Nature

149 cards about Nature, with explanations, methods and source links.

Cards about Nature

• Where is most of an octopus’s brain?

  In a human, nearly all the processing happens in one place, which looks like the sensible way to build an animal. An octopus is arranged differently enough that a single arm can feel its way along and settle how to grip. So where is the brain?

  Source: Hochner, Current Biology

• Do trees really help each other underground?

  The roots of most trees are wrapped in fungi that supply minerals and take sugars in return, and one fungus can be attached to several trees at once. Out of that grew a story about a forest where trees feed and warn one another. How much of it holds?

  Source: Karst, Jones and Hoeksema, Nature Ecology and Evolution

• Which animal came back alive from open space?

  When its surroundings dry out, a water bear does not die. It shrinks, pushes almost all the water out of itself, and enters a state where its metabolism nearly stops. In that state it withstands extreme cold, drought, pressure and radiation. So they flew one to orbit and opened the hatch.

  Source: Jönsson et al., Current Biology

• Do migrating birds actually see the magnetic field?

  Migrating birds navigate enormous distances at night and under cloud, so plainly they carry a compass. The leading hypothesis puts it somewhere unexpected: in the eye, in a protein that absorbs blue light. What would that mean for what they see?

  Source: Xu et al., Nature

• How do ants find a short route when none of them has the map?

  An ant that finds food walks home leaving a trail of pheromone behind it, and other ants tend to follow wherever the smell is stronger. No ant compares two routes, and none of them knows what is happening anywhere else. So how does the short one get picked?

  Source: Goss et al., Naturwissenschaften

• What happened when a brainless organism designed a rail network?

  Physarum is a giant single-celled organism with no nervous system whatsoever. It spreads in every direction, thickens the tubes that lead to food and lets the rest thin away. So researchers laid oat flakes at the positions of the cities around Tokyo and let it spread. What was left on the dish?

  Source: Tero et al., Science

• Which animal grows a whole leg back, bone and nerves included?

  When a mammal is injured the body closes the wound fast with scar tissue, which saves lives and blocks any rebuilding. In an axolotl something else entirely happens at the cut. What gets built there?

  Source: Tanaka, Cell

• What sets the limit on how tall a tree can get?

  A tree has no pump. Evaporation from the leaves puts the column of water inside its vessels under tension, and that tension is what pulls the water up. The taller the tree, the more tension it takes. Where does that stop?

  Source: Koch et al., Nature

• Why do cicadas come out every 13 or 17 years exactly?

  Some cicadas spend years underground and then hatch all at once, in their millions. The common cycle lengths are thirteen and seventeen years, and both of those are prime numbers. To test whether that is a coincidence, models compared prime cycles against cycles that are not prime. What did the prime number buy?

  Source: Williams & Simon, Annual Review of Entomology

• How does a chameleon change color without making any new pigment?

  The standing assumption was that a chameleon changes color by moving pigments around in its skin. To check it, researchers photographed the skin under an electron microscope and measured the spacing of the crystals inside it while the animal was changing color. What did they see there?

  Source: Teyssier et al., Nature Communications

• How do sea otters save kelp forests without touching them?

  Kelp forests grow along the Pacific coast, giant algae that house hundreds of species, and sea urchins eat them. The fur trade removed sea otters from whole regions. What happened to the forests?

  Source: Estes & Palmisano, Science

• Which bird travels between both poles every single year?

  The Arctic tern nests in the far north and winters near Antarctica, and for years the length of that trip was estimated from scattered sightings. Then tiny tracking devices were tied to the birds, and the birds were caught again a year later. What was the real route?

  Source: Egevang et al., PNAS

• Is there an animal that can start its life over?

  A jellyfish life cycle runs one way: a polyp fixed to a rock, then a swimming medusa that breeds and dies. In one very small species biologists found a second route, one that switches on when the animal is injured, starving or under stress. Where does it go from there?

  Source: Piraino et al., The Biological Bulletin

• How do penguins decide who has to stand on the cold outside?

  An emperor penguin stands through an Antarctic winter at extreme temperatures, so the males press together into a dense mass that is tens of degrees warmer inside. Whoever is on the edge takes the wind. How does anyone decide who stands there?

  Source: Gilbert et al., Physiology & Behavior

• What do elephants hear through the soles of their feet?

  Elephants make sounds at very low frequencies, some of them below the threshold of human hearing. Waves like that fade slowly and travel kilometers, through the air and through the ground alike, where they are seismic waves. An elephant that freezes in place and shifts its stance to press harder into the earth is doing something deliberate. What is it doing?

  Source: O’Connell-Rodwell et al., JASA

• Why does a wombat go to the trouble of leaving its mark up high?

  Wombats are nocturnal animals with poor eyesight, so they communicate mostly by scent. A mark only works if it stays somewhere prominent and raised, and on sloping ground anything simply rolls off. How do you solve that?

  Source: Yang et al., Soft Matter

• How does one rodent survive 18 minutes with no oxygen?

  The naked mole-rat lives in crowded burrows in Africa, in air low in oxygen and high in carbon dioxide. In any other mammal a complete absence of oxygen causes brain damage within a few minutes. What does it do differently?

  Source: Park et al., Science

• Is the electric eel an eel at all?

  The electric eel has no dorsal fin and none of the other features that define a true eel. The name is a common one that stuck to it centuries ago on the strength of its long shape alone. So what is it, and what else can it do?

  Source: de Santana et al., Nature Communications

• How does a small beetle fire liquid at boiling point?

  The bombardier beetle stores two chemicals in separate glands in its abdomen, and as long as they stay apart nothing happens. When it is attacked, a muscle pushes them into a rigid reaction chamber holding the enzymes that catalyse the reaction. What happens in there?

  Source: Arndt et al., Science

• What can a bumblebee learn but never invent on its own?

  To reach a drop of sugar a bee had to move a blue tab first, which paid nothing at all, and only then push a red one. A first step with no reward is exactly the thing that cannot be learned alone. So what worked?

  Source: Bridges et al., Nature

• Why do ducklings swim in a tight line behind their mother?

  Ducklings swim in a tight line behind their mother, and keeping the group together explains it easily enough. Except that a swimming duck leaves a wake of waves behind her, and a wake is usually a hindrance. So what are they getting back there?

  Source: Yuan et al., Journal of Fluid Mechanics

• Can a shark give birth without ever meeting a male?

  Three hammerhead sharks were held for years with no males, and one of them gave birth anyway. The simple explanation is that she had stored sperm from an old mating, which sharks do. So the DNA of mother and pup was compared. What came out?

  Source: Chapman et al., Biology Letters

• A scorpion gave up its tail to escape. How does it live on with no anus?

  Ananteris scorpions can detach the rear part of the abdomen when something grabs them, an autotomy that lets them escape. Along with the "tail" they lose about a quarter of their body weight, and that includes the anus, which does not grow back. How do they carry on?

  Source: García-Hernández & Machado, Integrative Zoology

• A fish has no cortex like ours. So how does it tell faces apart?

  Recognizing faces was taken to need a cortex of the kind mammals have, and fish do not have one. Archerfish hunt by spitting a jet of water, and that spit can serve as an answer. So photographs of faces were put in front of them. What did they do?

  Source: Newport et al., Scientific Reports

• How did a small fish pass a mirror test that was thought to be almost human?

  The mirror test was long treated as a rare mark of self-recognition, reserved for a handful of animals. Cleaner fish were exposed to a mirror, and then shown photographs of themselves and of strangers, and composites with one fish’s face on another’s body. How did they respond?

  Source: Kohda et al., PNAS

• How does a rock come out of the ground as an almost perfect cube?

  Pyrite is a mineral of iron and sulfur, and it comes out of the ground in almost perfect cubes with straight corners. Nobody cut them. How does a rock arrange itself into that shape?

  Source: Arrouvel & Eon, Materials Research

• Do the black and white stripes really cool a zebra down?

  A familiar idea says black and white reach different temperatures in the sun, so the stripes set up tiny air currents that carry heat away from the skin. If that is right, it can be tested on water-filled barrels wearing hides. The barrels stood outdoors for four months with their inside temperature logged. What happened in there?

  Source: Horváth et al., Scientific Reports

• What happened to the birds inside the two beams of light over Manhattan?

  The Tribute in Light sends two powerful beams up over Manhattan every September, in the season when migrating birds cross the city at night. Radar and acoustic sensors tracked what the birds did inside them, and the operators switched the lights off from time to time. What differed between on and off?

  Source: Van Doren et al., PNAS

• How does a group of male elephants decide it is time to leave?

  The coordinated departure rumble was known from tight-knit family groups, where it keeps a family together as it moves. Male elephants are described as living in loose social groups, so nobody expected to find it among them. Recordings at a waterhole in Namibia caught a run of low calls just before the males left together. Who starts it?

  Source: O’Connell-Rodwell et al., PeerJ

• Which street trees actually feed the birds of a city?

  A street tree is chosen by a municipality, usually for durability, root size and maintenance cost. Greater Los Angeles holds one of the most extensive urban forests on Earth, nearly all of it nonnative, planted after irrigation arrived in the early 1900s. Researchers followed where birds actually look for food across the city. Which trees feed them?

  Source: Wood and Esaian, Ecological Applications

• How many neighbors does a starling actually watch?

  A flock of thousands turning as one looks like it needs a leader, and models have shown for decades that simple local rules are enough. The rule everybody assumed is distance: watch whatever is within a few body lengths. Very little was known about the real interaction. What are the birds doing?

  Source: Ballerini et al., PNAS

• How cold can a frog get and still thaw out alive?

  Wood frogs survive winter by freezing, which is already strange, and the ones in Interior Alaska live at the northern edge of the species range. A frog from southern Ohio is the same animal with the same trick. The question is whether the Alaskan ones simply endure more, or do something different.

  Source: Costanzo et al., Journal of Experimental Biology

• Do elephants call each other by name?

  Personal names are universal in human language and almost absent elsewhere. Dolphins and parrots do address each other, by imitating the call of the one they are addressing, which is a different trick: a human name is not an impression of the person. Which kind do elephants use?

  Source: Pardo et al., Nature Ecology and Evolution

• Why do infected ants die in the same place and at the same hour?

  Ants infected by Ophiocordyceps fungi leave their canopy nests, climb down to understory vegetation and bite into a leaf vein before dying. The deaths cluster in patches, on sapling leaves about 25 centimeters above the soil, where conditions for the parasite are best. Which part of that is the fungus?

  Source: Hughes et al., BMC Ecology

• How does a shrimp break a shell underwater?

  Mantis shrimp break shells with brief, powerful strikes of their raptorial appendages, and the speeds involved are extreme enough that cavitation occurs in the gap between limb and prey. That raises a question about bookkeeping: how much of the damage is the limb, and how much is the water?

  Source: Patek and Caldwell, Journal of Experimental Biology

• How does a swarm of bees agree on where to live?

  Condorcet’s jury theorem says that when group members hold noisy but independent information about what is best, majority decisions tend to beat dictatorial ones. Add communication and the independence breaks: pooling improves, and errors amplify too. Honeybees choosing a nest site do both at once.

  Source: List, Elsholtz and Seeley, Philosophical Transactions of the Royal Society B

• What is hagfish slime actually for?

  A harassed hagfish produces a startling quantity of slime, and the precise ecological function of it was unclear. One proposal is defense against gill-breathing predators, whose gills might become entangled in the mixture of mucins and fibrous threads during an attack. That is a claim about water flow.

  Source: Lim et al., Journal of Experimental Biology

• Why don’t elephants get more cancer than we do?

  More cells and more years should mean more chances for a cell to go wrong, so the largest and longest-lived animals ought to be riddled with cancer. A survey of necropsy data across 36 mammalian species found that cancer mortality does not increase with body size or maximum life span at all.

  Source: Abegglen et al., JAMA

• Which animal grows crystals inside its young?

  Protein crystals for X-ray work are normally grown in a laboratory from pure, uniform samples, which is a long way from any living body. A few have been found inside cells. Inside the gut of a developing embryo, in a cockroach, there is a stranger case: crystals that are food.

  Source: Banerjee et al., IUCrJ

• Can a flower hear a bee coming?

  Flowers have no ears, no nerves and no brain, so the sound of an approaching bee ought to pass straight through them. A lab in Tel Aviv played a recording of a flying bee to open beach evening primrose blooms, then sampled the sugar in their nectar minutes later. Did anything in the flower change?

  Source: Veits et al., Ecology Letters

• What is a cat's tongue actually doing when it grooms?

  A cat's tongue feels like sandpaper, and the backward-facing spines on it are usually described as a rasp for stripping meat off bone. That leaves grooming unexplained, because a rasp does nothing useful down at the skin. Two engineers scanned tongues from six cat species and filmed grooming frame by frame. What are the spines for?

  Source: Noel & Hu, Proceedings of the National Academy of Sciences

• Do any other animals babble the way human babies do?

  Babbling looks like a human specialty: months of repeated, rhythmic, meaningless syllables before a baby asks for anything. Greater sac-winged bat pups learn their songs rather than inherit them, which makes them the obvious place to look for a practice stage. A team recorded pups in the wild and went through every bout. Does bat practice resemble a baby’s?

  Source: Fernandez et al., Science

• Why is a toucan's beak so absurdly large?

  A toco toucan's beak runs to about a third of the bird's length, and the standard answers are a display ornament or a tool for reaching fruit. Neither answer explains the dense network of blood vessels inside it. Tattersall and colleagues pointed an infrared camera at toucans across a range of air temperatures. What did the heat do?

  Source: Tattersall et al., Science

• Where exactly does an ant lose its footing on a pitcher plant?

  A Nepenthes pitcher has been credited with slippery wax crystals, downward-pointing cells and nectar laced with alkaloids, all of them inside the jar. Bohn and Federle went outside it and measured the friction of weaver ants walking on the rim, first dry and then wet. Is the rim doing the catching?

  Source: Bohn & Federle, Proceedings of the National Academy of Sciences

• Does a bee see the world differently once it starts moving?

  A moving insect faces far more visual change per second than a sitting one, and the usual account puts the speed-up in the brain rather than the eye. Photoreceptors do answer faster when they are warm, though. Rother and colleagues tethered bumblebees over an air-supported ball and recorded their eyes while the insects sat and then walked. What changed at the retina?

  Source: Proceedings of the Royal Society B

• Does the altitude of a coffee farm really reach the cup?

  Specialty buyers pay a premium for high-grown coffee, and the reason usually offered is cooler air and slower ripening on the tree. That skips the fermentation tank, where microbes rather than weather rework the bean. A group sampled Arabica from four elevations, sequenced what grew during wet processing, and had the roasts cupped. Where does altitude actually act?

  Source: Food Science & Nutrition

• What is an octopus doing when its skin flickers in its sleep?

  A resting octopus sometimes runs waves of color and texture across its skin while the arms stay still, and that could be anything from digestion to a twitching nerve. A lab filmed four Octopus insularis around the clock, scored skin, eyes and mantle automatically, and tested how hard each animal was to rouse. Is the flickering part of sleep?

  Source: iScience

• Is handedness something only humans have?

  New Caledonian crows cut tapered probes out of the long narrow leaves of pandanus trees, tearing from either the left edge or the right one. A side preference across a whole species has been treated as a uniquely human trait. Hunt and colleagues recorded which edge the crows worked from at localities far apart on the island. Does one side win?

  Source: Nature

• What does it cost a flamingo to stand on one leg all night?

  A flamingo will hold a one-legged stance for hours while asleep, and the obvious assumption is a great deal of quiet muscular work keeping the stack of joints in line. Chang and Ting put flamingo cadavers into the same pose, where no muscle can contribute anything, and separately measured body sway in live birds. How much muscle does the pose need?

  Source: Chang & Ting, Biology Letters

• Why is a goat's pupil a horizontal slot?

  Pupils come in slits, slots, circles and rectangles, and the shape tracks the animal's way of life rather than its family: a cat's is vertical, a goat's horizontal, a human's round. Banks and colleagues sorted terrestrial species by pupil shape against how they feed and when they are active, then modeled what each aperture does to the image. What does a horizontal slot buy?

  Source: Banks et al., Science Advances

• Which way does a sleeping duck point its open eye?

  Birds can sleep with half the brain at a time, which leaves the opposite eye open, and nobody could say what the arrangement was for. If the answer is watching for predators, a bird in an exposed spot should use more of it and aim the open eye at the danger. Rattenborg and colleagues recorded eyes and brain waves in mallards sleeping in rows of four. Did position in the row matter?

  Source: Rattenborg et al., Behavioural Brain Research

• Do zebra stripes put a fly off from far away, or only up close?

  Repelling biting flies is the best-supported account of why zebra pelage is striped, and the effect itself is solid. The mechanism is not, and most of the candidates assume the fly is put off at a distance. Tombak and colleagues released hungry Stomoxys flies in an enclosure with real pelts, zebra against plain tan impala, and counted the landings. At what range does the pattern work?

  Source: Tombak et al., Scientific Reports

• Why does living near water seem to be good for you?

  People with the coast, a lake or a river near home report better health than people without. Four explanations are usually offered: they move more, they recover mentally, they meet more people, and their surroundings are cleaner. Georgiou and colleagues gathered fifty studies and pooled them one pathway at a time. Which of the four carries the effect?

  Source: Georgiou et al., International Journal of Environmental Research and Public Health

• Is an octopus throwing silt at a neighbor, or just tidying up?

  Octopuses at one site in Jervis Bay gather shells, silt and algae into their arms and blast the material away with a jet from the siphon, which could be housekeeping and nothing more. Godfrey-Smith and colleagues filmed the throws and compared the throws during encounters with other octopuses against all the rest. Is anybody being aimed at?

  Source: Godfrey-Smith et al., PLOS ONE

• What drags rocks across the floor of Death Valley?

  Rocks on Racetrack Playa leave long engraved trails across flat dry mud. Since the nineteen forties the blame has gone to hurricane winds, rain-slicked clay, or ice flotation carrying the stones clear of the ground. Nobody had ever watched one move. Norris and colleagues bolted GPS units to rocks and left cameras and a weather station running through a winter. What happens when a rock moves?

  Source: Norris et al., PLOS ONE

• Does a mouse's squeak have anything in it worth calling a song?

  Male mice emit ultrasonic calls from about thirty kilohertz up to a hundred and ten when they meet a female or her pheromones, and that had been filed as excited squeaking. Holy and Guo recorded the calls and analyzed the order the sounds arrived in rather than the sounds themselves. Is there a structure in there?

  Source: Holy and Guo, PLOS Biology

• What opens the scales of a pine cone that has been dead for years?

  A pine cone spreads its scales in dry air and draws them back in damp, and it keeps doing so long after the tree dropped it, with nothing alive left inside. Each scale is built as a bilayer, one tissue that swells and one that resists. Eger and colleagues measured the water uptake and the stiffness of every layer and scanned scales wet and dry. How does swelling become bending?

  Source: Eger et al., Advanced Science

• Why does a reindeer's eye glow a different color in winter?

  Arctic reindeer go from continuous summer daylight to continuous winter darkness, and an eye tuned for one is a poor instrument in the other. Behind their retina sits a tapetum lucidum, the mirror that throws a torch beam back out of an eye at night. Stokkan and colleagues compared that mirror in summer animals against winter ones. Does it stay the same all year?

  Source: Stokkan et al., Proceedings of the Royal Society B

• Do grazing cows really line themselves up north to south?

  Observational work, some of it from satellite imagery, reported that resting cattle tend to lie on a north-south axis. That would mean a large mammal reading the magnetic field with no migration to spend it on. Nobody had tested the idea by intervening. Weijers and colleagues strapped strong neodymium magnets to cows in Portugal and recorded how the animals lay. Does the alignment survive a magnet?

  Source: Weijers, Hemerik and Heitkönig, PLOS ONE

• Does a dolphin have anything like a name?

  Most animals give away who is calling the way a voice does, through the texture one body imposes on every sound it makes. Bottlenose dolphins do something else, because each animal produces a distinctive whistle type of its own. Janik and Sayigh gathered fifty years of work on those whistles into one review. How far does the comparison with a name actually go?

  Source: Janik and Sayigh, Journal of Comparative Physiology A

• Why would an electric eel climb out of the water to attack?

  An electric eel discharging underwater is sharing its current with the whole river, and any one target standing in the shallows receives a fraction of it. A cornered eel does something stranger: it rises out of the water and presses the underside of its head against the threat. Catania measured the circuit that forms at that moment, with a human subject taking the strike. What does leaving the water buy the eel?

  Source: Catania, Current Biology

• Does a hovering hummingbird get its lift from both halves of the wingbeat?

  A hummingbird’s upstroke and downstroke mirror each other almost exactly, which is why the wingbeat had been modeled on an insect’s, with each half carrying about the same share of the weight. That assumption went into the standard aerodynamic models and into the experiments built to test them. Warrick and colleagues measured the wake of hovering rufous hummingbirds instead. Is the split really even?

  Source: Warrick et al., Nature

• Is there a best angle for skipping a stone?

  A flat stone thrown at a lake either bounces or goes straight in, and the thing that decides it is the angle between the stone’s face and the water. An earlier experiment had found a magic angle of twenty degrees, where the stone needs the least speed to come back up. Nagahiro and Hayakawa simulated the impact in three dimensions and built an equation model beside it. Does the theory land on the same angle?

  Source: Physical Review Letters

• When did the last mammoths actually disappear from the Yukon?

  A fossil record is a record of bones that happened to form, survive and then be found, which makes it lumpy in time and in space. Sediment holds a second archive: DNA shed by animals and plants and locked into frozen silt. Murchie and colleagues read thirty thousand years of it out of the Klondike. What does the sediment say that the bones do not?

  Source: Murchie et al., Nature Communications

• Which Namib beetle is the one that drinks the fog?

  Textbooks and biomimicry papers credit a bumpy-shelled Namib beetle with harvesting fog on the microstructure of its back, and the picture of it standing head-down on a dune is everywhere. Nørgaard and Dacke took four Namib darkling beetles, two smooth-shelled and two bumpy, watched which ones actually fog-bask, and weighed the water each back collected. Who is doing what?

  Source: Nørgaard and Dacke, Frontiers in Zoology

• How does a sponge keep its own filter from clogging?

  A sponge is a filter with almost nothing that moves, pulling seawater in through thousands of tiny inlet pores and pushing it out through a few large openings. Solid waste ought to leave the way the water does, by the outflow. Kornder and colleagues ran time-lapse video on a Caribbean tube sponge and analyzed what it was shedding. Which way does the rubbish actually go?

  Source: Current Biology

• What else is a hoverfly reading when it picks a flower?

  A pollinator can read a flower’s color, shape, scent and even its temperature, and bumblebees are known to add one more channel: the electric field around the bloom. Hoverflies are major pollinators in their own right, and nobody had asked the same of them. Khan and colleagues measured how a hoverfly picks up charge and how a floral field varies. Is there a fifth channel here too?

  Source: Scientific Reports

• Why does a cat walk past a bowl of sugar?

  Most mammals will take sweetness when it is offered and cats will not, which could be a preference, a habit, or an instrument that is simply missing. The mammalian sweet receptor is a pair of proteins that only works assembled, so one broken half would be enough to explain it. Li and colleagues sequenced both genes in domestic cats, tigers and cheetahs. Is anything actually missing?

  Source: PLoS Genetics

• How does a desert bird carry water home to its chicks?

  Namaqua sandgrouse nest as much as thirty kilometers from the nearest water, and the chicks cannot go to it. The adult male flies there instead, wades in, and comes back with water held in the feathers of his belly for the whole return flight. Mueller and Gibson scanned those feathers and measured the stiffness of each part. What is holding the water in?

  Source: Journal of the Royal Society Interface

• How slowly can the largest heart on earth beat?

  A diving animal slows its heart to make the oxygen in its blood last, and a blue whale is the extreme case of a big body with a slow pulse. The complication is how it eats. Lunge feeding swallows a room full of water at a time and costs a great deal of power. Goldbogen and colleagues tagged a foraging whale with a heart monitor that also logged depth. What does the heart do during a lunge?

  Source: Proceedings of the National Academy of Sciences

• Why can a dog give you that look and a wolf cannot?

  Dogs raise the inner corner of the eyebrow in a way that reliably gets a reaction out of people. Wolves, who are the same animal a few tens of thousands of years back, mostly do not. That might be training. It might also be anatomy. Kaminski and colleagues dissected dog and wolf heads and separately scored the eyebrow movement in living animals of both. Is the difference in the muscle?

  Source: Proceedings of the National Academy of Sciences

• Does a cat have to keep working to hold a purr going?

  Nearly every mammal sound comes from tissue in the larynx set oscillating by airflow, with no nerve firing on every cycle. A purr was long held to be the exception, driven by laryngeal muscles contracting in bursts twenty to thirty times a second under neural command. Direct evidence for that was thin. Herbst and colleagues blew air through eight excised cat larynges, with no nerves attached. Does anything purr?

  Source: Current Biology

• What does an ant colony do with a nestmate whose leg is infected?

  Many ants disinfect wounds with secretions from the metapleural gland, but several genera lost that gland over evolutionary time, Camponotus among them. Those colonies still have injured workers and still have soil full of pathogens. Frank and colleagues injured Camponotus floridanus workers at two different points on the leg and watched what nestmates did about it. What is left when the chemistry is gone?

  Source: Current Biology

• Can an ape treat its own injury with a plant?

  Self-medication turns up across the primates in forms like swallowing whole leaves, chewing bitter pith and rubbing fur, and all of those are things an animal does to itself generally rather than to an injury. Active treatment of a wound has exactly one prior report, in chimpanzees. Then a male Sumatran orangutan at a research site took a facial wound, and observers watched what he did over the following days. What did he reach for?

  Source: Scientific Reports

• Can sleep be useful if it only lasts four seconds at a time?

  A microsleep is the seconds-long lapse that makes a tired driver dangerous, and it is usually treated as a failure of wakefulness rather than as rest. A nesting chinstrap penguin cannot afford a proper sleep, with an egg predator about and neighbors attacking constantly. Libourel and colleagues put brain recorders on wild penguins in Antarctica. How much sleep can seconds at a time add up to?

  Source: Science

• What is a sea turtle actually sensing when it finds its way home?

  A migrating animal can read two things off the earth’s field: a direction, like a compass, and a position, like a map. The leading guess about the hardware is magnetite, since a brief strong pulse that would flip the magnetism of a crystal also disturbs how several animals orient. Which of the two senses the pulse hits has been hard to tell apart. Mackiewicz and colleagues ran the test on loggerheads in an assay that uses the map and not the compass. Which sense breaks?

  Source: Journal of Experimental Biology

• Is a whale blowing a ring of bubbles making a tool?

  Plenty of animals use tools and very few build them, which is the line that separates picking up a stick from making one. Humpback whales blow rings of bubbles around prey, and the group version is famous. Szabo and colleagues went after the solitary version in Southeast Alaska, with tags on the whales and drones overhead, and measured the geometry of each net. Is the whale shaping it, or just blowing?

  Source: Royal Society Open Science

• Does a plant under stress make any sound you could pick up?

  A stressed plant changes in ways anyone can see: color, smell, shape. Sound has never been on the list, partly because vibration inside a stem is not the same thing as a noise traveling through air. Khait and colleagues put microphones around tomato and tobacco plants, in an acoustic chamber and then in a greenhouse, and logged the plants’ physiology at the same time. Is there anything to record?

  Source: Cell

• Can a bird see what makes a square different from a lopsided shape?

  People pick out right angles, parallel sides and symmetry without being taught, and that intuition is treated as a foundation of elementary Euclidean geometry in us. Whether it is ours alone has been hard to ask, because most animal tests need training on each new case. Schmidbauer and colleagues trained carrion crows on a general odd-one-out task with arbitrary shapes, then handed them quadrilaterals they had never seen. What did the birds do?

  Source: Science Advances

• Why would a fish choose the turbulent water over the smooth?

  Field observers keep finding fish holding station in churning water when calmer flow is available a body length away. Behind an obstacle a trout adopts the Karman gait, swinging its body wide and beating its tail in time with the vortices coming off the cylinder. The obvious reading is that it is hiding in the slack water. Liao put electrodes in the swimming muscles to see what they were doing. How much work is the fish putting in?

  Source: Journal of Experimental Biology

• Can living beside a sick animal change the way you smell?

  Illness changes body odor, and healthy animals avoid the smell of sick ones, which is a reasonable defense against catching something. The next question is whether smelling sickness does anything to the animal doing the smelling. Gervasi and colleagues made mice ill with a bacterial endotoxin, housed healthy mice alongside them, and then tested whether those healthy cagemates smelled any different. Does exposure leave a trace?

  Source: Scientific Reports

• How does an octopus taste something it has only touched?

  An octopus exploring a crevice it cannot see identifies what it finds by touching it, and the molecules worth identifying down there are greasy ones that never dissolve into the water. The receptors doing the work are chemotactile receptors, which evolution built out of a receptor for a neurotransmitter. Allard and colleagues took a cryo-electron microscopy structure of one and set it beside its ancestor. What had to change?

  Source: Nature

• Does a sourdough starter taste of where it was made?

  Bakers talk about a sourdough starter the way winemakers talk about a vineyard, as something that picks up the microbes of its city and could not be reproduced anywhere else. Nobody had checked at scale. Landis and colleagues worked with a network of community scientists to collect five hundred starters from four continents and sequenced the lot. Does geography show up in the microbes?

  Source: eLife

• What is a glowing mushroom glowing for?

  Fungal bioluminescence has been noted since antiquity and the appealing explanation is advertising: a glow that brings in insects, which then carry spores away. Some bioluminescent fungi do attract insects differentially. Weinstein and colleagues asked the same of the Australian ghost fungus, checking when it glows, when insects are about, and whether a glowing specimen pulls anything in. Does the advertisement work?

  Source: IMA Fungus

• Does a filter-feeding shark eat while crossing an ocean?

  Basking sharks spend the summer filtering plankton off the shelf of the northeastern United States and Canada, then vanish south to the Caribbean for winter. For other highly migratory sharks the assumption is fasting: swim on stored energy and feed at the destination. Elcock and colleagues put satellite archival tags on basking sharks and recorded what depths they held through the crossing. Are they eating on the way?

  Source: PLOS ONE

• Does a giraffe actually listen to the birds riding on its neck?

  Red-billed oxpeckers live on large mammals, eating their ectoparasites and calling sharply when something approaches. Giraffes depend on spotting an ambush early, so the arrangement looks like a bargain with a built-in alarm. Whether giraffes read the calls that way was untested. Baotic and Szipl played oxpecker alarms to three giraffe populations, some living with lions and some without. Who takes the warning seriously?

  Source: BMC Biology

• How does a bat in the dark know it has found a pond?

  A bat needs water for drinking, for hunting over and for orienting by, and it has to find it by echolocation in the dark. Reading a single insect-sized target off an echo is well understood. How a bat classifies a large extended surface is not. Greif and Siemers put smooth plates out for wild bats of fifteen species, and for juveniles that had never seen water. What makes a surface read as a pond?

  Source: Nature Communications

• What does a seabird do when a cyclone is coming?

  A tropical seabird feeding far offshore has nowhere to shelter and no way to outrun a storm system by brute speed. Several cyclones crossed the breeding grounds in the middle of a tracking study of red-footed boobies and great frigatebirds, which handed the researchers an experiment nobody would have designed. Weimerskirch and Prudor compared what adults and inexperienced young birds did. Who stayed and who flew?

  Source: Scientific Reports

• What tells a soil fungus to start building a snare?

  Arthrobotrys oligospora lives quietly on dead matter until it decides to hunt, at which point it grows sticky rings and nets that catch roundworms. Building the trap is the moment it stops being a decomposer and becomes a predator, and something has to trigger it. Yang and colleagues sequenced the genome and then measured which genes switch on when nematode extract arrives. What flips the switch?

  Source: PLOS Pathogens

• Can a mollusc remember what it ate and how long ago?

  Recalling a particular past event means holding three things together: what happened, where, and when. Tests built on that trio have found the ability in some birds and some mammals, and nowhere else. A cuttlefish has a large brain built on an entirely different plan. Jozet-Alves and colleagues offered cuttlefish two foods that replenish at different rates and watched where they went to forage. Do they keep track?

  Source: Current Biology

• When does a pollinated flower stop advertising?

  Scent is expensive, and a flower that has already been pollinated gains nothing by keeping it up. The obvious moment to stop is the instant pollen lands on the stigma, which is when the flower first has contact with a pollinator. Negre and colleagues followed methylbenzoate, a major scent compound, through pollination in snapdragon and petunia. Is the trigger the arrival of the pollen?

  Source: The Plant Cell

• Does a parasitic vine know which plant it is growing toward?

  Dodder is a plant that has given up on making its own living. It twines onto a host, taps the stem and takes what it needs, and a seedling with no host within reach dies. Whether it can tell one potential host from another before touching anything is the question. The authors measured pigment levels and recorded electrical signals in Cuscuta racemosa offered different neighbors. Can it tell from a distance?

  Source: Frontiers in Plant Science

• Can something with no brain at all learn a rhythm?

  A plasmodium of the true slime mold Physarum is one enormous cell with no neurons in it, and it crawls across a surface looking for food. Hit it with dry cold air and it slows down, which is a reaction and nothing more. Saigusa and colleagues delivered three such episodes at a constant interval, then stopped and kept conditions pleasant. What happens when the fourth would have been due?

  Source: Physical Review Letters

• What has to happen before four parrots can pull together?

  Cooperation experiments almost always use two animals, often with a barrier between them, which answers questions about understanding a partner and says little about a crowd. Kea live in groups and have to tolerate each other at close quarters. Schwing and colleagues built a box that opens only when two, three or four chains are pulled at the same moment, with a reward that can be shared unevenly but never taken entirely. What decides whether it opens?

  Source: Learning & Behavior

• Can a bird decide in advance how many times to call?

  Producing a chosen number of sounds on purpose needs two things at once: a grip on number, and enough control over the voice to stop at the right point. Animals have shown plenty of the first and very little of the second. Liao and colleagues trained carrion crows to answer arbitrary cues, each standing for a value from one to four, by calling that many times. Can a crow hit the number?

  Source: Science

• When does a cooperating group stop cooperating?

  Cooperation pays when joint action produces more than each animal could get alone, and selection also rewards whoever can grab the shared result. How animals keep that second pressure in check has been argued mostly over primates. Li and colleagues set semi-wild Asian elephants on a loose-string apparatus that only works if two pull together, and then varied how much food was on offer. Where does it break?

  Source: PLOS Biology

• Which sense does a social animal actually run its social life on?

  An animal with eyes, antennae and chemical senses may still lean on one of them for everything social. Testing that means removing a sense and watching, and almost nobody has followed the blinded animals back out into the wild. Steele and Laidre put opaque covers over the eyes of social hermit crabs, then released blinded and control crabs both into the wild and into captive groups. What falls away?

  Source: The Science of Nature

• Why would a rat bother to free a trapped stranger?

  Norway rats will open a restrainer to release a trapped companion, which looks like a response to the other animal’s distress. If that is an evolved decision rule, it has to pay the helper somehow, and there are two classic ways: the trapped animal is a relative, or it will return the favor. Engelhardt and colleagues ran a two-stage experiment to separate them. Which one is doing the work?

  Source: iScience

• How does a plant send its bodyguards to the part under attack?

  A plant that recruits a predator to eat its pests is a familiar arrangement. Steering that predator to the right organ at the right time is a harder trick. On wild potato, predatory mites gather at the flowers of undamaged plants and move down fast once herbivorous mites start on the leaves. Munawar and colleagues went after the signal behind that move with inhibitors and gene silencing. What calls them down?

  Source: Current Biology

• Why do city birds sing at a higher pitch?

  Traffic noise sits low in the frequency range, and birds in noisy cities sing both louder and higher. The standard reading is that the higher pitch is an adaptation lifting the song clear of the masking. Some have gone further, suggesting urban and rural songs could diverge far enough to split populations. Nemeth and Brumm modeled what each change actually buys in transmission. Which one helps?

  Source: Nemeth and Brumm, The American Naturalist

• What decides where billions of migrating birds come down to rest?

  Nocturnal migrants crossing North America twice a year have to land somewhere to refuel, and where they land matters more than where they fly. Mapping those stopovers across a continent has been out of reach until recently. Horton and colleagues built seasonal maps of stopover density for the contiguous United States out of more than ten million remote sensing observations. What predicts them?

  Source: Nature Communications

• How does a new whale song cross an ocean?

  Male humpbacks sing complex displays that are learned rather than inherited, and a population will sometimes abandon its song outright and adopt a new one wholesale. That kind of upheaval needs contact: somebody has to hear the new song and carry it. Where that contact happens has stayed uncertain. Owen and colleagues compared recordings from a newly discovered stopover against several South Pacific wintering grounds. Where do the songs meet?

  Source: Royal Society Open Science

• Does more acidic seawater really scramble a reef fish’s senses?

  Carbon dioxide dissolving into the sea has driven ocean acidification fast enough to worry anybody who studies reefs. Several high-profile papers reported something stranger than physiological stress: fish under end-of-century conditions becoming completely attracted to the chemical cues of their predators. Clark and colleagues set out to reproduce those behavioral effects, and to check the statistics behind them. Do the results hold up?

  Source: Nature

• Can one plant run two different cons at the same time?

  Corallorhiza striata has no green leaves and makes no food, taking everything from a fungus it parasitizes, which is one deception already. Its flowers carry no nectar either, so whatever pollinates them is getting nothing. Running both cheats at once in a single life stage had been called highly improbable. Freudenstein and Barrett watched the plants in the field and worked through thousands of photo records. Who is being fooled?

  Source: American Journal of Botany

• What does an eye with twelve color channels actually see?

  Some mantis shrimp carry twelve photoreceptor types, each tuned to a narrow slice of the spectrum from deep ultraviolet out to far red. Human vision manages fine color discrimination on three. Twelve ought to deliver something extraordinary, and nobody could say what. Thoen and colleagues ran behavioral wavelength discrimination tests, training the animals to tell one color from a neighboring one. How fine can they cut it?

  Source: Science

• What combs frost into hair on a fallen branch?

  On dead broad-leaf wood, just below freezing, ice sometimes grows as a dense mass of fine white filaments rather than as a crust. Wegener proposed a fungus behind it back in nineteen eighteen and nobody settled the question. Hofmann and colleagues tried to reproduce hair ice on wood samples, then killed whatever was living in the wood with heat and with fungicide. Does the ice still grow?

  Source: Hofmann et al., Biogeosciences

• Why is there a gap of sky between one tree crown and the next?

  Look straight up in a dense stand and the crowns rarely meet, leaving a network of bright channels between them. Explanations have ranged from chemical signalling to light sensing, and the plainest one is mechanical: in wind, neighboring branches hit each other. Clatterbuck and colleagues measured branch growth, bud toughness and how hard crowns actually swing. Does the mechanical account carry it?

  Source: Clatterbuck et al., Forests

• What exactly does a wave do to make the sea glow?

  Blue light breaking along a night shoreline comes from plankton responding to water movement, and the connection has been known for a very long time. What a single cell is actually reacting to is not. Cussatlegras and Le Gal put Pyrocystis noctiluca into a Couette shearing apparatus and ran several kinds of flow past it, measuring the light each one produced. Which part of the motion sets them off?

  Source: Cussatlegras and Le Gal, Nonlinear Processes in Geophysics

• Where is a spider’s ear?

  Hearing in every animal known rests on an auditory organ built out of cells, and the size of that organ is limited by the size of the body around it. A spider is small and has no such organ. It does have a web, which is a large, taut structure of its own manufacture hanging in the air. Zhou and colleagues asked whether airborne sound reaches the spider through it. Is the web doing the listening?

  Source: PNAS

• How does a fish know what color it has just turned?

  An animal changing color cannot see most of its own body, which leaves an obvious gap: nothing checks whether the change came out right. Skin that detects light has been found in many color-changing species, and its function has stayed unclear. Schweikert and colleagues worked through the morphology, physiology and optics of dermal photoreception in the hogfish. What is the skin looking at?

  Source: Nature Communications

• Does a rescuing ant understand what is holding its nestmate?

  Helping is common across the animal world and actual rescue is rare. Ants will dig at buried nestmates and pull at their limbs, both of which a chemical distress call could release directly, with no understanding required. Nowbahari and colleagues bound test ants with nylon thread under sand and offered them to groups of five Cataglyphis cursor, varying who the trapped individual was. What do the rescuers do?

  Source: PLOS ONE

• How does a flamingo catch brine shrimp that swim faster than it does?

  A flamingo feeds with its head upside down, filtering through comb-like lamellae with a piston of a tongue. The equipment is well described; the moves are not. Nobody could say what the L-shaped beak, the S-curved neck, the stomping feet or the habit of feeding into the current are for. Ortega-Jimenez and colleagues filmed live birds with brine shrimp and ran the fluid dynamics. What is the bird doing to the water?

  Source: PNAS

• Does a coral do better with fish living inside it?

  Small aggregating damselfish shelter among the branches of a coral colony, and their presence is known to help the coral along in ordinary conditions, through water movement and the nutrients they supply. Whether any of that matters when the water gets too hot is another question, since bleaching is a stress the coral meets on its own. Chase and colleagues tracked colonies with and without resident fish through a thermal bleaching event. Does the lodger help?

  Source: PLOS ONE

• Can an animal build a tool out of pieces that are each useless?

  Putting non-functional parts together into something that works requires anticipating what the finished object will do, before it exists. Outside a few observations in captive great apes, no animal has been seen doing it, and in human children the ability arrives late. Bayern and colleagues gave eight naive New Caledonian crows combinable elements, each too short to reach the food. Does anything get built?

  Source: Scientific Reports

• Are chimpanzees eating bark because it is medicine?

  Wild chimpanzees sometimes eat things with no nutritional case for them: bark, dead wood, stripped pith, all low in nutrients and often loaded with bioactive toxins. Calling that self-medication has been easy to say and hard to show, because the alternative is simply that animals eat odd things. Freymann and colleagues watched two Budongo communities for eight months, noted who was ill, and took the plants to a laboratory. Do the plants do anything?

  Source: PLOS ONE

• Why do so many people put food out for garden birds?

  Feeding garden birds is a global habit on a scale that moves real quantities of seed, and it is one of the few routine contacts many urban households still have with wild animals. Why people do it has stayed poorly understood. Cox and Gaston surveyed households in urban towns in southern England against three candidate motivations: psychological benefit, concern for bird welfare, and a general orientation toward nature. Which one drives it?

  Source: PLOS ONE

• What exactly does a long walk give the person walking it?

  People finish a long-distance route saying it did them good, and that report is usually left as a report. The Five Ways to Wellbeing framework breaks the vague claim into five nameable things: connect, be active, take notice, learn, give. Munro and colleagues interviewed walkers on the West Highland Way as they walked it, in place rather than afterwards, and coded what they said against those five. Which ones actually show up?

  Source: Information Research

• Does how a dolphin hunts decide who it spends time with?

  At Laguna in southern Brazil, some resident bottlenose dolphins work with beach-casting fishermen, driving fish toward the nets and cueing the throw. Others in the same population never do it. Both groups use the same lagoon, so sharing water is not the question. Daura-Jorge and colleagues used photo-identification to map who associates with whom. Does the hunting tactic show up in the social network?

  Source: Biology Letters

• Does a bat carry a map of its valley, or just a set of routes?

  Finding your way along a path you have flown before needs only memory of that path. Working out a new route between two places, without having flown it, needs something else: a representation of how the whole area fits together. Whether any animal besides us holds one has been argued for decades, mostly because it is so hard to show outside a laboratory. Toledo and colleagues built a tracking system to follow wild Egyptian fruit bats. What do the flight paths show?

  Source: Science

• Can a plant tell the difference between wind and a caterpillar?

  Sound has been shown to affect how plants germinate and grow, and it has never been clear what any of that is for in the field. A caterpillar chewing a leaf puts real acoustic energy into the tissue, so there is at least something to detect. Appel and Cocroft played recorded feeding vibrations to Arabidopsis rosettes, then let caterpillars loose on them. Does the warning get through?

  Source: Oecologia

• Can a plant tell its neighbors which insect is eating it?

  A damaged plant releases a blend of volatiles, and the blend differs by which herbivore is doing the damage. Neighboring plants pick those volatiles up and prepare their own defenses, which is well established. The attractive next step is that the neighbor reads the species from the blend and prepares for that insect specifically. Paudel Timilsena and colleagues tested it with a specialist and a generalist caterpillar. Does the message carry a name?

  Source: Paudel Timilsena et al., Plant, Cell & Environment

• Could a building panel tell you it is damp?

  Mycelium-bound composites are being proposed as replacements for conventional materials, in acoustic and thermal panels and in packaging, and the usual plan is to kill the fungus once the block has grown. Leaving it alive would make the panel something else: a material that reacts. Phillips and colleagues kept the mycelium living and recorded its electrical activity while the moisture content changed. Does the material report anything?

  Source: Fungal Biology and Biotechnology

• Is the water at the bottom of the deepest trench on earth standing still?

  The Challenger Deep is the lowest point in any ocean, eleven kilometers of water above a narrow trench floor, and the intuition is that water down there barely moves. Almost nobody has measured it, because the instruments that go that deep are rare. Jiang and colleagues sent two super-deep gliders down in September and October of two thousand eighteen and read the water properties on the way. What is the water doing?

  Source: Geophysical Research Letters

• Does being touched calm an animal down even when nobody is touching it?

  Massage lowers stress in people, and grooming looks like it does something similar in primates, but the two explanations have never been separated. The contact might be doing the work, or the relationship behind the contact might be. On a reef, cleaner wrasse stroke their clients with pectoral and pelvic fins while working, a behavior called tactile stimulation. Soares and colleagues replaced the cleaner with a moving model. Does the touch alone help?

  Source: Nature Communications

• How old is kissing?

  Kissing turns up across the animal kingdom and nobody can say what it is for, since the fitness benefit is unclear. Part of the trouble is definition: a human one smuggles in human meaning. Brindle and colleagues defined it without us at the center: non-agonistic directed oral-oral contact within a species, with some movement of the lips and no food passed. Then they ran the trait back down the primate tree. Where does it start?

  Source: Evolution and Human Behavior

• What happens to a bat that eats over-ripe fruit?

  Ethanol is present in all fleshy fruit and the concentration climbs as the fruit ripens, so an animal living on fruit is dosing itself whether it means to or not. Egyptian fruit bats already discount food once it passes one percent ethanol, which suggests they treat it as a cost. Sanchez and colleagues flew bats down an indoor corridor after feeding them ethanol-rich or ethanol-free food. Does it actually impair them?

  Source: Behavioural Processes

• What does an African lizard do when a resort kitchen moves in next door?

  Rainbow lizards are everywhere in suburban Africa, living off arthropods and taking whatever else turns up, which is the textbook opportunistic foraging strategy. A seaside resort in southern Togo put a different kind of food within reach. Dendi and colleagues watched a population there feeding regularly on pizza, and offered them more than one variety. Do they take whatever is going?

  Source: African Journal of Ecology

• What happens to a tubeworm’s bacteria when the tubeworm dies?

  The hydrothermal vent tubeworm Riftia pachyptila has no gut and is fed entirely by bacteria living inside it, picked up from seawater by the settled larva rather than inherited from a parent. That arrangement needs a free-living population out there to be picked up from. Nobody had shown the bacteria ever getting back out. Klose and colleagues tested what happens when the host dies. Do they escape?

  Source: PNAS

• How much of the deep seafloor can make its own light?

  In the open water of the deep sea, a recent count put more than three quarters of individual macro-planktonic organisms in the category able to emit light. On the bottom, the censuses have been few and based on small numbers of observations, so the figure there has been anybody’s guess. Martini and colleagues went through twenty-five years of remotely operated vehicle dives off central California. What does the seafloor come out at?

  Source: Scientific Reports

• Why is one insect red the only one still worth making?

  Three separate groups of insects supplied red dye for most of recorded history: the cochineal dyes, the kermes dye and the lac dye. All three share a chemistry and differ in which acid carries the color. Cooksey reviewed the structures, the histories and what became of each of them. Which one survived into industry?

  Source: Cooksey, Biotechnic & Histochemistry

• What happens to reef fish once the coral becomes rubble?

  Invertivorous reef fishes move energy from seabed invertebrates up to larger predators, and they need varied bottom habitat to hunt across. Climate change and local stressors are turning more and more reef into coral rubble, which has little structure and yet holds plenty of prey. Goberdhan and colleagues combined twenty-eight years of Seychelles monitoring with disturbance and foraging experiments. Who feeds on rubble?

  Source: Coral Reefs

• Why is there a gap of sky between one tree crown and the next?

  Look straight up in a dense stand and the crowns rarely meet, leaving a network of bright channels between them. The phenomenon has a name, crown shyness, and explanations have ranged from chemical signalling to light sensing. The plainest candidate is mechanical: in wind, neighboring branches hit each other. Clatterbuck and colleagues set out to measure that. Does it hold up?

  Source: Clatterbuck et al., Forests

• What is the foam piling up along the tide line made of?

  Scoop up seawater in a clear glass and look closely and it is full of tiny particles: dissolved salts, proteins, fats, dead algae, detergents and other pollutants, and assorted bits of organic and artificial matter. Shake the glass and small bubbles form on the surface. The same thing happens along a coast on a far grander scale. What is it?

  Source: NOAA National Ocean Service

• How does one bee tell the hive where the flowers are?

  Some patterns of behavior in animals are innate rather than learned, and among the clearest examples is how they convey information to one another. A foraging honeybee that finds nectar returns to a dark hive full of bees that have not been there. Karl von Frisch spent years watching what happens next. What did he find them doing?

  Source: Nobel Prize Outreach

• What does an octopus do when it has to forage in broad daylight?

  Octopuses generally hide. The mimic octopus does the opposite. It forages in broad daylight on open sand flats in the shallow Indo-Pacific, hunting crustaceans and fish where it is exposed and vulnerable, and retreats to a burrow only at night. Something has to compensate for that. Divers found it off Sulawesi in nineteen ninety-eight. What is the trick?

  Source: National Geographic

• Which mouse-sized animal lives past thirty?

  Body size predicts lifespan across mammals fairly well, and a rodent the size of a mouse should get a few years. The naked mole rat gets more than thirty. It also shows negligible senescence, no age-related rise in mortality, and high fecundity right up to death, and it resists both spontaneous and experimentally induced cancer. Kim and colleagues sequenced its genome. What is in there?

  Source: Kim et al., Nature

• What is the loudest sound any animal makes, and what is it for?

  Comparing animal loudness is notoriously difficult. Proximity matters, and so does the medium: there is a difference of some sixty-one and a half decibels between the same sound passing through air and through water. Work out the comparison properly and one animal is far ahead of the rest, and the sound is not a call. What is it?

  Source: Guinness World Records

• Where does the compass of a migrating bird sit?

  Songbirds hold a magnetic bearing to better than five degrees, which is the only reason an eleven thousand kilometer crossing works at all. The leading account puts the sensor in the eye, in light-sensitive cryptochrome proteins in the retina. But every simulation of it had produced a signal that changes gently with heading, nowhere near sharp enough. Hiscock and colleagues went back to the physics. What was missing?

  Source: Hiscock et al., PNAS

• Which animal with a backbone is swimming today and was alive centuries ago?

  Long-lived animals share an awkward set of traits: slow growth, late maturity, low fecundity, slow recovery from any loss. That makes them easy to overfish and hard to study, because nobody lives long enough to watch one age. One vertebrate has recently taken the record, and the method that proved it is unusual. Which animal, and how would you even check?

  Source: Edwards et al., Frontiers in Marine Science

• How does a plant know that whatever touched it is worth the trouble?

  A Venus flytrap shuts after two touches on its trigger hairs, which is a cheap decision. Digesting is not: the sealed trap has to be flooded with acid and a cocktail of enzymes, and that costs the plant real resources. A raindrop is not food. So between the snap and the enzymes, something has to be checked. Bohm and colleagues looked for the check.

  Source: Böhm et al., Current Biology

• Does a crow read a face the way we do?

  Turn a photograph of a face upside down and human recognition falls off a cliff, far more than for any other kind of picture. That face inversion effect is taken as the signature of a special, holistic way of handling faces. Crows know each other as individuals and can tell human beings apart by the face. Brecht and colleagues asked whether they do it the same way.

  Source: Brecht et al., Journal of Comparative Physiology A

• Which forest of thousands of trunks is actually one living thing?

  An aspen stand in south-central Utah covers one hundred and six acres of the Fishlake National Forest. Every trunk in it is genetically identical to every other, because aspens spread by sending up shoots from a shared root system rather than by seed. Researchers named it Pando, Latin for I spread, believing it to be the largest living organism by mass on earth. And it is now in trouble.

  Source: Rogers et al., Utah State University Extension

• Which unlikely organ helps a pigeon find its way home?

  Magnetic sense is the most contested sense there is. One old idea put tiny magnetite crystals in the tissues; a newer one puts light-sensitive cryptochromes in the retina; last year brought electrical currents in the inner ear. Then an ornithologist and an immunologist got talking at a conference, and the immunologist mentioned something about iron in immune cells. Where did that lead?

  Source: Science

• Why does one animal produce droppings with flat faces and sharp corners?

  The bare-nosed wombat is a burrowing Australian marsupial, renowned for leaving cubes. Nothing about a gut suggests cubes. It is soft, it is wet, and everything in it is pushed along by muscle contraction, which is a terrible way to make a corner. Yang and colleagues dissected wombats and then built a model. Where does the shape come from?

  Source: Yang et al., Soft Matter

• Can something with no nerve cells remember where it has been?

  Memory has one widely accepted definition: the means by which information is stored and retrieved. Nothing in that wording requires a brain. Still, almost all cognition research keeps memory inside a nervous system, which leaves a single-celled organism with no neurons as an awkward test case. Reid reviews what the slime mold Physarum polycephalum has been shown to do. Where would it even keep anything?

  Source: Reid, Animal Cognition

• How hard does a penguin have to push to keep its nest clean?

  A penguin on a nest does not get up to relieve itself. It stays put and projects the material clear of the rim, which leaves a tidy nest and a ring of marks on the ice at a measurable distance. That distance is a clue, because getting material to travel it takes pressure. Meyer-Rochow and Gal decided to work out how much. What does the arithmetic give?

  Source: Meyer-Rochow and Gal, Polar Biology

• Which animal eats an alga and then lives on light?

  Several animals host living algae inside themselves and live partly off what those algae produce. Corals, giant clams and green hydra all do it, and in each case the partner is a whole organism doing its own work. One sea slug goes further. It keeps no alga at all, only the part of the alga that matters, and then lives like a plant.

  Source: Rumpho et al., Journal of Experimental Biology

• What happens on the seabed when a whale dies?

  The deep sea is energy-poor: whatever sinks from the sunlit water arrives as a thin rain of particles. Then a great whale dies, and tens of tonnes of flesh and bone land in one place. Smith and colleagues review what a decade of work on modern and fossil whale remains has found. It is not a single feast.

  Source: Smith et al., Annual Review of Marine Science

• Why would a bee push a wooden ball around for nothing?

  Young mammals and birds play, and the usual account is that it develops the brain: fox cubs pretend-fight, dolphins spin with no predator in sight. Insects were not thought to do anything of the kind. Then bumblebees in a London laboratory kept pushing wooden balls around after the sugar reward for doing so had been withdrawn.

  Source: Science

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