Stable Isotope Applications in Marine Mammal Ecology

Stable isotope analysis, chiefly of carbon (δ13C) and nitrogen (δ15N), has revolutionised our understanding of marine mammal ecology by providing indirect yet integrative measures of diet, trophic position and movement. By sampling metabolically active tissues (skin, blood, muscle) alongside inert materials (baleen plates, bone and vibrissae), researchers can reconstruct feeding histories over varying temporal scales. Mixing models applied to these isotope data disentangle the proportional contributions of prey sources, while spatially explicit “isoscapes” allow inferences about migratory routes and foraging grounds. Determinations of isotopic incorporation and tissue growth rates underpin accurate temporal assignment of dietary events. Across taxa, from baleen whales to sirenians and delphinids, stable isotope approaches have illuminated individual foraging specialisations, sex- and age-specific niche segregation, and population-level structure. These insights inform conservation strategies by identifying critical habitats, assessing resource plasticity under environmental change and detecting shifts in food-web dynamics at regional and global scales.

Research from Nature Portfolio

A recent study of an endangered dugong population used long-term stranding records to analyse skin δ13C and δ15N values across sex and maturity classes. Mixing models incorporating isotopic signatures of seagrass taxa revealed sex-specific foraging strategies: lactating females exhibited a broader dietary niche yet narrower spatial range compared to males. The work provides the first isotopic characterisation of dietary niches in dugongs and underscores the value of sustained monitoring programmes for vulnerable coastal herbivores. It also demonstrates how stable isotopes can unveil subtle ecological differences that are otherwise undetectable through direct observation.

Stable Isotope Applications in Marine Mammal Ecology publication trend

The graph below shows the total number of articles in stable isotope applications in marine mammal ecology across all publications each year (not limited to Nature Index journals).

Technical terms

δ13C and δ15N: Ratios of stable carbon and nitrogen isotopes expressed relative to international standards, used to infer basal carbon sources and trophic level respectively.

Isotopic niche: Multidimensional representation of an organism’s resource use based on its stable isotope values.

Mixing model: Statistical framework that quantifies the proportional contribution of multiple food sources to a consumer’s diet from its isotope values.

Isotopic incorporation rate: Time required for a given tissue to reach isotopic equilibrium with a new diet.

Isoscape: Geographic map of baseline isotope variation in the environment used to infer movement or origin of organisms.

References

1. C and N stable isotopes enlighten the trophic behaviour of the dugong (Dugong dugon). Scientific Reports (2024).
2. Order within chaos: potential migratory strategies and individual associations in fin whales feeding off Iceland. Movement Ecology (2024).
3. Estimating blue whale skin isotopic incorporation rates and baleen growth rates: Implications for assessing diet and movement patterns in mysticetes. PLOS ONE (2017).