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 Drafts and withdrawn editions are never mixed into this index.
The scarlet and blue skin on an adult male mandrill's muzzle is not fixed decoration. Its intensity rises and falls with testosterone and social standing, so a male who loses his position fades, and the colour signals status to rivals and females alike.
The fish produces a low-frequency boom by contracting muscles against its swim bladder, loud enough for divers to feel in the chest. Researchers now use passive acoustic recorders to find and count spawning aggregations by sound alone.
Each tadpole is carried on its mother's back to a separate pool of water trapped in a plant, and then fed for weeks on eggs she lays specifically as food. Without those meals the tadpole cannot complete development.
A largemouth bass does not chase down and bite its prey. It expands the mouth cavity explosively, dropping pressure so that water and prey are drawn in together, a suction strike completed in well under a tenth of a second.
It belongs to the order Carnivora, but its diet is overwhelmingly fruit and nectar, and it hangs from a fully prehensile tail. Among the several hundred carnivorans, only two species have a tail that can grip.
A bee that steals a stocked nest never needs to gather pollen, and the anatomy goes with the behaviour. Nomada females lack a scopa entirely and look more like small wasps than bees.
During copulation the male redback flips his abdomen over onto the female's mouthparts and is usually eaten while still transferring sperm. Field and laboratory work suggests the manoeuvre buys him longer copulation and more of the paternity.
At roughly a third of a millimetre, honey possum sperm are the longest recorded for any mammal, produced by an animal that weighs between about seven and sixteen grams, less than a house mouse. Male testes account for roughly four per cent of body mass.
A fresh anchovy tastes mild and unremarkable. The intense savoury flavour of the tinned fish is produced afterwards, by months of salting during which the fish's own enzymes break its proteins down into free amino acids.
Green, mossy grey, rust and a vivid gold form all occur in the same species, sometimes among siblings. The colour is not a subspecies or a regional variety but genuine polymorphism within a single interbreeding population.
When crowded, a grey reef shark adopts an unmistakable posture: back arched, snout raised, pectoral fins dropped, swimming in an exaggerated rolling figure. It is one of the clearest threat displays known in fishes, and it precedes a bite rather than replacing it.
Camelids produce antibodies made of heavy chains alone, without the light chains that all other mammalian antibodies require. The binding fragment of these, called a nanobody, is small enough to reach targets conventional antibodies cannot.
In the Smokies, males of Photinus carolinus produce a run of several flashes together, then a shared pause of several seconds. The darkness between bursts is as much a part of the display as the light.
Grey langurs eat strychnine tree fruit and other foliage loaded with alkaloids and tannins. A chambered, bacteria-filled foregut breaks the compounds down before they reach the animal's own digestion, a defence that a simple stomach cannot provide.
Given a mirror and a coloured mark on its throat, the bluestreak cleaner wrasse tried to scrape the mark off against surfaces. The behaviour held up in a larger follow-up by the same laboratory, and what it means for fish self-awareness is genuinely contested.
The ring of bright blue bumps below the tentacles is not ornament. Each bead is packed with stinging cells, and the anemone inflates and swings them against neighbours it does not recognise, driving territorial fights that can last hours.
Where octopuses and squid have camera eyes with lenses, the nautilus has an open pinhole eye flooded with seawater. It produces a dim, low-resolution image with no way to focus.
Tunas and some sharks warm particular regions of the body. The opah, described in 2015, circulates warmed blood through its gills in a counter-current arrangement that keeps the whole body above the surrounding water.
For most of the twentieth century the forest elephant was treated as a subspecies. Genetic evidence now places the two African elephants as separate lineages, and in 2021 the IUCN assessed them apart for the first time.
Before moving, Portia scans a scene from a distance, then follows an indirect route that can take an hour and removes the target from view for most of it. The spider arrives above the prey it can no longer see.
About 100 toads released in Queensland in 1935 were meant to eat cane beetles. The beetles live high on the stalks and are active by day, so the ground-dwelling nocturnal toads largely ignored them.
The neck frill is not an independent structure. Long cartilaginous rods in the frill connect to the hyoid apparatus of the throat, so when the lizard gapes wide the same movement fans the frill out into a disc that can approach 30 centimetres across.
In 1875 an observer estimated a Rocky Mountain locust swarm covering an area larger than several US states. Within about three decades the species was extinct, most plausibly because ploughing and irrigation destroyed the small valley habitat where it bred between outbreaks.
Kitti's hog-nosed bat and the Etruscan shrew both claim the title of world's smallest mammal, and neither wins outright. The bat is shorter in the body; the shrew is lighter on the scales.