Reviewing theory, design, and analysis of tethering experiments to enhance our understanding of predation

Abstract

Predation is a key process that influences the structure and functioning of ecosystems. Tethering experiments, which involve restraining prey or prey analogs in field settings, are used to evaluate predation with minimal manipulation of predators and the environment. However, tethering experiments alter the behavior of mobile prey, an issue that increases in severity with prey mobility and reliance on that mobility to evade predators, resulting in artifacts that complicate the interpretation of experimental findings. Given their widespread and rapidly evolving use, we review and reconsider the applications of tethering experiments in marine ecosystems, their utility in measuring predation, associated artifacts, theoretical, methodological, and statistical considerations and challenges, and how to overcome these. Breaking down the predation process into its successive stages (encounter, attack, capture, and consumption), we consider that tethering experiments effectively measure two major aspects of predation: (1) relative predation rates (requiring all four stages, and resulting in successful predation) and (2) predation risk (requiring only encounter and attack). We suggest that tethering experiments be designed to test hypotheses that target particular stages or all stages of the predation process and its drivers, through manipulating tethering experimental designs, conducting direct observations of tethering experiments, collecting additional community or environmental data, combining tethering with other experimental approaches, and through statistical analyses. This general approach facilitates both our understanding of the limitations and utility of tethering experiments to compare patterns and identify drivers of predation rates and risk in the field, topics of study that remain underrepresented in the literature.