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HiHigh hhlig hts 20220 © 2020. The Company of Biologists Ltd. Contents 3 Falcons’ vision up to speed for fast 28 Zebra finches adapt to cope well with lifestyle extreme conditions 4 Leaping small fish out-power breaching 29 Parrots discard dowdy pigments in whales favour of own brand 5 Antarctic bald notothens use spleen 30 Potassium leak short circuits trout heart scuba tank to keep down blood at high temperatures viscosity 31 Surfing behind rocks costs trout dear 6 Evolution built men to pack a punch when feeding 7 Australian jack jumper ant foragers 32 Pygmy mice whistle for the audience have no need for mental map 33 Cabbage whites have a unique take on 8 Weakly electric fishes’ secret social polarized light lives revealed 34 Chilly rattlesnakes strike slower, but not 9 Mantis shrimp pull punches in air for as slow as expected self-preservation 35 Minute mecysmaucheniid spider triggers 10 Stressed chickadees get hot under the fastest trap-jaws collar to save energy 36 Knuckle-walking chimpanzees go 3-D 11 Cameras do not lie: elephant seals with ‘Avatar’ technology prefer fish 37 Tobacco hornworms change stride when 12 African pygmy mouse upgrades the going gets different mitochondria to compensate for size 38 Flexible sea butterflies embrace to thrust 13 Fat loss triggers ant lifestyle change 39 Puffin hearing unaffected by 14 First two weeks crucial for white-nose amphibious lifestyle syndrome survivors 40 Hefty shells help hermit crabs cling on 15 Fish maintain tissue pH despite CO2 blast in surf 16 Hot limpets can’t hang on as tight as 41 Resilient aquifer stoneflies handle low cold ones oxygen well 17 Forest protects Heliconius butterflies 42 Intrepid lice survive extreme pressure from climate extremes when hitching rides on elephant seals 18 Two percent change switches motor 43 Catfish keep head flat when gulping muscle to brake 44 Lizards pant to keep cool 19 Simulated larvae reveal why fish fry lose their dinner 45 Cuvier’s beaked whales take record- 20 Cyber-frog leg leaps out of reality breaking dives in their stride 21 Feisty squid and fish flash back to 46 Lesser long-nosed bats have finely dazzle predatory elephant seals tuned sweet tooth 22 Swallow mums push metabolic limits 47 Champion annual killifish embryos when they can keep cool survive more than 16 months out of water 23 It’s cold out, but whale sharks stay warm within 48 Serotonin key for trap-jaw ant aggression 24 Testosterone soups up golden-collared 49 Colour is key when female chameleons manakin roll-snap at expense of choose Mr Right endurance 50 How whale-surfing remoras stay in 25 Hot minnows could struggle to navigate touch with their steeds as temperatures rise 51 Goby fins have fingertip sensitivity 26 Dinosaur eels build up their fin bones 52 Fiddler crabs ignore near misses when for life on land threatened from all sides 27 Why bark beetles roam near and far All articles written by Kathryn Knight 1 Are you an early-career researcher interested in: • gaining new research skills • expanding your research network • testing novel hypotheses with a team of collaborators? Travelling Fellowships Call for applications – including domestic travel We know that international travel may be restricted currently due to COVID-19, but you can to graduate students and post- doctoral researchers wishing laboratories in a collaborative project within your to make collaborative visits to own country. other laboratories. 2021 application deadlines Amount awarded: up to £2,500. • 8 March (for travel after 19 April) • 31 May (for travel after 12 July) • 16 August (for travel after 27 September) biologists.com/travelling-fellowships Falcons’ vision up to speed for fast lifestyle Few people are lucky enough to transform their passion from a hobby into a career, but Simon Potier from Lund University has done exactly that. ‘Falconry flows in my veins’, says Potier, who was immersed in the ancient sport from an early age. ‘My father is the main falconer at the Les Ailes de l’Urga falconry park’, says Potier adding that his dad owns more than 60 birds. Working with some of the fastest animals on the planet, it was inevitable that Simon Potier Potier would become fascinated by the birds’ vision. ‘Some of them have the highest spatial resolving power known in the animal kingdom’, he says, allowing the swift hunters to target prey with meticulous precision. However, Potier, Michael Pfaff and Almut Kelber realised that the raptors’ high-definition vision was only part of the equation. Closing in on fleeing victims at speeds in excess of 320 km h−1, raptors must be able to see events that are so fast that we would be oblivious to them. The question that Potier and colleagues wanted to ask was how fast could the birds see? Returning home to Normandy, where the birds of prey are based, with experienced falconer Margaux Lieuvin, Potier set up a room equipped with two LED lamps mounted on the wall. One lamp appeared to be on constantly [flashing 1000 Hz (times per second)], while the flashing rate of the second could be adjusted from 10 Hz until the bird could no longer distinguish the flicker. Positioning a perch in front of each lamp and setting the adjustable lamp to flash at the slowest rate, Potier and Lieuvin trained three Harris’s hawks (Parabuteo unicinctus), two peregrine falcons (Falco peregrinus) and a saker falcon (Falco cherrug) to fly and land on the perch in front of the constantly on lamp, rewarding the birds with a morsel of tasty chicken when they chose correctly. ‘We were quite surprised how fast the falcons learned to fly to one perch … [but] this is the advantage of using birds from falconry; they are trained to fly every day with humans’, says Potier. Then, the duo began gradually increasing the flicker rate of the adjustable lamp until the birds could no longer distinguish between the two lamps and began choosing their resting perch randomly. After months of patiently working with the animals, it was clear that the record-breaking peregrine falcon has the fastest visual response of the three species; they were able to distinguish lights flashing up to 129 Hz, more than twice as fast as humans. In contrast, the saker falcon was able to see flickers up to 102 Hz and the Harris’s hawks could only distinguish lights flashing at 81 Hz. Potier also realised that the birds’ high-speed vision fits with their different hunting strategies. Peregrine falcons need high-speed vision to pursue agile aviators on the wing, while Harris’s hawks, which specialise in dive-bombing slower rodents on the ground, can make do with slightly slower vision. However, he points out that chickens can detect flashing lights as well as Harris’s hawks can, and the vision of pied flycatchers – which respond to lights flashing up to 146 Hz – is even faster than that of peregrine falcons. It seems that birds that could be on the menu might need to see as well as the hunters that prey on them. In addition, Potier warns that lights that appear to be on continuously for us could be distressing for birds of prey that are sensitive to flickering. ‘Our study provides evidence that bright artificial illumination flickering at 100 Hz (common in Europe) or 120 Hz (in the USA) may not be suitable in enclosures for raptors, specifically falcons’, he says. 10.1242/jeb.219493 Potier, S., Lieuvin, M., Pfaff, M. and Kelber, A. (2020). How fast can raptors see? J. Exp. Biol. 223, jeb209031. doi:10.1242/jeb.209031 3 Leaping small fish out-power breaching whales When Emmett Johnston from Queen’s University, Belfast, UK, attached a motion sensing tag to a basking shark off the Irish coast, he expected the piece of kit to have a sedate ride. Nothing prepared Johnston and colleagues for the rollercoaster that the sensor went on in practice. ‘Having retrieved it, we watched the video and, to our amazement, the movie ended with the shark suddenly Gregory ‘Slobirdr’ Smith accelerating up through the water [CC BY 2.0 (https://creativecommons.org/licenses/by/2.0)]. column, hitting the water surface at 5 m s−1 and breaching for about a second’, says Lewis Halsey from the University of Roehampton, London, UK. The massive fish was behaving more like cavorting gray whales or leaping salmon than the lethargic filter feeder it was meant to be. The team calculated that each leap could use up to 1/17th of the animal’s daily metabolic budget (doi:10.1098/rsbl.2018.0537). However, after reviewing movies of breaching basking sharks filmed by observers on land, Halsey suspected that it might be possible to calculate the amount of energy an aquatic animal requires to make it into the air from the footage. ‘I thought there must be lots of video available of other aquatic species breaching’, says Halsey. Could he find a way to calculate how much power it takes for fish, whales and dolphins to surge out of the water from movies shot by citizen scientists? Halsey turned to the millennials’ TV channel of choice. ‘I kept searching YouTube with names of fish and cetaceans and various words for jumping until I couldn’t find any more’, he chuckles, recalling how, eventually, he ended up with almost 30 clips of species ranging from a 20 cm long African tetra to a 13 m long humpback whale. Then Halsey teamed up with Gil Iosilevskii from the Technion, Israel, to calculate the animals’ sheer power and speed as they burst out of the water.

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