Figure 2.

Carbon and nitrogen isotope ratios (mean ± 1 SE) of food web components on Santa Cruz Island. Isotope signatures increase with rank in the trophic web. Known fox and skunk prey [deer mice (Peromyscus maniculatus), Jerusalem crickets (Stenopelmatus fuscus), and toyon fruits (Heteromeles arbutifolia)—foxes only]. Seabirds contribute little to eagle diet (see Methods). Known fox/skunk prey and known eagle prey (foxes, piglets, and skunks) were significantly different from each other (represented by circles, K-nearest neighbor randomization test; Bonferroni correction, n = 5 for each sample, P < 0.05).