In the marginal value theorem, what two factors are balanced when foraging decisions are made?

In the marginal value theorem, what two factors are balanced when foraging decisions are made?

• A. Predator density.
• B. The rate of energy intake within the current patch versus travel time to a new patch.
• C. Moon phase.
• D. Trail pheromones.

Answer: (B)

The idea being tested is how a forager decides when to leave a resource patch to maximize energy over time. The two factors balanced are the current patch’s rate of energy gain (how much energy you’re getting per unit time right now) and the travel time to a new patch (the cost in time and potential energy you miss while moving to another patch). You stay in a patch as long as it’s yielding energy at a high rate, but once that instantaneous gain drops, the best choice is to move if the time and potential gains in the next patch would exceed continuing to extract energy here. In short, you weigh how fast you’re gaining energy now against how long it will take to get to and exploit a new patch, to maximize energy intake per unit time.

The idea being tested is how a forager decides when to leave a resource patch to maximize energy over time. The two factors balanced are the current patch’s rate of energy gain (how much energy you’re getting per unit time right now) and the travel time to a new patch (the cost in time and potential energy you miss while moving to another patch). You stay in a patch as long as it’s yielding energy at a high rate, but once that instantaneous gain drops, the best choice is to move if the time and potential gains in the next patch would exceed continuing to extract energy here. In short, you weigh how fast you’re gaining energy now against how long it will take to get to and exploit a new patch, to maximize energy intake per unit time.