Comparison of diet quantification methods.

<p>Comparison of the proportional contributions of marine mammals, terrestrial mammals (small, medium and large), birds, reptiles, invertebrates, plants, fish, and non-food material (e.g., gravel/sand) to 12 DNA-verified coyote scats as identified by three methods: frequency of occurrence (white), percent by volume (light gray) and isotopic mixing models (dark gray). Error bars depict one standard error.</p

Illustration of derived diet-to-scat C and N isotope discrimination factors for coyotes.

<p>The routes through diet-to-hair discrimination factors for red foxes (gray arrows) and through wolves (dashed gray arrows) are depicted. In both cases, the first step used our scat-to-hair ε¹³* and ε¹⁵* values (4.1 ± 1.5‰, 0.9 ± 1.3‰, respectively) to convert scat to hair; the dark gray oval surrounding the hair point depicts 1 SD around the enrichment factors. In step 2, we used published diet-to-hair enrichment factors for red foxes (C: 2.6 ± 0.4‰, N: 3.2 ± 0.3‰; [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0174897#pone.0174897.ref026" target="_blank">26</a>]) and wolves (C: 4.25 ± 0.4‰, N: 3.1 ± 0.2‰; [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0174897#pone.0174897.ref027" target="_blank">27</a>]) to convert hair to diet; gray error oval around the diet points depict the propagated standard deviation. Finally, in step 3, we calculated the values necessary to convert from diet to scat.</p

δ¹³C and δ¹⁵N values measured in tissues of 4 road kill coyotes.

<p>Symbol shades denote type of tissue sampled. Tissues from the same individual are connected by lines with different dash patterns.</p

Scat stable isotope sampling rationale.

<p>Step 1 is to separate the coyote scat—the fine-grained material binding the scat together—from the clearly undigested scat components. In step 2, the undigested materials are identified to the finest taxonomical level possible. In step 3, we conduct stable isotope analyses of both the coyote (scat matrix) and its known diet (identified undigested material). After correcting scat values for diet-to-scat discrimination, we expect that they should fall within the mixing space created by known dietary items.</p

List of coyote carcasses examined and tissues sample.

<p>List of coyote carcasses examined and tissues sample.</p

Scat isotope results.

<p>Carbon and nitrogen isotope values (δ¹³C and δ¹⁵N) measured in twelve coyote scats (corrected for discrimination; open circles) from Año Nuevo State Park, CA, plotted in reference to isotope values measured in dietary components found in the scat.</p

Apparent C and N isotope enrichment factors among sampled tissues of road kill coyote carcasses.

<p>Apparent C and N isotope enrichment factors among sampled tissues of road kill coyote carcasses.</p

Ontogenetic and Among-Individual Variation in Foraging Strategies of Northeast Pacific White Sharks Based on Stable Isotope Analysis

<div><p>There is growing evidence for individuality in dietary preferences and foraging behaviors within populations of various species. This is especially important for apex predators, since they can potentially have wide dietary niches and a large impact on trophic dynamics within ecosystems. We evaluate the diet of an apex predator, the white shark (<em>Carcharodon carcharias</em>), by measuring the stable carbon and nitrogen isotope composition of vertebral growth bands to create lifetime records for 15 individuals from California. Isotopic variations in white shark diets can reflect within-region differences among prey (most importantly related to trophic level), as well as differences in baseline values among the regions in which sharks forage, and both prey and habitat preferences may shift with age. The magnitude of isotopic variation among sharks in our study (>5‰ for both elements) is too great to be explained solely by geographic differences, and so must reflect differences in prey choice that may vary with sex, size, age and location. Ontogenetic patterns in δ¹⁵N values vary considerably among individuals, and one third of the population fit each of these descriptions: 1) δ¹⁵N values increased throughout life, 2) δ¹⁵N values increased to a plateau at ∼5 years of age, and 3) δ¹⁵N values remained roughly constant values throughout life. Isotopic data for the population span more than one trophic level, and we offer a qualitative evaluation of diet using shark-specific collagen discrimination factors estimated from a 3+ year captive feeding experiment (Δ¹³C_shark-diet and Δ¹⁵N_shark-diet equal 4.2‰ and 2.5‰, respectively). We assess the degree of individuality with a proportional similarity index that distinguishes specialists and generalists. The isotopic variance is partitioned among differences between-individual (48%), within-individuals (40%), and by calendar year of sub-adulthood (12%). Our data reveal substantial ontogenetic and individual dietary variation within a white shark population.</p> </div

The niche overlap between each individual and the population.

<p>A) The 90% confidence limit for the population (black ellipse) and for individual sharks (colored ellipses). B) The distribution of the proportional similarity index, <i>w_ij</i><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045068#pone.0045068-Lu1" target="_blank">[66]</a>, within the sampled population of California white sharks, which exhibits strong individuality with both specialists and generalists.</p

Summary of biological and collection data and proportional similarity index (<i>w_ij</i>) for white sharks.

<p>Abbreviations are as follows: California Academy of Sciences (CAS), Natural History Museum of Los Angeles County (LACM), G. Chan (GC), Moss Landing Marine Lab (MLML), K. Goldman (KG), S. Anderson (SA), and Long Marine Lab (LML).</p