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 Drafts and withdrawn editions are never mixed into this index.
Horses carry 64 chromosomes and donkeys 62, leaving the mule with an odd 63 that cannot pair evenly during the formation of eggs and sperm. A handful of fertile mule mares have nonetheless been documented and genetically confirmed.
The Asian water monitor is one of the world's largest lizards, yet it patrols the storm drains and park canals of Bangkok and Colombo in numbers. Tolerance of polluted water and a scavenger's appetite make urban waterways a workable habitat rather than a marginal one.
Anchor lines of up to twenty-five metres carry the web of Darwin's bark spider clear across Madagascan rivers, holding an orb of up to about 2.8 square metres in open air where flying insects concentrate.
Named for flipping stones and weed to reach the invertebrates beneath, the ruddy turnstone has one of the broadest diets of any shorebird. Recorded items extend to other birds' eggs, discarded human food and carrion washed up on the tideline.
A hunting black heron sweeps both wings forward over its head until the tips meet, forming a dome that touches the water. It holds the pose for a few seconds, peers down into the shade, and strikes.
Of the three blood-feeding bats, only the common vampire took readily to livestock. The hairy-legged vampire bat stayed with birds, and its anatomy shows it: a cupped tongue, a fringed lower incisor comb, and feet built for gripping a perching host.
The orange and blue bill of a breeding puffin is not permanent. Outer plates are shed after the breeding season, leaving a smaller, duller bill, and the winter face is grey rather than white, which is why winter puffins look like a different bird.
In the African jacana the usual roles are reversed. The larger female holds a territory containing several males, mates with each and lays a clutch for each, and every male then incubates and raises his brood without her help.
Almost all social wasps stop flying at dusk. Vespa crabro keeps foraging into the night and is drawn to lit windows, which is why it turns up indoors at hours when no other large wasp is on the wing.
Males mate almost continuously for a two-week window, then die within days. The cause is a stress-hormone cascade that suppresses immunity and breaks down body tissue, and it kills the entire male cohort at once.
An adult Taenia saginata absorbs everything it needs across its body surface. That surface, the tegument, is covered in microscopic projections that give it an absorptive area comparable in principle to an intestinal lining.
A fennec fox has the largest ears relative to body size of any canid. They sharpen its hearing for prey underground, but their main documented function is thermal: a large, thinly furred surface laced with blood vessels that dumps heat into the air.
In parts of Newfoundland and Iceland, capelin come ashore to breed. Waves carry masses of fish onto gravel beaches, where eggs are shed and fertilised in the swash before the survivors are washed back out.
Seagrass makes up a large share of what bonnetheads swallow while hunting crabs on the flats, and feeding trials with labelled seagrass showed the sharks assimilating its nutrients rather than passing it through. It is the only known omnivorous shark.
While other mole salamanders wait for spring rain, the marbled salamander breeds in autumn on the bare floor of an empty pool basin. The female guards her eggs on land until rising water floods them and triggers hatching.
Quokkas photograph as though grinning because of the way the mouth sits on a short, broad muzzle and because they pant with the mouth slightly open. The expression carries no information about how the animal feels.
The cephalofoil is not a hammer. Widening the head separates the nostrils and stretches the array of electroreceptive pores across a broader surface, improving the shark's ability to localise odour and the faint electric fields of buried prey.
A songbird's syrinx has two sound sources, one on each bronchus, and they can be controlled independently. The wood thrush uses both at once in the ee-oh-lay phrase, producing two different pitches simultaneously from a single bird.
Dumbo octopuses live thousands of metres down, where there is no sunlight for an ink cloud to obscure. The cirrate octopuses to which they belong have dispensed with the ink sac entirely.
Limacina builds its shell from aragonite, the more soluble form of calcium carbonate. As the ocean absorbs carbon dioxide and carbonate saturation falls, shells of wild-caught pteropods have been found visibly pitted and thinning.
Goliath frogs clear gravel and drag stones weighing up to about two kilograms to construct sheltered pools at river edges, where they lay eggs. The heaviest stones moved approach the weight of the frog itself.
Satellite tags have recorded a Cuvier's beaked whale nearly 3,000 metres down off southern California, and a separate whale off North Carolina submerged for three hours and 42 minutes. They are different animals, different studies, and both far beyond the species' calculated oxygen limit.
Northern flickers spend much of their foraging time hopping on open ground, hammering into soil and ant nests rather than tree trunks. Ants are the single largest item in their diet, around 45 per cent in the classic stomach-content surveys, and more than in any other North American woodpecker.
Built like a badger rather than a dog, the bush dog swims and dives readily, aided by webbing between its toes. Packs drive large rodents into water, where some members wait for the prey to surface.