Diet Optimization with a Nutrient or Toxin Constraint

Hirakawa, Hirofumi

doi:10.1006/tpbi.1995.1015

Cited by 24 publications

(41 citation statements)

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“…The DRM was developed for predators feeding on prey with indigestible bulk, and predicts that energy intake rate of predators depends on the digestive rate, which makes processing time rather than search/handling time the limiting factor (Verlinden and Wiley, 1989;Hirakawa, 1995;van Gils et al, 2005b). The subjects of the present study are well-known digestively constrained predators limited by the amount of shell mass that can be processed per unit time (Piersma et al, 1993a;van Gils et al, 2003;van Gils et al, 2005b).…”

Section: Discussionmentioning

confidence: 99%

Economic design in a long-distance migrating molluscivore: how fast-fuelling red knots in Bohai Bay, China, get away with small gizzards

Yang

Chen

et al. 2013

Journal of Experimental Biology

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SUMMARYWe carried out an observational and experimental study to decipher how resource characteristics, in interaction with the predator's phenotype, constrain a fitness-determining performance measure, i.e. refuelling in a migrant bird. Two subspecies of red knot (Calidris canutus rogersi and C. c. piersmai) use northern Bohai Bay, Yellow Sea, China, for the final prebreeding stopover, during their 10,000-15,000km long migrations between wintering and breeding areas. Here, they feed on small bivalves, especially 2-7mm long Potamocorbula laevis. With an average stay of 29days, and the need to store 80g of fat for the onward flights to high-Arctic breeding grounds, red knots need to refuel fast. Using existing knowledge, we expected them to achieve this on the basis of (1) prey with high flesh to shell mass ratios, (2) large gizzards to crush the ingested molluscs, or (3) a combination of the two. Rejecting all three predictions, we found that red knots staging in Bohai Bay had the smallest gizzards on record (4.9±0.8g, mean ± s.e.m., N=27), and also found that prey quality of P. laevis is much lower than predicted for the measured gizzard size (i.e. 1.3 rather than the predicted 4.5kJg -1 dry shell mass, DM shell ). The estimated handling time of P. laevis (0.2s) is much shorter than the observed time between two prey ingestions (0.7s), indicating that prey handling time is no constraint. Based on field observations of dropping rates and on indoor digestion trails, the shell processing rate was estimated at 3.9mg DM shell s -1 , i.e. three times higher the rate previously predicted for red knots eating as fast as they can with the measured gizzard size. This is explained by the small and easily crushed P. laevis enabling high processing rates. As P. laevis also occurred in high densities, the metabolizable energy intake rate of red knots with small gizzards at 5Js -1 was as high as at northward staging sites elsewhere in the world. Currently, therefore, food characteristics in Bohai Bay are such that red knots can refuel fast whilst economizing on the size of their gizzard. These time-stressed migrants thus provide an elegant example of symmorphosis. Supplementary material available online at

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Section: Discussionmentioning

confidence: 99%

Economic design in a long-distance migrating molluscivore: how fast-fuelling red knots in Bohai Bay, China, get away with small gizzards

Yang

Chen

et al. 2013

Journal of Experimental Biology

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“…We restricted our analyses in this paper to these six prey species. Prey too large to be ingested were excluded, applying [16,29,30]. This model accurately predicted the diet of red knots, under both experimental and field conditions [16,17,31].…”

Section: (A) Study Sitesmentioning

confidence: 99%

“…This model accurately predicted the diet of red knots, under both experimental and field conditions [16,17,31]. For mathematical details, we refer to Hirakawa [30] or van Gils et al [16], but we will briefly review the basics here. When multiple prey types are available, the DRM predicts the optimal diet composition that maximizes long-term average energy intake rate (Y in electronic supplementary material, table S1) under the constraints of finding, handling and digesting prey.…”

Section: (A) Study Sitesmentioning

confidence: 99%

Scaling up ideals to freedom: are densities of red knots across western Europe consistent with ideal free distribution?

et al. 2011

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Local studies have shown that the distribution of red knots Calidris canutus across intertidal mudflats is consistent with the predictions of an ideal distribution, but not a free distribution. Here, we scale up the study of feeding distributions to their entire wintering area in western Europe. Densities of red knots were compared among seven wintering sites in The Netherlands, UK and France, where the available mollusc food stocks were also measured and from where diets were known. We tested between three different distribution models that respectively assumed (i) a uniform distribution of red knots over all areas, (ii) a uniform distribution across all suitable habitat (based on threshold densities of harvestable mollusc prey), and (iii) an ideal and free distribution (IFD) across all suitable habitats. Red knots were not homogeneously distributed across the different European wintering areas, also not when considering suitable habitats only. Their distribution was best explained by the IFD model, suggesting that the birds are exposed to interference and have good knowledge about their resource landscape at the spatial scale of NW Europe, and that the costs of movement between estuaries, at least when averaged over a whole winter, are negligible.

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“…However, even in herbivores (Hirakawa 1997a;Verlinden and Wiley 1989) and molluscivores (van Gils et al 2005;Quaintenne et al 2010) that have essentially immobile prey, optimal foraging theory fails to predict the observed diet preferences. In these cases, the digestive rate model (DRM; Verlinden and Wiley 1989;Hirakawa 1995Hirakawa , 1997b) is shown to better predict animal diet preference, but the DRM itself is the result of generalizing the prey model (i.e., rate maximization) to include the effect of digestive constraints.…”

Section: Consequentlymentioning

confidence: 99%

“…The DRM of Hirakawa (1995) is a correction of related foraging constraint models from Pulliam (1974), Stephens and Krebs (1986), and Verlinden and Wiley (1989). It maximizes the same rate expression from Eq.…”

Section: Consequentlymentioning

confidence: 99%

When rate maximization is impulsive

Pavlic

Passino

2010

Behav Ecol Sociobiol

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Although optimal foraging theory predicts that natural selection should favor animal behaviors that maximize long-term rate of gain, behaviors observed in the laboratory tend to be impulsive. In binary-choice experiments, despite the long-term gain of each alternative, animals favor short handling times. Most explanations of this behavior suggest that there is hidden rationality in impulsiveness. Instead, we suggest that simultaneous and mutually exclusive binary-choice encounters are often unnatural and thus immune to the effects of natural selection. Using a simulation of an imperfect forager, we show how a simple strategy (i.e., an intuitive model of animal behavior) that maximizes long-term rate of gain under natural conditions appears to be impulsive under operant laboratory conditions. We then show how the accuracy of this model can be verified in the laboratory by biasing subjects with a short pre-experiment ad libitum high-quality feeding period. We also show a similar behavioral mechanism results in diet preferences that are qualitatively consistent with the digestive rate model of foraging (i.e., foraging under digestive rate constraints).

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Diet Optimization with a Nutrient or Toxin Constraint

Cited by 24 publications

References 0 publications

Economic design in a long-distance migrating molluscivore: how fast-fuelling red knots in Bohai Bay, China, get away with small gizzards

Economic design in a long-distance migrating molluscivore: how fast-fuelling red knots in Bohai Bay, China, get away with small gizzards

Scaling up ideals to freedom: are densities of red knots across western Europe consistent with ideal free distribution?

When rate maximization is impulsive

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