Rorqual whales exhibit an extreme lunge filter-feeding strategy characterized by acceleration to high speed and engulfment of a large volume of prey-laden water 1–4. Although tagging studies have ...quantified the kinematics of lunge feeding, the timing of engulfment relative to body acceleration has been modeled conflictingly because it could never be directly measured 5–7. The temporal coordination of these processes has a major impact on the hydrodynamics and energetics of this high-cost feeding strategy 5–9. If engulfment and body acceleration are temporally distinct, the overall cost of this dynamic feeding event would be minimized. However, greater temporal overlap of these two phases would theoretically result in higher drag and greater energetic costs. To address this discrepancy, we used animal-borne synchronized video and 3D movement sensors to quantify the kinematics of both the skull and body during feeding events. Krill-feeding blue and humpback whales exhibited temporally distinct acceleration and engulfment phases, with humpback whales reaching maximum gape earlier than blue whales. In these whales, engulfment coincided largely with body deceleration; however, humpback whales pursuing more agile fish demonstrated highly variable coordination of skull and body kinematics in the context of complex prey-herding techniques. These data suggest that rorquals modulate the coordination of acceleration and engulfment to optimize foraging efficiency by minimizing locomotor costs and maximizing prey capture. Moreover, this newfound kinematic diversity observed among rorquals indicates that the energetic efficiency of foraging is driven both by the whale’s engulfment capacity and the comparative locomotor capabilities of predator and prey.
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•Tags with both video and 3D accelerometry were deployed on feeding rorquals•Skull movement could be observed in concert with animal orientation and motion•Lunging whales displayed prey-dependent inter- and intra-species kinematic diversity•Humpback whales most likely sacrifice energy efficiency to increase foraging flexibility
Rorqual lunge feeding has been assumed to be kinematically similar across species. Cade et al. use new video and accelerometry tags to show that blue whales, krill specialists, and humpback whales, foraging generalists, have similarly stereotypical lunges on krill—but humpbacks feeding on fish demonstrate kinematic diversity in lunge timing.
The unique engulfment filtration strategy of microphagous rorqual whales has evolved relatively recently (<5 Ma) and exploits extreme predator/prey size ratios to overcome the maneuverability ...advantages of swarms of small prey, such as krill. Forage fish, in contrast, have been engaged in evolutionary arms races with their predators for more than 100 million years and have performance capabilities that suggest they should easily evade whale-sized predators, yet they are regularly hunted by some species of rorqual whales. To explore this phenomenon, we determined, in a laboratory setting, when individual anchovies initiated escape from virtually approaching whales, then used these results along with in situ humpback whale attack data to model how predator speed and engulfment timing affected capture rates. Anchovies were found to respond to approaching visual looming stimuli at expansion rates that give ample chance to escape from a sea lion-sized predator, but humpback whales could capture as much as 30–60% of a school at once because the increase in their apparent (visual) size does not cross their prey’s response threshold until after rapid jaw expansion. Humpback whales are, thus, incentivized to delay engulfment until they are very close to a prey school, even if this results in higher hydrodynamic drag. This potential exaptation of a microphagous filter feeding strategy for fish foraging enables humpback whales to achieve 7× the energetic efficiency (per lunge) of krill foraging, allowing for flexible foraging strategies that may underlie their ecological success in fluctuating oceanic conditions.
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 as 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
on wild cetaceans spanning ∼3 to >20 m in length using two types of suction cup-attached tag 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.
Southern Hemisphere humpback whales (Megaptera novaeangliae) generally undertake annual migrations from polar summer feeding grounds to winter calving and nursery grounds in subtropical and tropical ...coastal waters. Evidence for such migrations arises from seasonality of historic whaling catches by latitude, Discovery and natural mark returns, and results of satellite tagging studies. Feeding is generally believed to be limited to the southern polar region, where Antarctic krill (Euphausia superba) has been identified as the primary prey item. Non-migrations and / or suspended migrations to the polar feeding grounds have previously been reported from a summer presence of whales in the Benguela System, where feeding on euphausiids (E. lucens), hyperiid amphipods (Themisto gaudichaudii), mantis shrimp (Pterygosquilla armata capensis) and clupeid fish has been described. Three recent research cruises (in October/November 2011, October/November 2014 and October/November 2015) identified large tightly-spaced groups (20 to 200 individuals) of feeding humpback whales aggregated over at least a one-month period across a 220 nautical mile region of the southern Benguela System. Feeding behaviour was identified by lunges, strong milling and repetitive and consecutive diving behaviours, associated bird and seal feeding, defecations and the pungent "fishy" smell of whale blows. Although no dedicated prey sampling could be carried out within the tightly spaced feeding aggregations, observations of E. lucens in the region of groups and the full stomach contents of mantis shrimp from both a co-occurring predatory fish species (Thyrsites atun) and one entangled humpback whale mortality suggest these may be the primary prey items of at least some of the feeding aggregations. Reasons for this recent novel behaviour pattern remain speculative, but may relate to increasing summer humpback whale abundance in the region. These novel, predictable, inter-annual, low latitude feeding events provide considerable potential for further investigation of Southern Hemisphere humpback feeding behaviours in these relatively accessible low-latitude waters.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Cetaceans are known for their intelligence and display of complex behaviours including object use. For example, bowhead whales (Balaena mysticetus) are known to rub on rocks and some humpback whale ...(Megaptera novaeangliae) populations undertake lateral bottom feeding. Such underwater behaviour is difficult to observe but can play a critical role in the whales’ survival and well-being. Distinguishing social behaviours from those which serve a specific function remains challenging due to a lack of direct observations and detailed descriptions of such behaviours. A CATS (Customized Animal Tracking Solutions) suction cup tag with on board video and a 3D inertial measurement unit was deployed on three different humpback whales to assess their behaviour in the Gold Coast bay, Australia. Here, we present evidence of humpback whales (tagged and untagged individuals) performing bottom contact with prolonged rolling on sandy substrate. In addition, we showed that fish were actively feeding from the whales’ skin during this behaviour. We detail the behaviour and discuss possible drivers, with a focus on cetacean innovation, possible ectoparasite removal, and habitat preferences.
Marine predators face the challenge of reliably finding prey that is patchily distributed in space and time. Predators make movement decisions at multiple spatial and temporal scales, yet we have a ...limited understanding of how habitat selection at multiple scales translates into foraging performance. In the ocean, there is mounting evidence that submesoscale (i.e. less than 100 km) processes drive the formation of dense prey patches that should hypothetically provide feeding hot spots and increase predator foraging success. Here, we integrated environmental remote-sensing with high-resolution animal-borne biologging data to evaluate submesoscale surface current features in relation to the habitat selection and foraging performance of blue whales in the California Current System. Our study revealed a consistent functional relationship in which blue whales disproportionately foraged within dynamic aggregative submesoscale features at both the regional and feeding site scales across seasons, regions and years. Moreover, we found that blue whale feeding rates increased in areas with stronger aggregative features, suggesting that these features indicate areas of higher prey density. The use of fine-scale, dynamic features by foraging blue whales underscores the need to take these features into account when designating critical habitat and may help inform strategies to mitigate the impacts of human activities for the species.
Understanding the function of baleen whale acoustic signals requires the investigation of calling behaviors relative to location, timing, and behavioral state. Previous studies of gray whale (
...Eschrichtius robustus
) vocal behavior have principally used passive recorders and been conducted primarily on breeding grounds and along migratory routes, and not areas associated with foraging. We conducted an analysis of accelerometer and acoustic data collected during 12 deployments of animal-borne tags in 2016, 2019, and 2021 on gray whales that return annually to northern Puget Sound, Washington. We identified 141 calls from gray whales in approximately 128 hours of accelerometer and/or acoustic data collected from tag deployments. The most prominent were pulsive ‘rumble-like’ calls, upsweeping tones, and moans. Using the tag’s accelerometer to identify calls produced by tagged animals enabled us to explore the behavioral context behind call production, revealing that vocalizations were made primarily at slow speeds (mean 1.03 ± 0.26 m/s
-1
), shallow depths (mean 7.63 ± 4.99 m), and temporally proximate to surface behavior (mean 43.3 ± 39.66 sec) most similar to non-foraging associated depth (mean 5.78 ± 1.46 m and speed (mean 1.46 ± 1.11 m/s
-1
) profiles. Vocalizations originating from the tagged animal occurred closer to the conclusion of a foraging event (mean 87.7 ± 119.32 min) than the beginning, with only 7% of all calls occurring during periods of feeding. This study demonstrates that gray whales remain vocal on foraging grounds and that call-associated accelerometry signals can be a valuable tool in identifying individual callers in animal-borne acoustic data.
Uncovering the mechanisms and implications of natural behavior is a goal that unites many fields of biology. Yet, the diversity, flexibility, and multi-scale nature of these behaviors often make ...understanding elusive. Here, we review studies of animal pursuit and evasion — two special classes of behavior where theory-driven experiments and new modeling techniques are beginning to uncover the general control principles underlying natural behavior. A key finding of these studies is that intricate sequences of pursuit and evasion behavior can often be constructed through simple, repeatable rules that link sensory input to motor output: we refer to these rules as behavioral algorithms. Identifying and mathematically characterizing these algorithms has led to important insights, including the discovery of guidance rules that attacking predators use to intercept mobile prey, and coordinated neural and biomechanical mechanisms that animals use to avoid impending collisions. Here, we argue that algorithms provide a good starting point for studies of natural behavior more generally. Rather than beginning at the neural or ecological levels of organization, we advocate starting in the middle, where the algorithms that link sensory input to behavioral output can provide a solid foundation from which to explore both the implementation and the ecological outcomes of behavior. We review insights that have been gained through such an algorithmic approach to pursuit and evasion behaviors. From these, we synthesize theoretical principles and lay out key modeling tools needed to apply an algorithmic approach to the study of other complex natural behaviors.
Hein et al. review studies of animal pursuit and evasion behavior to show how simple, repeatable behavioral rules, or ‘behavioral algorithms’, have become central to current understanding of how these impressive natural behaviors are generated. They argue that identifying and modeling behavioral algorithms could provide a powerful approach for answering a much broader set of emerging questions about the mechanisms, ecology, and evolution of natural behavior.
The scale dependence of locomotor factors has long been studied in comparative biomechanics, but remains poorly understood for animals at the upper extremes of body size. Rorqual baleen whales ...include the largest animals, but we lack basic kinematic data about their movements and behavior below the ocean surface. Here, we combined morphometrics from aerial drone photogrammetry, whale-borne inertial sensing tag data and hydrodynamic modeling to study the locomotion of five rorqual species. We quantified changes in tail oscillatory frequency and cruising speed for individual whales spanning a threefold variation in body length, corresponding to an order of magnitude variation in estimated body mass. Our results showed that oscillatory frequency decreases with body length (∝length
) while cruising speed remains roughly invariant (∝length
) at 2 m s
We compared these measured results for oscillatory frequency against simplified models of an oscillating cantilever beam (∝length
) and an optimized oscillating Strouhal vortex generator (∝length
). The difference between our length-scaling exponent and the simplified models suggests that animals are often swimming non-optimally in order to feed or perform other routine behaviors. Cruising speed aligned more closely with an estimate of the optimal speed required to minimize the energetic cost of swimming (∝length
). Our results are among the first to elucidate the relationships between both oscillatory frequency and cruising speed and body size for free-swimming animals at the largest scale.
In the marine environment, dynamic physical processes shape biological productivity and predator-prey interactions across multiple scales. Identifying pathways of physical-biological coupling is ...fundamental to understand the functioning of marine ecosystems yet it is challenging because the interactions are difficult to measure. We examined submesoscale (less than 100 km) surface current features using remote sensing techniques alongside ship-based surveys of krill and baleen whale distributions in the California Current System. We found that aggregative surface current features, represented by Lagrangian coherent structures (LCS) integrated over temporal scales between 2 and 10 days, were associated with increased (a) krill density (up to 2.6 times more dense), (b) baleen whale presence (up to 8.3 times more likely) and (c) subsurface seawater density (at depths up to 10 m). The link between physical oceanography, krill density and krill-predator distributions suggests that LCS are important features that drive the flux of energy and nutrients across trophic levels. Our results may help inform dynamic management strategies aimed at reducing large whales ship strikes and help assess the potential impacts of environmental change on this critical ecosystem.
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