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| Open AccessSnail-inspired robotic swarms: a hybrid connector drives collective adaptation in unstructured outdoor environments
The authors introduce a 3D terrestrial robotic swarm equipped with a snail-inspired two-mode connection system for self-reconfigurability and mobility in unstructured environments.
- Da Zhao
- , Haobo Luo
- & Tin Lun Lam
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| Open AccessUnexpectedly uneven distribution of functional trade-offs explains cranial morphological diversity in carnivores
Functional trade-offs can affect phenotypic variation. Here, the authors examine trade-offs between bite force and speed in 132 carnivore species, finding that optimising for velocity can be obtained in more ways than optimising for force, and this may impact morphological variability.
- Gabriele Sansalone
- , Stephen Wroe
- & Carmelo Fruciano
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| Open AccessDynamic similarity and the peculiar allometry of maximum running speed
How fast can animals run? Here, the authors show that maximum running speed is limited by different musculoskeletal constraints across animal size: kinetic energy capacity in small animals, and work capacity in large animals.
- David Labonte
- , Peter J. Bishop
- & Christofer J. Clemente
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| Open AccessArticular surface interactions distinguish dinosaurian locomotor joint poses
Criteria for evaluating joint articulation in vertebrates are lacking. Here, the authors propose an approach for combining measurements of 3D articular overlap, symmetry, and congruence into a single metric, and apply this to examine the walking stride of Deinonychus antirrhopus.
- Armita R. Manafzadeh
- , Stephen M. Gatesy
- & Bhart-Anjan S. Bhullar
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| Open AccessMorphological evolution of bird wings follows a mechanical sensitivity gradient determined by the aerodynamics of flapping flight
Morphological trait evolution is partly driven by biomechanical function, but a general framework for this relationship is lacking. Here, the authors test two possible frameworks and find that mechanical sensitivity provides the best prediction of morphological evolution in bird wings
- Jonathan A. Rader
- & Tyson L. Hedrick
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Article
| Open AccessScaling the tail beat frequency and swimming speed in underwater undulatory swimming
Mechanisms by which aquatic animals optimize their tailbeat frequency for swimming have not been fully explained. Here, the authors propose scaling laws for undulatory swimmers, relating beat frequency to length considering muscle biology and fluid interaction.
- Jesús Sánchez-Rodríguez
- , Christophe Raufaste
- & Médéric Argentina
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| Open AccessDecoupling body shape and mass distribution in birds and their dinosaurian ancestors
Here, the authors track the evolution of mass distribution through bird evolution challenging suggested coupling between body shape and centre-of-mass position, and instead showing that crouched bipedalism evolved after powered flight.
- Sophie Macaulay
- , Tatjana Hoehfurtner
- & Karl T. Bates
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| Open AccessExceptional preservation and foot structure reveal ecological transitions and lifestyles of early theropod flyers
The shape of bird toe pads and foot scales can be used to infer their behaviour. Here, the authors examine fossil evidence of toe pads and scales, in addition to claws and bones, from birds and close relatives, illustrating diverse lifestyles and ecological roles among early theropod flyers.
- Michael Pittman
- , Phil R. Bell
- & Thomas G. Kaye
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| Open AccessRaptors avoid the confusion effect by targeting fixed points in dense aerial prey aggregations
Flocking, schooling, and swarming prey are thought to benefit from a confusion effect. However, here the authors show that hawks attacking swarming bats avoid confusion by steering towards a fixed point in the swarm instead of targeting any one individual.
- Caroline H. Brighton
- , Laura N. Kloepper
- & Graham K. Taylor
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| Open AccessBody size, shape and ecology in tetrapods
Here, the authors examine how body size, shape, and segment proportions correspond to ecology in models of 410 tetrapods. They find variable allometric relationships, differential scaling in small and large animals, and body proportions as a potential niche occupation mechanism.
- Alice E. Maher
- , Gustavo Burin
- & Karl T. Bates
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Article
| Open AccessLearning efficient navigation in vortical flow fields
Navigation and trajectory planning in environments with background flow, relevant for robotics, are challenging provided information only on local surrounding. The authors propose a reinforcement learning approach for time-efficient navigation of a swimmer through unsteady two-dimensional flows.
- Peter Gunnarson
- , Ioannis Mandralis
- & John O. Dabiri
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Article
| Open AccessShape-preserving erosion controlled by the graded microarchitecture of shark tooth enameloid
Shark teeth have short lifespans yet can be subject to significant mechanical damage. Here, the authors report on a site-specific damage mechanism in shark teeth enameloid, which maintains tooth functional shape, providing experimental evidence that tooth architecture may have influenced the diversification of shark ecologies over evolution.
- Shahrouz Amini
- , Hajar Razi
- & Peter Fratzl
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| Open AccessBirds repurpose the role of drag and lift to take off and land
Recent work has suggested that lift and drag may be employed differently in slow, flapping flight compared to classic flight aerodynamics. Here the authors develop a method to measure vertical and horizontal aerodynamic forces simultaneously and use it to quantify lift and drag during slow flight.
- Diana D. Chin
- & David Lentink
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Article
| Open AccessNEXAFS imaging to characterize the physio-chemical composition of cuticle from African Flower Scarab Eudicella gralli
Biology serves as inspiration in materials development; this requires improved understanding of the surface chemistry responsible for processes which are being mimicked. Here, the authors report on the use of near edge X-ray absorption fine structure (NEXAFS) imaging to analyze the surface chemistry of insect cuticle.
- Joe E. Baio
- , Cherno Jaye
- & Tobias Weidner
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Article
| Open AccessVocal state change through laryngeal development
Vocal development in humans and primate model systems is typically attributed to changing neural circuits. Here the authors show in marmoset monkeys that biomechanical changes in the vocal organ underlie the transition from infant cries to adult contact calls, demonstrating that vocal development is not solely due to neural control.
- Yisi S. Zhang
- , Daniel Y. Takahashi
- & Coen P. H. Elemans
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| Open AccessInformation-based centralization of locomotion in animals and robots
Model-based centralization schemes, though able to quantify locomotion control in animals and bio-inspired robots, are limited to specific systems. Here, the authors report a generalized information-based centralization scheme that unifies existing models and can be applied to different systems.
- Izaak D. Neveln
- , Amoolya Tirumalai
- & Simon Sponberg
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| Open AccessHawks steer attacks using a guidance system tuned for close pursuit of erratically manoeuvring targets
Hunting styles and flight morphologies of aerial predators are adapted to their habitat structure and prey behaviour. Here, the authors reconstruct flight trajectories of Harris’ Hawks Parabuteo unicinctus and find that these follow a mixed guidance law that is not thrown off by erratic manoeuvres of prey.
- Caroline H. Brighton
- & Graham K. Taylor
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| Open AccessA balance between aerodynamic and olfactory performance during flight in Drosophila
In addition to their aerodynamic properties, insect wings also move odor plumes closer to sensory organs. Li et al. show that Drosophila wings may trade optimal aerodynamic performance for improved olfactory function during flight.
- Chengyu Li
- , Haibo Dong
- & Kai Zhao
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| Open AccessControllable water surface to underwater transition through electrowetting in a hybrid terrestrial-aquatic microrobot
Some animals have multimodal locomotive capabilities to survive in different environments. Inspired by nature, Chen et al. build a centimeter-scaled robot that is capable of walking on water, underwater, on land, and transiting among all three, whose ‘feet’ break water by modifying surface tension.
- Yufeng Chen
- , Neel Doshi
- & Robert J. Wood
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| Open AccessHygroscopic compounds in spider aggregate glue remove interfacial water to maintain adhesion in humid conditions
Spider aggregate glue avoids failure in humid environments but the fundamental mechanism behind it is still unknown. Here, the authors demonstrate that humidity-dependent structural changes of glycoproteins and sequestering of liquid water by low molecular mass compounds prevents adhesion failure of the glue in humid environments.
- Saranshu Singla
- , Gaurav Amarpuri
- & Ali Dhinojwala
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| Open AccessWing bone geometry reveals active flight in Archaeopteryx
Archaeopteryx had a mix of traits seen in non-flying dinosaurs and flying birds, leading to debate on whether it had powered flight. Here, Voeten et al. compare wing bone architecture from Archaeopteryx and both flying and non-flying archosaurs, supporting that Archaeopteryx had powered flight but with a different stroke than that of modern birds.
- Dennis F. A. E. Voeten
- , Jorge Cubo
- & Sophie Sanchez
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| Open AccessStructural absorption by barbule microstructures of super black bird of paradise feathers
Physical structure is known to contribute to the appearance of bird plumage through structural color and specular reflection. Here, McCoy, Feo, and colleagues demonstrate how a third mechanism, structural absorption, leads to low reflectance and super black color in birds of paradise feathers.
- Dakota E. McCoy
- , Teresa Feo
- & Richard O. Prum
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Article
| Open AccessThe biomechanical origin of extreme wing allometry in hummingbirds
Hummingbirds are known to defy the predicted scaling relationships between body and wing size. Here, Skandalis et al. develop a ‘force allometry’ framework to show that, regardless of wing size, hummingbird species have the same wing velocity during flight.
- Dimitri A. Skandalis
- , Paolo S. Segre
- & Douglas L. Altshuler
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| Open AccessUnpredictability of escape trajectory explains predator evasion ability and microhabitat preference of desert rodents
Biomechanical understanding of animal gait and maneuverability has primarily been limited to species with more predictable, steady-state movement patterns. Here, the authors develop a method to quantify movement predictability, and apply the method to study escape-related movement in several species of desert rodents.
- Talia Y. Moore
- , Kimberly L. Cooper
- & Ramanarayan Vasudevan
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| Open AccessCellular preservation of musculoskeletal specializations in the Cretaceous bird Confuciusornis
Birds have a more crouched posture compared to their theropod dinosaur ancestors. Here, Jiang and colleagues describe a lower hindlimb of the Early Cretaceous birdConfuciusorniswith soft tissues apparently preserved even as molecules, indicating a somewhat more modern posture in ancient birds.
- Baoyu Jiang
- , Tao Zhao
- & John R. Hutchinson
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| Open AccessClimbing favours the tripod gait over alternative faster insect gaits
Numerous selective forces shape animal locomotion patterns and as a result, different animals evolved to use different gaits. Here, Ramdyaet al. use live and in silicoDrosophila, as well as an insect-model robot, to gain insights into the conditions that promote the ubiquitous tripod gait observed in most insects.
- Pavan Ramdya
- , Robin Thandiackal
- & Dario Floreano
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| Open AccessWater striders adjust leg movement speed to optimize takeoff velocity for their morphology
How water striders escape from danger by jumping vertically from the water surface without sinking is an open question in biomechanics. Yanget al. show that water strider species with varying leg lengths and body masses tune their leg movements to maximize jump speeds without breaking the surface of the water.
- Eunjin Yang
- , Jae Hak Son
- & Ho-Young Kim
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| Open AccessMechanical evidence that Australopithecus sediba was limited in its ability to eat hard foods
Dietary adaptations of extinct early humans are often inferred from dental microwear data. Here, the authors employ mechanical analyses to show that Australopithecus sedibahad limited ability to consume hard foods.
- Justin A. Ledogar
- , Amanda L. Smith
- & David S. Strait
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| Open AccessSuction-based propulsion as a basis for efficient animal swimming
Swimming animals are generally assumed to generate forward thrust by pushing surrounding water rearwards. Here, Gemmell et al.show that efficient swimming in lampreys and jellyfish is achieved primarily through suction, as vortex-associated low pressure regions are synchronized by undulations of the body.
- Brad J. Gemmell
- , Sean P. Colin
- & John O. Dabiri
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| Open AccessSurprising trunk rotational capabilities in chimpanzees and implications for bipedal walking proficiency in early hominins
Greater trunk flexibility in humans is thought to be a major adaptation to bipedal walking compared to chimpanzees. Here Thompson et al. show that chimpanzees are capable of human-like trunk rotations during bipedalism, suggesting bipedal proficiency was present in early hominins.
- Nathan E. Thompson
- , Brigitte Demes
- & Susan G. Larson
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| Open AccessMulti-jet propulsion organized by clonal development in a colonial siphonophore
Physonect siphonophores are highly mobile jellyfish with complex colonial organization. Here, Costelloet al. show that division of labour among developmental stages controls the direction and propulsion of the colony, with older individuals providing thrust and younger individuals providing torque.
- John H. Costello
- , Sean P. Colin
- & Kelly R. Sutherland
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Bone remodelling in humans is load-driven but not lazy
Mechanical strain causes bone remodelling when it exceeds threshold levels of a proposed ‘lazy zone’, in which bone density is unresponsive to mechanical strain. Here the authors show that human bone remodeling is entirely load-driven, suggesting that no such ‘lazy’ state exists for human bones.
- Patrik Christen
- , Keita Ito
- & Bert van Rietbergen
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Synergistic roles for lipids and proteins in the permanent adhesive of barnacle larvae
Using their unique bioadhesives, barnacles can adhere to a great variety of surfaces. Here, Gohad et al.show that the barnacle larval bioadhesive contains lipids and phosphoproteins that are organized in a complex structure and work together to maximize adhesion.
- Neeraj V. Gohad
- , Nick Aldred
- & Andrew S. Mount
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Bending rules for animal propulsion
Animal propulsors—wings and fins—typically bend during motion. Here, the authors analysed video data on animal propulsor bending and find that, for propulsion within inertially dominated flows, the flexion angles and the positions of the point of flexion are similar across the animal kingdom.
- Kelsey N. Lucas
- , Nathan Johnson
- & John H. Costello
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Muscle function and hydrodynamics limit power and speed in swimming frogs
Muscle power limits animal speed, but the extent of the effect is unknown. Here the authors examine the relationship between swimming speed, size and muscle function in the aquatic frog Xenopus laevis, and find that muscle–environmental interactions vary with body size, limiting muscle power and swimming speed.
- Christofer J. Clemente
- & Christopher Richards
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Convergent evolution in locomotory patterns of flying and swimming animals
Undulating flight, an efficient mode of locomotion in flying birds, can theoretically also result in efficient locomotion in water. Here we demonstrate gait patterns resembling undulating flight in four marine vertebrate species comprising sharks and pinnipeds.
- Adrian C. Gleiss
- , Salvador J. Jorgensen
- & Rory P. Wilson
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An adaptive explanation for the horse-like shape of seahorses
Seahorses evolved from pipefish, which have a remarkably different body shape. Here, by examining seahorse feeding behaviour and using a mathematical model, Van Wassenberghet al. demonstrate that the head, neck and trunk posture of the seahorse allows for the effective capture of their prey.
- Sam Van Wassenbergh
- , Gert Roos
- & Lara Ferry
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Upright human gait did not provide a major mechanical challenge for our ancestors
The emergence of bipedalism in humans is considered to be an evolutionary challenge. In this study, however, the authors show that humans, dogs and chickens create a virtual pivot point above their centre of mass during walking, thereby mimicking an external support.
- H.-M. Maus
- , S.W. Lipfert
- & A. Seyfarth