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 Drafts and withdrawn editions are never mixed into this index.
Every other marine mammal insulates with fat. The sea otter has almost none, relying on the densest fur known, and pays for it with a metabolic rate several times that expected for its size and a near-constant need to eat.
Buried up to a metre down, the frog stores water in an enlarged bladder and wraps itself in a cocoon of layered shed skin that leaves only the nostrils open, then waits, sometimes for years, for rain.
Lions can roar because the deep layer of their vocal folds is loaded with fat and elastin, giving the fold a flat, squared edge that vibrates at low pressure. The shape, not the size of the animal, does most of the work.
Most birds keep three or four toes on each foot. The ostrich has reduced its foot to two, and the outer one barely touches the ground, leaving a single broad hoof-like toe to carry the fastest running bird alive.
Invasive sea lamprey devastated Great Lakes fisheries in the mid-twentieth century. Control now rests largely on TFM, a lampricide screened out of thousands of candidate compounds because larval lamprey cannot detoxify it as well as most fish can.
Horseshoe crab blood is blue, because it carries copper-based haemocyanin rather than iron-based haemoglobin. Its amoebocytes clot on contact with bacterial endotoxin, a reaction turned into the standard safety test for vaccines and implanted devices.
By the early 1900s the wood duck had been reduced to scattered remnants by market hunting and the clearance of bottomland forest. Hunting protection and, later, an enormous programme of artificial nest boxes helped return it to abundance across its range.
Juvenile shrimp enter the sponge's glass lattice through gaps too small for adults. Once grown, a male and female cannot leave, and the dried skeleton with its trapped pair was traditionally given as a wedding gift in Japan.
Most songbirds close their learning window in their first year and sing the same repertoire until they die. The northern mockingbird is an open-ended learner, adding fresh imitations across successive seasons so that older males carry larger repertoires.
A pseudogene in the feline genome disables one of the two proteins needed to build a functional sweet receptor. No cat, domestic or wild, detects sugars by taste, which fits a lineage that has eaten nothing but meat for millions of years.
An adult hellbender keeps lungs but barely uses them for gas exchange. The loose, wrinkled flaps along its flanks are respiratory surface, and the animal rocks its body to keep fresh water moving across them.
A fulmar chick alone on a ledge projects a foul stomach oil at anything that approaches. The oil mats the plumage of an attacking bird, and seabirds that have been sprayed can lose waterproofing badly enough to die.
The name promises something the species mostly does not do. Cannibalism after mating is easy to produce in a small laboratory arena, but in the field male black widows commonly mate and leave, and some go on to mate again.
A main sett is not a burrow but an inherited excavation, extended by generation after generation. Some carry hundreds of metres of tunnel and dozens of entrances, and individual setts have been recorded in continuous use for over a century.
A female Megarhyssa detects a horntail larva several centimetres inside a trunk, then works a hair-thin ovipositor through solid wood to lay a single egg on it. The ovipositor is longer than her body.
A katydid's ears are on its forelegs, just below the knee joint. Air reaches them through a tube running from a spiracle on the thorax, and inside sits a row of graded sensory cells that separates sound by frequency much as the mammalian cochlea does.
Individual oystercatchers specialise. Some slip the bill between the valves of a mussel and cut the muscle; others hammer through the shell. The two techniques wear the bill into different shapes, and a bird generally keeps its method for life.
Other sea turtle hatchlings vanish into the open sea for years. Flatback hatchlings do not. They stay over the Australian continental shelf for their whole lives, skipping the oceanic drifting stage that defines the early years of every other marine turtle.
Eucalypt and melaleuca blossom is a night-time resource, and grey-headed flying foxes work it hard. Because they commute tens of kilometres between camp and feeding trees, they move pollen and seed across distances no insect pollinator matches.
An influential 1990s experiment reported that kestrels prefer arenas marked with vole urine when ultraviolet light is present. Later measurements of raptor eyes and of the marks themselves have undermined the mechanism, so the ultraviolet-trail story should be read as contested rather than established.
In a common agama colony, one male holds the territory and wears the bright orange head and blue body. Subordinate males stay brown and cryptic. Remove or defeat the dominant, and a subordinate can develop the display colouration within days.
Most adult butterflies live on sugar and die within weeks. Heliconius collect pollen on the proboscis, work it into a mass, release enzymes to dissolve out amino acids, and drink the result, which lets them live for months.
In 2002 surveys found fewer than one hundred mature Iberian lynx in two isolated Spanish populations. Coordinated captive breeding, reintroduction and rabbit habitat work have since multiplied the population many times over, and its Red List status has been downgraded twice.
The reflective layer behind a reindeer's retina is golden in summer and deep blue by midwinter. The shift scatters more light back through the retina, buying sensitivity in the long polar dusk at the cost of a sharper image.