Using Digital Tags With Integrated Video and Inertial Sensors to Study Moving Morphology and Associated Function in Large Aquatic Vertebrates

Foraging dives of southern right whales (Eubalaena australis) in relation to larger zooplankton size prey availability in Golfo Nuevo, Península Valdés, Argentina

Southern right whales (SRWs, Eubalaena australis) have been observed feeding both at and below the surface (< 10 m) in Golfo Nuevo (42°42' S, 64°30' W), Península Valdés, Argentina, an area traditionally recognized as calving ground. In addition, we documented diving feeding behavior in SRWs during their stay in this gulf, which has not been previously described. We assessed this behavior using suction-cup-attached video-imaging tags (CRITTERCAMs) on individual whales. A total of eight CRITTERCAM deployments were successful, and feeding events were documented in all SRWs successfully equipped with CRITTERCAMs. The highest speeds occurred during the ascent phase, and the average diving time was 6 min 45 s ± 3 min 41 s for SRWs. Concurrently, zooplankton samples were collected from the subsurface and bottom of the water in areas where tagged whales dived to assess differences in composition, abundance, and biomass. Copepods dominated the upper layer, while euphausiids were more abundant in the deeper sample. Furthermore, zooplankton total biomass was five times higher at depth (2515.93 mg/m3) compared to the subsurface (500.35 mg/m3). Differences in zooplankton characteristics between depths, combined with CRITTERCAM videos, indicated that SRWs exploit high concentrations of organisms near the seafloor during daytime feeding dives. This study provides baseline insights into how SRWs utilize Península Valdés during their stay in the area.

Acoustic recording tags provide insight into the springtime acoustic behavior of sei whales in Massachusetts Bay

The acoustic ecology of sei whales (Balaenoptera borealis) is poorly understood due to limited direct observation of the behavioral context of sound production and individual behavior. Suction cup-attached acoustic recording tags were deployed on sei whales to unambiguously assign call types and explore the acoustic behavior of this endangered species. Twelve tag deployments resulted in ∼173 h of acoustic data and 1030 calls. Sound types included downsweeps and three previously undescribed call types. Knocks were short duration (<1 s), with an average peak frequency of 330 Hz. Pulse type 1 and pulse type 2 calls, typically produced in sequences, were short in duration (0.08 and 0.28 s) and low in average peak frequency (50 and 26 Hz), with relatively high received levels. Average call rates for all call types combined were three calls per hour, but increased during twilight. Sex differences in call type usage included a higher use of pulses by females and knocks by males. Calls were almost exclusively produced at depths <10 m, although whales rarely dove deeper in this study. These data provide a more comprehensive picture of the acoustic and behavioral ecology of sei whales than previously possible, which can inform future conservation efforts for this endangered species.

Field physiology in the aquatic realm: ecological energetics and diving behavior provide context for elucidating patterns and deviations

Comparative physiology has developed a rich understanding of the physiological adaptations of organisms, from microbes to megafauna. Despite extreme differences in size and a diversity of habitats, general patterns are observed in their physiological adaptations. Yet, many organisms deviate from the general patterns, providing an opportunity to understand the importance of ecology in determining the evolution of unusual adaptations. Aquatic air-breathing vertebrates provide unique study systems in which the interplay between ecology, physiology and behavior is most evident. They must perform breath-hold dives to obtain food underwater, which imposes a physiological constraint on their foraging time as they must resurface to breathe. This separation of two critical resources has led researchers to investigate these organisms' physiological adaptations and trade-offs. Addressing such questions on large marine animals is best done in the field, given the difficulty of replicating the environment of these animals in the lab. This Review examines the long history of research on diving physiology and behavior. We show how innovative technology and the careful selection of research animals have provided a holistic understanding of diving mammals' physiology, behavior and ecology. We explore the role of the aerobic diving limit, body size, oxygen stores, prey distribution and metabolism. We then identify gaps in our knowledge and suggest areas for future research, pointing out how this research will help conserve these unique animals.

Minke whale feeding rate limitations suggest constraints on the minimum body size for engulfment filtration feeding

Bulk filter feeding has enabled gigantism throughout evolutionary history. The largest animals, extant rorqual whales, utilize intermittent engulfment filtration feeding (lunge feeding), which increases in efficiency with body size, enabling their gigantism. The smallest extant rorquals (7-10 m minke whales), however, still exhibit short-term foraging efficiencies several times greater than smaller non-filter-feeding cetaceans, raising the question of why smaller animals do not utilize this foraging modality. We collected 437 h of bio-logging data from 23 Antarctic minke whales (Balaenoptera bonaerensis) to test the relationship of feeding rates (λf) to body size. Here, we show that while ultra-high nighttime λf (mean ± s.d.: 165 ± 40 lunges h-1; max: 236 lunges h-1; mean depth: 28 ± 46 m) were indistinguishable from predictions from observations of larger species, daytime λf (mean depth: 72 ± 72 m) were only 25-40% of predicted rates. Both λf were near the maxima allowed by calculated biomechanical, physiological and environmental constraints, but these temporal constraints meant that maximum λf was below the expected λf for animals smaller than ~5 m-the length of weaned minke whales. Our findings suggest that minimum size for specific filter-feeding body plans may relate broadly to temporal restrictions on filtration rate and have implications for the evolution of filter feeding.

Fast and Furious: Energetic Tradeoffs and Scaling of High-Speed Foraging in Rorqual Whales

Although gigantic body size and obligate filter feeding mechanisms have evolved in multiple vertebrate lineages (mammals and fishes), intermittent ram (lunge) filter feeding is unique to a specific family of baleen whales: rorquals. Lunge feeding is a high cost, high benefit feeding mechanism that requires the integration of unsteady locomotion (i.e., accelerations and maneuvers); the impact of scale on the biomechanics and energetics of this foraging mode continues to be the subject of intense study. The goal of our investigation was to use a combination of multi-sensor tags paired with UAS footage to determine the impact of morphometrics such as body size on kinematic lunging parameters such as fluking timing, maximum lunging speed, and deceleration during the engulfment period for a range of species from minke to blue whales. Our results show that, in the case of krill-feeding lunges and regardless of size, animals exhibit a skewed gradient between powered and fully unpowered engulfment, with fluking generally ending at the point of both the maximum lunging speed and mouth opening. In all cases, the small amounts of propulsive thrust generated by the tail were unable to overcome the high drag forces experienced during engulfment. Assuming this thrust to be minimal, we predicted the minimum speed of lunging across scale. To minimize the energetic cost of lunge feeding, hydrodynamic theory predicts slower lunge feeding speeds regardless of body size, with a lower boundary set by the ability of the prey to avoid capture. We used empirical data to test this theory and instead found that maximum foraging speeds remain constant and high (∼4 m s^–1) across body size, even as higher speeds result in lower foraging efficiency. Regardless, we found an increasing relationship between body size and this foraging efficiency, estimated as the ratio of energetic gain from prey to energetic cost. This trend held across timescales ranging from a single lunge to a single day and suggests that larger whales are capturing more prey—and more energy—at a lower cost.

Scaling of maneuvering performance in baleen whales: larger whales outperform expectations

Despite their enormous size, whales make their living as voracious predators. To catch their much smaller, more maneuverable prey, they have developed several unique locomotor strategies that require high energetic input, high mechanical power output and a surprising degree of agility. To better understand how body size affects maneuverability at the largest scale, we used bio-logging data, aerial photogrammetry and a high-throughput approach to quantify the maneuvering performance of seven species of free-swimming baleen whale. We found that as body size increases, absolute maneuvering performance decreases: larger whales use lower accelerations and perform slower pitch-changes, rolls and turns than smaller species. We also found that baleen whales exhibit positive allometry of maneuvering performance: relative to their body size, larger whales use higher accelerations, and perform faster pitch-changes, rolls and certain types of turns than smaller species. However, not all maneuvers were impacted by body size in the same way, and we found that larger whales behaviorally adjust for their decreased agility by using turns that they can perform more effectively. The positive allometry of maneuvering performance suggests that large whales have compensated for their increased body size by evolving more effective control surfaces and by preferentially selecting maneuvers that play to their strengths.

Physiological Consequences of Oceanic Environmental Variation: Life from a Pelagic Organism's Perspective

To better understand life in the sea, marine scientists must first quantify how individual organisms experience their environment, and then describe how organismal performance depends on that experience. In this review, we first explore marine environmental variation from the perspective of pelagic organisms, the most abundant life forms in the ocean. Generation time, the ability to move relative to the surrounding water (even slowly), and the presence of environmental gradients at all spatial scales play dominant roles in determining the variation experienced by individuals, but this variation remains difficult to quantify. We then use this insight to critically examine current understanding of the environmental physiology of pelagic marine organisms. Physiologists have begun to grapple with the complexity presented by environmental variation, and promising frameworks exist for predicting and/or interpreting the consequences for physiological performance. However, new technology needs to be developed and much difficult empirical work remains, especially in quantifying response times to environmental variation and the interactions among multiple covarying factors. We call on the field of global-change biology to undertake these important challenges.

Morphological differences in skulls and feeding apparatuses between Antarctic (Balaenoptera bonaerensis) and common (Balaenoptera acutorostrata) minke whales, and the implication for their feeding ecology

The differences in rorqual feeding ecology have been linked to the presence of different morphological markers. The Antarctic minke whale (Balaenoptera bonaerensis Burmeister, 1867) and the common minke whale (Balaenoptera acutorostrata Lacépède, 1804) are closely related species, but their morphological differences have not been fully investigated. In this study, we compared 21 skull and 11 feeding apparatus (baleen and mouth-related parts) measurement points between these two species using hundreds of individuals covering a wide range of body lengths in both sexes. Their engulfment capacities were estimated using these measurements. Our results show that Antarctic minke whales have (i) proportionally larger skulls to the body length, (ii) more dorsoventrally and laterally curved rostra, (iii) proportionally larger feeding apparatuses to the condylobasal length, and (iv) significantly larger engulfment capacity than common minke whales. These differences could indicate that Antarctic minke whales have developed a feeding strategy suitable for feeding on krill, which forms large schools. In contrast, common minke whales have adapted to prey on small pelagic fishes that are agile and form small schools.

Baleen whale prey consumption based on high-resolution foraging measurements

Baleen whales influence their ecosystems through immense prey consumption and nutrient recycling^1-3. It is difficult to accurately gauge the magnitude of their current or historic ecosystem role without measuring feeding rates and prey consumed. To date, prey consumption of the largest species has been estimated using metabolic models^3-9 based on extrapolations that lack empirical validation. Here, we used tags deployed on seven baleen whale (Mysticeti) species (n = 321 tag deployments) in conjunction with acoustic measurements of prey density to calculate prey consumption at daily to annual scales from the Atlantic, Pacific, and Southern Oceans. Our results suggest that previous studies^3-9 have underestimated baleen whale prey consumption by threefold or more in some ecosystems. In the Southern Ocean alone, we calculate that pre-whaling populations of mysticetes annually consumed 430 million tonnes of Antarctic krill (Euphausia superba), twice the current estimated total biomass of E. superba¹⁰, and more than twice the global catch of marine fisheries today¹¹. Larger whale populations may have supported higher productivity in large marine regions through enhanced nutrient recycling: our findings suggest mysticetes recycled 1.2 × 10⁴ tonnes iron yr^-1 in the Southern Ocean before whaling compared to 1.2 × 10³ tonnes iron yr^-1 recycled by whales today. The recovery of baleen whales and their nutrient recycling services^2,3,7 could augment productivity and restore ecosystem function lost during 20th century whaling^12,13.

Diving physiology of marine mammals and birds: the development of biologging techniques

In the 1940s, Scholander and Irving revealed fundamental physiological responses to forced diving of marine mammals and birds, setting the stage for the study of diving physiology. Since then, diving physiology research has moved from the laboratory to the field. Modern biologging, with the development of microprocessor technology, recorder memory capacity and battery life, has advanced and expanded investigations of the diving physiology of marine mammals and birds. This review describes a brief history of the start of field diving physiology investigations, including the invention of the time depth recorder, and then tracks the use of biologging studies in four key diving physiology topics: heart rate, blood flow, body temperature and oxygen store management. Investigations of diving heart rates in cetaceans and O2 store management in diving emperor penguins are highlighted to emphasize the value of diving physiology biologging research. The review concludes with current challenges, remaining diving physiology questions and what technologies are needed to advance the field. This article is part of the theme issue 'Measuring physiology in free-living animals (Part I)'.

Scaling of oscillatory kinematics and Froude efficiency in baleen whales

High efficiency lunate-tail swimming with high-aspect-ratio lifting surfaces has evolved in many vertebrate lineages, from fish to cetaceans. Baleen whales (Mysticeti) are the largest swimming animals that exhibit this locomotor strategy, and present an ideal study system to examine how morphology and the kinematics of swimming scale to the largest body sizes. We used data from whale-borne inertial sensors coupled with morphometric measurements from aerial drones to calculate the hydrodynamic performance of oscillatory swimming in six baleen whale species ranging in body length from 5 to 25 m (fin whale, Balaenoptera physalus; Bryde's whale, Balaenoptera edeni; sei whale, Balaenoptera borealis; Antarctic minke whale, Balaenoptera bonaerensis; humpback whale, Megaptera novaeangliae; and blue whale, Balaenoptera musculus). We found that mass-specific thrust increased with both swimming speed and body size. Froude efficiency, defined as the ratio of useful power output to the rate of energy input ( Sloop, 1978), generally increased with swimming speed but decreased on average with increasing body size. This finding is contrary to previous results in smaller animals, where Froude efficiency increased with body size. Although our empirically parameterized estimates for swimming baleen whale drag were higher than those of a simple gliding model, oscillatory locomotion at this scale exhibits generally high Froude efficiency as in other adept swimmers. Our results quantify the fine-scale kinematics and estimate the hydrodynamics of routine and energetically expensive swimming modes at the largest scale.

Acoustic tracking of fin whales: Habitat use and movement patterns within a Canadian Pacific fjord system

Fin whale 20 Hz calls were detected, localized, and tracked using a 10 km aperture network of three acoustic receivers deployed for 11 months in a Pacific Canadian fjord system. The area has been historically important for fin whales and is located along a route that tankers will begin using in 2024. A total of 6712 calls were localized, and trajectories were fitted for 55 acoustic tracks. Fin whale tracks occurred throughout the monitoring site. Call activity peaked in September and was low during winter months. Swimming characteristics varied significantly between day- and nighttime: at night, whales swam faster (7.1 vs 4.0 km/h median, +75.2%), which resulted in longer (+34.7%), less predictable (-70.6%) tracks as compared to daylight hours. Call frequencies varied between 16 and 32 Hz. Beside stereotypical song frequencies, fin whales also used irregular frequency components, which contributed the majority of calls in the summer but did not occur in the winter. The results suggest that the area is primarily used as a summer feeding ground, where fin whales follow a diel behavioral cycle. The observed activity patterns will aid in the assessment of strike risk and harassment mitigation and provide a baseline to document behavioral change.

Biomechanically distinct filter-feeding behaviors distinguish sei whales as a functional intermediate and ecologically flexible species

With their ability to facultatively switch between filter-feeding modes, sei whales represent a functional and ecological intermediate in the transition between intermittent and continuous filter feeding. Morphologically resembling their lunge-feeding, rorqual relatives, sei whales have convergently evolved the ability to skim prey near the surface of the water, like the more distantly related balaenids. Because of their intermediate nature, understanding how sei whales switch between feeding behaviors may shed light on the rapid evolution and flexibility of filter-feeding strategies. We deployed multi-sensor bio-logging tags on two sei whales and measured the kinematics of feeding behaviors in this poorly understood and endangered species. To forage at the surface, sei whales used a unique combination of surface lunges and skim-feeding behaviors. The surface lunges were slow and stereotyped, and were unlike lunges performed by other rorqual species. The skim-feeding events featured a different filtration mechanism from the lunges and were kinematically different from the continuous filter feeding used by balaenids. While foraging below the surface, sei whales used faster and more variable lunges. The morphological characteristics that allow sei whales to effectively perform different feeding behaviors suggest that sei whales rapidly evolved their functionally intermediate and ecologically flexible form to compete with larger and more efficient rorqual species.

Machine learning enables improved runtime and precision for bio-loggers on seabirds

Unravelling the secrets of wild animals is one of the biggest challenges in ecology, with bio-logging (i.e., the use of animal-borne loggers or bio-loggers) playing a pivotal role in tackling this challenge. Bio-logging allows us to observe many aspects of animals’ lives, including their behaviours, physiology, social interactions, and external environment. However, bio-loggers have short runtimes when collecting data from resource-intensive (high-cost) sensors. This study proposes using AI on board video-loggers in order to use low-cost sensors (e.g., accelerometers) to automatically detect and record complex target behaviours that are of interest, reserving their devices’ limited resources for just those moments. We demonstrate our method on bio-loggers attached to seabirds including gulls and shearwaters, where it captured target videos with 15 times the precision of a baseline periodic-sampling method. Our work will provide motivation for more widespread adoption of AI in bio-loggers, helping us to shed light onto until now hidden aspects of animals’ lives.

Joseph Korpela et al. demonstrate the use of machine-learning assisted bio-loggers on black-tailed gulls and streaked shearwaters. As video recording is only activated through variations in movement detected by low-cost accelerometers, this method represents improvements to runtime and precision over existing bio-logging technology.

Remoras pick where they stick on blue whales

Animal-borne video recordings from blue whales in the open ocean show that remoras preferentially adhere to specific regions on the surface of the whale. Using empirical and computational fluid dynamics analyses, we show that remora attachment was specific to regions of separating flow and wakes caused by surface features on the whale. Adhesion at these locations offers remoras drag reduction of up to 71-84% compared with the freestream. Remoras were observed to move freely along the surface of the whale using skimming and sliding behaviors. Skimming provided drag reduction as high as 50-72% at some locations for some remora sizes, but little to none was available in regions where few to no remoras were observed. Experimental work suggests that the Venturi effect may help remoras stay near the whale while skimming. Understanding the flow environment around a swimming blue whale will inform the placement of biosensor tags to increase attachment time for extended ecological monitoring.

Why whales are big but not bigger: Physiological drivers and ecological limits in the age of ocean giants

The largest animals are marine filter feeders, but the underlying mechanism of their large size remains unexplained. We measured feeding performance and prey quality to demonstrate how whale gigantism is driven by the interplay of prey abundance and harvesting mechanisms that increase prey capture rates and energy intake. The foraging efficiency of toothed whales that feed on single prey is constrained by the abundance of large prey, whereas filter-feeding baleen whales seasonally exploit vast swarms of small prey at high efficiencies. Given temporally and spatially aggregated prey, filter feeding provides an evolutionary pathway to extremes in body size that are not available to lineages that must feed on one prey at a time. Maximum size in filter feeders is likely constrained by prey availability across space and time.

Whale breaching says it loud and clear

A whale leaping above the surface expends an enormous amount of energy, displaying its health and strength to peers and potential mates.

Energetic and physical limitations on the breaching performance of large whales

The considerable power needed for large whales to leap out of the water may represent the single most expensive burst maneuver found in nature. However, the mechanics and energetic costs associated with the breaching behaviors of large whales remain poorly understood. In this study we deployed whale-borne tags to measure the kinematics of breaching to test the hypothesis that these spectacular aerial displays are metabolically expensive. We found that breaching whales use variable underwater trajectories, and that high-emergence breaches are faster and require more energy than predatory lunges. The most expensive breaches approach the upper limits of vertebrate muscle performance, and the energetic cost of breaching is high enough that repeated breaching events may serve as honest signaling of body condition. Furthermore, the confluence of muscle contractile properties, hydrodynamics, and the high speeds required likely impose an upper limit to the body size and effectiveness of breaching whales.

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.

New views of humpback whale flow dynamics and oral morphology during prey engulfment

The rise of inexpensive, user-friendly cameras and editing software promises to revolutionize data collection with minimal disturbance to marine mammals. Video sequences recorded by aerial drones and GoPro cameras provided close-up views and unique perspectives of humpback whales engulfing juvenile salmon at or just below the water surface in Southeast Alaska and Prince William Sound. Although humpback feeding is famous for its flexibility, several stereotyped events were noted in the 47 lunges we analyzed. Engulfment was rapid (mean 2.07 s), and the entrance through which the tongue inverts into the ventral pouch was seen as water rushes in. Cranial elevation was a major contributor to gape, and pouch contraction sometimes began before full gape closure, with reverberating waves indicating rebounding flow of water within the expanded pouch. Expulsion of filtered water began with a small splash at the anterior of the mouth, followed by sustained excurrent flow in the mouth's central or posterior regions. Apart from a splash of rebounding water, water within the mouth was surprisingly turbulence-free during engulfment, but submersion of the whale's head created visible surface whirlpools and vortices which may aggregate prey for subsequent engulfment.

Body Flexibility Enhances Maneuverability in the World's Largest Predator

Blue whales are often characterized as highly stable, open-ocean swimmers who sacrifice maneuverability for long-distance cruising performance. However, recent studies have revealed that blue whales actually exhibit surprisingly complex underwater behaviors, yet little is known about the performance and control of these maneuvers. Here, we use multi-sensor biologgers equipped with cameras to quantify the locomotor dynamics and the movement of the control surfaces used by foraging blue whales. Our results revealed that simple maneuvers (rolls, turns, and pitch changes) are performed using distinct combinations of control and power provided by the flippers, the flukes, and bending of the body, while complex trajectories are structured by combining sequences of simple maneuvers. Furthermore, blue whales improve their turning performance by using complex banked turns to take advantage of their substantial dorso-ventral flexibility. These results illustrate the important role body flexibility plays in enhancing control and performance of maneuvers, even in the largest of animals. The use of the body to supplement the performance of the hydrodynamically active surfaces may represent a new mechanism in the control of aquatic locomotion.

LG, Flores-Martínez JJ, Wilkinson GS, Yovel Y. Acoustic evaluation of behavioral states predicted from GPS tracking: a case study of a marine fishing bat

BACKGROUND

Multiple methods have been developed to infer behavioral states from animal movement data, but rarely has their accuracy been assessed from independent evidence, especially for location data sampled with high temporal resolution. Here we evaluate the performance of behavioral segmentation methods using acoustic recordings that monitor prey capture attempts.

METHODS

We recorded GPS locations and ultrasonic audio during the foraging trips of 11 Mexican fish-eating bats, Myotis vivesi, using miniature bio-loggers. We then applied five different segmentation algorithms (k-means clustering, expectation-maximization and binary clustering, first-passage time, hidden Markov models, and correlated velocity change point analysis) to infer two behavioral states, foraging and commuting, from the GPS data. To evaluate the inference, we independently identified characteristic patterns of biosonar calls ("feeding buzzes") that occur during foraging in the audio recordings. We then compared segmentation methods on how well they correctly identified the two behaviors and if their estimates of foraging movement parameters matched those for locations with buzzes.

RESULTS

While the five methods differed in the median percentage of buzzes occurring during predicted foraging events, or true positive rate (44-75%), a two-state hidden Markov model had the highest median balanced accuracy (67%). Hidden Markov models and first-passage time predicted foraging flight speeds and turn angles similar to those measured at locations with feeding buzzes and did not differ in the number or duration of predicted foraging events.

CONCLUSION

The hidden Markov model method performed best at identifying fish-eating bat foraging segments; however, first-passage time was not significantly different and gave similar parameter estimates. This is the first attempt to evaluate segmentation methodologies in echolocating bats and provides an evaluation framework that can be used on other species.

Fin whale singing decreases with increased swimming speed

The attributes of male acoustic advertisement displays are often related to a performer's age, breeding condition and motivation, but these relationships are particularly difficult to study in free-ranging marine mammals. For fin whale singers, we examined the relationships between a singer's swimming speed, song duration and amount of singing. We used a unique set of fin whale singing and swimming data collected in support of the US Navy's marine mammal monitoring programme associated with the Navy's Integrated Undersea Surveillance System. A goal of the programme is to improve understanding of the potential effects of anthropogenic sound sources on baleen whale behaviours and populations. We found that as whales swam faster, some continued to sing, while others did not. If swimming speed is an indication of male stamina, then singing while swimming faster could be a display by which females and/or other males assess a singer's physical fitness and potential reproductive quality. Results have implications for interpreting fin whale singing behaviour and the possible influences of anthropogenic sounds on fin whale mating strategies and breeding success.

Using on-board sound recordings to infer behaviour of free-moving wild animals

Technological advances in the last 20 years have enabled researchers to develop increasingly sophisticated miniature devices (tags) that record an animal's behaviour not from an observational, external viewpoint, but directly on the animals themselves. So far, behavioural research with these tags has mostly been conducted using movement or acceleration data. But on-board audio recordings have become more and more common following pioneering work in marine mammal research. The first questions that come to mind when recording sound on-board animals concern their vocal behaviour. When are they calling? How do they adjust their behaviour? What acoustic parameters do they change and how? However, other topics like foraging behaviour, social interactions or environmental acoustics can now be addressed as well and offer detailed insight into the animals' daily life. In this Review, we discuss the possibilities, advantages and limitations of on-board acoustic recordings. We focus primarily on bats as their active-sensing, echolocating lifestyle allows many approaches to a multi-faceted acoustic assessment of their behaviour. The general ideas and concepts, however, are applicable to many animals and hopefully will demonstrate the versatility of on-board acoustic recordings and stimulate new research.

A "Welcoming" Introduction to a Canadian Northwest Coast Thematic Papers Issue

In this commentary, I provide an introduction to and the context for the four articles in the thematic series published to celebrate the Editorial Board Meeting of the Anatomical Record in Vancouver, British Columbia, Canada in July of 2017. The articles describe various aspects of whale anatomy and the potential for a new generation of digital tags to provide information on functional anatomy of free swimming animals in the wild. The whales described are all native to the northwest coast of North America, as well as being found elsewhere, and the authors are related in some way to the University of British Columbia in Vancouver. Anat Rec, 300:1930-1934, 2017. © 2017 Wiley Periodicals, Inc.

Determining forward speed from accelerometer jiggle in aquatic environments

How fast animals move is critical to understanding their energetic requirements, locomotor capacity, and foraging performance, yet current methods for measuring speed via animal-attached devices are not universally applicable. Here we present and evaluate a new method that relates forward speed to the stochastic motion of biologging devices since tag jiggle, the amplitude of the tag vibrations as measured by high sample rate accelerometers, increases exponentially with increasing speed. We successfully tested this method in a flow tank using two types of biologging devices and tested the method in situ on wild cetaceans spanning ∼3 to &gt;20 m in length using two types of suction cup-attached and two types of dart-attached tag. This technique provides some advantages over other approaches for determining speed as it is device-orientation independent and relies only on a pressure sensor and a high sample rate accelerometer, sensors that are nearly universal across biologging device types.