Measured foraging strategies often cluster around values that maximize the ratio of energy gained over energy spent while foraging (efficiency), rather than values that would maximize the long-term net rate of energy gain (rate). The reasons for this are not understood. This paper focuses on time and energy constraints while foraging to illustrate the relationship between efficiency and rate-maximizing strategies and develops models that provide a simple framework to analyze foraging strategies in two distinct foraging contexts. We assume that while capturing and ingesting food for their own use (which we term feeding), foragers behave so as to maximize the total net daily energetic gain. When gathering food for others or for storage (which we term provisioning), we assume that foragers behave so as to maximize the total daily delivery, subject to meeting their own energetic requirements. In feeding contexts, the behavior maximizing total net daily gain also maximizes efficiency when daily intake is limited by the assimilation capacity. In contrast, when time available to forage sets the limit to gross intake, the behavior maximizing total net daily gain also maximizes rate. In provisioning contexts, when daily delivery is constrained by the energy needed to power self-feeding, maximizing efficiency ensures the highest total daily delivery. When time needed to recoup energetic expenditure limits total delivery, a low self-feeding rate relative to the rate of energy expenditure favors efficient strategies. However, as the rate of self-feeding increases, foraging behavior deviates from efficiency maximization in the direction predicted by rate maximization. Experimental manipulations of the rate of self-feeding in provisioning contexts could be a powerful tool to explore the relationship between rate and efficiency-maximizing behavior. Key words: Efficiency, energy gain, foraging strategies, provisioning. [Behav Ecol 5:28-34 (1994) ' I 'he economic analysis of foraging behavior is _L based on the assumption that foragers behave so as to maximize a goal function assumed to be linked to fitness (Stephens and Krebs, 1986). The goal function incorporates costs and benefits and is referred to as a fitness currency. Studies of foraging behavior have considered a variety of currencies including the rate of energy gain and energetic efficiency, defined as the ratio of energy gained over energy spent while foraging. Other currencies, largely variations on the previous themes, have also been considered (e.g., family gain: Kacelnik, 1984; overall delivery rate: Houston, 1986; see also Fagerstrom et a]., 1983; Montgomerie et al., 1984). Different currencies have made successful predictions in different studies, but the rationale underlying the use of one currency instead of another is not always clear.Efficiency was recognized and discarded as a potential currency in some of the first papers on foraging theory. The argument for rejecting efficiency as a currency goes as follows: If a forager can gain 2 J for the expenditure o...
A variety of competing hypotheses have been described to explain yield decline in Chinese-fir (Cunninghamia lanceolata (Lamb.) Hook.) plantations. The difficulty in implementing field experiments suggests ecosystem modeling as a viable option for examining alternative hypotheses. We present a conceptual model of Chinese-fir yield decline and explore its merits using the ecosystem-based FORECAST model. Model results suggest that yield decline is caused primarily by a decline in soil fertility, largely as a consequence of slash burning in conjunction with short rotations. However, as tree leaf area declines, there is a transition (over subsequent rotations) from seed rain based competition to bud bank based competition, increasing the competitive impact of minor vegetation on tree growth. Short rotations increase understory survival between rotations and may cause a gradual shift from tree dominance to shrub/herb dominance over subsequent rotations. These effects are most evident on nutrient-poor sites, but understory competition poses a significant yield decline risk on good sites as well. We conclude that sustainable production in Chinese-fir plantations requires the avoidance of activities that compromise soil fertility and increase understory competition. The risk and severity of yield decline would be reduced by increasing rotation lengths and avoiding plantations on infertile sites.Résumé : Plusieurs hypothèses concurrentes ont été décrites pour expliquer le déclin du rendement des plantations de sapin chinois (Cunninghamia lanceolata (Lamb.) Hook.). La difficulté d'établir des expériences de terrain nous amène à considérer la modélisation des écosystèmes comme une option viable pour examiner des hypothèses concurrentes. Nous présentons un modèle conceptuel du déclin du rendement du sapin chinois et évaluons sa performance à l'aide du modèle FORECAST qui a l'écosystème pour fondement. Les résultats du modèle indiquent que le déclin du rendement est principalement causé par une diminution de la fertilité du sol qui serait en grande partie attribuable au brûlage des déchets de coupe jumelé à de courtes rotations. Cependant, avec la diminution de la surface foliaire des arbres, une transition s'opère (au fil des rotations), passant d'une compétition basée sur la pluie de graines vers une compétition basée sur la banque de bourgeons, ce qui augmente l'impact compétitif de la végétation basse sur la croissance des arbres. Les courtes rotations ont pour effet d'augmenter la survie des plantes de sous-bois entre les rotations et peuvent causer une transition graduelle d'une dominance des arbres vers une dominance des arbustes et des herbacées au fil des rotations. Ces effets sont plus manifestes dans les stations pauvres en nutriments, mais la compétition par les plantes de sous-bois risque aussi de diminuer significativement le rendement des bonnes stations. Nous concluons que pour obtenir une production soutenue des plantations de sapin chinois, on doit éviter les activités qui compromettent la fertilité du sol et...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.