Seasonal variation in coyote (Canis Latrans) diet at the San Joaquin River, San Luis, and Merced National Wildlife Refuges

Seasonal variation of coyote (Canis latrans) diet was poorly understood in the northern San Joaquin Valley, specifically the coyotes’ relative use of native mammals and birds, native plants, and crops. This study revealed microherbivore consumption within the refuge and outlying agricultural areas and some specific relationships between food item occurrences. I examined approximately 360 coyote fecal samples for undigested plant and animal matter to determine if diet varied within four seasonal periods and three locations. I hypothesized that: 1) seasonal use of items varied with seasonal availability, 2) non-seasonal food items were seen year round, 3) and food item use varied between the three sampling locations: the San Joaquin River, Merced, and San Luis National Wildlife Refuges. Scats were collected between May 2013 and March 2014 at three month intervals to create comprehensive sampling units. California voles (Microtus californicus) occurred predominantly in the diet for all seasons and all three refuges, consistent with hypothesis 2. Additionally, leporids (rabbits and hares) were prevalent in the diet. Birds were important at Merced and San Luis, but not San Joaquin River, likely because of a lack of managed wetlands. Hypothesis testing, binary linear regression and multiple binary linear regression, revealed that there was a significant difference between all combinations of locations and the three seasons, and that diet could be used to predict location and season, supporting hypotheses 1 and 3. Other testing revealed relationships between food items, such as the inverse use of tomatoes with California voles, or how the Winter and Spring seasons had similar dietary composition compared to Fall, which has greatest dietary disparity against all seasons. Similarly, the Merced and San Luis refuges had the most similar diets, with noticeable disparity from the San Joaquin River refuge. These results have implications in wildlife management. Specifically, this study revealed crop use by coyotes and how it changes seasonally between the three regions. Furthermore, coyotes consume wild plant matter, which may play a role in seed dispersal. Of greatest note, coyotes ate very little or no livestock between May 2013 and March 2014, which contradicts previous speculations about annual cattle kills caused by coyotes.