Abstract:To understand how predators optimize foraging strategies, extensive knowledge of predator behavior and prey distribution is needed. Blue whales employ an energetically demanding lunge feeding method that requires the whales to selectively feed where energetic gain exceeds energetic loss, while also balancing oxygen consumption, breath holding capacity, and surface recuperation time. Hence, blue whale foraging behavior is primarily driven by krill patch density and depth, but many studies have not fully conside… Show more
“…Studies focused on estimating abundance or density of baleen whales in a particular geographic region (hereafter referred to as population sampling) and, 2. Studies examining individual animal behaviour [150], morphology [151], pigmentation patterns, and a range of health and welfare metrics such as scarring and entanglement rates [152], respiratory microbiomes [13,153], body size and condition [126], and even internal body temperature [154] (hereafter referred to as individual sampling). Distinct operational protocols for these two general application types are required, as different aircraft, sensors, control systems and flight plans are needed to safely and efficiently collect robust data.…”
Section: Behavioural Impacts Of Drones On Dolphinsmentioning
The use of drones to study marine animals shows promise for the examination of numerous aspects of their ecology, behaviour, health and movement patterns. However, the responses of some marine phyla to the presence of drones varies broadly, as do the general operational protocols used to study them. Inconsistent methodological approaches could lead to difficulties comparing studies and can call into question the repeatability of research. This review draws on current literature and researchers with a wealth of practical experience to outline the idiosyncrasies of studying various marine taxa with drones. We also outline current best practice for drone operation in marine environments based on the literature and our practical experience in the field. The protocols outlined herein will be of use to researchers interested in incorporating drones as a tool into their research on marine animals and will help form consistent approaches for drone-based studies in the future.
“…Studies focused on estimating abundance or density of baleen whales in a particular geographic region (hereafter referred to as population sampling) and, 2. Studies examining individual animal behaviour [150], morphology [151], pigmentation patterns, and a range of health and welfare metrics such as scarring and entanglement rates [152], respiratory microbiomes [13,153], body size and condition [126], and even internal body temperature [154] (hereafter referred to as individual sampling). Distinct operational protocols for these two general application types are required, as different aircraft, sensors, control systems and flight plans are needed to safely and efficiently collect robust data.…”
Section: Behavioural Impacts Of Drones On Dolphinsmentioning
The use of drones to study marine animals shows promise for the examination of numerous aspects of their ecology, behaviour, health and movement patterns. However, the responses of some marine phyla to the presence of drones varies broadly, as do the general operational protocols used to study them. Inconsistent methodological approaches could lead to difficulties comparing studies and can call into question the repeatability of research. This review draws on current literature and researchers with a wealth of practical experience to outline the idiosyncrasies of studying various marine taxa with drones. We also outline current best practice for drone operation in marine environments based on the literature and our practical experience in the field. The protocols outlined herein will be of use to researchers interested in incorporating drones as a tool into their research on marine animals and will help form consistent approaches for drone-based studies in the future.
“…Physical properties of the water column structure in the Kahurangi upwelling system, including cooler surface temperatures and sub-surface water column features ( e.g. mixed layer depth, thermocline temperature, thermocline strength), lead to enhanced krill availability, and consequently increased foraging opportunities for blue whales in the summertime 21 , 44 . Figure 1 Map of the study region within the South Taranaki Bight (STB) of New Zealand, with location denoted by the white rectangle on inset map in the upper right panel.…”
Understanding relationships between physical drivers and biological response is central to advancing ecological knowledge. Wind is the physical forcing mechanism in coastal upwelling systems, however lags between wind input and biological responses are seldom quantified for marine predators. Lags were examined between wind at an upwelling source, decreased temperatures along the upwelling plume’s trajectory, and blue whale occurrence in New Zealand’s South Taranaki Bight region (STB). Wind speed and sea surface temperature (SST) were extracted for austral spring–summer months between 2009 and 2019. A hydrophone recorded blue whale vocalizations October 2016-March 2017. Timeseries cross-correlation analyses were conducted between wind speed, SST at different locations along the upwelling plume, and blue whale downswept vocalizations (D calls). Results document increasing lag times (0–2 weeks) between wind speed and SST consistent with the spatial progression of upwelling, culminating with increased D call density at the distal end of the plume three weeks after increased wind speeds at the upwelling source. Lag between wind events and blue whale aggregations (n = 34 aggregations 2013–2019) was 2.09 ± 0.43 weeks. Variation in lag was significantly related to the amount of wind over the preceding 30 days, which likely influences stratification. This study enhances knowledge of physical-biological coupling in upwelling ecosystems and enables improved forecasting of species distribution patterns for dynamic management.
“…Muscle use is closely linked to the manner in which engulfment is carried out. In krill-feeding lunges, bio-logging sensor kinematics ( Cade et al 2016 ) and drone footage ( Torres et al 2020 ) suggest most large rorquals to engulf the prey and water while decelerating from a state of high velocity to one of low but non-zero velocity ( Fig. 1 ), in a mode denoted here as coasting engulfment ( Potvin et al 2020 ).…”
Humpback and blue whales are large baleen-bearing cetaceans which use a unique prey-acquisition strategy - lunge feeding - to engulf entire patches of large plankton or schools of forage fish and the water in which they are embedded. Dynamically, and while foraging on krill, lunge-feeding incurs metabolic expenditures estimated at up to 20.0 MJ. Because of prey abundance and its capture in bulk, lunge feeding is carried out at high acquired-to-expended energy ratios of up to 30 at the largest body sizes (∼27m). We use bio-logging tag data and the work-energy theorem to show that when krill-feeding at depth while using a wide range of prey approach swimming speeds (2 to 5m/s), rorquals generate significant and widely varying metabolic power output during engulfment, typically ranging from 10 to 50 times the basal metabolic rate of land mammals. At equal prey field density, such output variations lower their feeding efficiency 2- to 3-fold at high foraging speeds, thereby allowing slow and smaller rorquals to feed more efficiently than fast and larger rorquals. The analysis also shows how the slowest speeds of harvest so far measured may be connected to the biomechanics of the buccal cavity and the prey’s ability to collectively avoid engulfment. Such minimal speeds are important as they generate the most efficient lunges.
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