@article {942,
	title = {Measuring the impact of dynamic antipredator traits on predator-prey-resource interactions},
	journal = {Ecology},
	volume = {89},
	year = {2008},
	note = {J
JUN},
	month = {2008///},
	pages = {1640 - 1649},
	abstract = {This article analyzes the limitations of the most widely used method for quantifying the impact of dynamic antipredator traits on food chain dynamics and discusses alternative approaches. The standard method for a predator-prey-resource chain estimates the effects of the prey{\textquoteright}s defensive behavior by comparing population densities or fitness measures in a {\textquoteright}{\textquoteright}predator cue{\textquoteright}{\textquoteright} treatment to those in a no-predator treatment. This design has been interpreted as providing a measure of the {\textquoteright}{\textquoteright}nonconsumptive effect{\textquoteright}{\textquoteright} of the predator on the prey and the {\textquoteright}{\textquoteright}trait-mediated indirect effect{\textquoteright}{\textquoteright} of the predator on the resource. Other approaches involve measurements of the impact of the behavior in the presence of functional predators. The questions addressed here are: (1) How consistent are the results of different approaches? (2) How time-dependent are their results? (3) How well do they correspond to theoretical measures of effect size? (4) How useful are the measurements in understanding system dynamics? A model of a tritrophic system in which the prey species adjusts a defensive trait adaptively is used to evaluate the experimental designs. Measures of changes in prey fitness or population density in a cue treatment generally include offsetting effects of the cost of the behavior and the benefit of more resources. This means that the sign of the effect, as well as its magnitude, may change depending on when the experiment is terminated. Because predation is not present in the cue treatment, few conclusions can be drawn about the impact of the behavior on population densities or fitness of the prey in a natural setting with predators. Cue experiments often do not accurately separate trait-mediated from density-mediated effects on the resource. Most scalar measures of effects are sensitive to experimental duration and initial densities. Use of a wider range of experimental designs to measure trait-related effects is called for},
	keywords = {DYNAMICS, interactions, predation, PREDATOR, predators, PREY, SIZE},
	isbn = {0012-9658},
	url = {ISI:000256540300017},
	author = {Abrams,P.A.}
}
@article {943,
	title = {Measuring the population-level consequences of predator-induced prey movement},
	journal = {Evolutionary Ecology Research},
	volume = {10},
	year = {2008},
	note = {J
MAR},
	month = {2008///},
	pages = {333 - 350},
	abstract = {Questions: (1) What impact does adaptive movement away from areas of high predation risk have on the dynamics of a prey species and its resource? (2) What can experiments that introduce or remove predator cues tell us about the answer to question (1)? Mathematical methods: These questions are addressed using a two-patch meta-community model in which predators and/or their cues are incorporated into a system consisting of a prey species and its resource. Predators and/or cues may be introduced to one or both patches. Key assumptions: Prey species move adaptively to maximize their instantaneous rate of increase, but also make some random movement. Predators move randomly or do not move. Resources seldom or never move between patches. Consumer species have saturating functional responses. Conclusions: (1) Adaptive movement can stabilize or destabilize the dynamics of the tri-trophic system. (2) Monitoring densities in a single patch may give a misleading indication of the global change in densities. (3) Adaptive prey movement in response to predator cues may increase or decrease prey density. (4) Predator introduction may cause an increase or decrease in the size of the prey population. (5) Short-term experiments with local measurements may greatly overestimate the impact of predators on prey and the behavioural component of that impact. (6) The dynamics and interspecific effects in a system with predators and adaptive avoidance by prey cannot in general be deduced from separate experiments with cues alone and with predators in the absence of the cues. (7) Conclusions from recent empirical studies should be reassessed in light of these results},
	keywords = {CONSEQUENCES, DYNAMICS, predation, PREDATOR, predators, PREY, RISK, SIZE},
	isbn = {1522-0613},
	url = {ISI:000256015000002},
	author = {Abrams,P.A.}
}
