Lunge feeding by rorqual whales (Balaenopteridae) is associated with a high energetic cost that decreases diving capacity, thereby limiting access to dense prey patches at depth. Despite this cost, rorquals exhibit high rates of lipid deposition and extremely large maximum body size. To address this paradox, we integrated kinematic data from digital tags with unsteady hydrodynamic models to estimate the energy budget for lunges and foraging dives of blue whales (Balaenoptera musculus), the largest rorqual and living mammal. Our analysis suggests that, despite the large amount of mechanical work required to lunge feed, a large amount of prey and, therefore, energy is obtained during engulfment. Furthermore, we suggest that foraging efficiency for blue whales is significantly higher than for other marine mammals by nearly an order of magnitude, but only if lunges target extremely high densities of krill. The high predicted efficiency is attributed to the enhanced engulfment capacity, rapid filter rate and low mass-specific metabolic rate associated with large body size in blue whales. These results highlight the importance of high prey density, regardless of prey patch depth, for efficient bulk filter feeding in baleen whales and may explain some diel changes in foraging behavior in rorqual whales.

/pdf/mechanics-hydrodynamics-and-energetics-of-blue-whale-lunge-4z4ew8yuon.pdf

Mechanics, hydrodynamics and energetics of blue whale lunge feeding: efficiency dependence on krill density

Many marine animals use sound passively or actively for communication, foraging, predator avoidance, navigation, and to sense their environment. The advent of acoustic recording tags has allowed biologists to get the on-animal perspective of the sonic environment and, in combi- nation with movement sensors, to relate sounds to the activities of the tagged animal. These power- ful tools have led to a wide range of insights into the behaviour of marine animals and have opened new opportunities for studying the ways they interact with their environment. Acoustic tags demand new analysis methods and careful experimental design to optimize the consistency between research objectives and the realistic performance of the tags. Technical details to consider are the suitability of the tag attachment to a given species, the accuracy of the tag sensors, and the recording and attach- ment duration of the tag. Here we consider the achievements, potential, and limitations of acoustic recording tags in studying the behaviour, habitat use and sensory ecology of marine mammals, the taxon to which this technology has been most often applied. We examine the application of acoustic tags to studies of vocal behaviour, foraging ecology, acoustic tracking, and the effects of noise to assess both the breadth of applications and the specific issues that arise in each.

/pdf/studying-the-behaviour-and-sensory-ecology-of-marine-mammals-16d5cg6oot.pdf

Studying the behaviour and sensory ecology of marine mammals using acoustic recording tags: a review

Ultra-High Foraging Rates of Harbor Porpoises Make Them Vulnerable to Anthropogenic Disturbance

Summary

To gain insight into the foraging behaviour of deep diving seals, we developed a long-term jaw-motion recorder, which successfully measured the feeding attempts of four post-breeding female northern elephant seals for 55–68 days during migration in the north-east Pacific Ocean.


Using the jaw-motion recorders in conjunction with satellite tracking data, we first reveal the three-dimensional fine-scale distribution of deep foraging activity in the north-east Pacific Ocean.


A large number of jaw-motion events (23 817–58 766 during 2925–4178 dives, per seal) were observed with diel patterns suggesting their dependency on small mesopelagic prey. Calculations using at-sea field metabolic-rate and the photographs concurrently obtained by the head-mounted camera indicated feeding on small mesopelagic prey (10–20 g) including lantern fish (F. Myctophidae).


The foraging behaviour of the northern elephant seal contrasts with echolocating toothed whales, which make fewer feeding attempts, suggesting the whales forage more selectively. We hypothesize that the continuous diving mode exhibited by this seal could be attributed to their reliance on small prey and their less efficient ‘passive sensors’ for prey search, that is, their vision or whiskers to detect prey.

https://besjournals.onlinelibrary.wiley.com/doi/pdf/10.1111/1365-2435.12083

Unravelling the mysteries of a mesopelagic diet: a large apex predator specializes on small prey

Porpoise echolocation has been studied previously, mainly in target detection experiments using stationed animals and steel sphere targets, but little is known about the acoustic behaviour of free-swimming porpoises echolocating for prey. Here, we used small onboard sound and orientation recording tags to study the echolocation behaviour of free-swimming trained porpoises as they caught dead, freely drifting fish. We analysed porpoise echolocation behaviour leading up to and following prey capture events, including variability in echolocation in response to vision restriction, prey species, and individual porpoise tested. The porpoises produced echolocation clicks as they searched for the fish, followed by fast-repetition-rate clicks (echolocation buzzes) when acquiring prey. During buzzes, which usually began when porpoises were about 1-2 body lengths from prey, tag-recorded click levels decreased by about 10 dB, click rates increased to over 300 clicks per second, and variability in body orientation (roll) increased. Buzzes generally continued beyond the first contact with the fish, and often extended until or after the end of prey handling. This unexplained continuation of buzzes after prey capture raises questions about the function of buzzes, suggesting that in addition to providing detailed information on target location during the capture, they may serve additional purposes such as the relocation of potentially escaping prey. We conclude that porpoises display the same overall acoustic prey capture behaviour seen in larger toothed whales in the wild, albeit at a faster pace, clicking slowly during search and approach phases and buzzing during prey capture.

Acoustic behaviour of echolocating porpoises during prey capture

Summary 1 Empirical testing of optimal foraging models for breath-hold divers has been difficult Here we report data from sound and movement recording DTags placed on 23 short-finned pilot whales off Tenerife to study the foraging strategies used to catch deep-water prey 2 Day and night foraging dives had a maximum depth and duration of 1018 m and 21 min Vocal behaviour during dives was consistent with biosonar-based foraging, with long series of echolocation clicks interspersed with buzzes Similar buzzes have been associated with prey capture attempts in other echolocating species 3 Foraging dives seemed to adapt to circadian rhythms Deep dives during the day were deeper, but contained fewer buzzes (median 1), than night-time deep dives (median 5 buzzes) 4 In most deep (540‐1019 m) daytime dives with buzzes, a downward directed sprint reaching up to 9 m s ‐1 occurred just prior to a buzz and coincided with the deepest point in the dive, suggestive of a chase after escaping prey 5 A large percentage (10‐36%) of the drag-related locomotion cost of these dives (15 min long) is spent in sprinting (19‐79 s) This energetic foraging tactic focused on a single or few prey items has not been observed previously in deep-diving mammals but resembles the high-risk/high-gain strategy of some terrestrial hunters such as cheetahs 6 Deep sprints contrast with the expectation that deep-diving mammals will swim at moderate speeds optimized to reduce oxygen consumption and maximize foraging time at depth Pilot whales may have developed this tactic to target a deep-water niche formed by large/calorific/fast moving prey such as giant squid

/pdf/cheetahs-of-the-deep-sea-deep-foraging-sprints-in-short-27t6iu9oy6.pdf

Cheetahs of the deep sea: deep foraging sprints in short-finned pilot whales off Tenerife (Canary Islands)

https://dialnet.unirioja.es/descarga/articulo/2656785.pdf

Francisca Díaz

Papers

Cheetahs of the deep sea: deep foraging sprints in short-finned pilot whales off Tenerife (Canary Islands)

Nuevos descubrimientos sobre cetáceos de buceo profundo en Canarias: relación con su conservación