Data from: Large‐scale molecular diet analysis in a generalist marine mammal reveals male preference for prey of conservation concern

Sex‐specific diet information is important in the determination of predator impacts on prey populations. Unfortunately, the diet of males and females can be difficult to describe, particularly when they are marine predators. We combined two molecular techniques to describe haul‐out use and prey preferences of male and female harbor seals (Phoca vitulina) from Comox and Cowichan Bay (Canada) during 2012–2013. DNA metabarcoding quantified the diet proportions comprised of prey species in harbor seal scat, and qPCR determined the sex of the individual that deposited each scat. Using 287 female and 260 male samples, we compared the monthly sex ratio with GLMs and analyzed prey consumption relative to sex, season, site, and year with PERMANOVA. The sex ratio between monthly samples differed widely in both years (range = 12%–79% males) and showed different patterns at each haul‐out site. Male and female diet differed across both years and sites: Females consumed a high proportion of demersal fish species while males consumed more salmonid species. Diet composition was related to both sex and season (PERMANOVA: R2 = 27%, p < 0.001; R2 = 24%, p < 0.001, respectively) and their interaction (PERMANOVA: R2 = 11%, p < 0.001). Diet differences between males and females were consistent across site and year, suggesting fundamental foraging differences, including that males may have a larger impact on salmonids than females. Our novel combination of techniques allowed for both prey taxonomic and spatiotemporal resolution unprecedented in marine predators.

区分性别的饮食信息，对于明确捕食者对猎物种群的影响至关重要。然而，准确描述雌雄个体的饮食组成往往颇具挑战，针对海洋捕食者而言尤为如此。本研究结合两种分子技术，对2012至2013年间来自加拿大库姆斯湾与考伊琴湾的港海豹（Phoca vitulina）的停歇地使用情况及雌雄捕食偏好展开分析。研究人员通过DNA元条形码（DNA metabarcoding）技术对港海豹粪便中的猎物物种占比进行定量分析，并利用qPCR（定量聚合酶链反应）技术确定每一份粪便样本所属个体的性别。本研究共获取287份雌性海豹样本与260份雄性海豹样本，通过广义线性模型（Generalized Linear Models, GLMs）对比了月度样本的性别比例，并借助置换多元方差分析（Permutational Multivariate Analysis of Variance, PERMANOVA）分析了猎物消耗情况与性别、季节、采样地点及年份之间的关联。两年间的月度样本性别比例差异显著，雄性占比区间为12%至79%，且不同停歇地的性别比例变化模式各不相同。雌雄港海豹的饮食组成在两年及所有采样地点中均存在显著差异：雌性海豹的饮食中底层鱼类占比极高，而雄性海豹则更多捕食鲑形目鱼类。饮食组成与性别、季节及其交互作用均存在显著关联（置换多元方差分析结果：R²分别为27%、24%及11%，所有p值均小于0.001）。雌雄个体间的饮食差异在不同采样地点与年份中均保持一致，这表明二者的觅食策略存在根本性差异，其中雄性海豹对鲑形目鱼类的影响可能大于雌性。本研究创新性地结合两种分子技术，实现了海洋捕食者研究中前所未有的猎物分类学与时空分辨率分析。