# WildBionics

> WildBionics is a bilingual (English/German) open-source compendium that connects biology with physics, mathematics, chemistry, computer science and Physical AI (embodied, robotic AI) – through animals, plants, geology and bionics. Its time axis runs from the Big Bang to humanoid robots and the open question of superintelligence. Every article views one natural phenomenon through several "lenses" (biology, physics, mathematics, computer science, Physical AI) and cites peer-reviewed sources with DOIs.

- Content licence: CC BY-SA 4.0 – reuse is welcome with attribution to "WildBionics (https://wildbionics.com)".
- Code licence: MIT. Source and issue tracker: https://github.com/hstoecker/wildbionics
- English lives at the site root, German under /de/. Translations share a `ref` and are linked with hreflang.
- Maintainer: Hendrik Stöcker (https://github.com/hstoecker)

## Articles

- [Electric Eel: 860 Volts from Living Batteries](https://wildbionics.com/articles/electric-eel/): Electric eels stack thousands of cells like batteries in a torch – one eel reached 860 volts. How the shock remote-controls prey, from ions to circuits.
- [Sabre-Toothed Cat: Weak Bite, Sabres at Risk of Breaking](https://wildbionics.com/articles/smilodon-bite/): Smilodon had huge sabres but a weak bite. Its bones and tooth mechanics suggest it pinned prey with its forelimbs, then bit the neck.
- [How Fast Was T. rex? Footprints, Bones and Physics](https://wildbionics.com/articles/trex-running/): Could T. rex run? A bone-stress model says it most likely only walked; footprints agree but cannot test it. How we know – from physics to chemistry.
- [How We Walk: Pendulums, Springs and Humanoid Robots](https://wildbionics.com/articles/walking/): Walking is a pendulum, running a spring. Why we switch gaits near 2 m/s, how tendons save energy and how humanoid robots learn to walk.
- [The Robin's Quantum Compass](https://wildbionics.com/articles/robin-magnetic-compass/): European robins sense the tilt of Earth's magnetic field. The leading explanation is a quantum effect in their eyes: a light-driven radical pair.
- [How Insects Fly: Vortices, Halteres and RoboBees](https://wildbionics.com/articles/insect-flight/): Insect wings make more lift than classical aerodynamics allows – thanks to a vortex on the leading edge. How bees and flies fly, and how robots copy them.
- [Early Atmosphere: How Single Cells Changed the Sky](https://wildbionics.com/articles/early-atmosphere/): Early Earth had a fainter Sun and air without oxygen. Greenhouse gases kept it warm – until cyanobacteria filled the sky with oxygen.
- [Swimming in Honey: the Physics of Bacteria](https://wildbionics.com/articles/bacteria-low-reynolds/): For a bacterium, water is as thick as honey: inertia plays no role. How E. coli still swims – with a rotating corkscrew, runs and tumbles.
- [How Cats Drink: Inertia Against Gravity](https://wildbionics.com/articles/cat-lapping/): A cat does not scoop water with its tongue. It touches the surface, pulls up a thin water column and bites it off before gravity wins.
- [Schrödinger's Cat: The Thought Experiment Explained](https://wildbionics.com/articles/schroedingers-cat/): Schrödinger's cat is a 1935 thought experiment: a cat in a box, alive and dead at once. It shows why quantum rules seem to vanish in everyday life.
- [The Lotus Effect: How Leaves Clean Themselves](https://wildbionics.com/articles/lotus-effect/): Lotus leaves stay clean in muddy water: wax crystals on tiny bumps hold an air cushion, so drops bead up at over 160°, roll off and carry the dirt away.
- [How Cats Land on Their Feet: Angular Momentum Explained](https://wildbionics.com/articles/cat-righting/): A falling cat turns over without pushing off anything. Its total angular momentum stays zero – it rotates by changing its shape.
- [How Bats See with Sound: Echolocation Explained](https://wildbionics.com/articles/bat-echolocation/): Bats hunt in the dark by shouting ultrasound and listening to the echoes: the delay gives the distance, the pitch shift the speed of their prey.
- [How Geckos Stick to Walls: van der Waals Forces](https://wildbionics.com/articles/gecko-adhesion/): Geckos run up glass without glue or suction: billions of tiny spatulae on their toes stick by van der Waals forces – and let go in milliseconds.
- [The Pistol Shrimp and the Physics of Cavitation](https://wildbionics.com/articles/pistol-shrimp-cavitation/): How a pistol shrimp boils water without heat: its claw fires a jet that forms a cavitation bubble, a flash of light and a shock wave. Physics, maths and code.

## Key facts

### Electric Eel: 860 Volts from Living Batteries
- A 2019 study recorded a discharge of 860 V from one eel of the newly described species Electrophorus voltai – well above the 650 V previously cited for electric eels [3].
- Each firing electrocyte produces only about 0.15 V; large electric eels stack thousands of them in series to reach more than 600 V, and parallel stacks allow peak currents approaching 1 A at short circuit [1].
- Each high-voltage pulse typically triggers an action potential in the motor neurons of nearby prey: the eel remote-controls its prey’s muscles, freezing it in a whole-body contraction [6] [4].
- When it struggles with large prey, the eel often curls to bring its tail to the opposite side, more than doubling the electric field in the prey, then exhausts its muscles with repeated volleys of pulses at about 100 Hz [5].
- In its defensive leap, a comparatively small eel drove peak currents of 40–50 mA through a human arm – far above the threshold for pain receptors [8].
- Electric organs evolved at least six times independently in fishes [2].

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[2] Gallant, J. R., Traeger, L. L., Volkening, J. D., Moffett, H., Chen, P. H., Novina, C. D., Phillips, G. N., Anand, R., Wells, G. B., Pinch, M., Güth, R., Unguez, G. A., Albert, J. S., Zakon, H. H., Samanta, M. P., Sussman, M. R. (2014). Genomic basis for the convergent evolution of electric organs. Science 344, 1522–1525. https://doi.org/10.1126/science.1254432
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### Sabre-Toothed Cat: Weak Bite, Sabres at Risk of Breaking
- Bite force from the jaw muscles of Smilodon fatalis was relatively weak – in a 3D computer model about one third of that of a lion of comparable size; the skull was better suited to bites on prey that was already restrained [7].
- The upper arm bones of Smilodon fatalis were reinforced by thicker bone walls than in any living cat – interpreted by the authors as a sign of powerful forelimbs used to subdue prey and protect the long canines from breaking [1].
- In Tseng's digital eruption model of one specimen (AMNH FM55576; Table S1), the fully erupted sabre is, at the gum line, about 32 mm long from front to back but only 18 mm wide; by beam theory, a load from the side stresses it about 1.8 times as much as the same load from the front – calculated in this article from those measurements [6].
- CT scans combined with an enamel growth rate measured earlier from oxygen isotopes act as a clock: the upper canine erupted at about 6 mm per month, and finished erupting at an estimated 34–41 months of age [16].
- Whether sabre-toothed cats and dire wolves competed for the same prey at Rancho La Brea is debated: a multi-proxy study found little competition for prey [4], other researchers question that conclusion [18].

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### How Fast Was T. rex? Footprints, Bones and Physics
- Adult Tyrannosaurus rex weighed about 6,000–8,000 kg, with body lengths of 11–12 m and legs 3–3.3 m long [4].
- Biomechanical estimates of its top speed range from 5 to 15 m/s; some, mostly qualitative, anatomical studies even proposed up to 20 m/s [5].
- A computer model that also checks bone stress found that true running – with all feet off the ground – would probably have overloaded the skeleton: T. rex was most likely limited to walking gaits [5].
- The first known trackways of tyrannosaurids, from western Canada, point to walking speeds of about 6.4–8.5 km/h [7].
- Whether original proteins and soft tissues survive in T. rex bones is an open controversy: reports of flexible vessels and collagen [21] [17] stand against interpretations as biofilms and recent organic material [25] [18]; a reanalysis of the protein data found laboratory contaminants alongside bird-like haemoglobin and collagen [27].

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### How We Walk: Pendulums, Springs and Humanoid Robots
- In walking, the body vaults over a stiff leg like an inverted pendulum: kinetic and potential energy are traded back and forth, and this exchange can account for up to 70 % of the energy changes within a stride, leaving 30 % to the muscles [1].
- In running, the leg works like a spring: tendons and the arch of the foot store energy when the foot lands and return it by elastic recoil, like a bouncing rubber ball [1] [7].
- People switch from walking to running at a Froude number v²/(g L) of about 0.5 – short-legged or long-legged, and even in simulated reduced gravity [11]. In a treadmill study, adults switched at 2.06 m/s [13].
- The pendulum sets a speed limit: gravity must hold the body on its arc over the foot, so in the pendulum model a walker cannot go faster than about √(g L), about 3 m/s for a leg 0.9 m long – derived from the inverted-pendulum model [11] and calculated in this article.
- Passive dynamic walkers – machines without motors or control – walk down a gentle slope with a humanlike gait, powered only by gravity [14] [15]. Today, humanoid robots learn to walk with reinforcement learning in simulation and transfer it to the real robot [18].

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### The Robin's Quantum Compass
- European robins have a magnetic compass that reads the inclination of Earth's field lines – the angle at which they dip into the ground – not the polarity of the field [2].
- The compass appears to work through the eyes: robins with bilateral lesions in Cluster N, a light-processing brain region, lose their magnetic orientation but keep their sun and star compasses [7].
- The leading hypothesis is a quantum effect: light creates radical pairs in cryptochrome proteins in the retina, and Earth's field (about 50 µT) changes how their electron spins evolve [4] [3].
- Radio-frequency fields disorient robins – including the electromagnetic noise of a city [6] [9].
- Cryptochrome 4 from the robin is magnetically sensitive in the test tube, more so than the same protein from chicken or pigeon [1].

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### How Insects Fly: Vortices, Halteres and RoboBees
- Honeybees hover with a short stroke of about 90° and a high wingbeat frequency of about 230 Hz; fruit flies beat their 2.5 mm wings about 200 times per second through 145–165° [1].
- Insect wings produce typically 2–3 times more lift than conventional aerodynamics can account for. Most insects get it from a leading-edge vortex that stays attached to the wing and spirals out towards the tip [2] [6].
- Flies sense rotations with halteres – tiny, dumbbell-shaped organs that evolved from the hind wings. They beat like wings and detect the Coriolis forces of a turning body, like a gyroscope [8] [9].
- Smaller flyers must beat faster: for bodies of the same shape, the wingbeat frequency needed to hover grows as one over the square root of the size. A formula with mass and wing area explains 75 % of the variation in wingbeat frequency across insects [3].
- Harvard's RoboBee weighed 80 mg in its controlled flights of 2013; a four-winged successor of 90 mg flew untethered in 2019 with solar cells and electronics on board, 259 mg in total [16] [17].

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### Early Atmosphere: How Single Cells Changed the Sky
- During the Archean eon, the air contained less than a millionth of today's oxygen, but about 10 to 2,500 times more carbon dioxide and 100 to 10,000 times more methane [1].
- Four billion years ago the Sun was 25–30 % fainter than today [1]. With today's atmosphere, the early Earth would have been frozen for its first two billion years – yet there is ample evidence of liquid water and life [5].
- Most researchers explain this faint young Sun paradox with more greenhouse gases, but the problem is not considered fully solved [5] [1].
- Oxygen flooded the atmosphere 2.4 to 2.3 billion years ago, the Great Oxidation Event. It came from the photosynthesis of cyanobacteria and their ancestors [1].
- The rocks record the change: a special pattern in sulfur isotopes, made by ultraviolet light in an air without ozone, disappears between 2.45 and 2.09 billion years ago [7].
- Oxygen reached near-modern levels in air and sea only about two billion years after it first rose [4].

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### Swimming in Honey: the Physics of Bacteria
- For a bacterium, viscosity dominates and inertia plays no role: E. coli swims at a Reynolds number of only a few hundred-thousandths – Purcell estimated 0.00003. If its motor stops, it coasts about 0.1 ångström – less than the width of an atom [1].
- To swim like a bacterium, a human would have to be in a pool of molasses and move no part of the body faster than 1 cm per minute [1]. Honey alone is not enough: in honey a swimmer still reaches a Reynolds number of several hundred.
- E. coli swims by rotating its helical flagella, driven by rotary motors at about 100 revolutions per second [4] [5].
- Its path alternates between straight runs and short tumbles. Runs that lead to more food last longer – a simple rule that steers the cell up the gradient [1].
- Magnetic microrobots copy the corkscrew of the bacterial flagellum and are steered by external magnetic fields; they are being developed for medicine [9] [10] [12].

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### How Cats Drink: Inertia Against Gravity
- Most animals drink by suction. Cats and dogs cannot, because their cheeks are incomplete – so they lap [2] [1].
- A cat does not scoop: the tip of its tongue, curled backwards, rests on the water surface without dipping in. Water sticks to the upper side of the tongue [1] [4].
- Moving up fast, the tongue pulls a column of water behind it. The cat exploits the water's inertia to defeat gravity and pull it into its mouth [1].
- The competition between inertia and gravity sets how often a cat laps. Across the cat family, lapping frequency falls only weakly with body mass, roughly as mass<sup>−1/6</sup> [1] [3].
- Dogs lap with the same scaling but in a different physical regime: they accelerate the tongue harder and curl it backwards to pull a bigger column – which makes them messy drinkers [3].
- The spines on a cat's tongue have hollow tips that wick up saliva; a 3D-printed copy became a grooming brush that is easier to clean [5].

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### Schrödinger's Cat: The Thought Experiment Explained
- Schrödinger's cat is a thought experiment from 1935 – no cat was ever put in a box. Erwin Schrödinger described it in an essay on the state of quantum mechanics [1].
- In the imagined setup, a tiny radioactive sample decays within one hour with a 50 % chance; a decay would trigger a Geiger counter, a hammer and a flask of poison [1].
- Taken literally, quantum mechanics would describe the cat as a superposition of alive and dead. Schrödinger used this absurd picture to criticise such a literal reading [1].
- Decoherence – the constant interaction with the environment – destroys superpositions of large objects extremely quickly [3]. For processes in the brain, estimates give 10<sup>−13</sup> to 10<sup>−20</sup> s [4].
- The largest objects shown in a superposition so far are molecules heavier than 25,000 atomic mass units, made of up to 2,000 atoms [6].
- Physicists create "cat states" in the lab: a single ion in two places at once [7], and light fields with up to 111 photons [9].
- In cat qubits, bit-flip errors fall exponentially as the two cat states are pulled further apart – a route to more robust quantum computers [10].

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### The Lotus Effect: How Leaves Clean Themselves
- On a lotus leaf, water forms a contact angle of more than 160° (measured 162–164°) and rolls off at a tilt of less than 4° [5] [6] [7].
- The leaf's upper side carries two levels of roughness: about 3,400 papillae per mm², each about 15 µm high [5] [8], covered with wax tubules 0.3–1 µm long and 80–120 nm thick [5].
- The wax alone is not enough: a flat film of lotus wax gives only 119° [6]. The high angle comes from the air trapped under the drop.
- According to the Cassie–Baxter model, a drop on a lotus leaf touches solid material on only roughly 10 % of the area beneath it (estimated in this article).
- Dirt particles stick to the surface of rolling drops and are carried off the leaf – the self-cleaning lotus effect, a term Wilhelm Barthlott coined in 1992 [2].
- Self-cleaning façade paints such as Lotusan have been on the market since around 2000 [20] [2]; making such surfaces durable remains the main challenge [22].

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[2] Barthlott, W. (2026). The purity of sacred lotus: superhydrophobic self-cleaning plant surfaces and the consequences revisited. Planta 263, 80. https://doi.org/10.1007/s00425-026-04937-9
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[15] Watson, D. A., Thornton, M. R., Khan, H. A., Diamco, R. C., Yilmaz-Aydin, D., Dickerson, A. K. (2024). Water striders are impervious to raindrop collision forces and submerged by collapsing craters. Proceedings of the National Academy of Sciences 121, e2315667121. https://doi.org/10.1073/pnas.2315667121
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[18] Koh, J.-S., Yang, E., Jung, G.-P., Jung, S.-P., Son, J. H., Lee, S.-I., Jablonski, P. G., Wood, R. J., Kim, H.-Y., Cho, K.-J. (2015). Jumping on water: Surface tension–dominated jumping of water striders and robotic insects. Science 349, 517–521. https://doi.org/10.1126/science.aab1637
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### How Cats Land on Their Feet: Angular Momentum Explained
- Scientists have studied how falling cats turn over since 1894. A cat turns in the air without pushing off anything – its total angular momentum stays zero [1].
- The trick is a change of shape: cats twist and bend their spine, which changes the moment of inertia of the front and rear body [1]. A simple model of two cylinders joined at the waist already reproduces the turn [2].
- The tail is not needed: no difference in air-righting has been reported between cats with and without a tail [1].
- The air-righting reflex is mature in kittens by about 33 days and is mainly controlled by the balance organ – kittens blind since birth learn it just as well [4].
- Landing on its feet does not mean landing unhurt: of 119 cats treated after falls from buildings, 96.5 % survived, but 46.2 % had broken limbs [6].
- Robots use the same physics: a lizard-sized robot stabilises its body with an active tail [8], and a legged robot uses only its legs to turn in low gravity [9].

Sources:
[1] Jusufi, A., Goldman, D. I., Revzen, S., Full, R. J. (2008). Active tails enhance arboreal acrobatics in geckos. Proceedings of the National Academy of Sciences 105, 4215–4219. https://doi.org/10.1073/pnas.0711944105
[2] Kane, T. R., Scher, M. P. (1969). A dynamical explanation of the falling cat phenomenon. International Journal of Solids and Structures 5, 663–670. https://doi.org/10.1016/0020-7683(69)90086-9
[3] Frohlich, C. (1979). Do springboard divers violate angular momentum conservation?. American Journal of Physics 47, 583–592. https://doi.org/10.1119/1.11759
[4] Cremieux, J., Veraart, C., Wanet, M. C. (1984). Development of the air righting reflex in cats visually deprived since birth. Experimental Brain Research 54, 564–566. https://doi.org/10.1007/BF00235481
[5] Whitney, W. O., Mehlhaff, C. J. (1987). High-rise syndrome in cats. Journal of the American Veterinary Medical Association 191, 1399–1403. https://doi.org/10.2460/javma.1987.191.11.1399
[6] Vnuk, D., Pirkić, B., Matičić, D., Radišić, B., Stejskal, M., Babić, T., Kreszinger, M., Lemo, N. (2004). Feline high-rise syndrome: 119 cases (1998–2001). Journal of Feline Medicine and Surgery 6, 305–312. https://doi.org/10.1016/j.jfms.2003.07.001
[7] Arabyan, A., Tsai, D. (1998). A distributed control model for the air-righting reflex of a cat. Biological Cybernetics 79, 393–401. https://doi.org/10.1007/s004220050488
[8] Libby, T., Moore, T. Y., Chang-Siu, E., Li, D., Cohen, D. J., Jusufi, A., Full, R. J. (2012). Tail-assisted pitch control in lizards, robots and dinosaurs. Nature 481, 181–184. https://doi.org/10.1038/nature10710
[9] Rudin, N., Kolvenbach, H., Tsounis, V., Hutter, M. (2022). Cat-like jumping and landing of legged robots in low gravity using deep reinforcement learning. IEEE Transactions on Robotics 38, 317–328. https://doi.org/10.1109/TRO.2021.3084374

### How Bats See with Sound: Echolocation Explained
- Bat echolocation calls range from about 11 kHz to 212 kHz; most insect-eating bats call between 20 and 60 kHz – above the range of human hearing [2].
- Bat calls are among the most intense airborne sounds of any animal [2]: bats that hunt over water reach average source levels of about 137 dB SPL, with maxima above 140 dB SPL [3].
- In Simmons' classic experiments, big brown bats and three other species told apart targets whose distances differed by only 1–3 cm [4].
- When closing in on prey, a bat calls faster and faster – in the final feeding buzz up to about 200 calls per second [2].
- Horseshoe bats lower their call frequency the faster they fly, so that the Doppler-shifted echo returns consistently at the frequency they hear best [2] [10].
- The tiger moth Bertholdia trigona jams the sonar of attacking big brown bats with ultrasonic clicks [9].
- Robots with one ultrasonic speaker and two microphones have mapped offices and greenhouses by sound, combining the echoes with their own movement data [11] [5].

Sources:
[1] Griffin, D. R. (1944). Echolocation by blind men, bats and radar. Science 100, 589–590. https://doi.org/10.1126/science.100.2609.589
[2] Jones, G., Holderied, M. W. (2007). Bat echolocation calls: adaptation and convergent evolution. Proceedings of the Royal Society B: Biological Sciences 274, 905–912. https://doi.org/10.1098/rspb.2006.0200
[3] Surlykke, A., Kalko, E. K. V. (2008). Echolocating bats cry out loud to detect their prey. PLoS ONE 3, e2036. https://doi.org/10.1371/journal.pone.0002036
[4] Simmons, J. A. (1973). The resolution of target range by echolocating bats. Journal of the Acoustical Society of America 54, 157–173. https://doi.org/10.1121/1.1913559
[5] Eliakim, I., Cohen, Z., Kosa, G., Yovel, Y. (2018). A fully autonomous terrestrial bat-like acoustic robot. PLOS Computational Biology 14, e1006406. https://doi.org/10.1371/journal.pcbi.1006406
[6] Simmons, J. A., Fenton, M. B., O'Farrell, M. J. (1979). Echolocation and pursuit of prey by bats. Science 203, 16–21. https://doi.org/10.1126/science.758674
[7] ter Hofstede, H. M., Ratcliffe, J. M. (2016). Evolutionary escalation: the bat–moth arms race. Journal of Experimental Biology 219, 1589–1602. https://doi.org/10.1242/jeb.086686
[8] Barber, J. R., Conner, W. E. (2007). Acoustic mimicry in a predator–prey interaction. Proceedings of the National Academy of Sciences 104, 9331–9334. https://doi.org/10.1073/pnas.0703627104
[9] Corcoran, A. J., Barber, J. R., Conner, W. E. (2009). Tiger moth jams bat sonar. Science 325, 325–327. https://doi.org/10.1126/science.1174096
[10] Schnitzler, H.-U., Denzinger, A. (2011). Auditory fovea and Doppler shift compensation: adaptations for flutter detection in echolocating bats using CF-FM signals. Journal of Comparative Physiology A 197, 541–559. https://doi.org/10.1007/s00359-010-0569-6
[11] Steckel, J., Peremans, H. (2013). BatSLAM: simultaneous localization and mapping using biomimetic sonar. PLoS ONE 8, e54076. https://doi.org/10.1371/journal.pone.0054076

### How Geckos Stick to Walls: van der Waals Forces
- A gecko's toes carry millions of hair-like setae, each 30–130 µm long, that branch into hundreds of spatulae 0.2–0.5 µm wide [1].
- The spatulae stick mainly by van der Waals forces: gecko toes hold equally well on water-repellent and water-attracting surfaces [2]. Humidity adds to the force at the level of a single spatula [4].
- A single seta can hold 200 µN. All 6.5 million setae of a tokay gecko together could in theory carry about 130 kg [3].
- Geckos release a foot in about 15 ms: once the setal shaft is tilted to about 30° against the wall, the seta lets go [3].
- Splitting one contact into many smaller ones increases adhesion – which is why heavier animals have finer attachment hairs [5].
- Gecko-inspired dry adhesives let robots climb glass [10] and grip objects up to a metre across in microgravity [11].

Sources:
[1] Autumn, K., Liang, Y. A., Hsieh, S. T., Zesch, W., Chan, W. P., Kenny, T. W., Fearing, R., Full, R. J. (2000). Adhesive force of a single gecko foot-hair. Nature 405, 681–685. https://doi.org/10.1038/35015073
[2] Autumn, K., Sitti, M., Liang, Y. A., Peattie, A. M., Hansen, W. R., Sponberg, S., Kenny, T. W., Fearing, R., Israelachvili, J. N., Full, R. J. (2002). Evidence for van der Waals adhesion in gecko setae. Proceedings of the National Academy of Sciences 99, 12252–12256. https://doi.org/10.1073/pnas.192252799
[3] Autumn, K., Peattie, A. M. (2002). Mechanisms of adhesion in geckos. Integrative and Comparative Biology 42, 1081–1090. https://doi.org/10.1093/icb/42.6.1081
[4] Huber, G., Mantz, H., Spolenak, R., Mecke, K., Jacobs, K., Gorb, S. N., Arzt, E. (2005). Evidence for capillarity contributions to gecko adhesion from single spatula nanomechanical measurements. Proceedings of the National Academy of Sciences 102, 16293–16296. https://doi.org/10.1073/pnas.0506328102
[5] Arzt, E., Gorb, S., Spolenak, R. (2003). From micro to nano contacts in biological attachment devices. Proceedings of the National Academy of Sciences 100, 10603–10606. https://doi.org/10.1073/pnas.1534701100
[6] Hansen, W. R., Autumn, K. (2005). Evidence for self-cleaning in gecko setae. Proceedings of the National Academy of Sciences 102, 385–389. https://doi.org/10.1073/pnas.0408304102
[7] Tian, Y., Pesika, N., Zeng, H., Rosenberg, K., Zhao, B., McGuiggan, P., Autumn, K., Israelachvili, J. (2006). Adhesion and friction in gecko toe attachment and detachment. Proceedings of the National Academy of Sciences 103, 19320–19325. https://doi.org/10.1073/pnas.0608841103
[8] Autumn, K., Dittmore, A., Santos, D., Spenko, M., Cutkosky, M. (2006). Frictional adhesion: a new angle on gecko attachment. Journal of Experimental Biology 209, 3569–3579. https://doi.org/10.1242/jeb.02486
[9] Gamble, T., Greenbaum, E., Jackman, T. R., Russell, A. P., Bauer, A. M. (2012). Repeated origin and loss of adhesive toepads in geckos. PLoS ONE 7, e39429. https://doi.org/10.1371/journal.pone.0039429
[10] Kim, S., Spenko, M., Trujillo, S., Heyneman, B., Santos, D., Cutkosky, M. R. (2008). Smooth vertical surface climbing with directional adhesion. IEEE Transactions on Robotics 24, 65–74. https://doi.org/10.1109/TRO.2007.909786
[11] Jiang, H., Hawkes, E. W., Fuller, C., Estrada, M. A., Suresh, S. A., Abcouwer, N., Han, A. K., Wang, S., Ploch, C. J., Parness, A., Cutkosky, M. R. (2017). A robotic device using gecko-inspired adhesives can grasp and manipulate large objects in microgravity. Science Robotics 2, eaan4545. https://doi.org/10.1126/scirobotics.aan4545
[12] Kendall, K. (1975). Thin-film peeling-the elastic term. Journal of Physics D: Applied Physics 8, 1449–1452. https://doi.org/10.1088/0022-3727/8/13/005
[13] Huber, G., Gorb, S. N., Spolenak, R., Arzt, E. (2005). Resolving the nanoscale adhesion of individual gecko spatulae by atomic force microscopy. Biology Letters 1, 2–4. https://doi.org/10.1098/rsbl.2004.0254
[14] Russell, A. P. (2002). Integrative functional morphology of the gekkotan adhesive system (Reptilia: Gekkota). Integrative and Comparative Biology 42, 1154–1163. https://doi.org/10.1093/icb/42.6.1154
[15] Peattie, A. M., Majidi, C., Corder, A., Full, R. J. (2007). Ancestrally high elastic modulus of gecko setal β-keratin. Journal of the Royal Society Interface 4, 1071–1076. https://doi.org/10.1098/rsif.2007.0226

### The Pistol Shrimp and the Physics of Cavitation
- The loud snap of a pistol shrimp does not come from the claw halves hitting each other. It comes from a collapsing cavitation bubble [1].
- Closing the claw fires a water jet of roughly 25 m/s – an estimate from high-speed video of the snapping claw [1] [8]. At that speed the pressure in the jet falls below the vapour pressure of water, and a vapour bubble forms [1].
- The bubble collapses in less than a millisecond, sending out a shock wave that can stun prey – and a short flash of light, dubbed shrimpoluminescence [2].
- Inside the collapsing bubble, temperatures reach at least 5,000 K [2].
- Engineers have 3D-printed a working replica of the claw that reproduces the flash and the shock wave [3].
- Snapping shrimp are among the main sources of biological noise in shallow seas: a single snap reaches a source level of 183–189 dB re 1 µPa at 1 m [7].

Sources:
[1] Versluis, M., Schmitz, B., von der Heydt, A., Lohse, D. (2000). How snapping shrimp snap: through cavitating bubbles. Science 289, 2114–2117. https://doi.org/10.1126/science.289.5487.2114
[2] Lohse, D., Schmitz, B., Versluis, M. (2001). Snapping shrimp make flashing bubbles. Nature 413, 477–478. https://doi.org/10.1038/35097152
[3] Tang, X., Staack, D. (2019). Bioinspired mechanical device generates plasma in water via cavitation. Science Advances 5, eaau7765. https://doi.org/10.1126/sciadv.aau7765
[4] Lord Rayleigh (1917). On the pressure developed in a liquid during the collapse of a spherical cavity. The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science 34, 94–98. https://doi.org/10.1080/14786440808635681
[5] Hughes, M. (1996). Size assessment via a visual signal in snapping shrimp. Behavioral Ecology and Sociobiology 38, 51–57. https://doi.org/10.1007/s002650050216
[6] Mellon, D. Jr., Stephens, P. J. (1978). Limb morphology and function are transformed by contralateral nerve section in snapping shrimps. Nature 272, 246–248. https://doi.org/10.1038/272246a0
[7] Au, W. W. L., Banks, K. (1998). The acoustics of the snapping shrimp Synalpheus parneomeris in Kaneohe Bay. The Journal of the Acoustical Society of America 103, 41–47. https://doi.org/10.1121/1.423234
[8] Koukouvinis, P., Bruecker, C., Gavaises, M. (2017). Unveiling the physical mechanism behind pistol shrimp cavitation. Scientific Reports 7, 13994. https://doi.org/10.1038/s41598-017-14312-0

## Deutsch

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- [Schrödingers Katze: das Gedankenexperiment erklärt](https://wildbionics.com/de/artikel/schroedingers-katze/): Schrödingers Katze ist ein Gedankenexperiment von 1935: eine Katze, lebendig und tot zugleich. Es zeigt, warum Quantenregeln im Alltag verschwinden.
- [Der Lotuseffekt: Wie sich Blätter selbst reinigen](https://wildbionics.com/de/artikel/lotuseffekt/): Lotosblätter bleiben im Schlamm sauber: Wachskristalle auf winzigen Noppen halten ein Luftpolster, Tropfen perlen mit über 160° ab und nehmen Schmutz mit.
- [Wie Katzen auf den Füßen landen: der Drehimpuls erklärt](https://wildbionics.com/de/artikel/katzen-stellreflex/): Eine fallende Katze dreht sich, ohne sich irgendwo abzustoßen. Ihr Drehimpuls bleibt null – sie dreht sich, indem sie ihre Form ändert.
- [Wie Fledermäuse mit Schall sehen: Echoortung erklärt](https://wildbionics.com/de/artikel/echoortung-fledermaeuse/): Fledermäuse jagen im Dunkeln mit Ultraschall: Die Laufzeit des Echos verrät die Entfernung, seine Tonhöhe die Geschwindigkeit der Beute.
- [Wie Geckos an Wänden haften: Van-der-Waals-Kräfte](https://wildbionics.com/de/artikel/gecko-haftung/): Geckos laufen ohne Kleber Glaswände hoch: Milliarden winziger Spatulae an ihren Zehen haften über Van-der-Waals-Kräfte – und lösen sich in Millisekunden.
- [Der Knallkrebs und die Physik der Kavitation](https://wildbionics.com/de/artikel/knallkrebs-kavitation/): Wie ein Knallkrebs Wasser ohne Hitze sieden lässt: Seine Schere erzeugt Strahl, Kavitationsblase, Lichtblitz und Stoßwelle. Mit Physik, Mathe und Code.

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