Energy‐mediated responses to changing prey size and distribution in marine top predator movements and population dynamics

Bioenergetic models describe the processes through which animals acquire energy from resources in the environment and allocate it to different life history functions. They capture some of the fundamental mechanisms regulating individuals, populations and ecosystems and have thus been used in a wide variety of theoretical and applied contexts. Here, I review the development of bioenergetic models for marine mammals and their application to management and conservation. For these long-lived, wide-ranging species, bioenergetic approaches were initially used to assess the energy requirements and prey consumption of individuals and populations. Increasingly, models are developed to describe the dynamics of energy intake and allocation and predict how resulting body reserves, vital rates and population dynamics might change as external conditions vary. The building blocks required to develop such models include estimates of intake rate, maintenance costs, growth patterns, energy storage and the dynamics of gestation and lactation, as well as rules for prioritizing allocation. I describe how these components have been parameterized for marine mammals and highlight critical research gaps. Large variation exists among available analytical approaches, reflecting the large range of life histories, management needs and data availability across studies. Flexibility in modelling strategy has supported tailored applications to specific case studies but has resulted in limited generality. Despite the many empirical and theoretical uncertainties that remain, bioenergetic models can be used to predict individual and population responses to environmental change and other anthropogenic impacts, thus providing powerful tools to inform effective management and conservation.

Section: Marine Mammal Dynamic Bioenergetic Modellingmentioning

confidence: 99%

A review of bioenergetic modelling for marine mammal populations

Pirotta

2022

“…Climate change, which is rapid in some regions, is predicted to have considerable impacts on the distribution, biomass, energy density and body size of prey species ( Flores et al, 2012 ; Yasumiishi et al, 2020 ; Florko et al, 2021 ). Such changes have clear bioenergetic implications for marine mammals and the ecosystems they inhabit ( Costa, 2008 ; Laidre et al, 2020 ; Gallagher et al, 2022 ). Since the prey landscape is a major driver of the spatiotemporal distribution of marine mammals ( Sveegaard et al, 2012 ; Zerbini et al, 2016 ; Sigler et al, 2017 ; Straley et al, 2018 ; Pendleton et al, 2020 ), knowledge of prey fields and how they may be changing provides insight into the potential impact of anthropogenic disturbances on energy budgets ( Keen et al, 2021 ).…”

Section: Resultsmentioning

confidence: 99%

“…Many of the conservation challenges facing marine mammals today revolve around bioenergetics, such as environmental variability, climate change, fisheries interactions, predation risk, offshore development, and noise pollution ( Wirsing et al, 2008 ; Davidson et al, 2012 ; Kovacs et al, 2012 ; Avila et al, 2018 ). For example, climate change may alter an individual’s energy intake through changes in prey distribution, abundance, and energy density ( von Biela et al, 2019 ; Gallagher et al, 2022 ). It can also affect energy expenditure through changes in habitat availability ( Pagano and Williams, 2021 ) or thermal landscapes ( Cunningham et al, 2021 ).…”

Section: Introductionmentioning

confidence: 99%

Key questions in marine mammal bioenergetics

McHuron

Adamczak

Arnould

et al. 2022

Bioenergetic approaches are increasingly used to understand how marine mammal populations could be affected by a changing and disturbed aquatic environment. There remain considerable gaps in our knowledge of marine mammal bioenergetics, which hinder the application of bioenergetic studies to inform policy decisions. We conducted a priority-setting exercise to identify high-priority unanswered questions in marine mammal bioenergetics, with an emphasis on questions relevant to conservation and management. Electronic communication and a virtual workshop were used to solicit and collate potential research questions from the marine mammal bioenergetic community. From a final list of 39 questions, 11 were identified as ‘key’ questions because they received votes from at least 50% of survey participants. Key questions included those related to energy intake (prey landscapes, exposure to human activities) and expenditure (field metabolic rate, exposure to human activities, lactation, time-activity budgets), energy allocation priorities, metrics of body condition and relationships with survival and reproductive success and extrapolation of data from one species to another. Existing tools to address key questions include labelled water, animal-borne sensors, mark-resight data from long-term research programs, environmental DNA and unmanned vehicles. Further validation of existing approaches and development of new methodologies are needed to comprehensively address some key questions, particularly for cetaceans. The identification of these key questions can provide a guiding framework to set research priorities, which ultimately may yield more accurate information to inform policies and better conserve marine mammal populations.

“…via changes in prey composition, size distribution or energetic content), how different species are responding and robustly projecting how this will propagate in the future (e.g. Gallagher et al . 2021b ) remains critical to inform conservation and management.…”

Section: Discussion/conclusionmentioning

confidence: 99%

“…resource availability) ( Pirotta et al ., 2018a ; Keen et al ., 2021 ). Globally, climate change is altering ecosystems, and assessing the effects of this and other anthropogenic stressors (and their complex interactions) remains a critical knowledge gap ( National Academies of Sciences Engineering and Medicine, 2017 ; Hazen et al ., 2019 ; Malhi et al ., 2020 ; Gallagher et al . 2021b ; Pirotta et al ., 2022 ).…”

Section: Introductionmentioning

confidence: 99%

Estimating energetic intake for marine mammal bioenergetic models

Booth

Guilpin

Darias-O'Hara

et al. 2023

Self Cite

Bioenergetics is the study of how animals achieve energetic balance. Energetic balance results from the energetic expenditure of an individual and the energy they extract from their environment. Ingested energy depends on several extrinsic (e.g prey species, nutritional value and composition, prey density and availability) and intrinsic factors (e.g. foraging effort, success at catching prey, digestive processes and associated energy losses, and digestive capacity). While the focus in bioenergetic modelling is often on the energetic costs an animal incurs, the robust estimation of an individual’s energy intake is equally critical for producing meaningful predictions. Here, we review the components and processes that affect energy intake from ingested gross energy to biologically useful net energy (NE). The current state of knowledge of each parameter is reviewed, shedding light on research gaps to advance this field. The review highlighted that the foraging behaviour of many marine mammals is relatively well studied via biologging tags, with estimates of success rate typically assumed for most species. However, actual prey capture success rates are often only assumed, although we note studies that provide approaches for its estimation using current techniques. A comprehensive collation of the nutritional content of marine mammal prey species revealed a robust foundation from which prey quality (comprising prey species, size and energy density) can be assessed, though data remain unavailable for many prey species. Empirical information on various energy losses following ingestion of prey was unbalanced among marine mammal species, with considerably more literature available for pinnipeds. An increased understanding and accurate estimate of each of the components that comprise a species NE intake are an integral part of bioenergetics. Such models provide a key tool to investigate the effects of disturbance on marine mammals at an individual and population level and to support effective conservation and management.