Overall Dynamic Body Acceleration Research Articles

The relationship among acceleration, metabolism, and tail beat frequency of channel catfish (Ictalurus punctatus) during critical swimming speed tests

Accelerometers collect real-time, high-resolution data over extended time periods providing insight into behavior, movement, and physiology of free-swimming animals in captive or natural environments. In aquaculture settings, acceleration can also be used as a proxy for metabolism, providing useful information to inform bioenergetic models and indices of fish welfare. However, defining the acceleration-metabolic relationship for species of interest is a critical first step before information can be applied. Because catfish aquaculture has a large economic impact in the USA, examining the use of acceleration as a proxy for continuous measures of metabolism could prove beneficial. Here, accelerometers were used in channel catfish (Ictalurus punctatus) to examine the relationship between acceleration as measured by overall dynamic body acceleration (ODBA) and metabolism as measured by oxygen consumption (MO2), and how these variables changed with increasing water velocity during critical swimming speed tests. Tail beat frequency was used to validate ODBA measurements. There was a clear relationship between ODBA and water velocity, and metabolism and water velocity, with ODBA increasing 3.2-fold and metabolism increasing 2-fold as water velocity increased. Tail beat frequency also increased 1.5-fold with each increase in water velocity, validating our acceleration results. There was also a clear relationship between ODBA and metabolism, with metabolism increasing 1.1-fold as the ODBA values increased. Results in this study show accelerometers can act as a proxy for metabolic measures in channel catfish and provide the basis for further applications in bioenergetics or operational welfare to benefit the aquaculture industry.

Accelerometry reveals limits to use of an energy-saving anthropogenic food source by a threatened species: A case of Carnaby's cockatoos (Zanda latirostris) and canola.

The use of anthropogenic resources is becoming increasingly common as species adapt to human-induced environmental changes, but their use can expose species to new risks. Understanding how animals exploit these resources is important for guiding conservation management, particularly where species are threatened. The introduction of canola cropping to breeding areas of endangered Carnaby's cockatoo (Zanda latirostris) has been attributed to an increase in the birds' reproductive success; however, the seed may be protein-limiting for nestling growth and its use by cockatoos has been implicated in the emergence of a new disease. We used high-resolution accelerometer-capable GPS tags to track eight birds. Accelerometer data were used to calculate overall dynamic body acceleration (ODBA), a proxy for energy expenditure, and to identify and quantify canola and native vegetation foraging behaviours. We used linear mixed models to determine which factors affected patterns of resource use and to determine whether, and to what extent, canola use was associated with reduced energetic and movement costs. We then compared the energetic content of canola seed and native food sources to inform patterns of behaviour and habitat use revealed by our tracking data. Use of canola was associated with reduced movement costs and energy expenditure. However, there was an apparent reluctance to increase foraging on canola above a threshold of time, even when conditions reduced time available to utilise native food sources. While anthropogenic resources may appear to improve population trends in some cases, careful investigations of patterns of resource use are necessary to guide appropriate conservation management efforts. For Carnaby's cockatoos, conservation efforts should focus on retention, protection and expansion of native food sources.

The heat is on: impacts of rising temperature on the activity of a common European mammal

Climate conditions severely impact the activity and, consequently, the fitness of wildlife species across the globe. Wildlife can respond to new climatic conditions, but the pace of human-induced change limits opportunities for adaptation or migration. Thus, how these changes affect behavior, movement patterns, and activity levels remains unclear. In this study, we investigate how extreme weather conditions affect the activity of European hares (Lepus europaeus) during their peak reproduction period. When hares must additionally invest energy in mating, prevailing against competitors, or lactating, we investigated their sensitivities to rising temperatures, wind speed, and humidity. To quantify their activity, we used the overall dynamic body acceleration (ODBA) calculated from tri-axial acceleration measurements of 33 GPS-collared hares. Our analysis revealed that temperature, humidity, and wind speed are important in explaining changes in activity, with a strong response for high temperatures above 25°C and the highest change in activity during temperature extremes of over 35°C during their inactive period. Further, we found a non-linear relationship between temperature and activity and an interaction of activity changes between day and night. Activity increased at higher temperatures during the inactive period (day) and decreased during the active period (night). This decrease was strongest during hot tropical nights. At a stage of life when mammals such as hares must substantially invest in reproduction, the sensitivity of females to extreme temperatures was particularly pronounced. Similarly, both sexes increased their activity at high humidity levels during the day and low wind speeds, irrespective of the time of day, while the effect of humidity was stronger for males. Our findings highlight the importance of understanding the complex relationships between extreme weather conditions and mammal behavior, critical for conservation and management. With ongoing climate change, extreme weather events such as heat waves and heavy rainfall are predicted to occur more often and last longer. These events will directly impact the fitness of hares and other wildlife species and hence the population dynamics of already declining populations across Europe.

Exposure to whale watching vessels affects dive ascents and resting behavior in sperm whales

Disturbance from whale watching can induce a wide range of behavioral responses in cetaceans, some of which can affect their energetic balance and, ultimately, their long-term fitness. However, assessing disturbance effects on deep-diving cetaceans remains challenging, as the majority of their activities occurs underwater and are difficult to monitor from surface observations. To surpass this limitation, we attached high-resolution multi-sensor tags (DTAGs) on 24 sperm whales (Physeter macrocephalus) off the Azores, an area of intense whale watching, to evaluate changes in movement and acoustic parameters related to foraging effort and dives, locomotion effort, and non-foraging behavior. These parameters were compared between periods of exposure and non-exposure to whale watching vessels, using linear mixed-effect models to assess the presence of short-term effects, accounting for individual differences in behavior. We found no significant changes in foraging effort (number of buzzes, bottom phase depth, proportion of search and foraging phases) and overall dive behavior (dive duration, proportion of dive phases, and descending or ascending pitch) between non-exposure and exposure periods. In contrast, variation in body pitch during non-foraging periods increased during exposure but not variation in body roll. Taken together, these results suggest increased movements during resting activity, which may carry energetic costs to whales and impact their health. Vertical velocity during ascents was also significantly higher in response to vessel exposure, suggesting that sperm whales increased the frequency of fluke strokes, which was consistent with a higher Overall Dynamic Body Acceleration (ODBA) during ascents, incurring in higher energy expenditure. If the detected changes are repeated across multiple exposures, they might affect the individual’s energetic budget, and consequently their fitness. Our study contributes to a better understanding of the short-term behavioral responses of sperm whales to whale watching vessels and highlights the need for further studies examining the potential consequences from repeated disturbance to individuals.

Personality drives activity and space use in a mammalian herbivore

BackgroundAnimal personality has emerged as a key concept in behavioral ecology. While many studies have demonstrated the influence of personality traits on behavioral patterns, its quantification, especially in wild animal populations, remains a challenge. Only a few studies have established a link between personality and recurring movements within home ranges, although these small-scale movements are of key importance for identifying ecological interactions and forming individual niches. In this regard, differences in space use among individuals might reflect different exploration styles between behavioral types along the shy-bold continuum.MethodsWe assessed among-individual differences in behavior in the European hare (Lepus europaeus), a characteristic mammalian herbivore in agricultural landscapes using a standardized box emergence test for captive and wild hares. We determined an individuals’ degree of boldness by measuring the latencies of behavioral responses in repeated emergence tests in captivity. During capture events of wild hares, we conducted a single emergence test and recorded behavioral responses proven to be stable over time in captive hares. Applying repeated novel environment tests in a near-natural enclosure, we further quantified aspects of exploration and activity in captive hares. Finally, we investigated whether and how this among-individual behavioral variation is related to general activity and space use in a wild hare population. Wild and captive hares were treated similarly and GPS-collared with internal accelerometers prior to release to the wild or the outdoor enclosure, respectively. General activity was quantified as overall dynamic body acceleration (ODBA) obtained from accelerometers. Finally, we tested whether boldness explained variation in (i) ODBA in both settings and (ii) variation in home ranges and core areas across different time scales of GPS-collared hares in a wild population.ResultsWe found three behavioral responses to be consistent over time in captive hares. ODBA was positively related to boldness (i.e., short latencies to make first contact with the new environment) in both captive and wild hares. Space use in wild hares also varied with boldness, with shy individuals having smaller core areas and larger home ranges than bold conspecifics (yet in some of the parameter space, this association was just marginally significant).ConclusionsAgainst our prediction, shy individuals occupied relatively large home ranges but with small core areas. We suggest that this space use pattern is due to them avoiding risky, and energy-demanding competition for valuable resources. Carefully validated, activity measurements (ODBA) from accelerometers provide a valuable tool to quantify aspects of animal personality along the shy-bold continuum remotely. Without directly observing—and possibly disturbing—focal individuals, this approach allows measuring variability in animal personality, especially in species that are difficult to assess with experiments. Considering that accelerometers are often already built into GPS units, we recommend activating them at least during the initial days of tracking to estimate individual variation in general activity and, if possible, match them with a simple novelty experiment. Furthermore, information on individual behavioral types will help to facilitate mechanistic understanding of processes that drive spatial and ecological dynamics in heterogeneous landscapes.

Accelerating animal energetics: high dive costs in a small seabird disrupt the dynamic body acceleration-energy expenditure relationship.

Accelerometry has been widely used to estimate energy expenditure in a broad array of terrestrial and aquatic species. However, a recent reappraisal of the method showed that relationships between dynamic body acceleration (DBA) and energy expenditure weaken as the proportion of non-mechanical costs increases. Aquatic air breathing species often exemplify this pattern, as buoyancy, thermoregulation and other physiological mechanisms disproportionately affect oxygen consumption during dives. Combining biologging with the doubly labelled water method, we simultaneously recorded daily energy expenditure (DEE) and triaxial acceleration in one of the world's smallest wing-propelled breath-hold divers, the dovekie (Alle alle). These data were used to estimate the activity-specific costs of flying and diving and to test whether overall dynamic body acceleration (ODBA) is a reliable predictor of DEE in this abundant seabird. Average DEE for chick-rearing dovekies was 604±119kJday-1 across both sampling years. Despite recording lower stroke frequencies for diving than for flying (in line with allometric predictions for auks), dive costs were estimated to surpass flight costs in our sample of birds (flying: 7.24× basal metabolic rate, BMR; diving: 9.37× BMR). As expected, ODBA was not an effective predictor of DEE in this species. However, accelerometer-derived time budgets did accurately estimate DEE in dovekies. This work represents an empirical example of how the apparent energetic costs of buoyancy and thermoregulation limit the effectiveness of ODBA as the sole predictor of overall energy expenditure in small shallow-diving endotherms.

Empirical Evidence for Energy Efficiency Using Intermittent Gliding Flight in Northern Bald Ibises

Birds face exceptionally high energy demands during their flight. One visible feature of some species is alternating between flapping and gliding, which should allow them to save energy. To date, there is no empirical evidence of an energetic benefit to this. To understand the physiology behind the strategy, we equipped hand-raised Northern Bald Ibises (Geronticus eremita) with data loggers during human-guided migration. We monitored the position of the birds, wingbeats, overall dynamic body acceleration (ODBA), and heart rates as a proxy for energy expenditure. The energy expenditure was significantly affected by the length of flapping and gliding bouts. A pronounced decrease in heart rate was measured after already 1 s of gliding. Additionally, the heart rate at flapping bouts up to 30 s increased steadily but stabilized thereafter. The gilding proportion during intermittent flight affected the energy saving compared to continuous flapping. At a gliding proportion of about 20%, we measured a maximum of 11% saving based on heart rate measurement. At higher gliding proportions, the additional energy saving was negligible. Furthermore, as during flight, not all energy is used for mechanical work, we found a greater decrease rate of ODBA at different gliding proportions compared to heart rate. Nevertheless, the combination of the two methods is essential to determine birds’ movement and energy expenditure. This study provides empirical evidence that intermittent flight is energetically beneficial and can reduce the high costs of flights.

Prey interactions in tiger sharks: Accounting for visual perception in animal-borne cameras

The ‘evolutionary arms race’ between predator and prey is responsible for many physiological, morphological, and behavioural adaptations and some of the most compelling examples relate to the generation and detection of visual signals. Better understanding of adaptations can arise from approaching predator-prey dynamics from the point of view of the animals themselves, such as through animal-borne cameras. As we learn more about an animal's visual system, we can take this further and analyse visual scenes through their eyes. In this study video cameras mounted on tiger sharks were used to analyse motion cues of sea turtles using two-dimensional motion detector (2DMD) models. Sharks were also equipped with tri-axial motion-sensors to compare visual motion cues to behaviour, using the behavioural metrics of overall dynamic body acceleration (ODBA), path tortuosity, tailbeat frequency and tailbeat acceleration signal amplitude. When comparing the behaviours of sharks in the minute before and after interactions with sea turtles, we found lower ODBA of sharks associated with sea turtles that produced greater visual motion cues. These turtles also invoked swimming by sharks that was more tortuous than when no turtle was encountered. Together, these behaviours suggest that tiger sharks may potentially stalking turtles that produced greater motion cues. Many sea turtles did not stand out from the background motion suggesting they remain motionless as a form of camouflage. This study provides insights into the use of visual cues in prey identification by tiger sharks and the camouflage strategies used by sea turtles to avoid predation.

Short-term behavioural impacts of air-exposure in three species of recreationally angled freshwater fish

Fish captured and released by recreational anglers are often exposed to air to enable hook removal and for admiration (e.g., photography). It is necessary to identify thresholds for air exposure that minimize sublethal alterations to inform best practice guidelines yet doing so in ecological-relevant field settings is challenging. We developed a novel attachment method for tri-axial accelerometer and depth biologgers to quantify short-term post-release behaviour in recreationally angled northern pike (Esox lucius), smallmouth bass (Micropterus dolomieu), and walleye (Sander vitreus) following a range of air exposure treatments (i.e., 0, 15, 30, 60, and 180 s). The biologgers were attached to the fish using a quick-release Velcro® harnesses that facilitated easy retrieval of the device from free-swimming fish without the need to recapture the individual. For this study, biologgers were retrieved after a 10 min observational period. Overall dynamic body acceleration (ODBA) was calculated from accelerometric data to estimate post-release swimming activity. Clustering of ODBA via k-means was used to classify distinct movement patterns: resting, steady-state swimming, and high intensity swimming occurrences. In northern pike, ODBA in the first minute after release was significantly higher in the 0 s air exposure treatment compared to the 15 s, 30 s, 60 s, and 180 s treatments, however the same patterns were not observed for smallmouth bass or walleye. We did not observe differences in the time spent resting, time spent steady-state swimming, or the number of high intensity swimming occurrences among air exposure treatments across all study species. This proof-of-concept study demonstrated the utility of this non-invasive bio-logger approach for the short-term study of catch-and-release and also revealed that for the species and context (e.g., water temperatures of 17–25 º C) studied here, air exposure had relatively little negative short-term impact on behaviour or reflex impairment. Nonetheless, we encourage air exposure to be minimized as longer fight times or higher water temperatures may interact with air exposure to increase behaviour impairments and negatively impact survival.

The Use of Animal's Body, Scrotal Temperature and Motion Monitoring in Evaluating Boar Semen Production Capacity.

Simple SummaryThe evaluation of male animals’ fertilizing capacity is based on laboratory-performed tests, as well as on the in vivo and in vitro reproductive outcome. Boar fertility is strongly associated with a pig farm’s financial status and income. The scientific community attempts to increase the predictive reliability of male fertility to ensure the profitability of the pig industry. In this direction, a different approach, using biomedical thermal and motion sensors, is utilized. This study investigates the correlation of collected data by biomedical sensors with variables well known as their predictable value semen quality. Strong correlations are revealed, encouraging the further application of biomedical methods in the assessment of boars’ fertilizing ability.Biomedical measurements by specialized technological equipment have been used in farm animals to collect information about nutrition, behavior and welfare. This study investigates the relation of semen quality (CASA analysis, viability, morphology, membrane biochemical activity and DNA fragmentation) with boar behavior during ejaculation. Sensors were placed on the boar’s body. Movement features were collected using an inertial measurement unit (IMU), comprising an accelerometer, a gyroscope and a magnetometer. Boar, scrotal and dummy temperatures were measured by an infrared (IR) camera and an IR thermometer, while the face salivation of the boar was recorded by a moisture meter (also based on IR technology). All signals and images were logged on a mobile device (smartphone or tablet) using a Bluetooth connection and then transferred wirelessly to the cloud. The data files were then processed using scripts in MATLAB 2021a (MathWorks, Natick, Massachusetts) to derive the necessary indices. Ninety-four ejaculates from five boars were analyzed in this study. The statistical analysis was performed in the Statistics and Machine Learning Toolbox of MATLAB 2021a using a linear mixed effects model. Significant and strong negative correlations (R2 > 0.5, p ≤ 0.05) were observed between boar, dummy and scrotal temperature with the progressive, rapid and slow movement of spermatozoa, VCL (curvilinear velocity), VSL (straight line velocity) and ALH (amplitude of lateral head displacement) kinematics. The volume of the ejaculate was correlated with the scrotal and dummy temperature. Dummy’s temperature was negatively correlated with BCF (beat/cross-frequency), viability and total time of ejaculation, while it was positively correlated with abnormal morphology. Body temperature was negatively correlated with BCF. Positive correlations were noticed between VAP (average path velocity) and total time of ejaculation with body acceleration features, as well as between the overall dynamic body acceleration (ODBA) and total time of ejaculation. In conclusion, the use of biomedical sensors can support the evaluation of boar sperm production capacity, providing valuable information about semen quality.

Dynamic body acceleration as a proxy to predict the cost of locomotion in bottlenose dolphins.

Estimates of the energetic costs of locomotion (COL) at different activity levels are necessary to answer fundamental eco-physiological questions and to understand the impacts of anthropogenic disturbance to marine mammals. We combined estimates of energetic costs derived from breath-by-breath respirometry with measurements of overall dynamic body acceleration (ODBA) from biologging tags to validate ODBA as a proxy for COL in trained common bottlenose dolphins (Tursiops truncatus). We measured resting metabolic rate (RMR); mean individual RMR was 0.71-1.42 times that of a similarly sized terrestrial mammal and agreed with past measurements that used breath-by-breath and flow-through respirometry. We also measured energy expenditure during submerged swim trials, at primarily moderate exercise levels. We subtracted RMR to obtain COL, and normalized COL by body size to incorporate individual swimming efficiencies. We found both mass-specific energy expenditure and mass-specific COL were linearly related with ODBA. Measurements of activity level and cost of transport (the energy required to move a given distance) improve understanding of the COL in marine mammals. The strength of the correlation between ODBA and COL varied among individuals, but the overall relationship can be used at a broad scale to estimate the energetic costs of disturbance and daily locomotion costs to build energy budgets, and investigate the costs of diving in free-ranging animals where bio-logging data are available. We propose that a similar approach could be applied to other cetacean species.

Overall dynamic body acceleration measures activity differently on large versus small aquatic animals

Abstract Acceleration‐based proxies for activity and energy expenditure are widely used in bio‐logging studies of animal movement and locomotion to explore biomechanical strategies, energetic costs of behaviour, habitat use and the impact of anthropogenic disturbance. The foremost such proxy is overall dynamic body acceleration (ODBA) along with variants VeDBA and PDBA. This technique, which involves summing the magnitude of high‐pass‐filtered acceleration signals (the so‐called dynamic acceleration) over a reference interval, has been applied to animals as diverse as shags, lobsters, humans and whales. The relationship between ODBA and energy use has been tested empirically on animals small enough to house in laboratory facilities and arguments have been offered for why the method should be generally applicable; however, validations on larger animals are scant. Here, we examine how body size impacts ODBA and its variants under steady locomotion in large aquatic animals, using cetaceans as model species. To do this, we first develop a simplified mathematical model for the acceleration signals that would be measured by a tag on a swimming animal. We then test this model with empirical data gathered using bio‐logging tags on whale species spanning 1.3 m harbour porpoises to 12‐m sperm whales. We show that the motions measured by ODBA can be fundamentally different in small versus large aquatic animals. Whereas dynamic acceleration in small animals is predominantly due to specific acceleration (i.e. actual accelerative motions generated by muscle action), in larger aquatic animals, body rotations (i.e. cyclical angular displacements associated with swimming) can dominate the measured acceleration. As body rotations do not necessarily increase in magnitude as swimming speed increases, ODBA may underestimate the relative cost of behaviours or responses to disturbance in large aquatic animals. This does not lessen the value of ODBA for small animals, but it raises a caution against uncritical use on larger animals. For large aquatic animals, activity proxies that specifically remove body rotations using gyroscopes or magnetometers may provide more consistent estimates of energy use although these methods are yet to be validated.

Bottlenose dolphin habitat and management factors related to activity and distance traveled in zoos and aquariums.

High-resolution non-invasive cetacean tagging systems can be used to investigate the influence of habitat characteristics and management factors on behavior by quantifying activity levels and distance traveled by bottlenose dolphins (Tursiops truncatus and Tursiops aduncus) in accredited zoos and aquariums. Movement Tags (MTags), a bio-logging device, were used to record a suite of kinematic and environmental information outside of formal training sessions as part of a larger study titled “Towards understanding the welfare of cetaceans in zoos and aquariums” (colloquially called the Cetacean Welfare Study). The purpose of the present study was to explore if and how habitat characteristics, environmental enrichment programs, and training programs were related to the distance traveled and energy expenditure of dolphins in accredited zoos and aquariums. Bottlenose dolphins in accredited zoos and aquariums wore MTags one day per week for two five-week data collection periods. Overall dynamic body acceleration (ODBA), a proxy for energy expenditure, and average distance traveled per hour (ADT) of 60 dolphins in 31 habitats were examined in relation to demographic, habitat, and management factors. Participating facilities were accredited by the Alliance for Marine Mammal Parks and/or Aquariums and the Association of Zoos & Aquariums. Two factors were found to be related to ADT while six factors were associated with ODBA. The results showed that enrichment programs were strongly related to both ODBA and ADT. Scheduling predictable training session times was also positively associated with ADT. The findings suggested that habitat characteristics had a relatively weak association with ODBA and were not related to ADT. In combination, the results suggested that management practices were more strongly related to activity levels than habitat characteristics.

Ice-fishing handling practices and their effects on the short-term post-release behaviour of Largemouth bass

Numerous studies have investigated the impacts of catch-and-release on the post-release behaviour of fish during periods characterized by warm air and water temperatures. Comparatively little is known about the post-release behaviour of fish caught while ice fishing. Largemouth bass (LMB), a popular sportfish in North America, is sometimes encountered during ice fishing and is often released due to angler conservation ethic or to comply with regulations. To examine the impacts of ice angling on the post-release behaviour of LMB, we exposed them to a range of handling practices and assessed their skin temperatures prior to release, as well as short-term post-release swimming activity using biologgers equipped with a tri-axial accelerometer, temperature and pressure sensors. Skin temperature of LMB had a significant positive relationship with windchill temperature. Generally, the longer that LMB were exposed to air or placed on the ice, the colder their skin became. Overall, water depth and water temperature selected by LMB increased with time during the post-release period. Overall dynamic body acceleration (ODBA), a proxy for locomotory activity, decreased as time progressed in the release period, while ODBA decreased with increasing depth and water temperatures. LMB with warmer skin temperatures had lower locomotory activity compared to those with colder skin temperatures. Further, the effect of skin temperature on locomotory activity became more amplified with increasing depth and warming water temperatures selected by LMB post-release. Anglers practicing catch-and-release angling during the winter should adopt best handling practices by reducing the time fish are removed from the water when windchill temperatures are sub-freezing to avoid alteration in post-release behaviour.

Differences in the behavioral characteristics between green and loggerhead turtles in a setnet bycatch simulation

Sea turtles that have entered the submerged bag net of setnets repeatedly push their heads up against the ceiling netting (referred to here as push-ups) to ascend to breathe. Consecutive push-ups are essential to the success of escaping in a turtle releasing system developed to reduce the incidental death in setnets. Existence of differences in behavioral characteristics were suggested among turtle species, but no detailed evaluation has been performed. The objectives of this study were to establish extraction methods of the consecutive push-ups with a tri-axial acceleration logger, and to clarify the differences in the behavioral characteristics between green Chleonia mydas and loggerhead Caretta caretta turtles under the simulated condition of bycatch in setnets for appropriate adaptation and modification of this system. The behavior of each turtle mounted with an acceleration logger in an experimental bag net was recorded using a video camera. The consecutive push-ups were extracted by filtering the time-series body angle converted from the static surge acceleration and the overall dynamic body acceleration (ODBA) from the triaxial dynamic acceleration. A threshold of 20° in body angle and 1.0 m/s2 in ODBA was detected among 89 % of all consecutive push-ups in green turtles. On the other hand, the ODBA was not adopted as the extract condition in loggerhead turtles, although a threshold of 20° in the body angle detected 93 % correctly. Mode of ODBA (1.0–1.5 m/s2) in the green turtles was larger than that in the loggerhead turtles (0.5–1.0 m/s2) during consecutive push-ups. In contrast, the number and duration of the consecutive push-ups in the green turtles were less than those of loggerhead turtles. Consequently, modifying the gear with a larger inclination angle of the ceiling netting should be considered for the setnets where the bycatch of green turtles dominates.

Hunting by the Stroke: How Foraging Drives Diving Behavior and Locomotion of East-Greenland Narwhals (Monodon monoceros)

Deep diving air-breathing species by necessity must balance submergence time and level of exercise during breath-holding: a low activity level preserves oxygen stores and allows longer duration submergence whereas high activity levels consume oxygen quickly and shorten submergence time. In this study, we combined high-resolution multi sensor animal-borne tag data to investigate diving behavior and locomotion styles of the narwhal (Monodon monoceros) (n= 13, mean record length 91 h)–a deep diving Arctic species. Narwhals in this study dove down to >800 m but despite the deep diving abilities, one-third of the dives (33%) were shallow (>100 m) and short in duration (<5 min). Narwhals utilized energy saving measures such as prolonged gliding during descent with increasing target depth but stroked actively throughout the ascent indicating excess oxygen storages. Foraging behavior, as detected by the presence of buzzes, was a key factor influencing dive depth and spinning behavior—the rolling movement of the animal along its longitudinal axes. Narwhals in East Greenland utilized two foraging strategies, while transiting and while stationary, with different target depths and buzzing rates. The first targeted deep-dwelling, possibly solitary prey items and the latter, more schooling prey closer to the surface. The buzzing rate during stationary foraging was on average twice as high as during transiting foraging. Spinning was an integrated part of narwhal swimming behavior but the amount of spinning was correlated with foraging behavior. The odds for spinning during all dive phases were 2–3 times higher during foraging than non-foraging. Due to the spinning behavior, stroking rate might be better suited for estimating energy consumption in narwhals than ODBA (overall dynamic body acceleration). The narwhal is considered as one of the most sensitive species to climate change–the results from this study can act as a baseline essential for evaluating changes in the behavior and energy usage of narwhals caused by stressors evolving in the Arctic.

Scalloped hammerhead sharks swim on their side with diel shifts in roll magnitude and periodicity

BackgroundGreat hammerhead sharks (Sphyrna mokarran) routinely swim on their sides and periodically roll from side to side. A previous study used wind tunnel tests with a rigid model hammerhead shark to demonstrate that the rolling behavior could improve swimming efficiency using the tall first dorsal fin as a lift-generating surface. Scalloped hammerhead sharks (Sphyrna lewini) also have proportionally taller dorsal fins compared to pectoral fins than most shark species and similar to that of great hammerhead sharks, and thus might exhibit similar rolling behavior. This was assessed by deploying multi-sensor accelerometer instrument packages on free-swimming adult scalloped hammerhead sharks to directly measure swimming depth, body orientation and swimming performance. Specific objectives were to (1) determine whether scalloped hammerhead sharks exhibit side swimming and rolling behavior, (2) characterize the patterns of these behaviors, and (3) evaluate the purpose of these behaviors.ResultsWe obtained 196.7 total days (4720 h) of data from 9 free-swimming adult scalloped hammerhead sharks equipped with multi-instrument biologgers with deployment durations ranging from 7 to 29 days. All sharks exhibited rolling behavior throughout the entire period of observation. The roll angle magnitude and periodicity of rolling showed a clear diel pattern. During daytime, the sharks spent an average of 48% of the time swimming at a roll angle > 30°, with an average roll angle of 41° and rolling periodicity of around 4 min. At night, the sharks spent an average 82% of their time at an angle > 30°, with an average roll angle of 60° and rolling periodicity of around 13 min. In addition to an increase in degree of roll and roll duration, overall dynamic body acceleration (ODBA) also increased at night, and tailbeat frequency was more regular and consistent than during daytime.ConclusionWe observed rolling behavior in scalloped hammerhead sharks similar to that observed in great hammerhead sharks. The diel changes in roll angle and periodicity were accompanied by other changes in swimming behavior. These changes are possibly due to interplay between reducing cost of transport and social interactions with conspecifics.

From a calf's perspective: humpback whale nursing behavior on two US feeding grounds.

Nursing influences growth rate and overall health of mammals; however, the behavior is difficult to study in wild cetaceans because it occurs below the surface and can thus be misidentified from surface observations. Nursing has been observed in humpback whales on the breeding and calving grounds, but the behavior remains unstudied on the feeding grounds. We instrumented three dependent calves (four total deployments) with combined video and 3D-accelerometer data loggers (CATS) on two United States feeding grounds to document nursing events. Two associated mothers were also tagged to determine if behavior diagnostic of nursing was evident in the mother’s movement. Animal-borne video was manually analyzed and the average duration of successful nursing events was 23 s (±7 sd, n = 11). Nursing occurred at depths between 4.1–64.4 m (along the seafloor) and in close temporal proximity to foraging events by the mothers, but could not be predicted solely by relative positions of mother and calf. When combining all calf deployments, successful nursing was documented eleven times; totaling only 0.3% of 21.0 hours of video. During nursing events, calves had higher overall dynamic body acceleration (ODBA) and increased fluke-stroke rate (FSR) compared to non-nursing segments (Mixed effect models, ODBA: F1,107 = 13.57756, p = 0.0004, FSR: F1,107 = 32.31018, p < 0.0001). In contrast, mothers had lower ODBA and reduced FSR during nursing events compared to non-nursing segments. These data provide the first characterization of accelerometer data of humpback whale nursing confirmed by animal-borne video tags and the first analysis of nursing events on feeding grounds. This is an important step in understanding the energetic consequences of lactation while foraging.

Active acoustic telemetry tracking and tri-axial accelerometers reveal fine-scale movement strategies of a non-obligate ram ventilator

BackgroundCalifornia horn sharks (Heterodontus francisci) are nocturnally active, non-obligate ram ventilating sharks in rocky reef habitats that play an important ecological role in regulating invertebrate communities. We predicted horn sharks would use an area restricted search (ARS) movement strategy to locate dense resource patches while minimizing energetic costs of travel and nighttime activity. As ectotherms, we predicted environmental temperature would play a significant role in driving movement and activity patterns.MethodsContinuous active acoustic tracking methods and acceleration data loggers were used to quantify the diel fine-scale spatial movements and activity patterns of horn sharks. First passage time was used to identify the scale and locations of patches indicative of ARS. Activity was assessed using overall dynamic body acceleration (ODBA) as a proxy for energy expenditure. Behavior within a patch was characterized into three activity patterns: resting, episodic burst activity, and moderate, consistent activity.ResultsAfter resting in daytime shelters, individuals travelled to multiple reefs throughout the night, traversing through depths of 2–112 m and temperatures of 10.0–23.8 °C. All sharks exhibited area restricted search patch use and arrived at their first patch approximately 3.4 ± 2.2 h (mean ± SD) after sunset. Sharks exhibited moderate, consistent activity in 54% of the patches used, episodic burst activity in 33%, and few (13%) were identified as resting at night. ODBA peaked while sharks were swimming through relatively deeper (~ 30 m), colder channels when traversing from one patch to the next. There was no consistent pattern between ODBA and temperature.ConclusionsWe provide one of the largest fine-scale, high-resolution paired data sets for an elasmobranch movement ecology study. Horn sharks exhibited ARS movement patterns for various activity patterns. Individuals likely travel to reefs known to have profitable and predictable patches, potentially tolerating less suitable environmental temperatures. We demonstrate how gathering high-resolution information on the movement decisions of a community resident enhances knowledge of community structure and overall ecosystem function.

Dynamic body acceleration increases by 20% during flight ontogeny of greylag geese Anser anser

Despite our knowledge of the biophysical and behavioural changes during flight ontogeny in juvenile birds, little is known about the changes in the mechanical aspects of energy expenditure during early flight development, particularly in migratory species. Here, we investigate in a unique experimental setup how energy expended during flights changes over time beginning with early ontogeny. We calculate overall dynamic body acceleration (ODBA) as a proxy for energy expenditure in a group of hand raised greylag geese Anser anser trained to fly behind a microlight aircraft. We propose two potential hypotheses; energy expenditure either increases with increasing physiological suitability (the ‘physical development hypothesis’), or decreases as a result of behavioural improvements mitigating flight costs (the ‘behavioural development hypothesis’). There was a significant temporal increase of flight duration and ODBA over time, supporting the ‘physical development hypothesis’. This suggests that early on in flight ontogeny behavioural development leading to flight efficiency plays a weaker role in shaping ODBA changes than the increased physical ability to expend energy in flight. We discuss these findings and the implications of flight development on the life history of migratory species.