An approach for quantifying effects of multiple predators that forage on different time scales

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• 作者：Melisa C. Wong^a ; ^{Melisa.Wong@dfo-mpo.gc.ca} ; Justine d'Entremont^b ; Myriam A. Barbeau^b
• 关键词：Behaviours ; Carcinus maenas ; Experimental design ; Mytilus edulis ; Nucella lapillus ; Per capita consumption rate
• 刊名：Journal of Experimental Marine Biology and Ecology
• 出版年：2012
• 期刊代码：66_00220981
• 类别：abs
• 出版时间：1 June, 2012
• 卷：420-421
• 期：Complete
• 页码：100-109
• 文件大小：493 K

摘要

We used a comprehensive experimental design, consisting of a full suite of predator environments, behavioural observations, and calculation of per capita consumption rates, to examine multiple predator effects on prey when green crabs (Carcinus maenas) and dogwhelks (Nucella lapillus) foraged on blue mussels (Mytilus edulis). Predator environments (i.e., isolated predators, conspecific pairs, and interspecific pair) were used to identify multiple predator effects on prey by comparing observed predation to that predicted from the multiplicative risk model. Behavioural data and per capita consumption rates provided insight into mechanisms underlying observed multiple predator effects on prey. Experiments were conducted at various spatial scales in the laboratory and field. In all experiments, dogwhelks reduced or ceased feeding when a green crab was present compared to isolated dogwhelks, although overall predation was not influenced. Independent multiple predator effects on prey, where observed and predicted consumption did not differ, were usually maintained because crabs and whelks forage on dissimilar time scales. Contrary to other studies, interference competition through aggressive encounters was not observed for dogwhelk and green crab conspecifics, or the interspecific pair, and non-independent multiple predator effects on prey in the form of risk reduction did not result. Spatial scale appeared to influence some outcomes of predator interactions. In large tanks, green crab conspecifics and the interspecific pair caused risk enhancement for prey. This resulted from increased search time, increased per capita consumption rate, and decreased handling time per prey of crabs, and was likely induced by longer residence time of water in the large tanks compared to smaller tanks. In small tanks, dogwhelks with a conspecific had higher per capita consumption rates than isolated dogwhelks, suggesting risk enhancement for prey. However, dogwhelks were unable to consume enough prey over the experiment to allow detection of a non-independent multiple predator effect on prey by comparing observed to predicted consumption. Predator species that operate on different time scales of predation may have independent multiple predator effects on prey even when changes to individual predator behaviours or per capita consumption rates occur. Examination of predator behaviours and per capita consumption rates, in addition to the full suite of predator environments, is essential to fully understand dynamics among multiple conspecific and interspecific predators, particularly when predator species forage on dissimilar time scales.