Lunge filter feeding biomechanics constrain rorqual foraging ecology across scale.
The Journal of experimental biology
Fundamental scaling relationships influence the physiology of vital rates, which in turn shape the ecology and evolution of organisms. For diving mammals, benefits conferred by large body size include reduced transport costs and enhanced breath-holding capacity, thereby increasing overall foraging efficiency. Rorqual whales feed by engulfing a large mass of prey-laden water at high speed and filtering it through baleen plates. However, as engulfment capacity increases with body length (Engulfment Volume Body Length 3.57), the surface area of the baleen filter does not increase proportionally (Baleen Area Body Length1.82), and thus the filtration time of larger rorquals predictably increases as the baleen surface area must filter a disproportionally large amount of water. We predicted that filtration time should scale with body length to the power of 1.75 (Filter Time Body Length1.75 ) We tested this hypothesis on four rorqual species using multi-sensor tags with corresponding unoccupied aircraft systems (UAS) -based body length estimates. We found that filter time scales with body length to the power of 1.79 (95% CI: 1.61 - 1.97). This result highlights a scale-dependent trade-off between engulfment capacity and baleen area that creates a biomechanical constraint to foraging through increased filtration time. Consequently, larger whales must target high density prey patches commensurate to the gulp size to meet their increased energetic demands. If these optimal patches are absent, larger rorquals may experience reduced foraging efficiency compared to smaller whales if they do not match their engulfment capacity to the size of targeted prey aggregations.
View details for DOI 10.1242/jeb.224196
View details for PubMedID 32820028
Seasonal activity levels of a farm-island population of striated caracaras (Phalcoboenus australis) in the Falkland Islands
View details for DOI 10.1186/s40317-020-00214-y
- A Case Study of a Near Vessel Strike of a Blue Whale: Perceptual Cues and Fine-Scale Aspects of Behavioral Avoidance FRONTIERS IN MARINE SCIENCE 2019; 6
Extreme bradycardia and tachycardia in the world's largest animal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2019; 116 (50): 25329–32
The biology of the blue whale has long fascinated physiologists because of the animal's extreme size. Despite high energetic demands from a large body, low mass-specific metabolic rates are likely powered by low heart rates. Diving bradycardia should slow blood oxygen depletion and enhance dive time available for foraging at depth. However, blue whales exhibit a high-cost feeding mechanism, lunge feeding, whereby large volumes of prey-laden water are intermittently engulfed and filtered during dives. This paradox of such a large, slowly beating heart and the high cost of lunge feeding represents a unique test of our understanding of cardiac function, hemodynamics, and physiological limits to body size. Here, we used an electrocardiogram (ECG)-depth recorder tag to measure blue whale heart rates during foraging dives as deep as 184 m and as long as 16.5 min. Heart rates during dives were typically 4 to 8 beats min-1 (bpm) and as low as 2 bpm, while after-dive surface heart rates were 25 to 37 bpm, near the estimated maximum heart rate possible. Despite extreme bradycardia, we recorded a 2.5-fold increase above diving heart rate minima during the powered ascent phase of feeding lunges followed by a gradual decrease of heart rate during the prolonged glide as engulfed water is filtered. These heart rate dynamics explain the unique hemodynamic design in rorqual whales consisting of a large-diameter, highly compliant, elastic aortic arch that allows the aorta to accommodate blood ejected by the heart and maintain blood flow during the long and variable pauses between heartbeats.
View details for DOI 10.1073/pnas.1914273116
View details for Web of Science ID 000502577500056
View details for PubMedID 31767746
View details for PubMedCentralID PMC6911174
A low-cost, open-source inertial movement GPS logger for eco-physiology applications.
The Journal of experimental biology
Open-source technology has been increasingly used for developing low-cost animal-borne bio-loggers, however, a gap remains for a bio-logger that records both inertial movement and GPS positions. We address this need with the Tapered Wings Logger (TWLogger), an archival bio-logger that records high-resolution (e.g. 50-Hz) tri-axial accelerometry and magnetometry, temperature, and GPS. The TWLogger can be built for 90 USD, accepts user-defined sampling parameters, and with a 500-mAh battery weighs 25-g. We provide publicly available build instructions and custom analysis scripts. Bench tests recorded 50-Hz inertial movement and 2-min GPS for 31.8 ± 2.2 h (mean±SD, n=6) with GPS accuracy within 10.9±13.6 m. Field deployments on a medium-sized bird of prey in the wild achieved similar results (n=13). The customizable TWLogger has wide-ranging application across systems and thus offers a practical solution for eco-physiology applications.
View details for DOI 10.1242/jeb.211136
View details for PubMedID 31753906
- The advantages of diving deep: Fin whales quadruple their energy intake when targeting deep krill patches FUNCTIONAL ECOLOGY 2019
- Differential Vulnerability to Ship Strikes Between Day and Night for Blue, Fin, and Humpback Whales Based on Dive and Movement Data From Medium Duration Archival Tags FRONTIERS IN MARINE SCIENCE 2019; 6
Context-dependent variability in blue whale acoustic behaviour
ROYAL SOCIETY OPEN SCIENCE
2018; 5 (8): 180241
Acoustic communication is an important aspect of reproductive, foraging and social behaviours for many marine species. Northeast Pacific blue whales (Balaenoptera musculus) produce three different call types-A, B and D calls. All may be produced as singular calls, but A and B calls also occur in phrases to form songs. To evaluate the behavioural context of singular call and phrase production in blue whales, the acoustic and dive profile data from tags deployed on individuals off southern California were assessed using generalized estimating equations. Only 22% of all deployments contained sounds attributed to the tagged animal. A larger proportion of tagged animals were female (47%) than male (13%), with 40% of unknown sex. Fifty per cent of tags deployed on males contained sounds attributed to the tagged whale, while only a few (5%) deployed on females did. Most calls were produced at shallow depths (less than 30 m). Repetitive phrasing (singing) and production of singular calls were most common during shallow, non-lunging dives, with the latter also common during surface behaviour. Higher sound production rates occurred during autumn than summer and they varied with time-of-day: singular call rates were higher at dawn and dusk, while phrase production rates were highest at dusk and night.
View details for DOI 10.1098/rsos.180241
View details for Web of Science ID 000443443000040
View details for PubMedID 30225013
View details for PubMedCentralID PMC6124089