Marine resource use by modern and Holocene coyotes (Canis latrans) on the California coast

Background/Question/Methods

Coyotes (Canis latrans) have been shown to facilitate and benefit from marine subsidies and can also have cascading impacts on other predators and prey. Identifying the past and present role coyotes play in linking land and sea, and whether those links are lost or gained through time, will therefore have important implications for managing this expanding species. Our goals are (1) to establish the spatial and temporal dynamics of marine resource use by modern coyotes on the Central California Coast, and (2) to evaluate whether or not Holocene coastal coyotes had diets similar to or different from modern coyotes. To evaluate the nature and magnitude of a marine resource subsidy to modern coyotes, we combined traditional scat analysis with stable isotope analyses of feces. Conventional scat analysis allows for the quantification of particular prey types and species in coyote diets, whereas the carbon and nitrogen isotope (δ¹³C and δ¹⁵N, respectively) values of feces, like those of other animal tissues, reflect the isotopic composition of an animal’s diet. Our investigation of ancient coyote diets is based on the isotopic composition of bones from archaeological middens, which can be easily compared to isotopic data from the feces of modern coyotes.

Results/Conclusions

Preliminary scat isotopic composition and contents data support our hypothesis that modern coastal coyotes consume marine resources. Eight genetically verified coyote scats collected along a coast-to-inland gradient at Año Nuevo State Park have δ¹⁵N values that range from ~ 4‰ to 17‰ and δ¹³C values ranging from -28‰ to -20‰. Marine resource use is not a strategy employed by all individuals; three of the eight coyote scat samples contain physical evidence of marine foods (i.e., seal or sea lion hair). Holocene coyote bone collagen from Elkhorn Slough (n = 3), Quiroste Vallety (n = 1), and Moss Landing (n = 12) display a slightly reduced range in δ¹⁵N values (~ 4‰ to 14‰) in comparison to modern coyote scats. Although a few individuals have both higher δ¹⁵N and δ¹³C values (n = 3), most samples cluster around a mean δ¹⁵N value of 7.4 (±2.6)‰ and mean δ¹³C value of -19.0 (±2.0)‰, which are outside of the range expected for coyotes with partially marine diets. These data suggest that marine resources did not make up a major proportion of coastal coyote diets in the Holocene and that the use of marine foods has become more prominent in the modern.