Diving Physiology and Foraging Ecology of Marine Mammals

Marine mammals have evolved extraordinary adaptations that enable prolonged breath-hold diving and efficient prey capture in varied oceanic realms. Physiological specialisations include enhanced oxygen stores in blood and muscle (via high haematocrit and myoglobin concentrations), cardiovascular adjustments such as dive-induced bradycardia and selective peripheral vasoconstriction, and a collapsible lung architecture to tolerate high hydrostatic pressures. These mechanisms collectively form the dive reflex, permitting repeated descents to depths exceeding 2,000 m in some species. Foraging ecology is intimately linked to these physiological traits: dive profiles, prey encounter rates and habitat use reflect trade-offs between oxygen conservation and energy gain. Area-restricted search strategies concentrate effort in prey-rich patches, while mesopelagic foragers target midwater assemblages along gyre boundaries or continental margins. Advances in biologging—combining time-depth recorders, accelerometers, acoustic sensors and satellite telemetry—have revolutionised our ability to link dive behaviour with prey fields, oceanographic features and individual condition. These insights are crucial for understanding population dynamics, forecasting responses to climate-driven shifts in prey distribution and informing conservation measures. As sentinel species, marine mammals not only reveal the health of productive regions such as polar shelves and tropical upwelling zones, but also highlight emerging stressors from noise, pollution and changing thermal regimes.

Research from Nature Portfolio

Recent studies have revealed that the classic dive reflex is far more variable than once thought. High-resolution electrocardiogram data from free-diving cetaceans and pinnipeds demonstrate that both exercise intensity and depth modulate bradycardia, with frequent cardiac arrhythmias arising from competing autonomic signals. These findings challenge the notion of a uniform dive response and suggest latent terrestrial traits in marine-mammal cardiac control. Another investigation using integrated GPS, accelerometry and ocean current data has shown that southern elephant seals often enter quasi-planktonic drifting bouts within mesoscale eddies. During these quasi-planktonic phases, horizontal movement is minimal and energy expenditure is redirected to diving and prey pursuit, indicating that oceanic eddies act as focal points for trophic interactions. At the molecular level, transcriptomic analysis of fasting‐adapted seals has characterised rapid blubber gene expression changes following acute stress-axis activation. Key adipogenic and lipolytic pathways are transiently upregulated, providing potential biomarkers for stress and energy management in wild populations.

Diving Physiology and Foraging Ecology of Marine Mammals publication trend

The graph below shows the total number of articles in diving physiology and foraging ecology of marine mammals across all publications each year (not limited to Nature Index journals).

Technical terms

Dive reflex: The suite of autonomic responses (bradycardia, vasoconstriction, blood‐shift) that conserves oxygen during submersion.

Bradycardia: A reduction in heart rate during dives to extend aerobic dive duration.

Area‐restricted search (ARS): A concentrated movement pattern adopted in regions of high prey density.

Biologging: Deployment of animal‐borne sensors to record behaviour, physiology and environmental parameters.

Mesopelagic zone: The midwater ocean layer (200–1,000 m depth) often targeted by deep‐diving predators.

References

1. Exercise at depth alters bradycardia and incidence of cardiac anomalies in deep-diving marine mammals. Nature Communications (2015).
2. Quasi-planktonic behavior of foraging top marine predators. Scientific Reports (2015).
3. Blubber transcriptome response to acute stress axis activation involves transient changes in adipogenesis and lipolysis in a fasting-adapted marine mammal. Scientific Reports (2017).
4. CS-PHOC: weekly census counts of Southern Ocean phocids at Cape Shirreff, Livingston Island. Scientific Data (2024).
5. Circumpolar habitat use in the southern elephant seal: implications for foraging success and population trajectories. Ecosphere (2016).
6. Navigating uncertain waters: a critical review of inferring foraging behaviour from location and dive data in pinnipeds. Movement Ecology (2016).
7. Processing of acceleration and dive data on‐board satellite relay tags to investigate diving and foraging behaviour in free‐ranging marine predators. Methods in Ecology and Evolution (2017).