Fig 1.
Scat stable isotope sampling rationale.
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.
Fig 2.
δ13C and δ15N values measured in tissues of 4 road kill coyotes.
Symbol shades denote type of tissue sampled. Tissues from the same individual are connected by lines with different dash patterns.
Table 1.
List of coyote carcasses examined and tissues sample.
Table 2.
Apparent C and N isotope enrichment factors among sampled tissues of road kill coyote carcasses.
Fig 3.
Illustration of derived diet-to-scat C and N isotope discrimination factors for coyotes.
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‰; [26]) and wolves (C: 4.25 ± 0.4‰, N: 3.1 ± 0.2‰; [27]) 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.
Fig 4.
Comparison of diet quantification methods.
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.
Fig 5.
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.