Marine subsidy promotes spatial and dietary niche variation in an omnivore, the Keen’s mouse (Peromyscus keeni)

• Published in: Ecology and Evolution
• Main Authors: Davidson, Katie H., Starzomski, Brian M., El-Sabaawi, Rana, Hocking, Morgan D., Reynolds, John D., Wickham, Sara B., Darimont, Chris T.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Ecology and Evolution 2021
• Subjects: allochthonous; individual niche; islands; Keen's mouse; Peromyscus keeni; resource pulses; stable isotopes; wrack; British Columbia; Canada; Tula; First Nations
• Online Access: http://hdl.handle.net/1828/13767; https://doi.org/10.1002/ece3.8225

We thank the Tula Foundation and Hakai Institute for financial and logistical support for this research, which was a part of the larger “100 Islands” project. We also thank and acknowledge the Heiltsuk (Haíɫzaqv) and Wuikinuxv First Nations in whose traditional territories this research occurred. Thank you to A. Bateman and C. Service who advised on statistical analyses, C. Ernst and E. Rechsteiner with sampling methods development, and G. Hanke at the Royal British Columbia Museum for access to historical specimens for pilot analyses. We appreciate the contributions of our colleagues in the field and laboratory: A. Sheriff, C. Humchitt, T. Gharajeh, H. Hall, T. Bennington Jessop, N. Brown, O. Fitzpatrick, P. Hanly, B. Miller, D. Obrist, D. Buckle, K. Field, and I. Mihalik. We also thank two anonymous reviewers for their constructive feedback on this manuscript. Marine-derived resource subsidies can generate intrapopulation variation in the behaviors and diets of terrestrial consumers. How omnivores respond, given their multiple trophic interactions, is not well understood. We sampled mice (Peromyscus keeni) and their food sources at five sites on three islands of the Central Coast of British Columbia, Canada, to test predictions regarding variation in the spatial behavior and consumption of marine-subsidized foods among individuals. About 50% of detections (n = 27 recaptures) occurred at traps closest to shoreline (25 m), with capture frequencies declining significantly inland (up to 200 m). Stable isotope signatures (δ13C and δ15N), particularly δ15N, in plant foods, forest arthropod prey, and mouse feces were significantly enriched near shorelines compared with inland, while δ13C patterns were more variable. Bayesian isotope mixing models applied to isotope values in mouse hair indicated that over one-third (35–37%) of diet was comprised of beach-dwelling arthropods, a marine-derived food source. Males were more abundant near the shoreline than females and consumed more marine-derived prey, regardless of ...