Temporal changes in predator density are linked to shifts in prey behavior, mortality, and abundance in the field

Predators suppress prey populations and elicit defensive phenotypes in prey. The magnitude of predator effects depends upon several factors, including the density of predators, and their cue concentrations, in the environment. Predator density manipulations have often relied on laboratory studies that use unrealistic densities of predators and prey over unnatural temporal and spatial scales. Field studies can provide insights into predator-prey interactions under more realistic scenarios. However, field studies linking predator density and prey populations are limited by the challenge of manipulating predator densities or predicting predator densities in dynamic/stochastic environments. We exploited a somewhat predictable rise in predatory crab communities associated with ocean warming to evaluate the impacts of swimming crab density on ecologically important horn snails. Our approach combined long-term monitoring of crabs and snails with snail behavior surveys and snail tethering exper..., Study system and site California horn snails (hereafter, horn snails) are ubiquitous in tidal marshes and mudflats across the Southern California Bight (Lorda & Lafferty 2012). Throughout this region, horn snails are prey for several predators (Armitage & Fong 2006; Lorda et al. 2016)and are intermediate hosts for parasitic trematodes (Hechinger & Lafferty 2005; Lafferty et al. 2006b). Horn snails can be predated upon by predatory swimming crabs during high tides, when tidal inundation facilitates crab movements into mud flat and marsh habitats (Cote et al. 2001; Belgrad & Smith 2014). In southern California, the abundance of these swimming crabs (e.g., the Xantus’ swimming crab, Portunus xantusii, and the arched swimming crab, Callinectes arcuatus; hereafter swimming crabs) is connected to sea water temperature. Warm water events (e.g., marine heat waves, El Niños) are associated with influxes of swimming crabs (Zedler et al. 1992; Williams et al. 2001). Consistent with...,捕食者可抑制猎物种群规模，并诱导猎物产生防御表型。捕食者效应的强度受多种因素影响，包括捕食者密度及其在环境中的线索浓度（cue concentrations）。此前针对捕食者密度的操控研究多依托实验室开展，但这类实验所使用的捕食者与猎物密度均不符合自然情境，且实验的时空尺度也违背自然规律。野外研究能够在更贴近现实的场景中揭示捕食者-猎物互作关系。然而，野外研究中若要操控捕食者密度，或是在动态/随机环境中预测捕食者密度均存在极大挑战，因此关联捕食者密度与猎物种群的野外研究较为匮乏。本研究借助与海洋变暖相关的捕食性蟹类群落的可预测性增长，评估了游泳蟹密度对具有重要生态意义的角螺种群的影响。研究方法结合了蟹类与螺类的长期监测、螺类行为调查以及螺类拴系实验……研究系统与试验地点 加利福尼亚角螺（以下简称角螺）广泛分布于南加利福尼亚湾沿岸的潮汐沼泽与潮间带泥滩（Lorda & Lafferty 2012）。在该区域内，角螺既是多种捕食者的猎物（Armitage & Fong 2006; Lorda et al. 2016），同时也是寄生吸虫的中间宿主（Hechinger & Lafferty 2005; Lafferty et al. 2006b）。涨潮时段潮汐淹没生境，促使游泳蟹进入泥滩与沼泽栖息地，此时角螺会遭到捕食性游泳蟹的捕食（Cote et al. 2001; Belgrad & Smith 2014）。在南加利福尼亚海域，这类游泳蟹（例如赞氏游泳蟹*Portunus xantusii*与弓形游泳蟹*Callinectes arcuatus*；以下简称游泳蟹）的丰度与海水温度密切相关。暖水事件（如海洋热浪、厄尔尼诺现象）往往伴随游泳蟹种群的迁入（Zedler et al. 1992; Williams et al. 2001）。 与……相一致（原文截断）