Balaenopteridae Research Articles

Morphology and Mechanics of the Fin Whale Esophagus: The Key to Fast Processing of Large Food Volumes by Rorquals.

Lunge feeding rorqual whales feed by engulfing a volume of prey laden water that can be as large as their own body. Multiple feeding lunges occur during a single foraging dive and the time between each lunge can be as short as 30 s (Goldbogen etal. 2013). During this short inter-lunge time, water is filtered out through baleen to concentrate prey in the oral cavity, and then the prey is swallowed prior to initiating the next lunge. Prey density in the ocean varies greatly, and despite the potential of swallowing a massive volume of concentrated prey as a slurry, the esophagus of rorqual whales has been anecdotally described as unexpectedly narrow with a limited capacity to expand. How rorquals swallow large quantities of food down a narrow esophagus during a limited inter-lunge time remains unknown. Here, we show that the small diameter muscular esophagus in the fin whale is optimized to transport a slurry of food to the stomach. A thick wall of striated muscle occurs at the pharyngeal end of the esophagus which, together with the muscular wall of the pharynx, may generate a pressure head for transporting the food down the esophagus to the stomach as a continuous stream rather than separating the food into individual boluses swallowed separately. This simple model is consistent with estimates of prey density and stomach capacity. Rorquals may be the only animals that capture a volume of food too large to swallow as a single intact bolus without oral processing, so the adaptations of the esophagus are imperative for transporting these large volumes of concentrated food to the stomach during a time-limited dive involving multiple lunges.

The Soft Palate Enables Extreme Feeding and Explosive Breathing in the Fin Whale (Balaenoptera physalus).

The evolution of lunge feeding in rorqual whales was associated with the evolution of several unique morphological features that include non-synovial ligamentous temporomandibular joints, a tongue that can invert and extend backward to the umbilicus, walls of the oral cavity that can dramatically expand, and muscles and nerves that are stretchy. Also, among the acquired features was an enlargement of the rostral end of the soft palate into an oral plug that occludes the opening between the oral cavity and pharynx and prevents water incursion into the pharynx during the engulfment phase of a feeding lunge. During this engulfment phase of a lunge, the volume of water entering the oral cavity can exceed the volume of the whale itself. Here, using dissection of fetuses and adults and a magnetic resonance imaging dataset of a fetus, we examine the detailed anatomy of the soft palate in fin whales. We describe several innovative features relative to other mammals, including changes in the attachment and positions of the major extrinsic muscles of the palate, alterations in the morphology of the pterygoid processes related to the palate and pharynx, and the presence of distinct muscle layers in the part of the palate caudal to the oral plug. Based on the anatomy, we present a model for how the soft palate is positioned at rest, and how it functions during feeding, breathing, and swallowing.

Cheap gulp foraging of a giga-predator enables efficient exploitation of sparse prey.

The giant rorqual whales are believed to have a massive food turnover driven by a high-intake lunge feeding style aptly described as the world's largest biomechanical action. This high-drag feeding behavior is thought to limit dive times and constrain rorquals to target only the densest prey patches, making them vulnerable to disturbance and habitat change. Using biologging tags to estimate energy expenditure as a function of feeding rates on 23 humpback whales, we show that lunge feeding is energetically cheap. Such inexpensive foraging means that rorquals are flexible in the quality of prey patches they exploit and therefore more resilient to environmental fluctuations and disturbance. As a consequence, the food turnover and hence the ecological role of these marine giants have likely been overestimated.

Exposure of whales to entanglement risk in Dungeness crab fishing gear in Oregon, USA, reveals distinctive spatio-temporal and climatic patterns

Entanglement in fishing gear presents a major threat to marine mammals worldwide and a pressing concern for distinct populations of whales off the US West Coast. The lack of understanding of their fine-scale distribution in relation to fishing activity limits management efforts, specifically in Oregon. Based on year-round predictions of rorqual whale densities and fishing effort compiled from logbooks, we assess co-occurrence between commercial Dungeness crab fishing gear and whales over a decade (2011–2020) as an indicator of exposure to entanglement risk. Generalized Additive Models including temporal, climatic, and ocean upwelling predictors were used to investigate variations in exposure. Exposure peaked in April, at the onset of the upwelling season when whales were predicted to occur in greater numbers and closer to shore. Exposure remained constant until the end of the crab season in nearshore waters <40 fathoms (73 m) and decreased past these depths. Across years, exposure was lower during the marine heatwave (2014–2016) when fishing was more active nearshore and whales were predicted to be less abundant. Exposure was higher before (2011–2013) and after (2017–2020) the heatwave, which correspond to negative phases of the Pacific Decadal Oscillation associated with stronger upwelling, indicating more productive conditions favorable to whales. A recent increase in exposure was also due to a slight shift in fishing effort towards deeper waters. These findings illustrate the use of fine-scale species distribution models to assess space-use conflicts in dynamic marine ecosystems and can be used to guide fisheries management to reduce entanglement risk in Oregon.

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.

Formation of a fringe: A look inside baleen morphology using a multimodal visual approach.

Filter-feeding has been present for hundreds of millions of years, independently evolving in aquatic vertebrates' numerous times. Mysticete whales are a group of gigantic, marine filter-feeders that are defined by their fringed baleen and are divided into two groups: balaenids and rorquals. Recent studies have shown that balaenids likely feed using a self-cleaning, cross-flow filtration mechanism where food particles are collected and then swept to the esophagus for swallowing. However, it is unclear how filtering is achieved in the rorquals (Balaenopteridae). Lunging rorqual whales engulf enormous masses of both prey and water; the prey is then separated from the water through baleen plates lining the length of their upper jaw and positioned perpendicular to flow. Rorqual baleen is composed of both major (larger) and minor (smaller) keratin plates containing embedded fringe that extends into the whale's mouth, forming a filtering fringe. We used a multimodal approach, including microcomputed tomography (µCT) and scanning electron microscopy (SEM), to visualize and describe the variability in baleen anatomy across five species of rorqual whales, spanning two orders of magnitude in body length. For most morphological measurements, larger whales exhibited hypoallometry relative to body length. µCT and SEM revealed that the major and minor plates break away from the mineralized fringes at variable distances from the gums. We proposed a model for estimating the effective pore size to determine whether flow scales with body length or prey size across species. We found that pore size is likely not a proxy for prey size but instead, may reflect changes in resistance through the filter that affect fluid flow.

Integrating technologies provides insight into the subsurface foraging behaviour of a humpback whale (Megaptera novaeangliae) feeding on walleye pollock (Gadus chalcogrammus) in Juan de Fuca Strait, Canada.

Subsurface foraging is an important proportion of the activity budget of rorqual whales, yet information on their behaviour underwater remains challenging to obtain. Rorquals are assumed to feed throughout the water column and to select prey as a function of depth, availability and density, but there remain limitations in the precise identification of targeted prey. Current data on rorqual foraging in western Canadian waters have thus been limited to observations of prey species amenable to surface feeding, such as euphausiids and Pacific herring (Clupea pallasii), with no information on deeper alternative prey sources. We measured the foraging behaviour of a humpback whale (Megaptera novaeangliae) in Juan de Fuca Strait, British Columbia, using three complimentary methods: whale-borne tag data, acoustic prey mapping, and fecal sub-sampling. Acoustically detected prey layers were near the seafloor and consistent with dense schools of walleye pollock (Gadus chalcogrammus) distributed above more diffuse aggregations of pollock. Analysis of a fecal sample from the tagged whale confirmed that it had been feeding on pollock. Integrating the dive profile with the prey data revealed that the whale's foraging effort followed the general pattern of areal prey density, wherein the whale had a higher lunge-feeding rate at the highest prey abundance and stopped feeding when prey became limited. Our findings of a humpback whale feeding on seasonally energy-dense fish like walleye pollock, which are potentially abundant in British Columbia, suggests that pollock may be an important prey source for this rapidly growing whale population. This result is informative when assessing regional fishing activities for semi-pelagic species as well as the whales' vulnerability to fishing gear entanglements and feeding disturbances during a narrow window of prey acquisition.

Issue Information

Journal of MorphologyVolume 284, Issue 4 e21570 ISSUE INFORMATIONFree Access Issue Information First published: 15 February 2023 https://doi.org/10.1002/jmor.21570AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Graphical Abstract Cover Caption: Filter-feeding has been present for hundreds of millions of years, independently evolving in aquatic vertebrates' numerous times. Mysticete whales are a group of gigantic, marine filter-feeders that are defined by their fringed baleen and are divided into two groups: balaenids and rorquals. Recent studies have shown that balaenids likely feed using a self-cleaning, cross-flow filtration mechanism where food particles are collected and then swept to the esophagus for swallowing. However, it is unclear how filtering is achieved in the rorquals (Balaenopteridae). In this issue of the Journal of Morphology, Vandenberg and coauthors (e21574) used microcomputed tomography (μCT) and scanning electron microscopy (SEM), to visualize and describe the variability in baleen anatomy across five species of rorqual whales, spanning two orders of magnitude in body length. They found that pore size is likely not a proxy for prey size but instead, may reflect changes in resistance through the filter that affect fluid flow. Volume284, Issue4April 2023e21570 RelatedInformation

A New Fossil Rorqual Aff. Balaenoptera Bertae Specimen from the Shinazawa Formation (Late Pliocene to Early Pleistocene), Yamagata, Japan

More than 23 extinct species and 10 extant species of the Balaenopteridae are known. Our knowledge of the family Balaenopteridae is increasing quickly, however, few fossil records support a circum-North Pacific distribution of balaenopterid genera and species. Because of limited preservations, most rorqual fossils reported from the western North Pacific can only be identified to the family level. A skull from the Shinazawa Formation (late Pliocene to Early Pleistocene) in Yamagata, Japan, is identified as aff. Balaenoptera bertae by possessing two diagnostic features of the species: large occipital condyles, and a posteriorly elongate postglenoid process. Combination of four more features also support that the specimen is a closely related to B. bertae. The specimen is probably a slightly older individual than the holotype of B. bertae, based on the estimated bizygomatic width and slightly longer posterior process of the tympanoperiotic. The first and only report of B. bertae was from the Pliocene Purisima Formation in California, USA. The specimen from Japan is incompletely preserved, but shows the occurrence of B. bertae in the western North Pacific for the first time, as many living balaenopterids are distributed across the North Pacific, such as Balaenoptera musculus, B. physalus, B. borealis, B. acutorostrata, and Megaptera novaeangliae.

Heterochronic maturation of anatomical plugs for protecting the airway in rorqual whales (Balaenopteridae).

Recently, a unique mechanism for protecting the airway during lunge feeding was discovered in rorqual whales (Balaenopteridae). This mechanism is based on an oral plug structure in the soft palate with similarities in musculo-fatty composition to the nasal plugs protecting the respiratory tract of rorquals from water entry and barotrauma during diving. As a follow-up, we present here a developmental series on fetal, prenatal, juvenile and adult specimens across five species of rorquals, showing differential maturation of the nasal and oral respiratory protection plugs. Nasal plugs are fully formed to serve an immediate crucial function at birth. By contrast, the soft palate remains muscular until the onset of solid food intake, where a musculo-fatty oral plug is developed.

Fine-scale diversity of prey detected in humpback whale feces.

Predator diets are largely influenced by prey availability and abundance. Yet, in heterogenous marine environments, identifying the prey species consumed by diving mammals remains a fundamental challenge. For rorqual whales, the energetic constraints of prey engulfment require that the whales seek areas of high prey abundance and execute discrete lunge feeding events on patches of high-density prey. Prey occurrences in feces should therefore provide meaningful insight into the dominant taxa in food patches selected by the animal. We investigated the prey consumed by humpback whales in three regions in southern British Columbia (BC), Canada, using opportunistic fecal sampling, microscopy, and DNA metabarcoding of 14 fecal samples. Fish including Pacific herring (Clupea pallasii), hake (Merluccius productus), and eulachon (Thaleichthys pacificus) were the most common fish species potentially targeted by humpback whales in two regions. The krill Euphausia pacifica was the most prevalent invertebrate DNA detected in all three regions, while sergestid and mysid shrimp may also be important. High DNA read abundances from walleye pollock (Gadus chalcogrammus) and sablefish (Anoplopoma fimbria) were also recovered in one sample each, suggesting that juveniles of these semi-pelagic species may occasionally be targeted. In general, we observed heavily digested fecal material that drove substantial dissimilarities in taxonomic resolution between polymerase chain reaction-based and morphological analyses of the feces. Pacific herring and walleye pollock were the only prey species confirmed by both methods. Our results highlight that molecular and visual analyses of fecal samples provide a complementary approach to diet analysis, with each method providing unique insight into prey diversity.

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

SynopsisAlthough 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.

A satellite-linked tag for the long-term monitoring of diving behavior in large whales

Despite spending most time underwater, the technology in use to track whales over large geographic ranges via satellite has been largely limited to locational data, with most applications focusing on characterizing their horizontal movements. We describe the development of the RDW tag, a new Argos-based satellite telemetry device that incorporates sensors for monitoring the movements and dive behavior of large whales over several months without requiring recovery. Based on an implantable design, the tag features a saltwater conductivity switch, a tri-axial accelerometer, and an optional pressure transducer, along with onboard software for data processing and detection of behavioral events or activities of interest for transmission. We configured the software to detect dives and create per-dive summaries describing behavioral events associated with feeding activities in rorqual whales. We conducted a validation by proxy of the dive summary and event detection algorithms using field data from a medium-duration archival tag. We also conducted a simulation exercise to examine how the expected data recovery would vary under different dive behavior scenarios and compared those results to empirical values from field deployments of the RDW tag on blue (Balaenoptera musculus) and humpback (Megaptera novaeangliae) whales. The dive summary algorithm accurately reported dive depth and duration, while the accuracy of the lunge-feeding event detection algorithm was dependent on the precision of the accelerometer data that was used, with a predicted accuracy of 0.74 for correctly classifying feeding dives from 1/64-G precision data and 0.95 from 1-mG precision data. Simulated data recovery was lower with sparser transmission schedules, shorter mean dive durations, and lower rates of successfully received transmissions. Empirical data recovery was lower than expected from the simulation, suggesting the effect of additional factors, such as data gaps. By measuring key aspects of the per-dive behavior of large whales over multi-month timescales of movement, the RDW tags provide the ability to monitor previously unobservable behaviors across entire geographic ranges, extending the applications of satellite telemetry devices to new areas of whale physiology, behavior, ecology, and conservation.

Seasonal, Annual, and Decadal Distribution of Three Rorqual Whale Species Relative to Dynamic Ocean Conditions Off Oregon, USA

Whale populations recovering from historical whaling are particularly vulnerable to incidental mortality and disturbance caused by growing ocean industrialization. Several distinct populations of rorqual whales (including humpback, blue, and fin whales) migrate and feed off the coast of Oregon, USA where spatial overlap with human activities are on the rise. Effective mitigation of conflicts requires better foundational understanding of spatial and temporal habitat use patterns to inform conservation management. Based on a year-round, multi-platform distance sampling dataset (2016-2021, 177 survey days, 754 groups observed), this study generated density models to describe and predict seasonal distribution of rorqual whales in Oregon. Phenology analysis of sightings revealed a peak of humpback whale and blue whale density over the Oregon continental shelf in August and September respectively, and higher fin whale density in the winter (December). Additionally, we compared rorqual sighting rates across three decades of survey effort (since 1989) and demonstrate that rorqual whales are strikingly more prevalent in the current dataset, including distinct increases of blue and fin whales. Finally, density surface models relating whale densities to static and dynamic environmental variables acquired from data-assimilative ocean models revealed that summer and spring rorqual distribution were influenced by dynamic oceanographic features indicative of active upwelling and frontal zones (respectively 27% and 40% deviance explained). On the continental shelf, blue whales were predicted to occur closer to shore than humpback whales and in the more southern waters off Oregon. Summer and spring rorqual models, and humpback whale models, showed predictive performance suitable for management purposes, assessed through internal cross-validation and comparison to an external dataset (388 groups observed). Indeed, monthly hotspots of high predicted rorqual whale density across multiple years were validated by independent sightings (80% overlap in the summer model). These predictive models lay a robust basis for fine-scale dynamic spatial management to reduce impacts of human activities on endangered populations of rorqual whales in Oregon.

Social exploitation of extensive, ephemeral, environmentally controlled prey patches by supergroups of rorqual whales

Large groups of animals aggregate around resource hotspots, with group size often influenced by the heterogeneity of the environment. In most cases, the foraging success of individuals within groups is interdependent, scaling either constructively or destructively with group size. Here we used biologging tags, acoustic prey mapping, passive acoustic recording of social cues and remote sensing of surface currents to investigate an alternative scenario in which large, dense aggregations of southeast Atlantic humpback whales, Megaptera novaeangliae , and northeast Pacific blue whales, Balaenoptera musculus , were each associated with ephemeral krill aggregations large enough such that their availability to predators appeared to be influenced more by environmental features than by consumption, implying independence of group size and consumption rates. We found that the temporal scale and spatial extent of oceanographic drivers were consistent with the temporal scale and locations of predator aggregations, and additionally found that groups formed above bathymetric features known to promote zooplankton concentration. Additionally, we found calling behaviour counter-indicative of competition: blue whale foraging calls were anomalously high during observed aggregation time periods, suggesting signalling behaviour that could alert conspecifics to the location of high-quality resources. Modelled results suggest that the use of social information reduces the time required for individuals to discover and exploit high-quality resources, allowing for more efficient foraging without apparent costs to the caller. Thus, rorqual whales foraging in these environments appear to exhibit a social foraging strategy whereby a behaviour with negligible individual costs (signalling) provides information that enhances group foraging efficiency. The population density dependence of this social foraging strategy may help explain why some rorqual species were at first slow to recover from human exploitation, but have since increased more rapidly. • Large, dense prey patches were found near supergroups of rorqual whales. • Ephemeral patches formed when surface features intersected with bathymetry. • Blue whales increased social call production during observed aggregation events. • Rorqual whale foraging appears to be enhanced when social information is utilized.

Whale shark (Rhincodon typus) predatory flexible feeding behaviors on schooling fish

Whale sharks are known to feed primarily on zooplankton all over the world; however, recent findings suggest that they also prey on fish using behaviors that have not been fully described. Here, we provide detailed evidence of whale sharks interacting with schools of anchovy on four occasions in Bahia de Los Angeles, Baja California, Mexico. Three of these were predatory interactions in multi-species feeding frenzies, and one was a non-predatory interaction. In predatory interactions, whale sharks exhibited two types of feeding behaviors: (1) stationary suction-feeding, a previously described behavior for whale sharks, and (2) lunge-feeding, which has not been previously described in whale sharks, but has been observed among other large filter feeders, such as rorqual whales. The whale sharks moved simultaneously around the school of anchovy, lunging simultaneously or one after another into the school, with 66% (N = 17) of these lunges occurring in the same direction. In the non-predatory interaction, whale sharks exhibited “sit-and-wait" behavior. The evidence presented here, along with previous observations, suggests that whale sharks may change their feeding strategy from suction to lunge-feeding when other predators corner schooling fish.

Confronting assumptions about prey selection by lunge‐feeding whales using a process‐based model

Abstract The relative energetic benefits of foraging on one type of prey rather than another are not easily measured, particularly for large free‐ranging predators. Nonetheless, assumptions about preferred and alternative prey are frequently made when predicting how a predator may impact its environment, adapt to environmental change or interact with human activities. We developed and implemented a process‐based model to investigate the potential energetic benefit (PEB) of in situ foraging opportunities in rorqual whales. The model integrates and evaluates the energetic importance of measured prey patch characteristics (prey distribution, energy content and predator avoidance) and predator characteristics (morphometrics, foraging tactics and feeding rates). We applied the model to test the assumption that hatchery‐released juvenile salmon are an ‘easy meal’ for humpback whales compared to more common prey: herring and krill. In 11 out of the 13 foraging situations considered, whales were found to be feeding in a manner where net energy gain was greater than the energetic costs of non‐foraging swimming. Humpback whale PEB for hatchery‐released juvenile salmon fell within the range of the PEB for krill and herring but varied by species, from relatively high PEB for chum salmon to relatively low for coho salmon. Our model provides behavioural insight as well, indicating that shallow feeding may be more important for reducing energy expenditure through slower lunge speeds than for increasing prey capture. The model also provides a means of identifying prey patch characteristics, with prey aggregation playing the largest role in determining PEB despite being a poor overall proxy for PEB, supporting the use of the complex model framework. Modelling approaches are especially valuable where they can use reasonable assumptions to substitute for lack of reliable observations, thereby integrating a range of interacting factors into a single framework. Additionally, because process‐based models can be used to make predictions outside the range of previously observed conditions, they will be increasingly useful in a changing climate. A free Plain Language Summary can be found within the Supporting Information of this article.

Predator‐scale spatial analysis of intra‐patch prey distribution reveals the energetic drivers of rorqual whale super‐group formation

Abstract Animals are distributed relative to the resources they rely upon, often scaling in abundance relative to available resources. Yet, in heterogeneously distributed environments, describing resource availability at relevant spatial scales remains a challenge in ecology, inhibiting understanding of predator distribution and foraging decisions. We investigated the foraging behaviour of two species of rorqual whales within spatially limited and numerically extraordinary super‐aggregations in two oceans. We additionally described the lognormal distribution of prey data at species‐specific spatial scales that matched the predator's unique lunge‐feeding strategy. Here we show that both humpback whales off South Africa's west coast and blue whales off the US west coast perform more lunges per unit time within these aggregations than when foraging individually, and that the biomass within gulp‐sized parcels was on average higher and more tightly distributed within super‐group‐associated prey patches, facilitating greater energy intake per feeding event as well as increased feeding rates. Prey analysis at predator‐specific spatial scales revealed a stronger association of super‐groups with patches containing relatively high geometric mean biomass and low geometric standard deviations than with arithmetic mean biomass, suggesting that the foraging decisions of rorqual whales may be more influenced by the distribution of high‐biomass portions of a patch than total biomass. The hierarchical distribution of prey in spatially restricted, temporally transient, super‐group‐associated patches demonstrated high biomass and less variable distributions that facilitated what are likely near‐minimum intervals between feeding events. Combining increased biomass with increased foraging rates implied that overall intake rates of whales foraging within super‐groups were approximately double those of whales foraging in other environments. Locating large, high‐quality prey patches via the detection of aggregation hotspots may be an important aspect of rorqual whale foraging, one that may have been suppressed when population sizes were anthropogenically reduced in the 20th century to critical lows. A free Plain Language Summary can be found within the Supporting Information of this article.

Up in the air: drone images reveal underestimation of entanglement rates in large rorqual whales

Entanglement in fishing gear is a significant threat to many cetaceans. For the 2 largest species, the blue whaleBalaenoptera musculusand the fin whaleB. physalus, reports of entangled individuals are rare, leading to the assumption that entanglements are not common. Studies of interaction with fisheries in other species often rely on the presence of scars from previous entanglements. Here, scar detection rates were first examined in humpbackMegaptera novaeangliae, fin and blue whales using standard vessel-based photo-identification photographs collected between 2009 and 2016 in the Gulf of St. Lawrence, Canada. We then examined aerial images of fin whales collected with a drone in 2018 and 2019 and compared both methods. Entanglement rates were 6.5% for fin and 13.1% for blue whales using photo-identification images of individuals. Prominent scarring was observed around the tail and caudal peduncle, visible only when animals lifted those body sections above water when diving. For the small subset of pictures which captured the entire caudal peduncle, entanglement rates ranged between 60% for blue and 80% for fin whales. This result was similar to the 85% entanglement rate estimated in humpback whales. The assessment of aerial-based photography yielded an entanglement rate of 44.1 to 54.7% in fin whales. Scars were always around the peduncle, often the tail, rarely the dorsal fin and never around the pectoral fins, while the mouth cannot be examined from above. Thus, in species that do not regularly expose their tail or peduncle, aerial imagery is the preferred method to quantify entanglement rates by assessment of scars.

Whales sneak up on their prey by hiding in plain sight

![Graphic][1] Rorqual whales, including the humpback whale ( Megaptera novaeangliae ), are large and fast. But their massive bulk isn't particularly manoeuvrable; imagine trying to catch a mosquito with a passenger jet. For these animals that hunt small and evasive fish, their poor