An animal can take only one prey before leaving. Big prey offers 2 net energy units per handling minute; small prey offers 4. Both are available now, with no further search and other costs equal. Which offers the higher rate?

• Big prey, at 2 net energy units per handling minute
• Both prey, at 3 net energy units per handling minute
• Small prey, at 4 net energy units per handling minute

In an energy-rate foraging model, which quantity is maximised?

• Food energy gained per prey item before subtracting energetic costs
• Net energy gained per unit of total search, travel and handling time
• Prey captures per minute without weighting their energy content

Under the marginal-value model, when should a forager leave a patch with declining returns?

• When the patch's marginal gain rate equals the attainable long-run rate
• When the patch's remaining energy equals the energy spent travelling to it
• When its marginal gain rate reaches zero after the food supply is depleted

An energy-only model predicts use of a food-rich open patch. Foragers avoid it, and predator attacks are more frequent there. Which omitted cost does this evidence suggest?

• Higher risk of being attacked while feeding in the open
• Longer handling of prey while feeding in the open
• Lower energy content of prey available in the open patch

A focal patch's declining return curve stays unchanged, but the attainable long-run rate elsewhere rises. Why does the marginal-value model predict an earlier exit?

• The patch's food supply declines faster as the other patches improve
• The unchanged declining rate reaches the new, higher benchmark earlier
• The higher outside rate reduces travel time, shifting the patch's return curve

Prey A gives 30 net energy units in 15 handling minutes; B gives 16 in 4. Each is encountered separately. Rejecting either permits continued foraging at 3 units per minute, including search. With other costs equal, what does the rate model predict?

• Accept A and reject B, comparing total prey energy
• Reject A and accept B, comparing each rate with 3
• Accept both prey, comparing each gain with zero

One disagreement between an energy-rate model and observed foraging proves that energy per time is useless for every foraging decision.

A distant patch gives 60 net energy units in 10 feeding minutes plus 10 travel minutes. A nearby patch gives 48 units in 12 total minutes. Using the same visit boundary, which has the higher net-energy rate?

• Distant patch, at 6 units per minute when travel time is excluded
• Distant patch, because 60 units gained exceeds the nearby total of 48
• Nearby patch, at 4 units per minute across the full 12-minute visit