Mangrove habitats can serve as nursery areas for sharks and rays. Such environments can be thermally dynamic and extreme; yet, the physiological and behavioural mechanisms sharks and rays use to exploit such habitats are understudied. This study aimed to define the thermal niche of juvenile mangrove whiprays, Urogymnus granulatus. First, temperature tolerance limits were determined via the critical thermal maximum (CTMax) and minimum (CTMin) of mangrove whiprays at summer acclimation temperatures (28 °C), which were 17.5 °C and 39.9 °C, respectively. Then, maximum and routine oxygen uptake rates (ṀO2max and ṀO2routine, respectively), post-exercise oxygen debt, and recovery were estimated at current (28 °C) and heatwave (32 °C) temperatures, revealing moderate temperature sensitivities (i.e., Q10) of 2.4 (ṀO2max) and 1.6 (ṀO2routine), but opposing effects on post-exercise oxygen uptake. Finally, body temperatures (Tb) of mangrove whiprays were recorded using external temperature loggers, and environmental temperatures (Te) were recorded using stationary temperature loggers moored in three habitat zones (mangrove, reef flat, and reef crest). As expected, environmental temperatures varied between sites depending on depth. Individual mangrove whiprays presented significantly lower Tb relative to Te during the hottest times of the day. Electivity analysis showed tagged individuals selected temperatures from 24.0 to 37.0 °C in habitats that ranged from 21.1 to 43.5 °C. These data demonstrate that mangrove whiprays employ thermotaxic behaviours and a thermally insensitive aerobic metabolism to thrive in thermally dynamic and extreme habitats. Tropical nursery areas may, therefore, offer important thermal refugia for young rays. However, these tropical nursery areas could become threatened by mangrove and coral habitat loss, and climate change.

Social deep-diving odontocetes face the challenge of balancing near-surface proximity to oxygen and group members with foraging in the deep sea. Individuals rely on conspecifics for critical life functions, such as predator defence, but disperse during foraging to feed individually. To understand the role of social acoustic mediation during foraging in deep-diving toothed whales, we investigated the context of social burst-pulse call production in Risso\'s dolphin (Grampus griseus) using biologgers. Dolphins produced context-specific burst pulses predominantly during daytime foraging, preceding or following foraging dives and in the early descent of daytime deep dives. Individuals applied differential short and long burst-pulse calls intended for either near-surface receivers (horizontal transmission) or deep-foraging receivers (vertical transmission). Our results show that deep-diving toothed whales are reliant on acoustic communication during certain foraging contexts, to relay information including foraging conditions or an individual\'s location. Moreover, they accentuate the importance of maintaining acoustic contact with conspecifics, specifically when dispersed during deeper foraging. It also signifies that our oceanic top predators may be specifically vulnerable to the current strong increase in anthropogenic noise. Potential masking of the signals from group members communicating at a distance could undermine their social cohesion, and hence their capacity to maintain vital life functions.

In the era of big data, ecological research is experiencing a transformative shift, yet advancements in thermal ecology and the study of animal responses to climate conditions remain limited. This review discusses how big data analytics and artificial intelligence (AI) can significantly enhance our understanding of microclimates and animal behaviors under changing climatic conditions. We explore AI\'s potential to refine microclimate models and analyze data from advanced sensors and camera technologies, which capture detailed, high-resolution information. This integration allows researchers to dissect complex ecological and physiological processes with unprecedented precision. We describe how AI can enhance microclimate modeling through improved bias correction and downscaling techniques, providing more accurate estimates of the conditions that animals face under various climate scenarios. Additionally, we explore AI\'s capabilities in tracking animal responses to these conditions, particularly through innovative classification models that utilize sensors such as accelerometers and acoustic loggers. Moreover, the widespread usage of camera traps can benefit from AI-driven image classification models to accurately identify thermoregulatory responses, such as shade usage and panting. AI is therefore instrumental in monitoring how animals interact with their environments, offering vital insights into their adaptive behaviors. Finally, we discuss how these advanced data-driven approaches can inform and enhance conservation strategies. Detailed mapping of microhabitats essential for species survival under adverse conditions can guide the design of climate-resilient conservation and restoration programs that prioritize habitat features crucial for biodiversity resilience. In conclusion, the convergence of AI, big data, and ecological science heralds a new era of precision conservation, essential for addressing the global environmental challenges of the 21st century.

In migratory animals, the developmental period from inexperienced juveniles to breeding adults could be a key life stage in shaping population migration patterns. Nevertheless, the development of migration routines in early life remains underexplored. While age-related changes in migration routes and timing have been described in obligate migrants, most investigations into the ontogeny of partial migrants only focused on age-dependency of migration as a binary tactic (migrant or resident), and variations in routes and timing among individuals classified as \'migrants\' is rarely considered. To fill this gap, we study the ontogeny of migration destination, route and timing in a partially migratory red kite (Milvus milvus) population. Using an extensive GPS-tracking dataset (292 fledglings and 38 adults, with 1-5 migrations tracked per individual), we studied how nine different migration characteristics changed with age and breeding status in migrant individuals, many of which become resident later in life. Individuals departed later from and arrived earlier at the breeding areas as they aged, resulting in a gradual prolongation of stay in the breeding area by 2 months from the first to the fifth migration. Individuals delayed southward migration in the year prior to territory acquirement, and they further delayed it after occupying a territory. Migration routes became more direct with age. Individuals were highly faithful to their wintering site. Migration distance shortened only slightly with age and was more similar among siblings than among unrelated individuals. The large gradual changes in northward and southward migrations suggest a high degree of plasticity in temporal characteristics during the developmental window. However, the high wintering site fidelity points towards large benefits of site familiarity, prompting spatial migratory plasticity to be expressed through a switch to residency. The contrasting patterns of trajectories of age-related changes between spatial and temporal migration characteristics might reflect different mechanisms underlying the expression of plasticity. Investigating such patterns among species along the entire spectrum of migration tactics would enable further understanding of the plastic responses exhibited by migratory species to rapid environmental changes.

Seabirds are often considered sentinel species of marine ecosystems, and their blood and eggs utilized to monitor local environmental contaminations. Most seabirds breeding in the Arctic are migratory and thus are exposed to geographically distinct sources of contamination throughout the year, including per- and polyfluoroalkyl substances (PFAS). Despite the abundance and high toxicity of PFAS, little is known about whether blood concentrations at breeding sites reliably reflect local contamination or exposure in distant wintering areas. We tested this by combining movement tracking data and PFAS analysis (nine compounds) from the blood of prelaying black-legged kittiwakes (Rissa tridactyla) nesting in Arctic Norway (Svalbard). PFAS burden before egg laying varied with the latitude of the wintering area and was negatively associated with time upon return of individuals at the Arctic nesting site. Kittiwakes (n = 64) wintering farther south carried lighter burdens of shorter-chain perfluoroalkyl carboxylates (PFCAs, C9-C12) and heavier burdens of longer chain PFCAs (C13-C14) and perfluorooctanesulfonic acid compared to those wintering farther north. Thus, blood concentrations prior to egg laying still reflected the uptake during the previous wintering stage, suggesting that migratory seabirds can act as biovectors of PFAS to Arctic nesting sites.

Interpreting sound gives powerful insight into the health of ecosystems. Beyond detecting the presence of wildlife, bioacoustic signals can reveal their behavior. However, behavioral bioacoustic information is underused because identifying the function and context of animals\' sounds remains challenging. A growing acoustic toolbox is allowing researchers to begin decoding bioacoustic signals by linking individual and population-level sensing. Yet, studies integrating acoustic tools for behavioral insight across levels of biological organization remain scarce. We aim to catalyze the emerging field of behavioral bioacoustics by synthesizing recent successes and rising analytical, logistical, and ethical challenges. Because behavior typically represents animals\' first response to environmental change, we posit that behavioral bioacoustics will provide theoretical and applied insights into animals\' adaptations to global change.

Sleep is a prominent physiological state observed across the animal kingdom. Yet, for some animals, our ability to identify sleep can be masked by behaviors otherwise associated with being awake, such as for some sharks that must swim continuously to push oxygenated seawater over their gills to breathe. We know that sleep in buccal pumping sharks with clear rest/activity cycles, such as draughtsboard sharks (Cephaloscyllium isabellum, Bonnaterre, 1788), manifests as a behavioral shutdown, postural relaxation, reduced responsiveness, and a lowered metabolic rate. However, these features of sleep do not lend themselves well to animals that swim nonstop. In addition to video and accelerometry recordings, we tried to explore the electrophysiological correlates of sleep in draughtsboard sharks using electroencephalography (EEG), electromyography, and electrooculography, while monitoring brain temperature. The seven channels of EEG activity had a surprising level of (apparent) instability when animals were swimming, but also when sleeping. The amount of stable EEG signals was too low for replication within- and across individuals. Eye movements were not measurable, owing to instability of the reference electrode. Based on an established behavioral characterization of sleep in draughtsboard sharks, we offer the original finding that muscle tone was strongest during active wakefulness, lower in quietly awake sharks, and lowest in sleeping sharks. We also offer several critical suggestions on how to improve techniques for characterizing sleep electrophysiology in future studies on elasmobranchs, particularly for those that swim continuously. Ultimately, these approaches will provide important insights into the evolutionary confluence of behaviors typically associated with wakefulness and sleep.

Levels of dissolved oxygen in open ocean and coastal waters are decreasing (ocean deoxygenation), with poorly understood effects on marine megafauna. All of the more than 1000 species of elasmobranchs (sharks, skates, and rays) are obligate water breathers, with a variety of life-history strategies and oxygen requirements. This review demonstrates that although many elasmobranchs typically avoid hypoxic water, they also appear capable of withstanding mild to moderate hypoxia with changes in activity, ventilatory responses, alterations to circulatory and hematological parameters, and morphological alterations to gill structures. However, such strategies may be insufficient to withstand severe, progressive, or prolonged hypoxia or anoxia where anaerobic metabolic pathways may be used for limited periods. As water temperatures increase with climate warming, ectothermic elasmobranchs will exhibit elevated metabolic rates and are likely to be less able to tolerate the effects of even mild hypoxia associated with deoxygenation. As a result, sustained hypoxic conditions in warmer coastal or surface-pelagic waters are likely to lead to shifts in elasmobranch distributions. Mass mortalities of elasmobranchs linked directly to deoxygenation have only rarely been observed but are likely underreported. One key concern is how reductions in habitat volume as a result of expanding hypoxia resulting from deoxygenation will influence interactions between elasmobranchs and industrial fisheries. Catch per unit of effort of threatened pelagic sharks by longline fisheries, for instance, has been shown to be higher above oxygen minimum zones compared to adjacent, normoxic regions, and attributed to vertical habitat compression of sharks overlapping with increased fishing effort. How a compound stressor such as marine heatwaves alters vulnerability to deoxygenation remains an open question. With over a third of elasmobranch species listed as endangered, a priority for conservation and management now lies in understanding and mitigating ocean deoxygenation effects in addition to population declines already occurring from overfishing.

Sleep serves vital physiological functions, yet how sleep in wild animals is influenced by environmental conditions is poorly understood. Here we use high-resolution biologgers to investigate sleep in wild animals over ecologically relevant time scales and quantify variability between individuals under changing conditions. We developed a robust classification for accelerometer data and measured multiple dimensions of sleep in the wild boar (Sus scrofa) over an annual cycle. In support of the hypothesis that environmental conditions determine thermoregulatory challenges, which regulate sleep, we show that sleep quantity, efficiency and quality are reduced on warmer days, sleep is less fragmented in longer and more humid days, while greater snow cover and rainfall promote sleep quality. Importantly, this longest and most detailed analysis of sleep in wild animals to date reveals large inter- and intra-individual variation. Specifically, short-sleepers sleep up to 46% less than long-sleepers but do not compensate for their short sleep through greater plasticity or quality, suggesting they may pay higher costs of sleep deprivation. Given the major role of sleep in health, our results suggest that global warming and the associated increase in extreme climatic events are likely to negatively impact sleep, and consequently health, in wildlife, particularly in nocturnal animals.

UNASSIGNED: The impact of biologging devices on the aerodynamics or hydrodynamics of animals is still poorly understood. This stands in marked contrast to the ever more extensive use of such technologies in wild-living animals. Recently, increasing concerns have been raised about the impairing effects of these devices on the animals concerned. In the early days of biotelemetry, attention was focused solely on reducing weight, but now aerodynamic effects are also increasingly being considered. To investigate these effects, we trained Northern Bald Ibises to fly in a wind tunnel in which we measured heart rate and dynamic body acceleration (VeDBA) as proxies for energy expenditure in relation to different logger shapes and wind flow directions.
UNASSIGNED: Our data provide evidence that the position of biologging devices significantly influence the flight distances, and the shape of biologging devices has a considerable effect on heart rate and VeDBA, both of which have been used as proxies for energy expenditure. Unfavorable shape and positioning go beyond merely affecting the effort required during flapping flight. The energetically probably more important effect is that the devices impair the bird\'s ability to glide or soar and thus force them to perform the energetically much more demanding flapping flight more frequently. This effect was more pronounced in rising air than in horizontal airflow. A complementary study with wild Northern Bald Ibises during spring migration provides evidence that the position of the devices on the bird\'s back affects the length of the flight stages. Birds carrying the devices on the upper back, fixed by wing-loop harnesses, had significantly shorter flight stages compared to birds with a more caudally positioned device, fixed by leg-loop harnesses.
UNASSIGNED: The attachment of biologging devices on birds affects their performance and behavior and thus may influence their fitness and mortality. Our results show that detrimental effects can be reduced with relatively little effort, in particular through a strictly aerodynamic design of the housing and increased consideration of aerodynamics when attaching the device to the body. In birds, the attachment of biologging devices via leg loops to the lower back is clearly preferable to the common attachment via wing loops on the upper back, even if this affects the efficiency of the solar panels. Nevertheless, the importance of drag reduction may vary between systems, as the benefits of having a biologging devices close to the center of gravity may outweigh the increase in drag that this involves. Overall, more research is required in this field. This is both in the interest of animal welfare and of avoiding biasing the quality of the collected data.
UNASSIGNED: The online version contains supplementary material available at 10.1186/s40317-023-00322-5.