Optimal Foraging: Field Tests of Diet Choice and Habitat Switching

The application of optimal foraging theory to questions of predatorbehavior, and evidence bearing on the utility of this construct,are reviewed. Experimental tests of simple models predictingprey choice are examined with particular reference to the size-selectionof prey by fish. Laboratory estimates of model parameters arethen used to predict prey choice in the field and data fromseveral field tests are presented which corroborate these predictions.When parameters are habitat specific this permits predictionsof net return from foraging in different habitats and consequentlypredictions of habitat use and switching. Field data gatheredto test these predictions demonstrate that fish feed in thericher habitats and switch habitats when the profitability ofone drops below that of another. Examples are provided showinghow these models can then be used to relate behavioral and morphologicaldifferences between species and questions at higher levels suchas the nature of species interactions and community structure.It is suggested that this may be one of the more useful applicationsof optimal foraging theory. Finally, some of the criticismsof the theory and important questions requiring further studyare discussed.     

Optimal Foraging and Predator–Prey Dynamics

A system consisting of a population of predators and two types of prey is considered. The dynamics of the system is described by differential equations with controls. The controls model how predators forage on each of the two types of prey. The choice of these controls is based on the standard assumption in the theory of optimal foraging which requires that each predator maximizes the net rate of energy intake during foraging. Since this choice depends on the densities of populations involved, this allows us to link the optimal behavior of an individual with the dynamics of the whole system. Simple qualitative analysis and some simulations show the qualitative behavior of such a system. The effect of the optimal diet choice on the stability of the system is discussed.     

Optimal Foraging Theory and the Psychology of Learning

The development of optimization theory has made important contributionsto the study of animal behavior. But the optimization approachneeds to be integrated with other methods of ethology and psychology.For example, the ability to learn is an important componentof efficient foraging behavior in many species, and the psychologyof animal learning could contribute substantially to testingand extending the predictions of optimal foraging theory.     

The Optimal Foraging Analysis of Horticultural Production

This paper extends the application of optimal foraging theory to horticultural economies. The Machiguenga, a native Amazonian population of southeastern Peru, are used as a test case. The results demonstrate the theory's utility in structuring questions and predicting the outcome of horticultural production. By extending the range of foraging theory the evolution of subsistence strategies from hunting-gathering to agriculture can be examined in quantitative terms. The evolutionary sequence is illustrated with a hypothetical population. Additional insights are gained when the theory is used to structure specific production decisions. Disagreements concerning the scarcity of protein in Amazonian economies are shown to be a consequence of the measurement units employed.     

Optimal Foraging and Hominid Evolution: Labor and Reciprocity

We argue that cooperative foraging incorporating information exchange may have preceded tool use during the course of hominid evolution. In moving to the savanna, early hominids must have faced increasingly dispersed but sometimes more profitable food sources. The problem is finding such foods. Search costs can be reduced for each individual if a number of foragers cooperate by ranging over different parts of the habitat and by exchanging information about encountered food items. Given the probability of encountering a given food item and the return per individual for that item, it is possible to specify the optimal group size. Thus, in the patchy savanna environment, selection would have favored increased gregariousness and cooperation on the part of early hominids, setting the stage for the emergence of reciprocal exchanges of information and resources. However, such a system of reciprocity is open to manipulation. Outside the foraging context, the tension between reciprocity and manipulation would shape other social interactions. Communication and information exchange may have been more critical than labor and technology in evolving hominids from hominoids. Human sociality may find its origins in a shift in primate foraging tactics.     

Optimal phenology and body-size of Orb-weaving spiders: Foraging constrains

Summary Large orb-weaving spiders in temperate zones always mature in Autumn. A model based on laboratory feeding experiments and insect trap samples from an old-field in Michigan was used to simulate orb-weaver foraging behavior in various habitats and seasons. Seasons of peak energy return rates in habitats used by old-field orb-weavers indicate that prey availability plays a role in determining phenologies of large spiders. The minimum body-size to which the constraint applies in the model corresponds to the lower size-range of strictly Autumn-maturing orb-weaver species.     

Optimal Foraging Theory: A Review of Some Models and Their Applications

Hunter-Gatherer Foraging Strategies: Ethnographic and Archeological Analyses . Bruce Winterhalter and Eric Alden Smith , eds. Chicago: University of Chicago Press, 1981. x + 268 pp. $18.00 (cloth), $7.50 (paper).     

Home Range in a Patchy Environment: Optimal Foraging Predictions

Optimal foraging rules are used to simulate the home range ofa central place forager in an environment with a patchy resourcedistribution. The model makes the following predictions: (1)Home range size is inversely related to maximum resource densityand resource renewal rate. It is positively related to the animal'srate of movement. (2) The optimal home range shape in a patchyenvironment is elongate rather than circular, with a major tominor axisratio of about 2:1. This agrees well with observedvalues. (3) The proportion of the total home range used perforaging bout is positively related to the renewal rate of theenvironment. (4) The tendency of an animal to concentrate itsactivity in a subregion of the home range (rather than distributingits activity uniformly) will increase with the maximum resourcedensity. This tendency is measured as the ratio of the areawhich will contain 65% of the occurrences of an animal to thearea required to contain 95% of its occurrences. The valuesof the ratio predicted by this model agree closely with observedvalues.     

Optimal Foraging in Hummingbirds: Testing the Marginal Value Theorem

To a hummingbird, clusters of flowers on inflorescences representpatches and provide an ideal situation to test prediction ofoptimal patch-use. The basic question is what decision ruleshould a hummingbird use to decide whether or not to leave aninflorescence? The hypothesis is that hummingbirds will adoptthe decision rule that maximizes their net rate of energy gainwhile foraging. This hypothesis leads to an analogue of Charnov'smarginal value theorem which determines an optimal decisionrule. The optimal decision ruleis then used to predict aspectsof the hummingbirds' foraging, and these predictions are comparedwith field data The optimal decision rule is a function of how much informationis used by the hummingbirds. Data indicate that a decision toleave an inflorescence is a function of the number of flowersvisited, the number of flowers available on the inflorescence,and the amount of nectar obtained at the last flower. The optimaldecision rule was calculated assuming no additional informationis used.     

Stochastic Optimal Foraging: Tuning Intensive and Extensive Dynamics in Random Searches

Recent theoretical developments had laid down the proper mathematical means to understand how the structural complexity of search patterns may improve foraging efficiency. Under information-deprived scenarios and specific landscape configurations, Lévy walks and flights are known to lead to high search efficiencies. Based on a one-dimensional comparative analysis we show a mechanism by which, at random, a searcher can optimize the encounter with close and distant targets. The mechanism consists of combining an optimal diffusivity (optimally enhanced diffusion) with a minimal diffusion constant. In such a way the search dynamics adequately balances the tension between finding close and distant targets, while, at the same time, shifts the optimal balance towards relatively larger close-to-distant target encounter ratios. We find that introducing a multiscale set of reorientations ensures both a thorough local space exploration without oversampling and a fast spreading dynamics at the large scale. Lévy reorientation patterns account for these properties but other reorientation strategies providing similar statistical signatures can mimic or achieve comparable efficiencies. Hence, the present work unveils general mechanisms underlying efficient random search, beyond the Lévy model. Our results suggest that animals could tune key statistical movement properties (e.g. enhanced diffusivity, minimal diffusion constant) to cope with the very general problem of balancing out intensive and extensive random searching. We believe that theoretical developments to mechanistically understand stochastic search strategies, such as the one here proposed, are crucial to develop an empirically verifiable and comprehensive animal foraging theory.     

Optimal Foraging Theory Perspectives on the Strategies of Itinerant Beekeepers in Semiarid Northeast Brazil

Foraging theory has been widely used to understand patterns associated with obtaining resources and the optimal cost-benefit relationship between forager and resource. However, many analytical theoretical models do not consider the influence of social groups on forager strategy. We analyzed strategies for obtaining resources from two perspectives: individual and social. For the first, we tested hypotheses that addressed whether individual strategies followed the predictions of classic models of foraging theory. In the second approach, we investigated potential social influences on resource-obtaining strategies. Our results suggest that regardless of the strategy adopted by the forager (specialist or generalist), environmental factors, such as abundance, regulated success in obtaining resources. However, we observed that specialists had a greater advantage relative to generalists when resources were abundant. We also observed that forager decision-making was related to the social context of the individual forager, which influenced their strategies.     

Saccadic Momentum and Facilitation of Return Saccades Contribute to an Optimal Foraging Strategy

The interest in saccadic IOR is funneled by the hypothesis that it serves a clear functional purpose in the selection of fixation points: the facilitation of foraging. In this study, we arrive at a different interpretation of saccadic IOR. First, we find that return saccades are performed much more often than expected from the statistical properties of saccades and saccade pairs. Second, we find that fixation durations before a saccade are modulated by the relative angle of the saccade, but return saccades show no sign of an additional temporal inhibition. Thus, we do not find temporal saccadic inhibition of return. Interestingly, we find that return locations are more salient, according to empirically measured saliency (locations that are fixated by many observers) as well as stimulus dependent saliency (defined by image features), than regular fixation locations. These results and the finding that return saccades increase the match of individual trajectories with a grand total priority map evidences the return saccades being part of a fixation selection strategy that trades off exploration and exploitation.     

Optimal Foraging Theory and the Racecar Driver: The Impact of Student-Centered Learning on Anthropological Pedagogy

This article contributes to the field of anthropological pedagogy, adding to recent articles regarding needed change in anthropology teaching methods. All have in common the practice of anthropology in the classroom. The author used the theory of optimal foraging to encourage students to operationalize human behavior. The economic benefit that students reaped warrants discussion. Students rapidly and measurably improved several areas of their lifestyle including health, finance, and home. Pursuing an anthropology degree thus becomes a personal journey.     

Methodological Problems in Evolutionary Biology. XI. Optimal Foraging Theory Revisited

Optimality theory, particularly optimal foraging theory (OFT), has spurned controversy over decades. I argue that the controversy results from conceptual pitfalls. The focus in this article is on pitfalls underlying the concept of constraint. Constraints in OFT models are a means to distinguish between possible and impossible behaviours. I argue that the seemingly innocuous notion of (im)possibility is tricky. It is indeed linked here with troublesome philosophical problems concerning free will. To steer away from such problems in OFT, we need to distinguish between hard and soft constraints. Such a distinction is necessarily context-dependent. This implies that OFT, to a large extent, should take the form of natural history rather than general theory.