Simple models of feeding with time and enery contstraints

We analyze how the foraging currencies "rate" (net energy gainper unit time) and "efficiency" (net energy gain per unit energyexpenditure) relate to the workload adopted by a forager. Weconsider feeding (gathering food for immediate consumption)as opposed to provisioning and investigate the influence oftime and energy constraints. In our model the forager may varythe level of energy expenditure while foraging; increased expenditureincreases the rate of gain, but with diminishing returns. Weshow that rate maximizing requires a higher rate of energy expenditurethan efficiency-maximizing, and we compare the performance ofrate- and efficiency-maximizing tactics when the feeding strategyis (1) to maximize the total net gain while foraging; (2) tomaximize the total net daily gain; or (3) to meet a requirement.Generally, the rate-maximizing tactic only performs best whentime is limiting; otherwise, a lighter workload and slower feedingrate perform better. Under the restricted conditions analyzedhere, no general statement can be made about the best tacticwhen the strategy is to meet a requirement. These results mayhelp explain several instances of "submaximal" foraging describedin the literature.