14 research outputs found
Applying a Macro Lens to Microplastics: Modeling Microplastic Ingestion Risk to Humpback Whales in the Chesapeake Bay
No full textPlastic waste is an increasing threat to marine environments, with an estimated 1.2-2.4 million metric tones of waste entering marine systems through rivers yearly. Plastic debris can fragment into smaller particles, classified as microplastics (particles \u3c 5mm), due to weathering, oxidation, and other processes. When consumed by an organism, MPs can be retained in the stomach, resulting in false satiation, and may lead to translocation that creates damage at the cellular level. Filter feeding megafauna such as humpback whales are at risk of directly ingesting MPs suspended in the water column and may accumulate particles indirectly by consuming contaminated prey. Based on previous MP ingestion risk assessments, fish-feeding humpback whales in the California Current consume approximately 200,000 pieces of MP per day. While MP ingestion risk has been documented for humpback whales in the California Current, less is known about the risk in the Mid-Atlantic, specifically within the Chesapeake Bay. Determining exposure route and the extent of bioaccumulation are important first steps to assessing risk for individuals and populations. I will model microplastic ingestion risk to humpback whales in the Chesapeake Bay by incorporating CATS (Customized Animal Tracking Solutions) tag data, feeding rates, prey density, and empirical values of MP contamination in collected prey and water column samples. I will use heat assisted chemical digestion and filtration methods to extract the MPs in these samples. I will photograph and record size, color, and type (e.g. fragments, foams, and fibers) of the isolated MPs and perform Fourier-Transform Infrared Spectroscopy (FTIR) analysis to identify their source. Studying MPs across trophic levels is important for highlighting potential entry pathways for marine debris, critical for protecting natural resources, and guiding informed management implementation
Baleen–Plastic Interactions Reveal High Risk to All Filter-Feeding Whales from Clogging, Ingestion, and Entanglement
No full textBaleen whales are ecosystem sentinels of microplastic pollution. Research indicates that they likely ingest millions of anthropogenic microparticles per day when feeding. Their immense prey consumption and filter-feeding behavior put them at risk. However, the role of baleen, the oral filtering structure of mysticete whales, in this process has not been adequately addressed. Using actual baleen tissue from four whale species (fin, humpback, minke, and North Atlantic right) in flow tank experiments, we tested the capture rate of plastics of varying size, shape, and polymer type, as well as chemical residues leached by degraded plastics, all of which accumulated in the baleen filter. Expanded polystyrene foam was the most readily captured type of plastic, followed by fragments, fibers, nurdles, and spherical microbeads. Nurdle and microbead pellets were captured most readily by right whale baleen, and fragments were captured by humpback baleen. Although not all differences between polymer types were statistically significant, buoyant polymers were most often trapped by baleen. Plastics were captured by baleen sections from all regions of a full baleen rack, but were more readily captured by baleen from dorsal and posterior regions. Baleen–plastic interactions underlie various risks to whales, including filter clogging and damage, which may impede feeding. We posit that plastics pose a higher risk to some whale species due to a combination of factors, including filter porosity, diet, habitat and geographic distribution, and foraging ecology and behavior. Certain whale species in specific marine regions are of the greatest concern due to plastic abundance. It is not feasible to remove all plastic from the sea; most of what is there will continue to break into ever-smaller pieces. We suggest that higher priorities be accorded to lessening humans’ dependence on plastics, restricting entry points of plastics into the ocean, and developing biodegradable alternatives
Video_1_Evidence for Size-Selective Predation by Antarctic Humpback Whales.MP4
No full textAnimals aggregate around resource hotspots, but what makes one resource more appealing than another can be difficult to determine. In March 2020 the Antarctic fjord Charlotte Bay included >5× as many humpback whales as neighboring Wilhelmina Bay, a site previously known for super aggregations of whales and their prey, Antarctic krill. We used suction-cup attached bio-logging tags and active acoustic prey mapping to test the hypothesis that whale abundance in Charlotte Bay would be associated with higher prey biomass density, and that whale foraging effort would be concentrated in regions of Charlotte Bay with the highest biomass. Here we show, however, that patch size and krill length at the depth of foraging were more likely predictors of foraging effort than biomass. Tagged whales spent >80% of the night foraging, and whales in both bays demonstrated similar nighttime feeding rates (48.1 ± 4.0 vs. 50.8 ± 16.4 lunges/h). However, whales in Charlotte Bay foraged for 58% of their daylight hours, compared to 22% in Wilhelmina Bay, utilizing deep (280–450 m) foraging dives in addition to surface feeding strategies like bubble-netting. Selective foraging on larger krill by humpback whales has not been previously established, but suggests that whales may be sensitive to differences in individual prey quality. The utilization of disparate foraging strategies in different parts of the water column allows humpback whales to target the most desirable parts of their foraging environments.</p
Video_2_Evidence for Size-Selective Predation by Antarctic Humpback Whales.MP4
No full textAnimals aggregate around resource hotspots, but what makes one resource more appealing than another can be difficult to determine. In March 2020 the Antarctic fjord Charlotte Bay included >5× as many humpback whales as neighboring Wilhelmina Bay, a site previously known for super aggregations of whales and their prey, Antarctic krill. We used suction-cup attached bio-logging tags and active acoustic prey mapping to test the hypothesis that whale abundance in Charlotte Bay would be associated with higher prey biomass density, and that whale foraging effort would be concentrated in regions of Charlotte Bay with the highest biomass. Here we show, however, that patch size and krill length at the depth of foraging were more likely predictors of foraging effort than biomass. Tagged whales spent >80% of the night foraging, and whales in both bays demonstrated similar nighttime feeding rates (48.1 ± 4.0 vs. 50.8 ± 16.4 lunges/h). However, whales in Charlotte Bay foraged for 58% of their daylight hours, compared to 22% in Wilhelmina Bay, utilizing deep (280–450 m) foraging dives in addition to surface feeding strategies like bubble-netting. Selective foraging on larger krill by humpback whales has not been previously established, but suggests that whales may be sensitive to differences in individual prey quality. The utilization of disparate foraging strategies in different parts of the water column allows humpback whales to target the most desirable parts of their foraging environments.</p
Baleen whale inhalation variability revealed using animal-borne video tags
No full textEmpirical metabolic rate and oxygen consumption estimates for free-ranging whales have been limited to counting respiratory events at the surface. Because these observations were limited and generally viewed from afar, variability in respiratory properties was unknown and oxygen consumption estimates assumed constant breath-to-breath tidal volume and oxygen uptake. However, evidence suggests that cetaceans in human care vary tidal volume and breathing frequency to meet aerobic demand, which would significantly impact energetic estimates if the findings held in free-ranging species. In this study, we used suction cup-attached video tags positioned posterior to the nares of two humpback whales (Megaptera novaeangliae) and four Antarctic minke whales (Balaenoptera bonaerensis) to measure inhalation duration, relative nares expansion, and maximum nares expansion. Inhalation duration and nares expansion varied between and within initial, middle, and terminal breaths of surface sequences between dives. The initial and middle breaths exhibited the least variability and had the shortest durations and smallest nares expansions. In contrast, terminal breaths were highly variable, with the longest inhalation durations and the largest nares expansions. Our results demonstrate breath-to-breath variability in duration and nares expansion, suggesting differential oxygen exchange in each breath during the surface interval. With future validation, inhalation duration or nares area could be used alongside respiratory frequency to improve oxygen consumption estimates by accounting for breath-to-breath variation in wild whales
High‐speed chases along the seafloor put Bryde's whales at risk of entanglement
No full textRecent changes in the South African marine ecosystem and the introduction of an experimental octopus fishery have resulted in an unsustainably high rate of fatal Bryde's whale entanglements. Using suction-cup attached bio-loggers, we identified a previously undescribed feeding behavior used by Bryde's whales to catch prey, and this behavior may make them susceptible to entanglement and mortality in bottom-mounted fishing gear. As they chase down their prey, inshore Bryde's whales sprint and maneuver along the seafloor for extended periods of time, making multiple direction changes, and reaching extraordinarily high swimming speeds. These findings assisted in the implementation of mandatory changes to octopus fishing gear that have drastically reduced the number of entanglements. The novel finding that Bryde's whales use high-speed chases near the seafloor to catch their prey highlights the value of using species-specific, behavioral information for making conservation recommendations.</p
Fast and Furious: Energetic Tradeoffs and Scaling of High-Speed Foraging in Rorqual Whales
No full textAlthough 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
Tools for integrating inertial sensor data with video bio-loggers, including estimation of animal orientation, motion, and position
No full textAbstract Bio-logging devices equipped with inertial measurement units—particularly accelerometers, magnetometers, and pressure sensors—have revolutionized our ability to study animals as necessary electronics have gotten smaller and more affordable over the last two decades. These animal-attached tags allow for fine scale determination of behavior in the absence of direct observation, particularly useful in the marine realm, where direct observation is often impossible, and recent devices can integrate more power hungry and sensitive instruments, such as hydrophones, cameras, and physiological sensors. To convert the raw voltages recorded by bio-logging sensors into biologically meaningful metrics of orientation (e.g., pitch, roll and heading), motion (e.g., speed, specific acceleration) and position (e.g., depth and spatial coordinates), we developed a series of MATLAB tools and online instructional tutorials. Our tools are adaptable for a variety of devices, though we focus specifically on the integration of video, audio, 3-axis accelerometers, 3-axis magnetometers, 3-axis gyroscopes, pressure, temperature, light and GPS data that are the standard outputs from Customized Animal Tracking Solutions (CATS) video tags. Our tools were developed and tested on cetacean data but are designed to be modular and adaptable for a variety of marine and terrestrial species. In this text, we describe how to use these tools, the theories and ideas behind their development, and ideas and additional tools for applying the outputs of the process to biological research. We additionally explore and address common errors that can occur during processing and discuss future applications. All code is provided open source and is designed to be useful to both novice and experienced programmers
Energetic and physical limitations on the breaching performance of large whales
No full textThe 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
