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The giant rorqual whales are believed to have a massive food turnover driven by a high-intake lunge feeding style aptly described as the worlds largest biomechanical action. This high-drag feeding behavior is thought to limit dive times and constrain rorquals to target only the densest prey patches, making them vulnerable to disturbance and habitat change. Using biologging tags to estimate energy expenditure as a function of feeding rates on 23 humpback whales, we show that lunge feeding is energetically cheap. Such inexpensive foraging means that rorquals are flexible in the quality of prey patches they exploit and therefore more resilient to environmental fluctuations and disturbance. As a consequence, the food turnover and hence the ecological role of these marine giants have likely been overestimated.

The considerable power needed for large whales to leap out of the water may represent the single most expensive burst maneuver found in nature. However, the mechanics and energetic costs associated with the breaching behaviors of large whales remain poorly understood. In this study we deployed whale-borne tags to measure the kinematics of breaching to test the hypothesis that these spectacular aerial displays are metabolically expensive. We found that breaching whales use variable underwater trajectories, and that high-emergence breaches are faster and require more energy than predatory lunges. The most expensive breaches approach the upper limits of vertebrate muscle performance, and the energetic cost of breaching is high enough that repeated breaching events may serve as honest signaling of body condition. Furthermore, the confluence of muscle contractile properties, hydrodynamics, and the high speeds required likely impose an upper limit to the body size and effectiveness of breaching whales.

Flying animals of different masses vary widely in body proportions, but the functional implications of this variation are often unclear. We address this ambiguity by developing an integrative allometric approach, which we apply here to hummingbirds to examine how the physical environment, wing morphology and stroke kinematics have contributed to the evolution of their highly specialised flight. Surprisingly, hummingbirds maintain constant wing velocity despite an order of magnitude variation in body weight; increased weight is supported solely through disproportionate increases in wing area. Conversely, wing velocity increases with body weight within species, compensating for lower relative wing area in larger individuals. By comparing inter- and intraspecific allometries, we find that the extreme wing area allometry of hummingbirds is likely an adaptation to maintain constant burst flight capacity and induced power requirements with increasing weight. Selection for relatively large wings simultaneously maximises aerial performance and minimises flight costs, which are essential elements of humming bird life history.

Visualization of the vortex wake of a flying animal provides understanding of how wingbeat kinematics are translated into the aerodynamic forces for powering and controlling flight. Two general vortex flow patterns have been proposed for the wake of hovering hummingbirds: (1) The two wings form a single, merged vortex ring during each wing stroke; and (2) the two wings form bilateral vortex loops during each wing stroke. The second pattern was proposed after a study with particle image velocimetry that demonstrated bilateral source flows in a horizontal measurement plane underneath hovering Anna’s hummingbirds (Calypte anna). Proof of this hypothesis requires a clear perspective of bilateral pairs of vortices. Here, we used high-speed image sequences (500 frames per second) ofC. anna hover feeding within a white plume to visualize the vortex wake from multiple perspectives. The films revealed two key structural features: (1) Two distinct jets of downwards airflow are present under each wing; and (2) vortex loops around each jet are shed during each upstroke and downstroke. To aid in the interpretation of the flow visualization data, we analyzed high-speed kinematic data (1,000 frames per second) of wing tips and wing roots as C. anna hovered in normal air. These data were used to refine several simplified models of vortex topology. The observed flow patterns can be explained by either a single loop model with an hourglass shape or a bilateral model, with the latter being more likely. When hovering in normal air, hummingbirds used an average stroke amplitude of 153.6° (range 148.9°–164.4°) and a wingbeat frequency of 38.5 Hz (range 38.1–39.1 Hz). When hovering in the white plume, hummingbirds used shallower stroke amplitudes ( xˉ = 129.8°, range 116.3°–154.1°) and faster wingbeat frequencies ( xˉ  = 41.1 Hz, range 38.5–44.7 Hz), although the bilateral jets and associated vortices were observed across the full kinematic range. The plume did not significantly alter the air density or constrain the sustained muscle contractile frequency. Instead, higher wingbeat frequencies likely incurred a higher metabolic cost with the possible benefit of allowing the birds to more rapidly escape from the visually disruptive plume.

Bird flight is a remarkable adaptation that has allowed the approximately 10 000 extant species to colonize all terrestrial habitats on earth including high elevations, polar regions, distant islands, arid deserts, and many others. Birds exhibit numerous physiological and biomechanical adaptations for flight. Although bird flight is often studied at the level of aerodynamics, morphology, wingbeat kinematics, muscle activity, or sensory guidance independently, in reality these systems are naturally integrated. There has been an abundance of new studies in these mechanistic aspects of avian biology but comparatively less recent work on the physiological ecology of avian flight. Here we review research at the interface of the systems used in flight control and discuss several common themes. Modulation of aerodynamic forces to respond to different challenges is driven by three primary mechanisms: wing velocity about the shoulder, shape within the wing, and angle of attack. For birds that flap, the distinction between velocity and shape modulation synthesizes diverse studies in morphology, wing motion, and motor control. Recently developed tools for studying bird flight are influencing multiple areas of investigation, and in particular the role of sensory systems in flight control. How sensory information is transformed into motor commands in the avian brain remains, however, a largely unexplored frontier. Key words: Aves, comparative biomechanics, neuromuscular control, visual guidance, wing morphing. Le vol des oiseaux est une adaptation remarquable qui a permis aux quelque 10 000 especes actuelles de coloniser tous les habitats terrestres de la planete, dont les regions polaires et de haute altitude, les iles eloignees, les deserts arides et bien d'autres. Les oiseaux presentent de nombreuses adaptations physiologiques et biomecaniques pour le vol. Bien que l'aerodynamique, la morphologie, la cinematique des battements d'ailes, l'activite musculaire et le guidage sensoriel associes au vol d'oiseau soient souvent etudies de maniere independante, en realite, ces systemes sont naturellement integres. S'il y a abondance de nouvelles etudes sur ces aspects mecanistes de la biologie aviaire, moins de travaux recents se sont penches sur l'ecologie physiologique du vol des oiseaux. Nous passons en revue la recherche a l'interface des systemes utilises dans le controle du vol et abordons plusieurs themes communs. La modulation des forces aerodynamiques pour repondre a differents defis est assuree par trois principaux mecanismes, soit la vitesse des ailes autour de l'epaule, la forme a l'interieur de l'aile et l'angle d'attaque. Pour les oiseaux qui battent des ailes, la distinction entre la modulation par la vitesse et par la forme regroupe des etudes variees sur la morphologie, le mouvement des ailes et le controle moteur. Des outils recemment mis au point pour etudier le vol des oiseaux influencent plusieurs champs d'etude, notamment le role des systemes sensoriels dans le controle du vol. La transformation de l'information sensorielle en commandes motrices dans le cerveau des oiseaux demeure toutefois une frontiere largement inexploree. [Traduit par la Redaction] Mots-cles: oiseaux, biomecanique comparative, controle neuromusculaire, guidage visuel, morphing des ailes., Introduction The flying abilities of birds are impressive; casual observation of their soaring, hovering, and manoeuvring can lead one to assume that the graceful and poised motions are almost effortless. [...]

The evolution of avian flight remains one of biology's major controversies, with a long history of functional interpretations of fossil forms given as evidence for either an arboreal or cursorial [...]

How predators maximize energetic gains while minimizing the costs associated with exploiting heterogeneous prey remains a difficult ecological principle to test in natural systems.Deep‐diving, air‐breathing predators face conflicting demands of oxygen conservation to extend dive time and oxygen usage from the exercise required to find and capture prey. How predators balance these opposing factors is additionally complicated by prey patches that are heterogeneous spatially, temporally and in quality.Tags deployed on foraging fin whales revealed that deeper dives consisted of higher feeding rates (lunges/hr), as generally predicted by optimal foraging theory. By simultaneously measuring prey density and distribution in the local environment, we show that whales increased their dive depths in order to forage on the densest prey patches.Despite the increased travel time needed to find deeper prey during a breath‐hold dive, the increase in feeding rates of fin whales and modelled prey consumption quadrupled compared to shallow foraging. Because the cost of transport is low at this extreme in body size, we posit that feeding on the deep prey patches significantly increases the energetic efficiency of foraging.Given the increasing recognition that anthropogenic disturbance can curtail deep foraging dives in many cetacean species, endangered fin whales may be susceptible to significant energetic losses that may impact individual fitness and population health in some areas. A free Plain Language Summary can be found within the Supporting Information of this article. [ABSTRACT FROM AUTHOR]

Although ants are lauded for their strength, little is known about the limits of their load-carrying abilities.We determined the maximal loadcarrying capacity of leaf-cutter ants by incrementally adding mass to the leaves they carried. Maximal load-carrying ability scaled isometrically with body size, indicating that larger ants had the capacity to lift the same proportion of their body mass as smaller ants (8.78 times body mass). However, larger ants were captured carrying leaf fragments that represented a lower proportion of their body mass compared with their smaller counterparts. Therefore, when selecting leaves, larger ants retained a higher proportion of their load-carrying capacity in reserve. This suggests that either larger ants require greater power reserves to overcome challenges they encounter along the trail or leaf-cutter ants do not select loads that maximize the overall leaf transport rate of the colony. [ABSTRACT FROM AUTHOR]

Maneuverability is one of the most important and least understood aspects of animal locomotion. The hydrofoil-like flippers of cetaceans are thought to function as control surfaces that effect maneuvers, but quantitative tests of this hypothesis have been lacking. Here, we constructed a simple hydrodynamic model to predict the longitudinal-axis roll performance of fin whales, and we tested its predictions against kinematic data recorded by on-board movement sensors from 27 free-swimming fin whales. We found that for a given swimming speed and roll excursion, the roll velocity of fin whales calculated from our field data agrees well with that predicted by our hydrodynamic model. Although fluke and body torsion may further influence performance, our results indicate that lift generated by the flippers is sufficient to drive most of the longitudinal-axis rolls used by fin whales for feeding and maneuvering. [ABSTRACT FROM AUTHOR]

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Bird flight is a remarkable adaptation that has allowed the approximately 10 000 extant species to colonize all terrestrial habitats on earth including high elevations, polar regions, distant islands, arid deserts, and many others. Birds exhibit numerous physiological and biomechanical adaptations for flight. Although bird flight is often studied at the level of aerodynamics, morphology, wingbeat kinematics, muscle activity, or sensory guidance independently, in reality these systems are naturally integrated. There has been an abundance of new studies in these mechanistic aspects of avian biology but comparatively less recent work on the physiological ecology of avian flight. Here we review research at the interface of the systems used in flight control and discuss several common themes. Modulation of aerodynamic forces to respond to different challenges is driven by three primary mechanisms: wing velocity about the shoulder, shape within the wing, and angle of attack. For birds that flap, the distinction between velocity and shape modulation synthesizes diverse studies in morphology, wing motion, and motor control. Recently developed tools for studying bird flight are influencing multiple areas of investigation, and in particular the role of sensory systems in flight control. How sensory information is transformed into motor commands in the avian brain remains, however, a largely unexplored frontier. [ABSTRACT FROM AUTHOR]

The northern Chilean Patagonia region is a key feeding ground and a nursing habitat in the southern hemisphere for blue whales (Balaenoptera musculus). From 2014 to 2019, during 6 separate research cruises, the dive behavior of 28 individual blue whales was investigated using bio-logging tags (DTAGs), generating ≈190 h of data. Whales dove to significantly greater depths during the day compared to nighttime (day: 32.6 ± 18.7 m; night: 6.2 ± 2.7 m; P < 0.01). During the night, most time was spent close to the surface (86% ± 9.4%; P < 0.01) and at depths of less than 12 m. From 2016 to 2019, active acoustics (scientific echosounders) were used to record prey (euphausiids) density and distribution simultaneously with whale diving data. Tagged whales appeared to perform dives relative to the vertical migration of prey during the day. The association between diurnal prey migration and shallow nighttime dive behavior suggests that blue whales are at increased risk of ship collisions during periods of darkness since the estimated maximum ship draft of vessels operating in the region is also ≈12 m. In recent decades, northern Chilean Patagonia has seen a large increase in marine traffic due to a boom in salmon aquaculture and the passenger ship industry. Vessel strike risks for large whales are likely underestimated in this region. Results reported in this study may be valuable for policy and mitigation decisions regarding conservation of the endangered blue whale., (© 2020 The Authors. Integrative Zoology published by International Society of Zoological Sciences, Institute of Zoology/Chinese Academy of Sciences and John Wiley & Sons Australia, Ltd.)