Impervious surface cover and number of restaurants shape diet variation in an urban carnivore

In the past decade, studies have demonstrated that urban and nonurban wildlife populations exhibit differences in foraging behavior and diet. However, little is known about how environmental heterogeneity shapes dietary variation of organisms within cities. We examined the vertebrate prey components of diets of coyotes (Canis latrans) in San Francisco to quantify territory- and individual-level dietary differences and determine how within-city variation in land cover and land use affect coyote diet. We genotyped fecal samples for individual coyote identification and used DNA metabarcoding to quantify diet composition and individual niche differentiation. The highest contributor to coyote diet overall was anthropogenic food followed by small mammals. The most frequently detected species were domestic chicken, pocket gopher (Thomomys bottae), domestic pig, and raccoon (Procyon lotor). Diet composition varied significantly across territories and among individuals, with territories explaining most of the variation. Within territories (i.e., family groups), the amount of dietary variation attributed to among-individual differences increased with green space and decreased with impervious surface cover. The quantity of anthropogenic food in scats also was positively correlated with impervious surface cover, suggesting that coyotes consumed more human food in more urbanized territories. The quantity of invasive, human-commensal rodents in the diet was positively correlated with the number of food services in a territory. Overall, our results revealed substantial intraspecific variation in coyote diet associated with urban landscape heterogeneity and point to a diversifying effect of urbanization on population diet.近十年来，已有研究表明城市与非城市野生生物种群在觅食行为与食性上存在差异。然而，目前学界对城市内部环境异质性如何塑造生物食性变异的认知仍较为匮乏。本研究以旧金山的郊狼（Canis latrans）为研究对象，分析其食谱中的脊椎动物猎物组分，以量化领地尺度与个体尺度的食性差异，并探究城市内部土地覆盖与土地利用的变异如何影响郊狼食性。我们通过对粪便样本进行基因分型以识别个体郊狼，并利用DNA宏条形码技术（DNA metabarcoding）定量分析食谱组成与个体生态位分化情况。整体而言，郊狼食谱的最主要食物来源为人为源食物，其次为小型哺乳类。检出频率最高的物种依次为家鸡、囊鼠（Thomomys bottae）、家猪以及浣熊（Procyon lotor）。郊狼的食谱组成在不同领地间以及个体间均存在显著差异，其中领地尺度的差异能够解释大部分食性变异。在领地内部（即家族群范围内），由个体间差异导致的食性变异程度随绿地面积占比升高而增加，随不透水表面覆盖度升高而降低。粪便样本中人为源食物的占比同样与不透水表面覆盖度呈正相关，表明在城市化程度更高的领地中，郊狼会摄入更多人类食物。食谱中入侵性、与人共生的啮齿类动物占比，与领地内餐饮服务设施的数量呈正相关。综上，本研究结果表明郊狼的食性存在显著的种内变异，且该变异与城市景观异质性密切相关；同时也揭示了城市化对种群食性的多样化塑造效应。