Assessing cetacean body condition: Is total lipid content in blubber biopsies a useful monitoring tool?

Kershaw, Joanna L.; Brownlow, Andrew; Ramp, Christian; Miller, Patrick J. O.; Hall, Ailsa J.

doi:10.1002/aqc.3105

Cited by 19 publications

(20 citation statements)

References 81 publications

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“…Based on this, seasonal changes in the morphometric body condition of baleen whales might not be reflected in their outer blubber lipid concentration. In fact, Kershaw et al (2019) showed a lack of correlation between morphometric body condition (girth/ length) and outer lipid content (from the dorsal area immediately caudal to the dorsal fin) in stranded balaenopterids (n=9). Still, many baleen whale species show intra-seasonal changes in both morphometric body condition and blubber lipid concentration, suggesting there could be a positive relationship.…”

Section: Introductionmentioning

confidence: 93%

Variation in outer blubber lipid concentrations does not reflect morphological body condition in humpback whales

Christiansen

Sprogis

Groß

et al. 2020

Journal of Experimental Biology

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An animal's body condition provides valuable information for ecophysiological studies, and is an important measure of fitness in population monitoring and conservation. While both the external body shape of an animal and its internal tissues (i.e. fat content) can be used as a measure of body condition, the relationship between the two is not always linear. We compared the morphological body condition (external metric obtained through aerial photogrammetry) of migrating humpback whales (Megaptera novaeangliae) with their outer blubber lipid concentration (internal metric obtained through blubber biopsy sampling) off the coast of southwest Australia early and late in the breeding season (spanning ∼4.5 months). The external body condition index of juvenile and adult humpback whales decreased by 26.9 (from 18.8% to −8.1%) and 12.0 percentage points (from 8.6% to −3.4%), respectively, between the early and late phase. In contrast, we found no intra-seasonal change in blubber lipid concentration, and no difference between reproductive classes (juveniles, adults and lactating females); however, the small sample size prevented us from effectively testing these effects. Importantly, however, in the 33 animals for which paired metrics were obtained, we found no correlation between the morphometric body condition index and the blubber lipid concentration of individual whales. The lack of a linear relationship suggests that changes in outer blubber lipid concentration do not reflect external changes in body shape, thus limiting the utility of outer blubber lipid reserves for individual body condition evaluation. The wider spectrum of change in body morphometry captured with aerial photogrammetry supports the use of body morphometry as a reliable and well-tested method.

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Section: Introductionmentioning

confidence: 93%

Variation in outer blubber lipid concentrations does not reflect morphological body condition in humpback whales

Christiansen

Sprogis

Groß

et al. 2020

Journal of Experimental Biology

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“…In addition, blubber can be divided in different layers and each layer seems to serve a different function ( Hashimoto et al, 2015 ). Further research into the metabolic functioning of blubber is needed to develop appropriate markers to assess nutritional condition and health in free ranging cetaceans ( Kershaw et al, 2019 ; Derous et al, 2020 ).…”

Section: Discussionmentioning

confidence: 99%

“…These results mean that condition measures based on adiposity must be used with caution. Blubber thickness alone provides little insight into the health of cetaceans ( Kershaw et al, 2019 ; Derous et al, 2020 ). This is likely because blubber is a subcutaneous layer of fat and the evolutionary adaptation to marine life in these species lead to a thickening of that fat layer.…”

Section: Discussionmentioning

confidence: 99%

Comparative genomics of cetartiodactyla: energy metabolism underpins the transition to an aquatic lifestyle

Derous

Sahu

Douglas

et al. 2021

Conservation Physiology

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Foraging disruption caused by human activities is emerging as a key issue in cetacean conservation because it can affect nutrient levels and the amount of energy available to individuals to invest into reproduction. Our ability to predict how anthropogenic stressors affect these ecological processes and ultimately population trajectory depends crucially on our understanding of the complex physiological mechanisms that detect nutrient availability and regulate energy metabolism, foraging behavior and life-history decisions. These physiological mechanisms are likely to differ considerably from terrestrial mammalian model systems. Here, we examine nucleotide substitution rates in cetacean and other artiodactyl genomes to identify signatures of selection in genes associated with nutrient sensing pathways. We also estimated the likely physiological consequences of adaptive amino acid substitutions for pathway functions. Our results highlight that genes involved in the insulin, mTOR and NF-ĸB pathways are subject to significant positive selection in cetaceans compared to terrestrial artiodactyla. These genes may have been positively selected to enable cetaceans to adapt to a glucose-poor diet, to overcome deleterious effects caused by hypoxia during diving (e.g. oxidative stress and inflammation) and to modify fat-depot signaling functions in a manner different to terrestrial mammals. We thus show that adaptation in cetaceans to an aquatic lifestyle significantly affected functions in nutrient sensing pathways. The use of fat stores as a condition index in cetaceans may be confounded by the multiple and critical roles fat has in regulating cetacean metabolism, foraging behavior and diving physiology.

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“…However, there are females in the population with an annual cycle (Pallin et al, 2018) and these females are likely to be more susceptible to reduced fecundity if their body condition is compromised. There has been some advancement using drones to measure the body condition of whales (Christiansen et al, 2016) as well as the lipid content in their blubber (Kershaw et al, 2019). Using these techniques, future directions should therefore focus on validating the energetic model using empirical data on loss of body condition of females during migration, calf growth rates, and consequences of missed feeding opportunities in the calf.…”

Section: Discussionmentioning

confidence: 99%

Assessing Population-Level Effects of Anthropogenic Disturbance on a Marine Mammal Population

et al. 2021

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The Population Consequences of Disturbance (PCoD) model is a conceptual framework used to assess the potential for population-level consequences following exposure of animals to a disturbance activity or stressor. This framework is a four-step process, progressing from changes in individual behavior and/or physiology, to changes in individual health, then vital rates, and finally to population-level effects. Despite its simplicity, there are few complete PCoD models available for any marine mammal species due to a lack of data available to parameterize many of the steps. Here, we present an application of the PCoD framework for migrating humpback whales exposed to a simulated commercial seismic survey scenario. We approached the framework in two ways; first, progressing sequentially forwards through the steps and basing our assessment on lactating females. This cohort was considered to be the most vulnerable in terms of energetic costs of disturbance, and most likely to influence any change in population growth due to future breeding success. Field measurements of behavioral responses of migrating humpback whales to seismic air guns from a previous study were used to parameterize an agent-based model (ABM). This ABM was used to estimate the probability of response, where a response was defined as a change in the migratory movement of female-calf pairs, and the duration of any resulting delay in migration. We then estimated the energetic consequences of any delay in migration for the lactating females and created population growth models with which to assess any population-level effects. The results of the forwards approach suggested a low potential for population consequences of seismic surveys on migrating humpbacks. Working backwards through the framework, we investigated “worst case” scenarios that could potentially lead to a population-level effect. Here, we started with increasing calf mortality and assumed that an exposure time greater than 48 h would increase mortality risk. We determined the most likely context in which this exposure would occur (resting area) and then tested this context within an ABM. This backwards approach illustrates how the PCoD model can be used to make management decisions regarding animal populations and exposure to anthropogenic stressors.

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Assessing cetacean body condition: Is total lipid content in blubber biopsies a useful monitoring tool?

Cited by 19 publications

References 81 publications

Variation in outer blubber lipid concentrations does not reflect morphological body condition in humpback whales

Variation in outer blubber lipid concentrations does not reflect morphological body condition in humpback whales

Comparative genomics of cetartiodactyla: energy metabolism underpins the transition to an aquatic lifestyle

Assessing Population-Level Effects of Anthropogenic Disturbance on a Marine Mammal Population

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