Yuuki WatanabeNational Institute of Polar Research · Biology Group
Yuuki Watanabe
PhD
About
64
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Introduction
Skills and Expertise
Publications
Publications (64)
Animals exhibit various physiological and behavioural strategies for minimizing travel costs.
Fins of aquatic animals play key roles in efficient travel and, for sharks, the functions of dorsal
and pectoral fins are considered well divided: the former assists propulsion and generate
lateral hydrodynamic forces during turns and the latter generates...
Billions of birds migrate to exploit seasonally available resources. The ranges of migration vary greatly among species, but the underlying mechanisms are poorly understood. I hypothesise that flight mode (flapping or soaring) and body mass affect migration range through their influence on flight energetics. Here, I compiled the tracks of migratory...
Many pinnipeds frequently rest on land or ice, but some species remain in open waters for weeks or months, raising the question of how they rest. A unique type of dives, called drift dives, has been reported for several pinnipeds with suggested functions of rest, food processing, and predator avoidance. Prolonged surfacing periods have also been ob...
Significance
Most fishes are cold-blooded, but tunas and some sharks (e.g., white sharks) maintain their exercising muscles warmer than ambient waters. This ability is a remarkable example of convergent evolution because bony and cartilaginous fishes diverged as long as 450 million years ago. What are the ecological benefits driving the evolution o...
Understanding foraging is important in ecology, as it determines the energy gains and, ultimately, the fitness of animals. However, monitoring prey captures of individual animals is difficult. Direct observations using animal-borne videos have short recording periods, and indirect signals (e.g., stomach temperature) are never validated in the field...
Diel activity patterns and fine-scale behavior of large pelagic fishes have been poorly studied relative to their coastal counterparts. In particular, little is known about how predator activity varies with time of day and vertical habitat. Measuring changes in activity can be challenging as these animals swim continuously so traditional metrics su...
Regional endothermy has evolved several times in marine fishes, and two competing hypotheses are generally proposed to explain the evolutionary drivers behind this trait: thermal niche expansion and elevated cruising speeds. Evidence to support either hypothesis is equivocal, and the ecological advantages conferred by endothermy in fishes remain de...
Anthropogenic activities are dramatically changing marine ecosystems. Wildlife tourism is one of the fastest growing sectors of the tourism industry and has the potential to modify the natural environment and behaviour of the species it targets. Here, we used a novel method to assess the effects of wildlife tourism on the activity of white sharks (...
Animal behavior should optimize the difference between the energy they gain from prey and the energy they spend searching for prey. This is all the more critical for predators occupying the pelagic environment, as prey is sparse and patchily distributed. We theoretically derive two canonical swimming strategies for pelagic predators, that maximize...
Shark-mounted video of three S. mokarran swimming at South Bimini Island, Bahamas. Video supplied by Andy B. Casagrande IV.
Shark-mounted video of 295 cm S. mokarran swimming at Batt Reef, Queensland, Australia.
Video of two S. mokarran swimming rolled in public aquaria in the United States.
Supplementary Figures 1-12, Supplementary Tables 1-2, Supplementary Notes 1-5 and Supplementary References
Comprehension of ecological processes in marine animals requires information
regarding dynamic vertical habitat use. While many pelagic predators primarily
associate with epipelagic waters, some species routinely dive beyond the deep
scattering layer. Actuation for exploiting these aphotic habitats remains largely
unknown. Recent telemetry data fro...
Table S1. Summary of biological and X‐Tag information from 16 tagged sharks.
Data S1. Sampling rate analysis.
Figure S1. Six‐hour data subsample from accelerometer depth data logger.
Data S2. Data treatment.
Data S3. Generalized linear mixed model details.
Table S2. Summary of negative binomial models.
Table S3. Summary of linear mixed models...
1. Temperature strongly regulates the distribution and fitness of ectotherms, and many studies have measured the temperature-dependence of physiological performance in controlled laboratory settings. In contrast, little is known about how temperature influences ectotherm performance in the wild, so the ecological significance of physiological perfo...
Use of accelerometers is now widespread within animal biotelemetry as they provide a means of measuring an animal's activity in a meaningful and quantitative way where direct observation is not possible. In sequential acceleration data there is a natural dependence between observations of movement or behaviour, a fact that has been largely ignored...
Animal daily routines represent a compromise between maximizing foraging success and optimizing physiological performance, while minimizing the risk of predation. For ectothermic predators, ambient temperature may also influence daily routines through its effects on physiological performance. Temperatures can fluctuate significantly over the diel c...
Body size is a key determinant of metabolic rate, but logistical constraints have led to a paucity of energetics measurements from large water-breathing animals. As a result, estimating energy requirements of large fish generally relies on extrapolation of metabolic rate from individuals of lower body mass using allometric relationships that are no...
Alcids propel themselves by flapping wings in air and water that have vastly different densities. We hypothesized that alcids change wing kinematics and maintain Strouhal numbers (St = fA/U, where f is wingbeat frequency, A is the wingbeat amplitude, and U is forward speed) within a certain range, to achieve efficient locomotion during both flying...
Alcids propel themselves by fl apping wings in air and water that have vastly diff erent densities. We hypothesized that alc-ids change wing kinematics and maintain Strouhal numbers (St fA / U , where f is wingbeat frequency, A is the wingbeat amplitude, and U is forward speed) within a certain range, to achieve effi cient locomotion during both fl...
Reproductive migration is a critical phase in the life history of anguillid eels. Nevertheless, fine-scale behaviours of migrating eels remain unknown, primarily due to the difficulty in attaching high-resolution recording devices to, and recovering them from, these small-sized teleosts. We attached a small accelerometer with time-scheduled release...
Foraging theory predicts that breath-hold divers adjust the time spent foraging at depth relative to the energetic cost of swimming, which varies with buoyancy (body density). However, the buoyancy of diving animals varies as a function of their body condition, and the effects of these changes on swimming costs and foraging behaviour have been poor...
The remote measurement of data from free-ranging animals has been termed 'biologging' and in recent years this relatively small set of tools has been instrumental in addressing remarkably diverse questions - from 'how will tuna respond to climate change?' to 'why are whales big?'. While a single biologging dataset can have the potential to test hyp...
Food is heterogeneously distributed in nature, and understanding how animals search for and exploit food patches is a fundamental challenge in ecology. The classic marginal value theorem (MVT) formulates optimal patch residence time in response to patch quality. The MVT was generally proved in controlled animal experiments; however, owing to the te...
Flying and terrestrial animals should spend energy to move while supporting their weight against gravity. On the other hand, supported by buoyancy, aquatic animals can minimize the energy cost for supporting their body weight and neutral buoyancy has been considered advantageous for aquatic animals. However, some studies suggested that aquatic anim...
The body tilt angle of a fish has a large effect on the acoustic target strength. For an accurate estimation of fish abundance using acoustic methods, it is necessary to measure body tilt angles in free-ranging fish. We measured diurnal body tilt angle distributions of threeline grunt (Parapristipoma trilineatum) while swimming in schools in a fish...
Fine-scale behavior of crocodilians has rarely been recorded in the field despite the important ecological roles these reptiles play in wetland systems around the world. In this study, we attached multi-sensor data loggers to free-ranging American alligators Alligator mississippiensis in the northern Banana River Lagoon, Florida, to record their di...
The whole record of swimming depth of the Chinese sturgeon “F”, and its spectrogram (indicative of periodicity in up-and-down movements) where magnitude is expressed by color. Periods with high periodicity are indicated by black bands at the bottom.
Unusually deep water due to dam construc-tion has the potential to negatively effect endangered sturgeons, which lack a physiological mechanism to inflate their swimbladder and may be unable to remain buoyant under high pressure at depth. In a previous study, some juvenile sturgeons released in a deep (>100 m) reservoir lost buoyancy and stayed nea...
Efficient locomotion between prey resources at depth and oxygen at the surface is crucial for breath-hold divers to maximize time spent in the foraging layer, and thereby net energy intake rates. The body density of divers, which changes with body condition, determines the apparent weight (buoyancy) of divers, which may affect round-trip cost-of-tr...
Locomotory muscle function of ectothermic fishes is generally depressed in cold waters, making them vul-nerable to avian and mammalian predators whose body temperature remains high. Paradoxically, Greenland sharks Somniosus microcephalus exhibit the reverse of this usual predator–prey thermal pattern by apparently hunting seals in Arctic waters. To...
Many diving animals undergo substantial changes in their body density that are the result of changes in lipid content over their annual fasting cycle. Because the size of the lipid stores reflects an integration of foraging effort (energy expenditure) and foraging success (energy assimilation), measuring body density is a good way to track net reso...
Many pelagic fishes exhibit 'yo-yo' diving behavior, which may serve several possible functions, including energy conservation, prey searching and navigation. We deployed accelerometers and digital still cameras on 4 free-ranging tiger sharks Galeocerdo cuvier, to test whether their vertical movements are most consistent with energy conservation or...
Aerial flight and breath-hold diving present conflicting morphological and physiological demands, and hence diving seabirds capable of flight are expected to face evolutionary trade-offs regarding locomotory performances. We tested whether Kerguelen shags Phalacrocorax verrucosus, which are remarkable divers, have poor flight capability using newly...
Northern elephant seals, Mirounga angustirostris, travel between colonies along the west coast of North America and foraging areas in the North Pacific. They also have the ability to return to their home colony after being experimentally translocated. However, the mechanisms of this navigation are not known. Visual information could serve an import...
1. Breath-hold divers are widely assumed to descend and ascend at the speed that minimizes energy expenditure per distance travelled (the cost of transport (COT)) to maximize foraging duration at depth. However, measuring COT with captive animals is difficult, and empirical support for this hypothesis is sparse.
2. We examined the scaling relations...
Recently, animal-borne accelerometers have been used to record the pitch angle of aquatic animals during swimming. When evaluating pitch angle, it is necessary to consider a discrepancy between the angle of an accelerometer and the long axis of an animal. In this study, we attached accelerometers to 17 free-ranging scalloped hammerhead shark (Sphyr...
It has been predicted that geometrically similar animals would swim at the same speed with stroke frequency scaling with mass(-1/3). In the present study, morphological and behavioural data obtained from free-ranging penguins (seven species) were compared. Morphological measurements support the geometrical similarity. However, cruising speeds of 1....
Seals are born on land or ice and must acquire the diving and swimming skills required to forage and avoid predators during their early lives. While diving behavior, including swim speed and swimming style (e.g. prolonged gliding and stroke-and-glide swimming), of adult seals is well documented, knowledge regarding the diving behavior of pups is st...
The swimbladder of fishes is readily compressed by hydrostatic pressure with depth, causing changes in buoyancy. While modern fishes can regulate buoyancy by secreting gases from the blood into the swimbladder, primitive fishes, such as sturgeons, lack this secretion mechanism and rely entirely on air gulped at the surface to inflate the swimbladde...
The largest (up to 2 tons) and a globally distributed teleost--the ocean sunfish Mola mola--is commonly regarded as a planktonic fish because of its unusual shape including absence of caudal fin. This common view was recently questioned because the horizontal movements of the ocean sunfish tracked by acoustic telemetry were independent of ocean cur...
We used a fish-borne digital still-camera logger (DSL) to obtain visual information on surrounding environments encountered by homing chum salmon Oncorhynchus keta in the final period of migration at their southernmost distribution in Japan. Two salmon, a female and a male, were released with a DSL and were recovered 7 h and 8 d after release, resp...
Bio-logging system has been an important tool in the study of the diving behaviour and ecological study of aquatic animals, and the physical and chemical environment in the ocean. New digital technology has contributed to the development of more effective devices with smaller size, higher efficiency, larger capacity, and lower energy consumption. B...
It is obvious, at least qualitatively, that small animals move their locomotory apparatus faster than large animals: small insects move their wings invisibly fast, while large birds flap their wings slowly. However, quantitative observations have been difficult to obtain from free-ranging swimming animals. We surveyed the swimming behaviour of anim...
We developed a simple behavioral indicator of prey patch conditions in diving animals. This indicator is a proportion of observed patch residence time to the "standard" residence time (POS). The standard residence time was defined as an optimal patch residence time maximizing the proportion of bottom time to the duration of dive cycle. We quantifie...
Determination of when and where animals feed and how much they consume is fundamental to understand their ecology and role in ecosystems. However, the lack of reliable data on feeding habits of wild animals, and particularly in marine endotherms, attests to the difficulty in doing this. A promising recent development proposes using a Hall sensor-ma...
A small insects move its wings invisibly fast, while a large bird (Wandering albatross at Kerguelen Island, Indian Ocean) flaps its wings slowly.
Two examples of walking animals (emperor penguins at Cape Washington, Antarctica; 15-months-old boy at Iwate Prefecture, Japan). Although an accelerometer is attached on the back of the boy, it is obvious that smaller animals move their limb quickly to walk with their mothers.
Buoyancy is one of the primary external forces acting on air-breathing divers and it can affect their swimming energetics. Because the body composition of marine mammals (i.e. the relative amounts of lower-density lipid and higher-density lean tissue) varies individually and seasonally, their buoyancy also fluctuates widely, and individuals would b...
While modern sampling techniques, such as autonomous underwater vehicles, are increasing our knowledge of the fauna beneath Antarctic sea ice of only a few meters in depth, greater sampling difficulties mean that little is known about the marine life underneath Antarctic ice shelves over 100 m thick. In this study, we present underwater images show...
While modern sampling techniques, such as autonomous underwater vehicles, are increasing our knowledge of the fauna beneath Antarctic sea ice of only a few meters in depth, greater sampling difficulties mean that little is known about the marine life underneath Antarctic ice shelves over 100 m thick. In this study, we present underwater images show...
Diving animals such as seabirds and marine mammals are top predators foraging under water, and play an important role in the marine ecosystems through foraging behavior. Recently developed animal-borne digital video or still cameras have made it possible to directly observe and estimate the prey richness of a foraging patch with simultaneously reco...
The foraging behavior of predators is influenced by the distribution of prey at different spatial and temporal scales. In marine environments, aquatic animals move in 3 spatial dimensions; however, previous studies of the fine-scale movements of predators were limited to only the vertical component of diving behavior. Here, we have analyzed image d...
Some pinniped species appear to forage during both daylight and darkness. To determine any differences in the foraging tactics between day and night, we attached data loggers with a newly developed time-scheduled release system to 2 free-ranging female Baikal seals Phoca sibirica. The system released the loggers from the seals 24 h after deployment...
To better understand the foraging behavior of diving animals it is important to monitor aspects of the animal's environment, including prey distribution, which may influence their behavior. However, prior to recent technological advancements, monitoring the distribution of prey immediately surrounding a diving animal had been impossible. We attache...
We examined the behavioral adaptations of Weddell seals (Leptonychotes weddellii) that may help them to compensate for decreasing energy stores during lactation. Field studies were conducted from late October to early December in 1999 and 2000 at breeding colonies in Antarctica. Data loggers were attached to adult females with pups aged 12-49 days...
Projects
Project (1)
Doctorante: Lorène JEANTET
Directeur de thèse: CHEVALLIER Damien
Sites d'étude : Guyane, Antilles, Méditerranée.
Le réchauffement climatique observé depuis les années 1950 s’est accompagné de changements environnementaux majeurs. Les océans, sensibles aux modifications climatiques, ont vu leur température croître, leur salinité se modifier et leur acidification augmenter. Ces changements climatiques affectent directement et indirectement les écosystèmes marins. Les espèces marines ectothermes telles que les tortues marines, sont beaucoup plus sensibles aux variations climatiques. Ainsi, leur survie dépendra de leur capacité d’adaptation à de nouvelles conditions environnementales. Aujourd’hui, la situation des populations des tortues marines est jugée préoccupante. Sur sept espèces de tortues marines, six d’entre elles sont inscrites sur la liste rouge des espèces menacées. Dans ce contexte, la compréhension des mécanismes d’adaptation aux changements environnementaux est fondamentale pour leur conservation.
La stratégie alimentaire en migration et en inter-ponte détermine les performances reproductrices des tortues marines. La reproduction représente un cout énergétique important qui peut être compensé par la consommation de ressources. Néanmoins, cette dernière nécessite une recherche alimentaire qui peut également être couteuse en énergie, pouvant entrainer un bilan énergétique négatif en cas d’échec. Ainsi, différentes stratégies ont été observées au sein d’une même espèce chez les tortues marines, en fonction de leur environnement au cours de la saison de
reproduction. Les « reproducteurs sur revenu » entreprennent des recherches actives pour se nourrir, alors que les « reproducteurs sur capital » allouent l’énergie, stockée sur les zones d’alimentation (hors saison de reproduction), à la reproduction et l’oviposition. Peu d’études ont été réalisées sur le comportement en mer des tortues marines, ainsi que sur leur écophysiologie, du fait des contraintes logistiques et méthodologiques. En effet leur observation directe en mer est rendue inaccessible compte tenu qu’elles peuvent prospecter leur environnement à une échelle de plusieurs centaines, voir milliers de kilomètres selon l’espèce, et sont capables de plonger à plusieurs centaines de mètres. Le développement des accéléromètres a rendu possible l’enregistrement à distance d’un grand nombre de données hautes résolutions, assez précises pour en déduire le comportement fin de l’animal.
A notre connaissance, seulement 15 articles scientifiques relatent l’étude de comportement des tortues marines à partir de données accélérométriques. Les chercheurs ont utilisé les logger pour identifier les différents comportements exprimés par les tortues en mer grâce à l’interprétation des signaux accélérométriques obtenus. A partir des ces résultats, ils ont pu déterminer la stratégie alimentaire, réaliser un budget temps ou détailler le comportement de plongé des individus étudiés. Néanmoins, les signaux accélérométriques utilisés dans ces études, pour identifier les comportements des tortues marines en immersion, n’ont jamais été validés au préalable.
Dans ce contexte, il est primordial de valider dans un premier temps, l’identification de comportements fins des tortues marines à partir des signaux accélérométriques issu de loggers posés sur des individus évoluant en bassin, afin d’obtenir des interprétations plus rigoureuses des données accélérométriques d’individus en mer.
Le second objectif de cette thèse est d’étudier comment les tortues marines ajustent leur comportement de plongée à la surface (où elles respirent) et la profondeur à laquelle elles s’alimentent en fonction des conditions environnementales, et de déterminer leur bilan énergétique lié à chaque activité. L’utilisation de loggers combinant accéléromètres 3D-magnétomètres-capteurs de pression-GPS, nous permettra d’étudier le comportement fin de plongée (prise alimentaire et dépense énergétique) des tortues marines en lien avec leur environnement in situ. La combinaison des données comportementales aux données spatiales permettra de caractériser les habitats optimaux des tortues marines, et de définir des zones de conservation adaptées à leurs besoins.