Hossie Thomas J, MacFarlane Shawn, Clement Amy, Murray Dennis L
Department of Biology Trent University Peterborough ON Canada.
Ecol Evol. 2018 Feb 17;8(6):3131-3138. doi: 10.1002/ece3.3892. eCollection 2018 Mar.
Intraspecific aggression represents a major source of mortality for many animals and is often experienced alongside the threat of predation. The presence of predators can strongly influence ecological systems both directly by consuming prey and indirectly by altering prey behavior or habitat use. As such, the threat of attack by higher level predators may strongly influence agonistic interactions among conspecifics via nonconsumptive (e.g., behaviorally mediated) predator effects. We sought to investigate these interactions experimentally using larval salamanders () as prey and dragonfly nymphs () as predators. Specifically, we quantified salamander behavioral responses to perceived predation risk (PPR) from dragonfly nymphs and determined the degree to which PPR influenced intraspecific aggression (i.e., intraspecific biting and cannibalism) among prey. This included examining the effects of predator exposure on the magnitude of intraspecific biting (i.e., extent of tail damage) and the resulting change in performance (i.e., burst swim speed). Salamander larvae responded to PPR by reducing activity and feeding, but did not increase refuge use. Predator exposure did not significantly influence overall survival; however, the pattern of survival differed among treatments. Larvae exposed to PPR experienced less tail damage from conspecifics, and maximum burst swim speed declined as tail damage became more extensive. Thus, escape ability was more strongly compromised by intraspecific aggression occurring in the absence of predation risk. We conclude that multitrophic indirect effects may importantly modulate intraspecific aggression and should be considered when evaluating the effects of intraspecific competition.
种内攻击是许多动物死亡的主要原因之一，并且常常伴随着被捕食的威胁。捕食者的存在可以通过直接捕食猎物以及间接改变猎物行为或栖息地利用方式，对生态系统产生强烈影响。因此，高级捕食者的攻击威胁可能通过非消耗性（例如行为介导）的捕食者效应，强烈影响同种个体之间的争斗互动。我们试图以蝾螈幼虫作为猎物、蜻蜓若虫作为捕食者，通过实验来研究这些互动。具体而言，我们量化了蝾螈对来自蜻蜓若虫的感知捕食风险（PPR）的行为反应，并确定了PPR对猎物种内攻击（即种内撕咬和同类相食）的影响程度。这包括研究捕食者暴露对种内撕咬程度（即尾巴损伤程度）以及由此导致的性能变化（即爆发式游泳速度）的影响。蝾螈幼虫通过减少活动和进食来应对PPR，但并没有增加对避难所的使用。捕食者暴露并没有显著影响总体存活率；然而，不同处理组的存活模式有所不同。暴露于PPR的幼虫受到同种个体造成的尾巴损伤较少，并且随着尾巴损伤程度的增加，最大爆发式游泳速度下降。因此，在没有捕食风险的情况下发生的种内攻击对逃避能力的损害更大。我们得出结论，多营养级间接效应可能会重要地调节种内攻击，并且在评估种内竞争的影响时应予以考虑。
