Predator cannibalism can shift prey community composition toward dominance by small prey species

Cannibalism among predators is a key intraspecific interaction affecting their density and foraging behaviour, eventually modifying the strength of predation on heterospecific prey. Interestingly, previous studies showed that cannibalism among predators can increase or reduce predation on heterospecific prey; however we know less about the factors that lead to these outcomes. Using a simple pond community consisting of Hynobius retardatus salamander larvae and their associated prey, I report empirical evidence that cannibalism among predators can increase predation on large heterospecific prey but reduce that on small heterospecific prey. In a field-enclosure experiment in which I manipulated the occurrence of salamander cannibalism, I found that salamander cannibalism increased predation on frog tadpoles but reduced that on aquatic insects simultaneously. The contrasting effects are most likely to be explained by prey body size. In the study system, frog tadpoles were too large for non...

捕食者间的同类相食（cannibalism）是一类关键的种内相互作用（intraspecific interaction），可通过影响捕食者种群密度与觅食行为，最终改变其对异种猎物（heterospecific prey）的捕食强度。值得注意的是，既往研究表明，捕食者间的同类相食既可能增强也可能减弱对异种猎物的捕食压力；然而，目前学界对导致这两种截然相反结果的影响因子仍知之甚少。本研究以包含东北小鲵（Hynobius retardatus）幼体及其伴生猎物的简单池塘群落为研究对象，通过实证研究证实：捕食者间的同类相食可提升对大型异种猎物的捕食量，却降低对小型异种猎物的捕食量。在一项操控鲵类同类相食发生情况的野外围栏实验（field-enclosure experiment）中，本研究发现，鲵类同类相食会增加对蛙类蝌蚪的捕食，同时却减少对水生昆虫的捕食。这种截然相反的效应极有可能可通过猎物体型大小得到解释。在本研究系统中，蛙类蝌蚪对于非...