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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. 

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.

 

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. 

The largest animals are baleen filter feeders that exploit large aggregations of small-bodied plankton. Although this feeding mechanism has evolved multiple times in marine vertebrates, rorqual whales exhibit a distinct lunge filter feeding mode that requires extreme physiological adaptations—most of which remain poorly understood. Here, we review the biomechanics of the lunge feeding mechanism in rorqual whales that underlies their extraordinary foraging performance and gigantic body size. 

The scale-dependence of locomotor performance has long been studied in comparative biomechanics, but how animals move in their natural environment remains poorly understood. At the upper extreme of body mass, baleen whales (Mysteci) are predictably among the most efficient swimmers in terms of cost of transport through a combination of low mass-specific metabolic rate and high hydrodynamic efficiency. Such efficiency enables these oceanic giants to migrate vast distances and thus underlies a major component of their life history and functional ecology. However, we lack even basic kinematic data for most species. Here we combine morphometric data from flyover drone photography, whale-borne inertial sensing tag data, and computational fluid dynamics (CFD) to study the locomotion of four rorqual species. Focusing on fundamental kinematic parameters such as tailbeat frequency and forward speed, we quantified spatial and temporal changes in swimming performance for individual whales and compared these metrics across a wide body mass range. We also calculated thrust and drag using lunate tail hydrodynamic modeling (Fish 1993), and compared these values against those from CFD simulations carried out with realistic rigid-body models. Differences in excess of 100% between the two approaches point to the significant contributions of tail and head heaving to overall drag, and thus the need to account for them in rigid-body CFD simulations. Together these kinematic data and CFD modeling inform a new parametric factor designed at multiplying the rigid-body drag equation to predict the contribution of body heaving unsteady hydrodynamics in cetaceans.