Diet of a threatened endemic fox reveals variation in sandy beach resource use on California Channel Islands

• Published in: PloS one 2021-10, Vol.16 (10), p.e0258919
• Main Authors: Page, Henry M, Schamel, Juliann, Emery, Kyle A, Schooler, Nicholas K, Dugan, Jenifer E, Guglielmino, Angela, Schroeder, Donna M, Palmstrom, Linnea, Hubbard, David M, Miller, Robert J
• Format: Article
• Language: English
• Subjects: Abundance; Beaches; Biology and Life Sciences; Climate change; Climate variability; Climatic changes; Coastal ecosystems; Coastal zone; Diet; Earth Sciences; Endangered & extinct species; Environmental aspects; Food; Foraging behavior; Foraging habitats; Foxes; Habitat utilization; Habitats; Influence; Invertebrates; Islands; Macrocystis pyrifera; Management; Marine resources; Medicine and Health Sciences; Megalorchestia; Nutrient deficiency; Nutrition research; Population decline; Population density; Population growth; Prey; Protection and preservation; Shorelines; Stable isotopes; Terrestrial environments; Urocyon littoralis; Vibrissae
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0258919

The coastal zone provides foraging opportunities for insular populations of terrestrial mammals, allowing for expanded habitat use, increased dietary breadth, and locally higher population densities. We examined the use of sandy beach resources by the threatened island fox (Urocyon littoralis) on the California Channel Islands using scat analysis, surveys of potential prey, beach habitat attributes, and stable isotope analysis. Consumption of beach invertebrates, primarily intertidal talitrid amphipods (Megalorchestia spp.) by island fox varied with abundance of these prey across sites. Distance-based linear modeling revealed that abundance of giant kelp (Macrocystis pyrifera) wrack, rather than beach physical attributes, explained the largest amount of variation in talitrid amphipod abundance and biomass across beaches. [delta].sup.13 C and [delta].sup.15 N values of fox whisker (vibrissae) segments suggested individualism in diet, with generally low [delta].sup.13 C and [delta].sup.15 N values of some foxes consistent with specializing on primarily terrestrial foods, contrasting with the higher isotope values of other individuals that suggested a sustained use of sandy beach resources, the importance of which varied over time. Abundant allochthonous marine resources on beaches, including inputs of giant kelp, may expand habitat use and diet breadth of the island fox, increasing population resilience during declines in terrestrial resources associated with climate variability and long-term climate change.