Emily L. C. Shepard.

Fuel economy matters to both animals and machines, as the cost of transport can determine where, when, and how far locomotion is possible. However, established estimates of these values for animal flight come from laboratories and treat the atmosphere as constant, even though free-flying animals routinely extract energy from atmospheric flows. Using high-resolution movement data, we estimate the cost of transport for 50 bird and bat species flying in the wild. Our results revise the classic ranking of locomotion costs, suggesting that flying can be cheaper than swimming though almost as costly as running, depending on interactions between physical environment, morphology, and behavior. Linking transport costs to atmospheric conditions provides a mechanistic basis for predicting how changing windscapes will reshape the energetics, movements, and distributions of flying animals.

Risk is a key currency in animal ecology, yet studies of risk have almost exclusively focused on predation. Accidents, defined as a momentary loss of control, represent another potential source of injury and mortality. Such events are seldom documented and are generally assumed to be vanishingly rare in natural systems. Nonetheless, regular crash-based mortality has been documented in a population of northern gannets through monthly surveys conducted over three years in the 1970s. We revisit these data, using hindcasting, environmental records and computational fluid dynamics (CFD) models to investigate the environmental drivers of gannet crashes, and matrix population models to examine their demographic consequences under a range of environmental scenarios. Wind direction emerged as the sole predictor of crash-based mortality, with the probability of crashes increasing in north-westerly winds. CFD models revealed that north-westerlies are associated with a marked increase in turbulent kinetic energy along the breeding cliffs, relative to the other modal wind direction, which likely challenges flight control. A total of 367 crashes accounted for 5.4% of annual adult mortality. Removing this mortality led to a projected increase in population of 23.9% over 50 years, equivalent to an additional 10,583 individuals. Overall, this suggests that turbulence close to the substrate can result in fatal losses of flight control that can impact population-level processes. Our results also highlight the need for greater understanding of how airflows influence the risk of accidents across flying animals, both in current and changing wind regimes.

The study of animals’ activity and behavior in the wild is an extremely challenging task. Although tri‐axial accelerometers are invaluable for behavioral analyses, their use is more frequent in large charismatic endotherms with limited application in ectotherms. The scarce utilization of this methodology on small‐size reptiles is focused on animals’ activity and energetics, showing few records of rapid displays and behavior signals. Here, we present a novel multidisciplinary approach capable of advancing research on reptiles’ behavior. Our proposed approach uses advanced technologies for the digitization, reconstruction and visualization of reptiles and their behavior. We (i) record movement through tri‐axial accelerometers, video cameras, and motion capture systems; (ii) ground‐truth data through the video records; (iii) develop realistically accurate 3D avatars of the recorded movement for visualization purposes, and (iv) archive data on a Behavior Pattern Database. As case studies, we used two small Mediterranean reptiles, the lizard Laudakia cypriaca and the snake Dolichophis jugularis . Through our approach, we successfully recorded, ground‐truthed, and labeled for the first time, several detailed movements and behaviors of the two case study species. We developed an accurate digital overview of those movements using motion capture and 3D animal reconstruction. Finally, we structured a database for archiving all behavioral data and demonstrated how those archives can be used for advancing behavioral research, providing ecological insights into this animal group. Our approach can enhance research on reptiles’ behavior by contributing to the analysis of complex or isolated behaviors, poorly studied, such as signals and social interactions, providing valuable insights and assisting behavioral analysis.

The influence of wind on animal flight costs and flight decisions is well established. Far less is known about the effects of turbulence. Indeed, a mechanistic framework allowing researchers to predict the costs and consequences of turbulence for flapping flight is lacking. This is a notable knowledge gap, as turbulence is ubiquitous within the natural flight environment, and its characteristics and distribution are changing across the spectrum of animal flight heights as a result of, for example, land use change and increasing atmospheric instability. Here, I briefly assess naturally occurring and anthropogenic drivers of turbulence before considering how turbulence affects the metabolic costs of flight and how animals might respond in the wild. Turbulence has a measurable effect on flight costs when eddy diameter is comparable to the wingspan. The few metabolic data on this suggest that turbulence can increase flight power by 25–100%. The ability to meet the costs of turbulence should decrease with increasing body mass, because of the negative relationship between available power and mass. Larger flapping fliers may therefore show stronger behavioural responses to turbulence. Consistent with this, waterbirds and large seabirds show marked avoidance of offshore wind farms, but this has yet to be analysed in relation to turbulence. Overall, the integration of laboratory and field approaches should provide new insight into the conditions animals avoid, the associated costs (according to eddy size, velocity and flight morphology) and the implications for flight in changing airscapes.

Animal movement paths display substantial complexity and variability, leading researchers to seek underlying rules that govern these patterns and mathematical models that best describe them. Using high-resolution (≥ 10 Hz) movement from 43 vertebrate species across diverse taxa, mass, and lifestyles, we show that movement paths are universally composed of straight-line steps interspersed with sharp turns, echoing a pattern documented for lower taxa such as bacteria. We report how these vertebrate ‘fundamental step lengths’ and ‘fundamental turn angles’, which are intrinsically different from the straight-line paths detailed in studies using low resolution position data, vary with species’ mass, lifestyle, behaviour, and environmental context. To explain these, we posit that animals inherently move in a straight line until sensory information signals a perceived better heading, which instigates a turn. The constellation of fundamental step lengths and turn angles over varying time intervals affects how well different models of animal movement (such as random walk or Lévy flight) fit lower resolution data. By examining turns as decision points, we can seek drivers of animal movement patterns and thereby work to predict future paths under varying conditions.

The influence of wind on animal flight costs and flight decisions is well established. Far less is known about the effects of turbulence. Here, I briefly assess naturally occurring and anthropogenic drivers of turbulence, before considering how turbulence affects the metabolic costs of flight and how animals might respond in the wild. Turbulence has a measurable effect on flight costs when eddy diameter is similar to the wingspan. The few metabolic data on this show that turbulence can cause a 25-100% increase in flight costs, similar to that caused by moderate to strong headwinds. The ability to meet the costs of flying in turbulence should decrease with increasing body mass, following the reduction in available power (which also limits the range of possible flight speeds). More data are therefore needed on the metabolic costs of flight in relation to eddy characteristics (e.g. length scale and velocity), flight speed and morphology. This is pertinent since turbulence is ubiquitous in the natural environment and could influence the energy expended across flying animals. Anthropogenic activity is changing the nature, strength and distribution of turbulence, with the built environment and wind farms both typified by high turbulence intensities. In fact, the marked and consistent avoidance of offshore wind farms by large birds is consistent with an avoidance of turbulence, and analysis of flight trajectories in relation to the development of the far-wake region could provide new insight into the proximate and/ or ultimate drivers of avoidance. Summary statement: Turbulence is ubiquitous yet we know little about how it affects animal flight costs and decisions. This matters as anthropogenic activity is changing its distribution and magnitude.

SUMMARY: Regional patterns in wind underpin the low-cost migratory flyways of billions of birds and insects ^1-3 , but how large-scale changes in temperature affect flight is unknown. Flight costs should increase with rising temperatures, because lift decreases as density decreases, whereas weight remains unchanged. The effects of air density on flight costs are well-established in the context of high-altitude movements and migration ^4-7 . Here, we examine the impact of air density on low-flying birds, in relation to seasonal, regional and global changes in temperature. Using multi-sensor loggers, we find that air density was the most important predictor of wingbeat frequency in red-tailed tropicbirds ( Phaethon rubricauda ) breeding year-round in Mauritius. Lower air densities in the Austral summer were associated with a small but significant increase in mean wingbeat frequency, which translated to an estimated 1-2% increase in flight costs. The variation in flight costs increased by an order of magnitude when considered in space, rather than time, with flight costs varying by ≥ 10 % across the tropicbird’s range. Changes in air density can therefore be an important determinant of flight costs even when birds are operating close to sea-level. Indeed, mapping air density at sea-level revealed that global temperature gradients cause effective altitude to vary by >2 km when considered as seasonal averages. This “invisible topography” at sea-level could have influenced the biogeography of flight morphologies and life-history traits.

Understanding the behaviours and time budgets of translocated animals post‐release has the potential to improve rearing and release protocols, and therefore survival rate. Otididae (bustards) inhabit open landscapes across the Middle East and Asia, are highly mobile on the ground and have similar lifestyles and body plans. The Asian houbara Chlamydotis macqueenii is a bustard of conservation concern inhabiting the Middle East to Central Asia and is frequently reared in captivity for population management. We deployed tri‐axial accelerometers on 20 captive Asian houbaras in two seasons to catalogue basic behaviours, provide a template applicable to other bustard species and examine seasonal differences in behaviour. We created Boolean algorithms to define the following behaviours using raw acceleration data and derived metrics: stationary, eating/drinking and locomotion. We used video recordings to cross‐validate the algorithms, yielding recalls from 95 to 97%, and precisions between 97 and 98%. Houbaras spent significantly more time ‘stationary' and less time on ‘locomotion' in summer (June) compared to spring (March). Simple Boolean algorithms proved useful in identifying several behaviours and have the potential to be applicable to other bustard species, in captivity and in the wild post‐release. Keywords: accelerometer, animal behaviour, Asian houbara bustard, captive breeding, conservation translocation