A biomechanically parsimonious hypothesis for the evolution of flapping flight in terrestrial vertebrates suggests progression within an arboreal context from jumping to directed aerial descent, gliding with control via appendicular motions, and ultimately to powered flight. The more than 30 phylogenetically independent lineages of arboreal vertebrate gliders lend strong indirect support to the ecological feasibility of such a trajectory. Insect flight evolution likely followed a similar sequence, but is unresolved paleontologically. Recently described falling behaviors in arboreal ants provide the first evidence demonstrating the biomechanical capacity for directed aerial descent in the complete absence of wings. Intentional control of body trajectories as animals fall from heights (and usually from vegetation) likely characterizes many more taxa than is currently recognized. Understanding the sensory and biomechanical mechanisms used by extant gliding animals to control and orient their descent is central to deciphering pathways involved in flight evolution. a lizard that glided by accident: mosaics of cooption and adaptation in a tropical forest lacertid (Reptilia, Lacertidae). Bull. Averof M, Akam M. 1995. Insect-crustacean relationships: insights from comparative developmental and molecular studies.

Arboreal animals negotiate a highly three-dimensional world that is discontinuous on many spatial scales. As the scale of substrate discontinuity increases, many arboreal animals rely on leaping or gliding locomotion between distant supports. In order to successfully move through their habitat, gliding animals must actively modulate both propulsive and aerodynamic forces. Here we examined the take-off and landing kinetics of a free-ranging gliding mammal, the Malayan colugo (Galeopterus variegatus) using a custom-designed three-dimensional accelerometry system. We found that colugos increase the propulsive impulse to affect longer glides. However, we also found that landing forces are negatively associated with glide distance. Landing forces decrease rapidly as glide distance increases from the shortest glides, then level off, suggesting that the ability to reorient the aerodynamic forces prior to landing is an important mechanism to reduce velocity and thus landing forces. This ability to substantially alter the aerodynamic forces acting on the patagial wing in order to reorient the body is a key to the transition between leaping and gliding and allows gliding mammals to travel long distances between trees with reduced risk of injury. Longer glides may increase the access to distributed resources and reduce the exposure to predators in the canopy or on the forest floor.

Animals that glide produce aerodynamic forces that enable transit through the air in both arboreal and aquatic environments. The relative ease of gliding compared with flapping flight has led to a large diversity of taxa that have evolved some degree of flight capability. Glide paths are curved, reflecting the changing forces on the animal as it progresses through its aerial trajectory. These changing forces can be under control of the glider, which uses specific aspects of anatomy to modulate lift, drag, and rotational moments on the body. However, gliders share no single anatomical or behavioral feature, and some species are unspecialized for gliding, producing aerodynamic forces using posture and orientation alone. Animals use gliding in a broad range of ecological roles, suggesting that multiple performance metrics are relevant for consideration, but we are only beginning to understand how gliders produce and control their flight from takeoff to landing. In this review, we focus on the physical aspects of how glide trajectories are produced, and additionally discuss the range of morphologies and postures that are used to control aerial movements across the broad diversity of animal gliders.

No abstract

SUMMARY Traversing gaps with different orientations within arboreal environments has ecological relevance and mechanical consequences for animals. For example, the orientation of the animal while crossing gaps determines whether the torques acting on the body tend to cause it to pitch or roll from the supporting perch or fail as a result of localized bending. The elongate bodies of snakes seem well suited for crossing gaps, but a long unsupported portion of the body can create large torques that make gap bridging demanding. We tested whether the three-dimensional orientation of substrates across a gap affected the performance and behavior of an arboreal snake (Boiga irregularis). The snakes crossed gaps 65% larger for vertical than for horizontal trajectories and 13% greater for straight trajectories than for those with a 90 deg turn within the horizontal plane. Our results suggest that failure due to the inability to keep the body rigid at the edge of the gap may be the primary constraint on performance for gaps with a large horizontal component. In addition, the decreased performance when the destination perch was oriented at an angle to the long axis of the initial perch was probably a result of the inability of snakes to maintain balance due to the large rolling torque. For some very large gaps the snakes enhanced their performance by using rapid lunges to cross otherwise impassable gaps. Perhaps such dynamic movements preceded the aerial behavior observed in other species of arboreal snakes.

Conservation translocations—particularly those that weave diverse ways of knowing and seeing the world—promise to enhance species recovery and build ecosystem resilience. Yet, few studies to date have been led or co‐led by Indigenous peoples; or consider how centring Indigenous knowledge systems can lead to betterconservation translocation outcomes. In this Perspective, as Indigenous and non‐Indigenous researchers and practitioners working in partnership in Aotearoa New Zealand, we present a novel framework for co‐designing conservation translocations that centre Indigenous peoples and knowledge systems through Two‐Eyed Seeing. We apply this framework to Aotearoa New Zealand's threatened and underprioritized freshwater biodiversity. In particular, we highlight the co‐development of conservation translocations with Te Kōhaka o Tūhaitara and Te Nohoaka o Tukiauau that are weaving emerging genomic approaches into mātauraka Māori (Māori knowledge systems), including customary practices, processes and language. We envision the Two‐Eyed Seeing framework presented here will provide a critical point of reference for the co‐development of conservation translocations led or co‐led by Indigenous peoples elsewhere in the world to build more resilient biocultural heritage. A free Plain Language Summary can be found within the Supporting Information of this article.

Gliding has evolved independently at least six times in mammals. Multiple hypotheses have been proposed to explain the evolution of gliding. These include the evasion of predators, economical locomotion or foraging, control of landing forces, and habitat structure. Here we use a combination of comparative methods and ecological and biomechanical data collected from free-ranging animals to evaluate these hypotheses. Our comparative data suggest that the origins of gliding are often associated with shifts to low-quality diets including leaves and plant exudates. Further, data from free-ranging colugos suggest that although gliding is not more energetically economical than moving through the canopy, it is much faster, allowing shorter times of transit between foraging patches and therefore more time available to forage in a given patch. In addition to moving quickly, gliding mammals spend only a small fraction of their overall time engaged in locomotion, likely offsetting its high cost. Kinetic data for both take-off and landing suggest that selection on these behaviors could also have shaped the evolution of gliding. Glides are initiated by high-velocity leaps that are potentially effective in evading arboreal predators. Further, upon landing, the ability to control aerodynamic forces and reduce velocity prior to impact is likely key to extending distances of leaps or glides while reducing the likelihood of injury. It is unlikely that any one of these hypotheses exclusively explains the evolution of gliding, but by examining gliding in multiple groups of extant animals in ecological and biomechanical contexts, new insights into the evolution of gliding can be gained.

Animals use diverse solutions to land on vertical surfaces. Here we show the unique landing of the gliding gecko, Hemidactylus platyurus. Our high-speed video footage in the Southeast Asian rainforest capturing the first recorded, subcritical, short-range glides revealed that geckos did not markedly decrease velocity prior to impact. Unlike specialized gliders, geckos crashed head-first with the tree trunk at 6.0 ± 0.9 m/s (~140 body lengths per second) followed by an enormous pitchback of their head and torso 103 ± 34° away from the tree trunk anchored by only their hind limbs and tail. A dynamic mathematical model pointed to the utility of tails for the fall arresting response (FAR) upon landing. We tested predictions by measuring foot forces during landing of a soft, robotic physical model with an active tail reflex triggered by forefoot contact. As in wild animals, greater landing success was found for tailed robots. Experiments showed that longer tails with an active tail reflex resulted in the lower adhesive foot forces necessary for stabilizing successful landings, with a tail shortened to 25% requiring over twice the adhesive foot force.