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Noren SR, Rosen DAS. What are the Metabolic Rates of Marine Mammals and What Factors Impact this Value: A review. CONSERVATION PHYSIOLOGY 2023; 11:coad077. [PMID: 37790839 PMCID: PMC10545007 DOI: 10.1093/conphys/coad077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/12/2022] [Revised: 08/22/2023] [Accepted: 09/14/2023] [Indexed: 10/05/2023]
Abstract
Over the past several decades, scientists have constructed bioenergetic models for marine mammals to assess potential population-level consequences following exposure to a disturbance, stressor, or environmental change, such as under the Population Consequences of Disturbance (pCOD) framework. The animal's metabolic rate (rate of energy expenditure) is a cornerstone for these models, yet the cryptic lifestyles of marine mammals, particularly cetaceans, have limited our ability to quantify basal (BMR) and field (FMR) metabolic rates using accepted 'gold standard' approaches (indirect calorimeter via oxygen consumption and doubly labeled water, respectively). Thus, alternate methods have been used to quantify marine mammal metabolic rates, such as extrapolating from known allometric relationships (e.g. Kleiber's mouse to elephant curve) and developing predictive relationships between energy expenditure and physiological or behavioral variables. To understand our current knowledge of marine mammal metabolic rates, we conducted a literature review (1900-2023) to quantify the magnitude and variation of metabolic rates across marine mammal groups. A compilation of data from studies using 'gold standard' methods revealed that BMR and FMR of different marine mammal species ranges from 0.2 to 3.6 and 1.1 to 6.1 x Kleiber, respectively. Mean BMR and FMR varied across taxa; for both measures odontocete levels were intermediate to higher values for otariids and lower values of phocids. Moreover, multiple intrinsic (e.g. age, sex, reproduction, molt, individual) and extrinsic (e.g. food availability, water temperature, season) factors, as well as individual behaviors (e.g. animal at water's surface or submerged, activity level, dive effort and at-sea behaviors) impact the magnitude of these rates. This review provides scientists and managers with a range of reliable metabolic rates for several marine mammal groups as well as an understanding of the factors that influence metabolism to improve the discernment for inputs into future bioenergetic models.
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Affiliation(s)
- S R Noren
- Institute of Marine Science, University of California Santa Cruz, Center for Ocean Health, 115 McAllister Way, Santa Cruz, CA 95060, USA
| | - David A S Rosen
- Marine Mammal Research Unit, Institute for the Oceans and Fisheries, University of British Columbia, 2202 Main Mall, Vancouver, BC, Canada V6T 1Z4
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Moffett ER, Fryxell DC, Benavente JN, Kinnison MT, Palkovacs EP, Symons CC, Simon KS. The effect of pregnancy on metabolic scaling and population energy demand in the viviparous fish Gambusia affinis. Integr Comp Biol 2022; 62:icac099. [PMID: 35767874 DOI: 10.1093/icb/icac099] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Metabolism is a fundamental attribute of all organisms that influences how species affect and are affected by their natural environment. Differences between sexes in ectothermic species may substantially alter metabolic scaling patterns, particularly in viviparous or live-bearing species where females must support their basal metabolic costs and that of their embryos. Indeed, if pregnancy is associated with marked increases in metabolic demand and alters scaling patterns between sexes, this could in turn interact with natural sex ratio variation in nature to affect population-level energy demand. Here, we aimed to understand how sex and pregnancy influence metabolic scaling and how differences between sexes affect energy demand in Gambusia affinis (Western mosquitofish). Using the same method, we measured routine metabolic rate in the field on reproductively active fish and in the laboratory on virgin fish. Our data suggest that changes in energy expenditure related to pregnancy may lead to steeper scaling coefficients in females (b = 0.750) compared to males (b = 0.595). In contrast, virgin females and males had similar scaling coefficients, suggesting negligible sex differences in metabolic costs in reproductively inactive fish. Further, our data suggest that incorporating sex differences in allometric scaling may alter population-level energy demand by as much as 20-28%, with the most pronounced changes apparent in male-biased populations due to the lower scaling coefficient of males. Overall, our data suggest that differences in energy investment in reproduction between sexes driven by pregnancy may alter allometric scaling and population-level energy demand.
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Affiliation(s)
- Emma R Moffett
- Ecology and Evolutionary Biology, University of California, Irvine, USA
| | - David C Fryxell
- School of Environment, The University of Auckland, New Zealand
- Ecology and Evolutionary Biology, The University of California, Santa Cruz, USA
| | - J N Benavente
- School of Environment, The University of Auckland, New Zealand
| | - M T Kinnison
- School of Biology and Ecology,The University of Maine, USA
| | - E P Palkovacs
- Ecology and Evolutionary Biology, The University of California, Santa Cruz, USA
| | - C C Symons
- Ecology and Evolutionary Biology, University of California, Irvine, USA
| | - K S Simon
- School of Environment, The University of Auckland, New Zealand
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Hooker SK, Andrews RD, Arnould JPY, Bester MN, Davis RW, Insley SJ, Gales NJ, Goldsworthy SD, McKnight JC. Fur seals do, but sea lions don't - cross taxa insights into exhalation during ascent from dives. Philos Trans R Soc Lond B Biol Sci 2021; 376:20200219. [PMID: 34121462 PMCID: PMC8200655 DOI: 10.1098/rstb.2020.0219] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/07/2020] [Indexed: 11/12/2022] Open
Abstract
Management of gases during diving is not well understood across marine mammal species. Prior to diving, phocid (true) seals generally exhale, a behaviour thought to assist with the prevention of decompression sickness. Otariid seals (fur seals and sea lions) have a greater reliance on their lung oxygen stores, and inhale prior to diving. One otariid, the Antarctic fur seal (Arctocephalus gazella), then exhales during the final 50-85% of the return to the surface, which may prevent another gas management issue: shallow-water blackout. Here, we compare data collected from animal-attached tags (video cameras, hydrophones and conductivity sensors) deployed on a suite of otariid seal species to examine the ubiquity of ascent exhalations for this group. We find evidence for ascent exhalations across four fur seal species, but that such exhalations are absent for three sea lion species. Fur seals and sea lions are no longer genetically separated into distinct subfamilies, but are morphologically distinguished by the thick underfur layer of fur seals. Together with their smaller size and energetic dives, we suggest their air-filled fur might underlie the need to perform these exhalations, although whether to reduce buoyancy and ascent speed, for the avoidance of shallow-water blackout or to prevent other cardiovascular management issues in their diving remains unclear. This article is part of the theme issue 'Measuring physiology in free-living animals (Part I)'.
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Affiliation(s)
- Sascha K. Hooker
- Sea Mammal Research Unit, Scottish Oceans Institute, University of St Andrews, Fife KY16 8LB, UK
| | | | - John P. Y. Arnould
- School of Life and Environmental Sciences, Deakin University, Burwood, Victoria 3125, Australia
| | - Marthán N. Bester
- Mammal Research Institute, University of Pretoria, Hatfield 0028, Gauteng, South Africa
| | - Randall W. Davis
- Department of Marine Biology, Texas A&M University, Galveston, TX 77553, USA
| | - Stephen J. Insley
- Department of Biology, University of Victoria, Victoria, British Columbia, Canada, V8P 5C2
- Wildlife Conservation Society Canada, Whitehorse, Yukon Territory, Canada, Y1A 0E9
| | - Nick J. Gales
- Australian Antarctic Division, Kingston, Tasmania 7050, Australia
| | - Simon D. Goldsworthy
- South Australian Research and Development Institute, West Beach, South Australia 5024, Australia
- School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5005, Australia
| | - J. Chris McKnight
- Sea Mammal Research Unit, Scottish Oceans Institute, University of St Andrews, Fife KY16 8LB, UK
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Ladds M, Rosen D, Gerlinsky C, Slip D, Harcourt R. Diving deep into trouble: the role of foraging strategy and morphology in adapting to a changing environment. CONSERVATION PHYSIOLOGY 2020; 8:coaa111. [PMID: 34168880 PMCID: PMC8218901 DOI: 10.1093/conphys/coaa111] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2019] [Revised: 05/02/2020] [Accepted: 11/24/2020] [Indexed: 06/12/2023]
Abstract
Physiology places constraints on an animal's ability to forage and those unable to adapt to changing conditions may face increased challenges to reproduce and survive. As the global marine environment continues to change, small, air-breathing, endothermic marine predators such as otariids (fur seals and sea lions) and particularly females, who are constrained by central place foraging during breeding, may experience increased difficulties in successfully obtaining adequate food resources. We explored whether physiological limits of female otariids may be innately related to body morphology (fur seals vs sea lions) and/or dictate foraging strategies (epipelagic vs mesopelagic or benthic). We conducted a systematic review of the increased body of literature since the original reviews of Costa et al. (When does physiology limit the foraging behaviour of freely diving mammals? Int Congr Ser 2004;1275:359-366) and Arnould and Costa (Sea lions in drag, fur seals incognito: insights from the otariid deviants. In Sea Lions of the World Fairbanks. Alaska Sea Grant College Program, Alaska, USA, pp. 309-324, 2006) on behavioural (dive duration and depth) and physiological (total body oxygen stores and diving metabolic rates) parameters. We estimated calculated aerobic dive limit (cADL-estimated duration of aerobic dives) for species and used simulations to predict the proportion of dives that exceeded the cADL. We tested whether body morphology or foraging strategy was the primary predictor of these behavioural and physiological characteristics. We found that the foraging strategy compared to morphology was a better predictor of most parameters, including whether a species was more likely to exceed their cADL during a dive and the ratio of dive time to cADL. This suggests that benthic and mesopelagic divers are more likely to be foraging at their physiological capacity. For species operating near their physiological capacity (regularly exceeding their cADL), the ability to switch strategies is limited as the cost of foraging deeper and longer is disproportionally high, unless it is accompanied by physiological adaptations. It is proposed that some otariids may not have the ability to switch foraging strategies and so be unable adapt to a changing oceanic ecosystem.
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Affiliation(s)
- Monique Ladds
- Marine Ecosystems Team, Department of Conservation, Wellington 6011, New Zealand
- Marine Predator Research Group, Department of Biological Sciences,
Macquarie University, North Ryde 2113, Australia
| | - David Rosen
- Marine Mammal Research Unit, Institute for the Oceans and Fisheries,
University of British Columbia, Vancouver V6T 1Z4, Canada
| | - Carling Gerlinsky
- Marine Mammal Research Unit, Institute for the Oceans and Fisheries,
University of British Columbia, Vancouver V6T 1Z4, Canada
| | - David Slip
- Marine Predator Research Group, Department of Biological Sciences,
Macquarie University, North Ryde 2113, Australia
- Taronga Conservation Society Australia, Mosman 2088, Australia
| | - Robert Harcourt
- Marine Predator Research Group, Department of Biological Sciences,
Macquarie University, North Ryde 2113, Australia
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Ladds MA, Salton M, Hocking DP, McIntosh RR, Thompson AP, Slip DJ, Harcourt RG. Using accelerometers to develop time-energy budgets of wild fur seals from captive surrogates. PeerJ 2018; 6:e5814. [PMID: 30386705 PMCID: PMC6204822 DOI: 10.7717/peerj.5814] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2018] [Accepted: 09/22/2018] [Indexed: 11/20/2022] Open
Abstract
Background Accurate time-energy budgets summarise an animal's energy expenditure in a given environment, and are potentially a sensitive indicator of how an animal responds to changing resources. Deriving accurate time-energy budgets requires an estimate of time spent in different activities and of the energetic cost of that activity. Bio-loggers (e.g., accelerometers) may provide a solution for monitoring animals such as fur seals that make long-duration foraging trips. Using low resolution to record behaviour may aid in the transmission of data, negating the need to recover the device. Methods This study used controlled captive experiments and previous energetic research to derive time-energy budgets of juvenile Australian fur seals (Arctocephalus pusillus) equipped with tri-axial accelerometers. First, captive fur seals and sea lions were equipped with accelerometers recording at high (20 Hz) and low (1 Hz) resolutions, and their behaviour recorded. Using this data, machine learning models were trained to recognise four states-foraging, grooming, travelling and resting. Next, the energetic cost of each behaviour, as a function of location (land or water), season and digestive state (pre- or post-prandial) was estimated. Then, diving and movement data were collected from nine wild juvenile fur seals wearing accelerometers recording at high- and low- resolutions. Models developed from captive seals were applied to accelerometry data from wild juvenile Australian fur seals and, finally, their time-energy budgets were reconstructed. Results Behaviour classification models built with low resolution (1 Hz) data correctly classified captive seal behaviours with very high accuracy (up to 90%) and recorded without interruption. Therefore, time-energy budgets of wild fur seals were constructed with these data. The reconstructed time-energy budgets revealed that juvenile fur seals expended the same amount of energy as adults of similar species. No significant differences in daily energy expenditure (DEE) were found across sex or season (winter or summer), but fur seals rested more when their energy expenditure was expected to be higher. Juvenile fur seals used behavioural compensatory techniques to conserve energy during activities that were expected to have high energetic outputs (such as diving). Discussion As low resolution accelerometry (1 Hz) was able to classify behaviour with very high accuracy, future studies may be able to transmit more data at a lower rate, reducing the need for tag recovery. Reconstructed time-energy budgets demonstrated that juvenile fur seals appear to expend the same amount of energy as their adult counterparts. Through pairing estimates of energy expenditure with behaviour this study demonstrates the potential to understand how fur seals expend energy, and where and how behavioural compensations are made to retain constant energy expenditure over a short (dive) and long (season) period.
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Affiliation(s)
- Monique A Ladds
- School of Mathematics and Statistics, Victoria University of Wellington, Wellington, New Zealand.,Marine Predator Research Group, Macquarie University, Sydney, New South Wales, Australia
| | - Marcus Salton
- Marine Predator Research Group, Macquarie University, Sydney, New South Wales, Australia
| | - David P Hocking
- School of Biological Sciences, Monash University, Melbourne, Victoria, Australia
| | - Rebecca R McIntosh
- Marine Predator Research Group, Macquarie University, Sydney, New South Wales, Australia.,Research Department, Phillip Island Nature Parks, Phillip Island, Victoria, Australia
| | | | - David J Slip
- Marine Predator Research Group, Macquarie University, Sydney, New South Wales, Australia.,Taronga Conservation Society Australia, Sydney, New South Wales, Australia
| | - Robert G Harcourt
- Marine Predator Research Group, Macquarie University, Sydney, New South Wales, Australia
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Ladds MA, Rosen DAS, Slip DJ, Harcourt RG. Proxies of energy expenditure for marine mammals: an experimental test of "the time trap". Sci Rep 2017; 7:11815. [PMID: 28924150 PMCID: PMC5603582 DOI: 10.1038/s41598-017-11576-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Accepted: 08/23/2017] [Indexed: 11/25/2022] Open
Abstract
Direct measures of energy expenditure are difficult to obtain in marine mammals, and accelerometry may be a useful proxy. Recently its utility has been questioned as some analyses derived their measure of activity level by calculating the sum of accelerometry-based values and then comparing this summation to summed (total) energy expenditure (the so-called “time trap”). To test this hypothesis, we measured oxygen consumption of captive fur seals and sea lions wearing accelerometers during submerged swimming and calculated total and rate of energy expenditure. We compared these values with two potential proxies of energy expenditure derived from accelerometry data: flipper strokes and dynamic body acceleration (DBA). Total number of strokes, total DBA, and submergence time all predicted total oxygen consumption \documentclass[12pt]{minimal}
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\begin{document}$$({\boldsymbol{sV}}{{\boldsymbol{O}}}_{{\boldsymbol{2}}}$$\end{document}(sVO2 ml kg−1). However, both total DBA and total number of strokes were correlated with submergence time. Neither stroke rate nor mean DBA could predict the rate of oxygen consumption (\documentclass[12pt]{minimal}
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\begin{document}$$s\mathop{{\boldsymbol{V}}}\limits^{{\boldsymbol{.}}}{{\boldsymbol{O}}}_{{\boldsymbol{2}}}$$\end{document}sV.O2 ml min−1 kg−1). The relationship of total DBA and total strokes with total oxygen consumption is apparently a result of introducing a constant (time) into both sides of the relationship. This experimental evidence supports the conclusion that proxies derived from accelerometers cannot estimate the energy expenditure of marine mammals.
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Affiliation(s)
- Monique A Ladds
- School of Mathematics and Statistics, Victoria University of Wellington, Wellington, 6012, New Zealand. .,Marine Predator Research Group, Department of Biological Sciences, Macquarie University, North Ryde, 2113, NSW, Australia.
| | - David A S Rosen
- Marine Mammal Research Unit, Institute for the Oceans and Fisheries, University of British Columbia, 2202 Main Mall, Vancouver, BC V6T 1Z4, Canada
| | - David J Slip
- Marine Predator Research Group, Department of Biological Sciences, Macquarie University, North Ryde, 2113, NSW, Australia.,Taronga Conservation Society Australia, Bradley's Head Road, Mosman, 2088, NSW, Australia
| | - Robert G Harcourt
- Marine Predator Research Group, Department of Biological Sciences, Macquarie University, North Ryde, 2113, NSW, Australia
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Ladds MA, Rosen DA, Slip DJ, Harcourt RG. The utility of accelerometers to predict stroke rate in captive fur seals and sea lions. Biol Open 2017; 6:1396-1400. [PMID: 28798149 PMCID: PMC5612241 DOI: 10.1242/bio.027029] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
The energy expenditure of free-living fur seals and sea lions is difficult to measure directly, but may be indirectly derived from flipper stroke rate. We filmed 10 captive otariids swimming with accelerometers either attached to a harness (Daily Diary: sampling frequency 32 Hz, N=4) or taped to the fur (G6a+: 25 Hz, N=6). We used down sampling to derive four recording rates from each accelerometer (Daily Diary: 32, 16, 8, 4 Hz; G6a+: 25, 20, 10, 5 Hz). For each of these sampling frequencies, we derived 20 combinations of two parameters (RMW, the window size used to calculate the running mean; and m, the minimum number of points smaller than a local maxima used to detect a peak) from the dynamic acceleration of x, z and x+z, to estimate stroke rate from the accelerometers. These estimates differed by up to ∼20% in comparison to the actual number of foreflipper strokes counted from videos. RMW and the choice of axis used to make the calculations (x, z or x+z) had little effect on the overall differences, though the variability was reduced when using x+z. The best m varied depending on the axis used and the sampling frequency; a larger m was needed for higher sampling frequencies. This study demonstrates that when parameters are appropriately tuned, accelerometers are a simple yet valid tool for estimating the stroke rates of swimming otariids. Summary: Accelerometer data collected from captive fur seals and sea lions swimming were used to determine the best method for processing raw data to achieve the highest accuracy of stroke rate.
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Affiliation(s)
- Monique A Ladds
- Marine Predator Research Group, Department of Biological Sciences, Macquarie University, North Ryde, NSW 2113, Australia .,School of Mathematics and Statistics, Victoria University of Wellington, Wellington 6140, New Zealand
| | - David A Rosen
- Marine Mammal Research Unit, Department of Zoology, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
| | - David J Slip
- Marine Predator Research Group, Department of Biological Sciences, Macquarie University, North Ryde, NSW 2113, Australia.,Taronga Conservation Society Australia, Bradley's Head Road, Mosman, NSW 2088, Australia
| | - Robert G Harcourt
- Marine Predator Research Group, Department of Biological Sciences, Macquarie University, North Ryde, NSW 2113, Australia
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Ladds MA, Slip DJ, Harcourt RG. Intrinsic and extrinsic influences on standard metabolic rates of three species of Australian otariid. CONSERVATION PHYSIOLOGY 2017; 5:cow074. [PMID: 28852504 PMCID: PMC5570045 DOI: 10.1093/conphys/cow074] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Revised: 12/15/2016] [Accepted: 01/09/2017] [Indexed: 06/07/2023]
Abstract
The study of marine mammal energetics can shed light on how these animals might adapt to changing environments. Their physiological potential to adapt will be influenced by extrinsic factors, such as temperature, and by intrinsic factors, such as sex and reproduction. We measured the standard metabolic rate (SMR) of males and females of three Australian otariid species (two Australian fur seals, three New Zealand fur seals and seven Australian sea lions). Mean SMR ranged from 0.47 to 1.05 l O2 min-1, which when adjusted for mass was from 5.33 to 7.44 ml O2 min-1 kg-1. We found that Australian sea lion mass-specific SMR (sSMR; in millilitres of oxygen per minute per kilogram) varied little in response to time of year or moult, but was significantly influenced by sex and water temperature. Likewise, sSMR of Australian and New Zealand fur seals was also influenced by sex and water temperature, but also by time of year (pre-moult, moult or post-moult). During the moult, fur seals had significantly higher sSMR than at other times of the year, whereas there was no discernible effect of moult for sea lions. For both groups, females had higher sSMR than males, but sea lions and fur seals showed different responses to changes in water temperature. The sSMR of fur seals increased with increasing water temperature, whereas sSMR of sea lions decreased with increasing water temperature. There were no species differences when comparing animals of the same sex. Our study suggests that fur seals have more flexibility in their physiology than sea lions, perhaps implying that they will be more resilient in a changing environment.
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Affiliation(s)
- Monique A. Ladds
- Marine Predator Research Group, Department of Biological Sciences, Macquarie University, North Ryde, NSW 2113, Australia
| | - David J. Slip
- Marine Predator Research Group, Department of Biological Sciences, Macquarie University, North Ryde, NSW 2113, Australia
- Taronga Conservation Society Australia, Bradley's Head Road, Mosman, NSW 2088, Australia
| | - Robert G. Harcourt
- Marine Predator Research Group, Department of Biological Sciences, Macquarie University, North Ryde, NSW 2113, Australia
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