Publication Date:
2024-04-20
Description:
Individual foraging niche specialisation is recognised as an important determinant of ecological structure and function, particularly for species with high per-capita trophic influence like marine apex predators. Stable isotopes provide a powerful approach to understand the mechanisms and consequences of niche specialisation, especially in cryptic predators, yet have poor resolution for incorporating nutrition, which is a critical aspect of foraging interactions. Multidimensional nutritional ecology compartmentalises foods and diets as mixtures of nutrients (e.g. proteins, lipids, carbohydrates) to draw mechanistic links between individual nutrition, physiology, behaviour and fitness, the drivers of foraging decisions and their trophic implications. Yet difficulties in establishing time-integrated nutrient intakes has hampered progress in predator nutritional ecology. We employed a novel approach integrating stable isotopes and a multidimensional nutritional niche framework to investigate individual diet specialisation across multiple niche realisations in juvenile white sharks (Carcharodon carcharias). We sampled tooth files to generate individual isotopic profiles (δ13C, δ15N, δ34S) and characterise individual isotopic niches (δ-space). We then contextualised isotopic specialisation patterns by estimating individual prey use (p-space) using Bayesian mixing models, and further combined this with nutritional geometry framework models to quantify the nutritional dimension (N-space) of individual specialisation. Isotopic analyses indicated that juvenile white sharks mostly foraged as individual specialists within a broader, generalist, population niche. Mixing models showed individual differences in the consumption of dolphin, shark and batoid prey (rays), which comprised much of the overall diet. Despite δ-space and p-space variance, modelled nutrient intakes were similar for most sharks, which may suggest complementary feeding on nutritionally disparate prey among individual sharks towards a particular nutritional goal. Our approach helps to address the challenges of estimating time-integrated nutrient intakes in cryptic species, expanding our knowledge of individual diet specialisation into a nutritional dimension and revealing how specialisations may differ across niche realisations (prey use and nutritional niches). We argue that this can facilitate stronger links between individual diet specialisation, its intrinsic (e.g. nutritional goals, fitness) and extrinsic (e.g. trophic dynamics) outcomes.
Keywords:
Binary Object; Carcharodon carcharias; Individual specialisation; marine predators; multidimensional nutritional niche framework; nutritional ecology; Stable isotopes; tooth replacement
Type:
Dataset
Format:
text/tab-separated-values, 4 data points
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