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#MVT

3 public questions tagged with this topic.

Predator Prey Model

Which of the following supports MVT predictions?

Caenorhabditis elegans leaving a depleted food patch illustrates the marginal value theorem’s core prediction. The nematode commonly feeds on bacteria. As local bacteria are consumed, encounter rate and marginal food gain decline; continued residence eventually yields less than the expected return from dispersing and locating another patch. Sensory information about food concentration, recent intake, and environmental cues can regulate roaming and dwelling states, allowing departure behavior to track diminishing returns. The theorem predicts departure when current marginal gain falls to the habitat-wide average gain rate after travel costs are included. Paramecium growth with Didinium concerns predator–prey dynamics, not optimal patch residence. Tadpole cannibalism is a trophic interaction, and random diet change provides no evidence for an optimization rule. Strong support would require quantitative agreement between observed leaving times and manipulated patch quality or travel cost, not merely movement away from food. Nevertheless, leaving an experimentally depleted bacterial patch is the listed behavior most directly aligned with marginal-value reasoning.

Ref: Ecology: Concepts and Applications, Molles, 9th Ed., Ch. 14

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Predator Prey Model

According to MVT, a forager should leave a patch when:

The marginal value theorem states that a forager should leave a patch when its instantaneous capture or energy-gain rate has declined to the average rate attainable across the environment, including travel time between patches. Early in a patch visit, profitable items are readily found and marginal return is high. Continued exploitation depletes the patch, so each additional unit of time yields less. Once the marginal return equals the habitat-wide average, staying longer would lower long-term intake; departing for a new patch raises it. Maximum total energy within the current patch is not the objective because reaching complete depletion can waste substantial time. “Falls below minimum” lacks a defined comparison, and handling time need not become zero. Graphically, the optimal point is where a tangent drawn from the negative travel-time intercept touches the cumulative gain curve. This rule assumes knowledge or evolved estimation of patch quality and average environmental profitability. Predation risk, competition, and incomplete information may shift actual departure, but the equality of marginal and average gain is the theoretical benchmark.

Ref: Ecology: Concepts and Applications, Molles, 9th Ed., Ch. 14

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Predator Prey Model

Marginal value theorem (MVT) explains:

The marginal value theorem predicts how long a forager should remain in a resource patch when travel between patches consumes time. Within a patch, cumulative gain rises but usually decelerates because preferred items are depleted, prey hide, or interference increases. The instantaneous, or marginal, gain rate therefore falls with residence time. Leaving too early wastes travel investment, whereas staying too long yields returns below those available elsewhere. The optimal departure point occurs where the tangent from the travel-time intercept touches the cumulative gain curve; equivalently, current marginal gain equals the long-term average gain rate for the habitat. The theorem predicts longer residence in richer patches and, all else equal, longer residence when travel time between patches increases. It does not explain predator extinction, population oscillations, or mimicry, which operate at different biological levels. Tests often measure departure from artificial food patches or giving-up densities. Risk, information, and nutritional balance can modify behavior, but patch-residence optimization is the theory’s central mechanism.

Ref: Ecology: Concepts and Applications, Molles, 9th Ed., Ch. 14

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