![]() Clam predators, including blue crabs, locate clams by detecting chemical odors produced by clams as they pump water. For example, behavioral studies with hard clams (e.g., Mercenaria mercenaria), indicate they detect chemical cues emanating from predators and injured conspecifics, and respond by reducing their feeding (pumping) time. ![]() However, recent studies have shown that a given environmental factor, such as flow, may also impact prey behavior. These observations, combined with field studies examining green crab predation rates in varying flows in the Damariscotta River, initially led ecologists to the implicit assumption that predator foraging success would decline as environmental conditions (e.g., swift and/or turbulent flow) limit predators’ ability to locate and consume prey. For example, blue crabs ( Callinectes sapidus) often locate prey by following chemical odor plumes, but their chemoreceptive abilities and foraging success decline as flow velocities and turbulence increase. These processes strongly affect how organisms perceive chemical signals from potential predators and prey. Hydrodynamic forces such as flow velocity and turbulence can have significant effects on the structure of waterborne chemical odor plumes via mixing and dilution. Thus environmental conditions can impact consumers by decreasing their ability to detect or handle their prey, not by physically preventing them from inhabiting a given location, as is the case on wave-swept shores.īehavioral research suggests that environmental conditions such as hydrodynamics (i.e., flow rates) may have particularly large impacts in communities where predators hunt prey using chemical cues. Similarly, fish, insects, and copepods experienced diminished foraging success in more rapid flows that were not otherwise harmful. For example, green crab predation was significantly reduced in areas of the Damariscotta River ( a tidal estuary in southern Maine) with high flow velocities, even though green crabs were more abundant in high flow sites. For example, hydrodynamic stress associated with waves reduces the effectiveness of predators, as these conditions limit predator mobility and foraging activity, whereas predation becomes an important community-structuring agent on leeward shores protected from wave action.Įnvironmental conditions may not be stressful in the sense of presenting physical conditions that are life-threatening, but may nevertheless negatively impact predator foraging if they limit the ability of predators to find and/or consume prey. Consequently, models of community regulation note the importance of predation on community functioning in benign environments, an effect which declines in stressful conditions. A primary mechanism is the restriction of foraging time available to mobile predators due to the risk of injury accompanied by reduced locomotory performance or efficiency in adverse conditions. Lethal and nonlethal interactions between predators and prey alter patterns of energy flow, community diversity and composition, and the importance of competitive interactions.ĭespite the obvious importance of predators in communities, it is widely accepted that the effects of predators are minimized when environmental conditions interfere with their foraging activities. Predators in marine, freshwater, and terrestrial environments may affect prey populations and communities by consuming lower trophic levels (lethal or consumptive effect) or by altering prey traits including behavior, morphology, or habitat use (nonlethal or nonconsumptive effect). Top-down forces (i.e., predation) have long been recognized as important community structuring mechanisms. ![]()
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