Food preference and ad libitum intake of wild-captured Sitka mice, Peromyscus keeni sitkensis

Abstract

Food preferences of Sitka Mouse (Peromyscus keeni sitkensis) were studied in four experiments involving fruits from five major shrub species and sees from three tree and four shrub species. Each experiment consisted of individual animals being offered mixed species assortments of foods fed over a four-day period. Ad libitum intake trials were conducted with the same foods used in the preference experiments but with only one food per trial. Intake trials also included beetles (Seaphinotus and Pterostichus spp.) and Pink Salmon (Oncorhynchus gorbuscha). Salmonberry (Rubus spectabilis) and Stink Current (Ribes bracteosum) fruit and seeds emerged as highly preferred and valuable foods in terms of both relative preference and ad libitum intake. Devilsclub (Oplopanax horridus) and Elderberry (Sambucus racemosa) fruits were least preferred in both preference and intake, although their seeds were relatively palatable and nutritious (in terms of weight loss). Blueberry (Vaccinium ovalifolium) fruit was intermediate in both preference and intake. Tree seed palatability and intake ranked in order of Sitka Spruce (Picea sitchensis) (highest), Western Hemlock (Tsuga heterophylla), and Red Alder (Alnus rubra) (lowest). Ad libitum intake of beetles was low, and that of Pink Salmon was near zero. These results should be helpful in interpreting diet composition studies of Sitka Mouse throughout its range and possibly other Peromyscus species in wet coastal forests of the Pacific Northwest and Alaska.