Social behavior and ecosystem processes: River otter latrines and nutrient dynamics of terrestrial vegetation

Abstract

River otters (Lutra canadensis Schreber) inhabiting coastal environments scent, mark specific locations along the coast, known as latrine sites. In this study, we used stable isotope techniques to investigate the effects of this scent-marking behavior on terrestrial vegetation at the terrestrial-marine interface. Our analysis of stable isotope ratios of fur and feces indicated that river otters fed mainly on intertidal and subtidal fish. Eight different species of plants, growing in latrine sites of river otters, had significantly higher values of δ15N compared with the same plant species growing on nonlatrine sites. Elevated N concentrations occurred only in grasses and mosses growing in latrine sites. Our results indicate that, through their scent-marking behavior, coastal river otters transfer marine-derived nitrogen into the beach-fringe forest and thus fertilize the terrestrial vegetation in the terrestrial-marine interface.