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Time of day is recognized as an important behaviour modulator of wild animals mainly via physical environmental changes such as temperature and light intensity. These temporal factors can also affect animal movements (i.e., changes of locations) and consequent distribution. However, while it is commonly observed in diverse taxa that an animal’s attendance at a specific site concentrates within a narrow time window, how time influences the route selections of traveling animals in the course of their movements through to the end point is still not well understood. In this study, we quantified temporal and spatial patterns in the homing paths of streaked shearwaters Calonectris leucomelas, which are present at the breeding colony exclusively after sunset, to investigate how time constrains their movement strategy for homing from at-sea foraging areas. We tracked the foraging trips using GPS loggers in chick-rearing seasons for five years. In addition, in one year we conducted displacement experiments, releasing birds at sea at three different times of the day (midday, sunset and night-time) to impose time constraints on homeward movements. The movement paths revealed that the time of sunset was key to their decision of timing and in route selections during homing. Most birds returning from foraging trips reached the coastal area around sunset by adjusting travel timing and directions, despite variation in foraging areas, and flew along the coastline to the breeding island. Meanwhile, most birds released offshore stopped flights around sunset and waited on the water surface for sunrise before restarting their homeward movements. Birds therefore avoid offshore traveling at night, appearing to preferentially use diurnal cues for homing at sea. This study demonstrates the importance of timing as well as geographic features for homing decisions of streaked shearwaters and confirms that both spatial and temporal cognitive abilities are well developed in seabirds.

The identification of when, how and where animals feed is essential to estimate the amount of energy they obtain and to study the processes associated with prey search and consumption. We combined the use of animal-borne video cameras and accelerometers to characterise the body and head movements associated to four types of prey capture behaviours in the Magellanic Penguin (Spheniscus magellanicus). In addition, we evaluated how the K-Nearest Neighbour (K-NN) algorithm recognized these behaviours from acceleration data. Finally, we compared the total capture and the capture per unit time (CPUT) derived by identifying prey capture events using the K-NN algorithm to that derived by counting undulations in the dive profile (“wiggles”). During captures, body and head movements were highly variable in the tridimensional space. Energy expenditure (i.e., VeDBA values) during diving periods with prey captures was from three to four times higher than during controls diving periods (i.e., with no capture events). The K-NN classification resulted effective and showed accuracy scores above 90% when considering both head and body related features. In addition, when captures were estimated using the K-NN method, the CPUT was similar or higher to that estimated by counting wiggles. Our study contributes to the knowledge of the trophic ecology of this species and provides an alternative method for estimating prey consumption in the Magellanic Penguin and other diving seabirds.

Background Salmonids return to the river where they were born in a phenomenon known as mother-river migration. The underpinning of migration has been extensively examined, particularly regarding the behavioral correlations of external environmental cues such as the scent of the mother-river and geomagnetic compass. However, neuronal underpinning remains elusive, as there have been no biologging techniques suited to monitor neuronal activity in the brain of large free-swimming fish. In this study, we developed a wireless biologging system to record extracellular neuronal activity in the brains of free-swimming salmonids. Results Using this system, we recorded multiple neuronal activities from the telencephalon of trout swimming in a rectangular water tank. As proof of principle, we examined the activity statistics for extracellular spike waveforms and timing. We found cells firing maximally in response to a specific head direction, similar to the head direction cells found in the rodent brain. The results of our study suggest that the recorded signals originate from neurons. Conclusions We anticipate that our biologging system will facilitate a more detailed investigation into the neural underpinning of fish movement using internally generated information, including responses to external cues.

SummaryThe largest extinct volant birds (Pelagornis sandersiandArgentavis magnificens) and pterosaurs (PteranodonandQuetzalcoatlus) are thought to have used wind-dependent soaring flight, similar to modern large birds. There are two types of soaring: thermal soaring, used by condors and frigatebirds, which involves the use of updrafts to ascend and then glide horizontally over the land or the sea; and dynamic soaring, used by albatrosses, which involves the use of wind speed differences with height above the sea surface. Previous studies have suggested thatPelagornis sandersiused dynamic soaring, whileArgenthavis magnificens, Pteranodon, andQuetzalcoatlusused thermal soaring. However, the performance and wind speed requirements of dynamic and thermal soaring for these species have not yet been quantified comprehensively. We quantified these values using aerodynamic models and compared them with that of extant birds. For dynamic soaring, we quantified maximum flight speeds and maximum upwind flight speeds. For thermal soaring, we quantified the animal’s sinking speed circling at a given radius and how far it could glide losing a given height. Our results confirmed those from previous studies thatPteranodonandArgentavis magnificensused thermal soaring. Conversely, the results forPelagornis sandersiandQuetzalcoatluswere contrary to those from previous studies.Pelagornis sandersiused thermal soaring, andQuetzalcoatlushad a poor ability both in dynamic and thermal soaring. Our results demonstrate the need for comprehensive assessments of performance and required wind conditions when estimating soaring styles of extinct flying species.

Pelagic seabirds have evolved physiological and morphological characteristics that enable them to fly in an energy efficient manner over the oceans. Although there are some exceptions (e.g., Delord et al. 2020), most species come ashore only to breed or rest. However, recent tracking technologies have revealed some unexpected overland journeys. For example, brown pelicans Pelecanus occidentalis (Lamb et al. 2017), Arctic terns Sterna paradisaea (Redfern & Bevan 2020), and the focal species of this study, fledglings of streaked shearwaters Calonectris leucomelas (Yoda et al. 2017a; Fig. 1a), are known to migrate overland.

BackgroundEcholocating bats make a series of decisions to select their flight paths based on auditory information obtained by sonar as well as visual cues; accumulations of these flight routes are represented as daily movement patterns. However, there is still a lack of an understanding of continuous movements of echolocating bats in the wild (i.e., from meters to tens of kilometers). In this study, we investigated nightly flight paths of the Japanese greater horseshoe bat, Rhinolophus ferrumequinum nippon, using high-resolution GPS data loggers. Our aim was to identify foraging and commuting behavior based on the observed movement patterns and to investigate the relationship between these movement types and specific habitats. ResultsWe found that the majority of tagged bats alternated between foraging and commuting behavior throughout the tracking period, and one individual moved 23.6 km from its roost. The bats usually left a foraging area in the opposite direction from which they entered it, indicating that almost all of the stay sites were on their way to another destination. The distance between two successive foraging sites was on average 332 ± 398 m (mean ± standard deviation), and half of all foraging periods lasted less than 3 min. An analysis of habitat use revealed that the bats used conifer plantation and natural forests as pathways and feeding habitats. ConclusionsOur findings suggest that the structure of the forests have a great influence on the nocturnal behavior of the greater horseshoe bats. Although this study has a descriptive character due to a relatively small number of tagged individuals, it was possible to elucidate the small-scale interactions between wild Rhinolophus bats and their environment using the latest high-resolution GPS technology, which will allow us to give new insights into the foraging ecology of echolocating bats in the wild.

Between 25–30 November 2013, 2014 and 2015, miniaturized video cameras were attached to Magellanic Penguins (Spheniscus magellanicus; n = 14) in Punta Norte/San Lorenzo, Peninsula Valdes, Chubut, Argentina. The objective was to examine prey selection, consumption of untraceable prey, and inter- and intraspecific interactions. During 56.3 hr of video footage, 1,621 dives from 14 individuals were recorded. Magellanic Penguins swam through shoals of lobster krill (Munida gregaria morph subrugosa), selectively consuming the fish, primarily anchovies (Engraulis anchoita), that were dispersed along the shoal, but did not consume the lobster krill. Magellanic Penguins captured fish on dives of less than 2 m in depth. The tagged individuals foraged with conspecifics in 2% (n = 33) of the total recorded dives. In addition, a multispecies feeding association was also documented (n = 1). Results were constrained to the upper 40 m of the water column; below this depth light level was too low for detections by video. The development of cameras with a light source and wider-angle lens are crucial to improve our understanding of Magellanic Penguin foraging behavior.

How surface-feeding albatrosses feed on deep-sea squids has long been a mystery. We investigated foraging behavior during daylight hours of 20 Laysan albatrosses Phoebastria immutabilis breeding in Hawaii using GPS- and camera-loggers. The birds traveled to the North Pacific Transition Zone up to 600 km north of their breeding site. The camera images showed that Laysan albatrosses fed on large (～ 1 m body length), intact floating dead squids (6 events) and floating fragmented squids (10 events) over deep oceanic water (>2000 m) while they flew in a straight path without sinuous searching. Feeding events on squids were not observed during trips when fishing vessels were photographed and seemed to be distributed randomly and sparsely. Thus, this study suggests that Laysan albatrosses found large, presumably post-spawning, squids opportunistically while they were traveling during daylight hours. Although we did not find cetaceans in our surface pictures, we could not rule out the possibility that birds fed on squids, especially fragmented specimens, in the regurgitates of cetaceans at depth. This study demonstrates the usefulness of combining animal-borne GPS- and camera-loggers on wide-ranging top predators for studying the distribution of little known deep-sea squids and their importance in the diet of marine top predators.

We studied the breeding phenology of the Brown Booby Sula leucogaster on Nakanokamishima, southern Ryukyu Islands, Japan. During the breeding season (April–November) of 1989 we observed the presence and absence of 18 chicks and measured their growth on a total of 17 days. Egg hatching was observed during April and May. The estimated minimum pre-fledging period ranged from 60 to 100 days and the maximum pre-fledging period ranged from 86 to 122 days, whereas the minimum post-fledging dependence period ranged from 24 to 105 days and the maximum post-fledging dependence lasted from 74 to 124 days. All of the monitored fledglings left the colony by early-November, and the total period over which parents cared for their chicks was 119–197 days (minimum) and 146–208 days (maximum). Body weight and culmen length attained 95% of asymptotic values in 65 and 69 days of age and wing length in 91 days. Six out of 18 fledglings were seen again in the colony, three to seven years after initial independence.

To understand foraging strategies and behavioral flexibility in wild animals, it is important to evaluate the physiological costs imposed by foraging efforts and how these costs affect foraging and provisioning behavior. Oxidative stress is a possible physiological indicator associated with foraging behavior in wild seabirds, and may also affect their reproductive performance. However, no previous study has simultaneously recorded foraging behavior and the associated oxidative stress in wild seabirds. Using an integrative approach based on oxidative stress measurements and bio-logging techniques (i.e., the use of animal-borne sensors), we determined the relationships between foraging behavior and oxidative stress in chick-rearing streaked shearwaters Calonectris leucomelas in 2018 and 2019. To quantify their oxidative stress, we measured reactive oxygen metabolites (d-ROMs) and biological antioxidant potential (BAP) in their plasma. We found that the d-ROMs levels were positively related to the maximum distance from the colony and the number of takeoffs, especially in 2019 when shearwaters flew further to forage. In 2018, when they flew relatively short distances, the BAP levels were positively related to the levels of their physical activity (overall dynamic body acceleration; ODBA). We conclude that longer and less successful foraging may lead to increase oxidative stress, while successful foraging may mitigate the oxidative stress of foraging by providing dietary antioxidants. Our results highlight that the combined data from bio-logging and oxidative stress measurements aid in evaluating the underlying physiological costs of foraging behavior in wild animals.

Chicks of many burrow-nesting seabirds are known to repeatedly emerge from their nests (these trips being termed “excursions”) and exercise their wings prior to fledging, but this behavior is poorly documented in the literature, and thus the relationship between growth and exercise remains unclear. Here, we used infrared video cameras placed in front of streaked shearwater (Calonectris leucomelas) nests during the chick-emergence period to examine correlations between chick excursions and parameters known to be important for juvenile survival after fledging. In addition, we also attached acceleration-temperature loggers to several chicks in order to evaluate the relationship between excursion time and time spent exercising the wing muscles (i.e. flapping). Chicks that undertook longer excursions exhibited more rapid increases in wing length and larger body masses at fledging, and also fledged earlier. Correlations between fitness-related parameters and excursion time indicate that excursions during the emergence period might offer insights into the various relationships between growth and behavior and/or the mechanisms underlying offspring survival following fledging. This article is protected by copyright. All rights reserved.

Sex-related differences in foraging habitat are common among seabirds. Streaked Shearwaters Calonectris leucomelas breeding on Awashima Island in the Sea of Japan are considered to exhibit gender differences in foraging habitat: only males cross the windy Tsugaru Strait into the Pacific Ocean. Since males are larger, with greater wing loading than females, winds are expected to increase the effect of sexual size dimorphism on their flight performance, which may determine accessibility to foraging habitats. To assess the sex-related differences in foraging movements among years in which environmental and wind conditions differed, we analyzed foraging trips of male (N=243) and female (N=241) Streaked Shearwaters during the chick-rearing period by using GPS loggers in 2011, 2012, and 2013. Both males and females were found to travel through the Tsugaru Strait into the Pacific Ocean, but the frequency was higher for males than for females. Nevertheless, we found that wind velocities had no effect on ...

There is increasing evidence showing that wind velocity affects the flight and foraging behavior of seabirds; however, few studies have examined these effects on seabirds inhabiting tropical oceans where lighter wind conditions usually prevail. The Brown Booby Sula leucogaster is an example of a tropical seabird with relatively low wing loading; strong wind conditions may be expected to impede the stability of their flight. We examined how different wind conditions affected the duration and flying behavior of Brown Booby fledglings during foraging trips by means of direct observation of nest attendance and by attaching video loggers to birds. The duration of foraging trips by fledglings decreased with increasing wind speed, and during flight, the body rotation of fledglings became greater with increasing wind speed. As expected, fledglings were buffeted by strong winds due to their relative inexperience in flight combined with their low wing loading. Fledglings were probably forced to flap agains...

How do wild animals behave as they get older? We investigated the foraging behavior of black-tailed gulls (Larus crassirostris) of known age using GPS and acceleration loggers. We found that the older gulls reduced their mean flight speed and tended to feed on prey on land rather than on prey at sea. However, breeding performance of gulls did not change with age. Therefore, older gulls might experience senescence, but optimize their foraging behavior in relation to their age to maintain breeding performance.

Streaked shearwaters (Calonectris leucomelas) are pelagic seabirds that breed on isolated islands in East Asia. Sometimes, they fly long distances to search and forage for food over several hundred kilometers. During the chick-rearing period, efficient foraging is one of the most important tasks for parents because they have to obtain food not only for themselves but also for their chicks. To understand their foraging strategy of streaked shearwaters, their behavior and physiological cost should be quantified. In 2018, we attached GPS and acceleration loggers on breeding shearwaters (15 males and 11 females, including eight pairs) and collected blood samples from them at the deployment and recovery of the loggers. We confirmed that blood drawing from Streaked shearwaters did not have significant adverse effect on their foraging behaviors. We found oxidative and anti-oxidative markers via blood can be useful for assessing the physiological cost of their foraging behaviors. Our finding suggests that females were suffered from heavier stress than males, because females often conducted short trips and increased oxidative stress. To reveal how they perform foraging with minimal cost, we are going to analyze the relationship between foraging behavior and the associated physiological cost in detail.

Revealing the route selection of wild animals is of fundamental importance in understanding their movements and foraging strategy. In this study, we attached GPS loggers to black-tailed gulls Larus crassirostris and recorded their movement trajectories during their foraging trips. Using inverse reinforcement learning (IRL), we analyzed the factors that affected their route selection. During the training phase, using pre-defined feature maps, we estimated a reward map that may affect the decision making of black-tailed gulls. The reward map can be used for predicting the trajectories of the gulls during the test phase. In addition, the resultant weight vector enabled us to analyze to which degree the black-tailed gulls favor each area.

Magellanic penguins (Spheniscus magellanicus) have been reported to become stranded along the coasts of northern Argentina, Uruguay and southern Brazil during the austral winter 1, 2, 3. This location is more than a thousand kilometers distant from their northernmost breeding colony in northern Patagonia. Curiously, females typically outnumber males at stranding sites (approximately three females per male) [2]. To date, no conspicuous sex differences have been reported in their migratory movements [3], although records are lacking during the peak stranding season. Consequently, the reason(s) for the female-biased stranding remain unknown, despite the growing necessity for understanding their behavior outside the breeding season [3]. We recorded at-sea distributions of Magellanic penguins throughout the non-breeding period using animal-borne data loggers and found that females reached more northern areas than males and did not dive as deep during winter (Figure 1). Such sexual differences in spatial domains might be driven by mechanisms related to sexual size dimorphism, such as the avoidance of intraspecific competition for food resources [4], differences in thermal habitat preference [5] or differences in the ability to withstand the northward-flowing ocean circulation [6]. Individual penguins that winter in northern areas are likely to be at greater risk of natural [7] and anthropogenic threats [8], and probably more so in females, as more females than males tend to frequent areas closer to the sites where penguins strand. Our results highlight the importance of understanding the spatial domains of each sex throughout the annual cycle that are associated with different mortality risks. Fil: Yamamoto, Takashi. Nagoya University; Japón Fil: Yoda, Ken. Nagoya University; Japón Fil: Blanco, Gabriela Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Biología de Organismos Marinos; Argentina Fil: Quintana, Flavio Roberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Biología de Organismos Marinos; Argentina

Heart rate (HR) and heart rate variability (HRV) provide noninvasive measures of the relative activity of the parasympathetic nervous system (PNS), which promotes self-maintenance and restoration, and the sympathetic nervous system (SNS), which prepares an animal for danger. The PNS decreases HR, whereas the SNS increases HR. The PNS and SNS also contribute to oscillations in heartbeat intervals at different frequencies, producing HRV. HRV promotes resilience and adjustment capacity in the organism to intrinsic and extrinsic changes. Measuring HRV can reveal the condition and emotional state of animals, including aspects of their stress physiology. Until now, the functioning of the PNS and SNS and their relationship with other physiological systems have been studied almost exclusively in humans. In this study, we tested their influence on HR and HRV for the first time in a wild-caught seabird, the streaked shearwater (Calonectris leucomelas). We analyzed electrocardiograms collected from birds carrying externally attached HR loggers and that received injections that pharmacologically blocked the PNS, the SNS, or both, as well as those that received a saline (sham) injection or no injection (control). The PNS strongly dominated modulation of HR and also HRV across all frequencies, whereas the SNS contributed only slightly to low-frequency oscillations. The saline injection itself acted as a stressor, causing a dramatic drop in PNS activity in HRV and an increase in HR, though PNS activity continued to dominate even during acute stress. Dominant PNS activity is expected for long-lived species, which should employ physiological strategies that minimize somatic deterioration coming from stress.

Animals in the same population consistently differ in their physiology and behaviour, but the underlying mechanisms remain poorly understood. As the autonomic nervous system regulates wide-ranging physiological functions, many of these phenotypic differences may be generated by autonomic activity. We investigated for the first time in a free-living animal population (the streaked shearwater, Calonectris leucomelas , a long-lived seabird) whether individuals consistently differ in autonomic activity, over time and across contexts. We repeatedly recorded electrocardiograms from individual shearwaters, and from heart rate and heart rate variability quantified sympathetic activity, which drives the ‘fight-or-flight’ response, and parasympathetic activity, which promotes ‘rest-and-digest’ processes. We found a broad range of autonomic phenotypes that persisted even across years: heart rate consistently differed among individuals during periods of stress and non-stress and these differences were driven by parasympathetic activity, thus identifying the parasympathetic rest-and-digest system as a central mechanism that can drive broad phenotypic variation in natural animal populations.

Offspring transmit signals to parents to communicate their resource demands. Parents interpret these signals and should adjust provisioning efforts to meet offspring demands but only to the point at which the benefits of enhanced offspring quality stops exceeding the increased costs to future reproduction. We investigated both proximate behavioral mechanisms in these interactions and ultimate-level decisions for total parental investment in streaked shearwaters Calonectris leucomelas by recording begging calls, monitoring parental attendance, and altering states of chicks by supplementing food. In our study, chicks seemed to honestly communicate satiety and body condition via begging. The parents, however, did not downwardly adjust feeding rates, meal sizes delivered to chicks, and total investment in nests in which chicks were regularly supplementary-fed partial meals. But on nights when both parents visited the nest, the second-arriving parents recognized that chicks had already received a full meal because they reduced the food they gave to chicks and also lengthened their subsequent foraging trip. Our findings therefore suggest that although chick begging appeared to reflect need, parents only responded to variation in begging that indicated that chicks had already received a full meal. In a simulation, we show that this strategy prevents parents from exceeding the optimal amount of parental investment. Their insensitivity to slightly reduced begging after partial meals caused them to exceed optimal investment in supplementary-fed nests, suggesting that parental investment is largely regulated by responses to feeding rate of the other parent rather than being fine-tuned to cues about body condition of chicks.

Wildlife migration is a spectacular phenomenon [1]. Studies using telemetry - tracking devices attached on free-living animals - have shown that large topographic barriers and obstacles, such as oceans and deserts, elicit extreme feats of migration [2]. Overcoming the challenges of these obstacles might require experience and skill that young individuals lack [2-5]. Further, younger, inexperienced animals might determine their migration routes using navigation strategies different from those of older animals [6-9], but our knowledge of how orientation mechanisms and experience drive migration strategy is limited. We have studied how experienced (adults) and inexperienced (first-time migrating fledglings) streaked shearwaters (Calonectris leucomelas) approach the challenge of migration using animal-borne tracking devices. The study birds migrate from a colony on the north of a large topographic barrier, Honshu Island, Japan. Shearwaters use a wind- and wave-based flight pattern-dynamic soaring-to extract energy for highly efficient travel over oceans [10]. We therefore expected that shearwaters migrating southward from the colony would make substantial detours to avoid any landmasses. We found that migrating adults followed one of two paths that detour around landmasses that hinder direct southerly migration. In contrast, inexperienced fledglings followed a straight course in a south-oriented direction that forced them to complete a trans-mountain journey, suggesting that the birds rely on an innate compass. Thus, we suggest that fledglings would eventually override the simple compass navigation, which appears to be the primary driver for their extreme migration, before being able to interact appropriately with the marine environment.

The autonomic stress response, often referred to as the 'fight-or-flight' response, is a highly conserved physiological reaction to stress in vertebrates that occurs via a decrease in parasympathetic (PNS) activity, which promotes self-maintenance 'rest and digest' processes, and an increase in sympathetic (SNS) activity, which prepares an animal for danger ('fight-or-flight'). Though the PNS and SNS both innervate most organs, they often control different tissues and functions within those organs (though the pacemaker of the heart is controlled by both). Moreover the PNS and SNS are regulated independently. Yet until now, most studies of autonomic stress responses in non-model species focused only on the SNS response. We used external electrocardiogram loggers to measure heart rate and heart rate variability indexes that reflect PNS and SNS activity in a seabird, the Streaked Shearwater (Calonectris leucomelas), during the stress of handling, and during recovery in the nest burrow or during restraint in a cloth bag. We show for the first time in a free-living animal that the autonomic stress response is mediated primarily by a rapid decrease in PNS activity: handling stress induced a large and long-lasting depression of PNS 'rest-and-digest' activity that required two hours to recover. We also found evidence for a substantially smaller and shorter-lasting SNS 'fight-or-flight' response. Confinement in a cloth bag was less stressful for birds than handling, but more stressful than recovering in nest burrows. We show that quantifying autonomic activity from heart rate variability is effective for non-invasively studying stress physiology in free-living animals.

Jellyfish and other pelagic gelatinous organisms (“gelata”) are increasingly perceived as an important component of marine food webs but remain poorly understood. Their importance as prey in the oceans is extremely difficult to quantify due in part to methodological challenges in verifying predation on gelatinous structures. Miniaturized animal-borne video data loggers now enable feeding events to be monitored from a predator's perspective. We gathered a substantial video dataset (over 350 hours of exploitable footage) from 106 individuals spanning four species of non-gelatinous-specialist predators (penguins), across regions of the southern oceans (areas south of 30°S). We documented nearly 200 cases of targeted attacks on carnivorous gelata by all four species, at all seven studied localities. Our findings emphasize that gelatinous organisms actually represent a widespread but currently under-represented trophic link across the southern oceans, even for endothermic predators, which have high energetic demands. The use of modern technological tools, such as animal-borne video data loggers, will help to correctly identify the ecological niche of gelata. Fil: Thiebot, Jean-Baptiste. National Institute of Polar Research; Japón Fil: Arnould, John PY. Deakin University; Australia Fil: Gómez Laich, Agustina Marta. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Biología de Organismos Marinos; Argentina Fil: Ito, Kentaro. SOKENDAI Graduate University for Advanced Studies; Japón Fil: Kato, Akiko. Université de La Rochelle; Francia Fil: Mattern, Thomas. University of Otago; Nueva Zelanda Fil: Mitamura, Hiromichi. Kyoto University; Japón Fil: Noda, Takuji. Kyoto University; Japón Fil: Poupart, Timothée. Deakin University; Australia Fil: Quintana, Flavio Roberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Biología de Organismos Marinos; Argentina Fil: Raclot, Thierry. Université de Strasbourg; Francia Fil: Ropert-Coudert, Yan. Université de La Rochelle; Francia Fil: Sala, Juan Emilio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Biología de Organismos Marinos; Argentina Fil: Seddon, Philip J.. University of Otago; Nueva Zelanda Fil: Sutton, Grace J.. Deakin University; Australia Fil: Yoda, Ken. Nagoya University; Japón Fil: Takahashi, Akinori. SOKENDAI Graduate University for Advanced Studies; Japón

The acoustic performance and behaviour of free-ranging cetaceans requires investigation under natural conditions to understand how wild animals use sound. This is also useful to develop quantitative evaluation techniques for passive acoustic monitoring. There have been limited studies on the acoustics of the Indo-Pacific humpback dolphin; nevertheless, this species is of particular concern because of the anthropogenic activity in the coastal habitats. In the present study, we used a four-hydrophone array to estimate the apparent source levels (ASLs) of biosonar sequences (click trains), of this species in San-Niang Bay, China. As the dolphins approached the array, 173 click trains were found to meet the criteria of on-axis sounds produced within 60 m of the equipment. In total, 121 unclipped click trains were used for the ASL estimation. The qualified click trains contained 36.3 ± 32.5 clicks, lasting for 1.5 ± 1.5 s, with average inter-click intervals (ICIs) of 51.2 ± 38.3 ms. Average ICIs showed a bimodal distribution, with a cut-off at 20 ms. Short-range click trains, with short ICIs of

Ocean currents are in continuous motion and strongly influence oceanic ecosystems. In situ observation of currents is of primary importance for understanding how marine animals respond to ocean surface currents at various scales and for realizing effective ecosystem-based management and realistic oceanographic modelling. We developed a new method for obtaining in situ current measurements by using seabirds as Lagrangian current sensors akin to drifting buoys. We deployed high-resolution global positioning system (GPS) loggers on streaked shearwaters (Calonectris leucomelas) foraging in the Oyashio-Tsugaru Warm Current confluence in Japan, which is one of the most productive oceans in the world. The seabirds repeatedly performed foraging trips, including searching for prey and resting on the sea surface, over several hundred kilometres. The seabirds spent half of their time resting on the water surface and tended to be passive drifters. We inferred that the drift movements of C. leucomelas provided a direct and detailed description of the ocean surface currents, because currents deduced from their drift movements were in good agreement with ocean surface currents derived from in situ and satellite data. In addition, we extracted details of shearwaters’ intense searching flights associated with feeding (i.e. foraging spots) from GPS tracks. C. leucomelas did not forage at the core of anticyclonic eddies; rather, they used the boundary areas between eddies and the edge of eddies where primary productivity and prey density are thought to be high. Our study demonstrated that animal-borne GPS data can provide a detailed and cost-efficient tool for observing ocean surface currents and can reveal the ways in which marine animals respond to these currents at a fine scale.

Summary The doubly labelled water (DLW) method is an isotope-based technique that is used to measure the metabolic rates of free-living animals. We validated the DLW method for measuring metabolic rates in five rhinoceros auklets (Cerorhinca monocerata) compared with simultaneous measurements using the respirometric method. We calculated the CO2 production rate of four auklets (mean initial body mass: 552 g±36 s.d.) injected with DLW, using the one- and two-pool models. The metabolic rate during the 24-h measurements in a respirometric chamber for resting auklets averaged 16.30±1.66 kJ h−1 (n = 4). The metabolic rates determined using the one- and two-pool models in the DLW method for the same period as the respirometric measurement averaged 16.61±2.13 kJ h−1 (n = 4) and 16.16±2.10 kJ h−1 (n = 4), respectively. The mean absolute percent error between the DLW and respirometric methods was 8.04% using the one-pool model and was slightly better than that with the two-pool model. The differences in value between the DLW and respirometric methods are probably due to oxygen isotope turnover, which eliminated only 10–14% of the initial enrichment excess.

The energetics of adult Streaked Shearwaters Calonectris leucomelas during the chick-rearing period were examined on Awa Island, Japan, in 2008 and 2009. Basal metabolic rates (BMR) were quantified using an open-flow respirometry system and field metabolic rates (FMR) were quantified using a doubly labelled water (DLW) method. In addition, we used activity loggers to estimate time allocations for different activities at sea. BMR was 0.0124 kJ g-1 h-1 (±0.0153, N=4) on average and corresponded to 54% of the value predicted from allometric equations. FMR was 0.0634 kJ g-1 h-1 (±0.0331, N=3) and was equivalent to 5.1 times BMR, which was higher than values reported for albatrosses (2–4 times BMR). Shearwaters made 50.3 landings a day (±9.8, N=12) and spent 44.8% (±8.0, N=12) of their time sitting on the water. They landed on water approximately twice as often as albatrosses (which have been well-studied using DLW), but they both spent similar proportions of their time on water. Frequent landings at ...

Timing is crucial for animals for optimizing foraging, travelling and breeding behaviours in spatiotemporally heterogeneous environments. Some seabirds, commuting between land-based nesting colonies and widely dispersed foraging areas at sea, return to their colonies within several hours after sunset. This temporal pattern raises the question of how they manage to time arrivals over largely variable homeward distances. However, no study has investigated their at-sea behavioural patterns associated with arrival times. To explore this question, we tracked breeding streaked shearwaters, Calonectris leucomelas, with GPS data loggers, which continuously recorded fine-scale movement paths during their trips. Shearwaters adjusted the onset of their homeward journeys according to wide-ranging distances between their chosen foraging areas and breeding colonies, leaving earlier from further locations. The start time of homing was pushed forward correlating with the increased travel time expected from their homeward distance and average movement speed. This resulted in arrivals at the colony concentrated within a few hours after sunset independent of the distances. To our knowledge, similar temporal tuning of homing trips has not been reported previously. The strong correlation between the timing and distance of homeward journeys implies this behaviour is ecologically important. Further experiments will help clarify its generality in the animal kingdom as well as proximate mechanism(s) and ultimate function(s).

The post-fledging dependence period is extremely important because it allows young birds the opportunity to develop behavioural skills required for later life. We raised 12 hatchling Brown Boobies Sula leucogaster and attached a miniaturized GPS logger to each bird to examine how flight improves after fledging. The Boobies made daily trips and increased the maximum distance, total distance travelled each day, trip duration and flight speed. Young Boobies seemed to gradually acquire flight skills towards independence.

The lunar cycle has been shown to affect the behaviour of a variety of marine animals. However, changes in the behaviour of seabirds and marine mammals and how they respond to the lunar cycle have been less well documented, principally because of the technical difficulties in long-term recording of their at-sea behaviour. Because seabirds generally rely on visual cues at small spatial scales, ambient light levels by moonlight may have a strong influence on their foraging and predator avoidance behaviours at sea at night. We used global location sensor loggers attached to wintering streaked shearwaters to examine whether the birds' at-sea behaviour varied with the lunar phase. The shearwaters migrated from Japan to the seas off northern New Guinea. Their activities at night changed synchronously with the lunar phase: birds flew for longer periods and landed on water more frequently on nights with a full moon than when there was a new moon. Our results indicate that at-sea behaviour of pelagic seabirds is closely associated with the lunar cycle.

Externally-attached transmission and logging devices have greatly helped elucidate the biology of free-living animals over the last 50 yr. However, such devices may hinder animals so that the behaviour monitored is not representative of unequipped conspecifics. We suggest that if animals are equipped with devices of varying size, the change in recorded parameters with size can be used to extrapolate to the condition in unencumbered animals. Use of this approach with Adelie penguins Pygoscelis adeliae showed that unequipped birds are predicted to range farther, swim faster, dive deeper and be more efficient underwater than equipped birds. The derived data not only set baseline information for the species concerned but also allow us to put the deleterious effects of the devices into perspective.

Changes in sea-ice conditions can affect locomotion on land, diving behavior, and corresponding foraging success of penguins. In this study, locomotion on land and diving behavior were compared between early and late stages of the guard phase with different sea-ice conditions using miniaturized time-depth-acceleration data loggers for Adelie penguins Pygoscelis adeliae from 18 December 2001 to 11 January 2002 in Dumont d’Urville, Adelie Land (66.7°S, 140.0°E), Antarctica. Differences were found between early and late stages in the ratio of walking vs. tobogganing, proportion of time spent diving, diving depth as well as in the rate of parental tissue accumulation. In contrast, trip duration, distance traveled on land, and meal delivery rate to chicks did not differ between the stages. This study suggests that physical changes in sea-ice during the penguins’ chick-rearing period may affect certain on-land and/or at-sea behaviors which, in turn, may affect how resources are allocated to self-maintenance or chick-provisioning.

How do seabirds acquire diving skills after fledging? This is an important issue to complete our basic knowledge of life history in seabirds, but the mobility of juveniles obstructs the continuous recording of the development of diving behaviour. In this study, we raised hatchling brown boobies, Sula leucogaster, which are known to have a long post-fledging period. Once boobies began to fly, they made round trips between the sea and the nest, and begged for food from us, their surrogate parents. During this post-fledging care period, the development of diving behaviour was recorded using data loggers. In addition, we attached data loggers to adult brown boobies in the field and compared their diving performance with that of juveniles. The hand-raised juveniles had relatively slow development of diving ability during the first month after fledging. This slow development of behaviour with ontogeny might be the proximate cause for the extended post-fledging care period in this species. This study shows that the combination of bio-logging and hand raising of seabirds is a useful tool for assessing the ontogeny of diving behaviour in these animals.

Ad´ elie penguins Pygoscelis adeliae were tested as to whether they jump with optimal energy efficiency when moving out of the sea to the land. Adpenguins risk predation if the jump fails. Swimming penguins usually launch up the side of sea ice to a surface higher than sea level. Analysis of jumping behaviour recorded by a video camera showed that the trajectory of the centre of gravity of the birds during the aerial phase of jumping was parabolic, indicating that the success of landing depends on three parameters at the time of take-off from water: speed, angle and distance from the point of emergence to the ice edge. There was a negative relationship between distance and the take-off angle, suggesting that penguins adjust their take-off angle to the distance from the ice edge. The comparison among hypotheses revealed that penguins did not jump with optimal energy efficiency. Instead, they aimed for the refracted image of the edge of the cliff, which from underwater appears higher than it actually is. This direction-dependent rule seems to be more robust and reliable than the optimal energetic strategy.

In many species that have internal fertilization, seminal flow includes various elements and materials in addition to the fertilizing sperm. The roles of these components are unknown. One hypothesis is that they are nutritional gifts to the female as a paternal investment. We made game theoretical models from the point of view of sperm competition among males and examined this hypothesis. The evolutionary stable strategy (ESS) of the models showed that (1) when multiple mating in the female is relatively low, gifts in seminal flow or other types of gift may evolve, at least, a male does not resist a female digesting his sperm; and (2) the ratio of nutritional gift rapidly decreases to zero with the probability or frequency of multiple mating in the female. Hence, we concluded that nutritional gifts in seminal flow can exist only in species in which sperm competition among males is rare. Furthermore, we concluded that if an element or material eminently decreases when sperm competition becomes intense, it may be a gift as a paternal investment; if not, other hypotheses concerned with more agonistic roles are more feasible.

A new method using acceleration data loggers enabled us to measure the porpoising behaviour of Adélie penguins (Pygoscelis adeliae), defined as a continuous rapid swimming with rhythmic serial leaps. Previous hydrodynamic models suggested that leaping would be energetically cheaper when an animal swims continuously at depths of less than three maximum body diameters below the water surface. In the present study, free-ranging Adélie penguins leapt at a mean speed of 2.8 m s−1 above the predicted threshold speed (0.18–1.88 m s−1). Wild penguins reduced drag by swimming deeper (0.91 m) and did not swim continuously within the high-drag layer while submerged. This indicates that previous calculations may be incomplete. Moreover, leaps represented an average of only 3.8 % of the total distance travelled during the porpoising cycle, which would make energy savings marginal. Among the six penguins used in our study, two did not porpoise and three porpoised for less than 7 min, also indicating that this behaviour was not important during travel to and from foraging sites, as has been previously suggested. Birds mainly porpoised at the start and end of a trip. One explanation of porpoising might be an escape behaviour from predators.

Telomeres are regarded as markers of biological or cellular ageing because they shorten with the degree of stress exposure. Accordingly, telomere lengths should show different rates of change when animals are faced with different intensities of environmental challenges. However, a relationship between telomere length and the environment has not yet been tested within a natural setting. Here, we report longitudinal telomere dynamics in free-living, black-tailed gulls ( Larus crassirostris ) through the recapture of birds of a known age over 2–5 consecutive years. The rate of change in telomere lengths differed with respect to year but not sex or age. The years when gulls showed stable telomere lengths or increases in telomere lengths (from 2009 to 2010) and decreases in telomere lengths (from 2010 to 2011) were characterized by El Niño and the Great Japan Earthquake, respectively. Both events are suspected to have had long-lasting effects on food availability and/or weather conditions. Thus, our findings that telomere dynamics in long-lived birds are influenced by dramatic changes in environmental conditions highlight the importance of environmental fluctuations in affecting stress and lifespan.

Ocean-scale monitoring of pollution is challenging. Seabirds are useful indicators because they travel over a broad foraging range. Nevertheless, this coarse spatial resolution is not fine enough to discriminate pollution in a finer scale. Previous studies have demonstrated that pollution levels are higher in the Sea of Japan and South and East China Seas than the Northen Pacific Ocean. To test these findings in a wide-ranging animal, we tracked streaked shearwaters (Calonectris leucomelas) from four islands in Japan using global positioning system (GPS) and measured persistent organic pollutants (POPs) in the oil of their preen glands. The POPs did not change during 6 to 21 days when birds from Awashima were foraging only in the Sea of Japan, while it increased when they crossed to the Pacific through the Tsugaru Strait and foraged along the eastern coast of Hokkaido where industrial cities occur. These results indicate that POPs in the oil reflect relatively short-term exposure. Concentrations of POPs displayed greater variation among regions. Total polychlorinated biphenyls were highest in birds foraging in a small area of the semiclosed Seto Inland Sea surrounded by urbanized coast, p,p'-dichlorodiphenyltrichloroethane (DDT) was highest in birds foraging in the East China Sea, and total hexachlorocyclohexanes were highest in birds foraging in the Sea of Japan. All were lowest in birds foraging in the Pacific. This distribution of POPs concentration partly agrees with previous findings based on mussels, fish, and seawater and possibly reflects the mobility and emission sources of each type of POP. These results highlight the importance of information on the foraging area of highly mobile top predators to make them more effective monitors of regional marine pollution.

The biosonar (click train) production rate of ten Yangtze finless porpoises and their behavior were examined using animal-borne data loggers. The sound production rate varied from 0 to 290 click trains per 10-min time interval. Large individual differences were observed, regardless of body size. Taken together, however, sound production did not differ significantly between daytime and nighttime. Over the 172.5 h of analyzed recordings, an average of 99.0% of the click trains were produced within intervals of less than 60 s, indicating that during a 1-min interval, the number of click trains produced by each porpoise was typically greater than one. Most of the porpoises exhibited differences in average swimming speed and depth between day and night. Swimming speed reductions and usage of short-range sonar, which relates to prey-capture attempts, were observed more often during nighttime. However, biosonar appears to be affected not only by porpoise foraging, but also by their sensory environment, i.e., the turbid Yangtze River system. These features will be useful for passive acoustic detection of the porpoises. Calculations of porpoise density or abundance should be conducted carefully because large individual differences in the sound production rate will lead to large estimation error.

The mesopelagic zone of the northeast Pacific Ocean is an important foraging habitat for many predators, yet few studies have addressed the factors driving basin-scale predator distributions or inter-annual variability in foraging and breeding success. Understanding these processes is critical to reveal how conditions at sea cascade to population-level effects. To begin addressing these challenging questions, we collected diving, tracking, foraging success, and natality data for 297 adult female northern elephant seal migrations from 2004 to 2010. During the longer post-molting migration, individual energy gain rates were significant predictors of pregnancy. At sea, seals focused their foraging effort along a narrow band corresponding to the boundary between the sub-arctic and sub-tropical gyres. In contrast to shallow-diving predators, elephant seals target the gyre-gyre boundary throughout the year rather than follow the southward winter migration of surface features, such as the Transition Zone Chlorophyll Front. We also assessed the impact of added transit costs by studying seals at a colony near the southern extent of the species’ range, 1,150 km to the south. A much larger proportion of seals foraged locally, implying plasticity in foraging strategies and possibly prey type. While these findings are derived from a single species, the results may provide insight to the foraging patterns of many other meso-pelagic predators in the northeast Pacific Ocean.

In seabirds, the relationship between flight speed and wind direction/speed is thought to be particularly important for studying energy-saving strategy and foraging habitat selection. In this study, we examined whether the ground and calculated air speeds of four great cormorants (Phalacrocorax carbo) were affected by wind conditions using high-resolution GPS data loggers. The birds increased their ground flight speed in tailwinds, decreased it in headwinds, and changed their air speed in relation to wind components. However, they did not change their foraging sites according to the wind conditions. They were likely to respond to moderate wind conditions by adjusting their air speed without changing their foraging sites.