title: Nonconsumptive effects of a predator weaken then rebound over time.
abstract: Predators can influence prey traits and behavior (nonconsumptive effects [NCEs]), often with cascading effects for basal resources and ecosystem function. But critiques of NCE experiments suggest that their duration and design produce results that describe the potential importance of NCEs rather than their actual importance. In light of these critiques, we re-evaluated a toadfish (predator), crab (prey), and oyster (resource) NCE-mediated trophic cascade. In a 4-month field experiment, we varied toadfish cue (NCE) and crab density (approximating variation in predator consumptive effects, CE). Toadfish initially benefitted oyster survival by causing crabs to reduce consumption. But this NCE weakened over time (possibly due to prey hunger), so that after 2 months, crab density (CE) dictated oyster survivorship, regardless of cue. However, the NCE ultimately re-emerged on reefs with a toadfish cue, increasing oyster survivorship. At no point did the effect of toadfish cue on mud crab foraging behavior alter oyster population growth or sediment organic matter on the reef, which is a measure of benthic-pelagic coupling. Instead, both decreased with increasing crab density. Thus, within a system shown to exhibit strong NCEs in short-term experiments (days) our study supported predictions from theoretical models: (a) within the generation of individual prey, the relative influence of NCEs appears to cycle over longer time periods (months); and (b) predator CEs, not NCEs, drive longer-term resource dynamics and ecosystem function. Thus, our study implies that the impacts of removing top predators via activities such as hunting and overfishing will cascade to basal resources and ecosystem properties primarily through density-mediated interactions.
authors.affiliation: Department of Marine and Environmental Sciences, Northeastern University, Nahant, Massachusetts, 01908, USA.
authors.forename: David L
authors.initials: DL
authors.lastname: Kimbro
authors.affiliation: Department of Marine and Environmental Sciences, Northeastern University, Nahant, Massachusetts, 01908, USA.
authors.forename: Jonathan H
authors.initials: JH
authors.lastname: Grabowski
authors.affiliation: Department of Marine and Environmental Sciences, Northeastern University, Nahant, Massachusetts, 01908, USA.
authors.forename: A Randall
authors.initials: AR
authors.lastname: Hughes
authors.affiliation: Institute of Marine Sciences, University of North Carolina at Chapel Hill, Morehead City, North Carolina, 28557, USA.
authors.forename: Michael F
authors.initials: MF
authors.lastname: Piehler
authors.affiliation: Department of Biology and Marine Biology, University of North Carolina Wilmington, Wilmington, North Carolina, 28403, USA.
authors.forename: J Wilson
authors.initials: JW
authors.lastname: White
mesh_terms: D000818:Animals; D003386:Brachyura; D017753:Ecosystem; D020387:Food Chain; D010125:Ostreidae; D011157:Population Dynamics; D011158:Population Growth; D011235:Predatory Behavior
keywords: antipredator behavior; benthic-pelagic coupling; consumptive effect; ecosystem function; oyster reef; predator cue; prey state; risk; sediment organic matter; trophic cascade