990s the common dolphin was divided into short-beaked and long-beaked species on the strength of body shape. Later genetic work showed that long-beaked forms had arisen independently in several regions, and in 2016 they were folded back into one species.
Nearly all cephalopods have a single visual pigment. Watasenia scintillans has three, an anatomy that would allow it to distinguish wavelengths in the deep water where bioluminescence and residual daylight differ in colour.
The desert locust has two forms so different that they were once described as separate species. The switch is triggered by physical contact, specifically repeated touching of the hind legs, and can begin within hours of crowding.
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.
Before swallowing a bee or wasp, a European bee-eater strikes it against a perch and then rubs the abdomen along the branch, expelling most of the venom. Only stinging insects receive this treatment; harmless prey is swallowed directly.
Slate-coloured, Oregon, pink-sided, grey-headed and white-winged juncos look like separate birds and were once named as separate species. They are now lumped as one, and the plumage groups appear to have diverged very recently.
Cuttlefish have only a single visual pigment in the retina and cannot distinguish colour the way vertebrates do. They nonetheless produce camouflage that matches coloured backgrounds convincingly, both to human observers and to the fish that hunt them.
Unlike its black relative, the eastern green mamba is strongly arboreal. It hunts, rests, mates and sheds among branches, and its brilliant green body against sunlit leaves makes it far harder to see than the colour suggests.
Generations of Arctic foxes concentrate nutrients at a den through urine, faeces and prey remains. On nutrient-poor tundra the result is a visible green patch of much denser vegetation, detectable from the air.
The two coloured spirals are crowns of feathery radioles that filter plankton from the water and exchange gas. Almost all of the animal is hidden inside a calcareous tube bored into a living coral head.
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 red coral of Mediterranean jewellery is an octocoral with eight-tentacled polyps and a solid calcite core. It hosts no photosynthetic algae, grows in the dark under overhangs, and adds well under a millimetre of branch length in a year.
The European green crab has spread to five continents without any specialist trick. It survives brackish water, air exposure, near-freezing and warm temperatures, and long journeys in ballast tanks, and it eats almost anything it can crush.
Millepora builds a hard limestone structure and lives on reefs, but it is a hydrozoan, closer to Portuguese man o' war and hydra than to the stony corals it grows over. Its stinging polyps sit in pores too small to see.
Africa's smallest crocodile spends its nights walking the rainforest floor away from water, taking crabs, frogs and insects. By day it retreats into burrows dug into stream banks, sometimes with no open water at the entrance.
A roseate spoonbill sweeps its open bill side to side through murky water while walking forward. Sensitive nerve endings inside the spatula detect contact and trigger the bill to snap shut, so the bird can feed in water it cannot see into.
Reindeer detect light down to about 320 nanometres, well below the human limit. In snow, which reflects ultraviolet strongly, this turns lichen, urine and wolf fur into dark shapes against a bright field.
Green and black from above, the fire-bellied toad becomes a signal only when threatened, arching the spine and lifting its limbs to expose the orange underside in a posture called the unken reflex.
Tridacna gigas gets most of its energy not from filtering plankton but from symbiotic algae cultivated in its exposed mantle tissue. The colourful flesh is a solar array, which is why the animal must live in shallow, sunlit water.
The froth on a summer grass stem is not spit. A froghopper nymph sits head-down inside it, drinking dilute xylem sap and blowing the surplus into bubbles with air from its abdomen, producing a shelter that hides it and keeps it damp.
The yellow crown and cheek feathers of a budgerigar fluoresce under ultraviolet light, and in an experiment where that glow was masked with sunscreen, the treated bird became measurably less attractive to potential mates.
During El Niño years the algae marine iguanas eat collapse, and individuals lose length as well as weight. Repeated measurements of marked animals showed adults shortening by several centimetres and regrowing when food returned, a change that must involve bone as well as soft tissue.
The shimmering fan a peacock raises is built from elongated upper tail coverts, the feathers that normally cover the tail base. The real tail feathers are short, stiff and brown, hidden behind, doing the work of holding the display upright.
Ornamental koi are often described as an ancient Japanese tradition. The coloured varieties actually arose in the Niigata region in the early nineteenth century, when rice farmers noticed colour mutations among the food carp kept in their paddy ponds.
Rough-skinned newts carry tetrodotoxin, the same toxin found in pufferfish. Common garter snakes in the same forests have evolved resistance, and where resistant snakes are most common, the newts are most toxic.
A frogfish expands its mouth to about twelve times its resting volume and engulfs prey in roughly six milliseconds, faster than any potential victim can respond. The lure that brings prey in mimics a worm.
The upcurved casque of a rhinoceros hornbill is a thin keratin shell over a mostly empty space crossed by fine bony struts. Only one hornbill in the family has a genuinely solid casque, and that species has been hunted for it.
No blue pigment exists in a common kingfisher's feathers. The colour comes from microscopic structures in the barbs that scatter short wavelengths, which is why the same bird looks cyan, turquoise or dull brown depending on the angle of light.
Unlike the peregrine, a gyrfalcon usually attacks in fast level flight close to the ground, running down ptarmigan over open tundra. Its heavier build and broader wings suit sustained horizontal pursuit rather than a vertical stoop.
Cornered on the ground, a southern tamandua rears back, braces on its hind feet and the bare underside of its tail, and holds its clawed forelimbs out. The tail is a grip organ in the canopy and a stabiliser in a fight.
Matching the brown of a fallen leaf is only the beginning. The dead leaf mantis reproduces leaf veins, irregular edges that read as insect damage, and blotches resembling fungal spotting, and it sways as though moved by air.
A male Caribbean reef squid positioned between a female and a rival can display courtship colouration on the side facing the female and aggressive colouration on the side facing the rival, simultaneously.
The green male and the red-and-blue female differ so completely that eighteenth-century naturalists catalogued them as unrelated birds, naming each in turn. They were still treated as two species until the early twentieth century, when the pairing was settled by watching them breed.
All Ornithoptera, Troides and Trogonoptera species are listed under CITES, even common ones like Troides helena. The listing is not because each is rare but because birdwings are hard to tell apart in trade.
Nightingales sing round the clock, but the celebrated nocturnal song has a narrow purpose. Males that have not yet attracted a mate do most of the singing through the dark hours; once a female settles with them, night singing usually falls away or stops.
The bright red juvenile red salamander closely resembles the toxic red eft of the eastern newt, and experiments with captive birds suggest predators that have learned to avoid efts also avoid the harmless mimic.
Most amphibians make one crossing from water to land. The eastern newt makes two: larvae metamorphose into a bright orange land-dwelling eft that wanders the forest for years, then returns to the pond and becomes aquatic again as an adult.
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.
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.
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.
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.