Shape and sources of variations of the functional response of wildfowl: an experiment with mallards, <i>Anas platyrhynchos</i>

Fritz, Hervé; Durant, Daphné; Guillemain, Matthieu

doi:10.1034/j.1600-0706.2001.930314.x

Cited by 29 publications

(38 citation statements)

References 34 publications

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“…However, if scallops are too small ( £ 8 mm SH), a functional response would not likely be observed, since crabs (>95 mm carapace width) have difficulty detecting and handling them (Barbeau and Scheibling 1994b). Effects of prey size similar to our study have also been observed when mallards (Anas platyrhynchos) consume three sizes of food pellets (Fritz et al 2001), and aquatic insects (Chaoborus americanus) four sizes of crustaceans (Daphnia pulex) (Spitze 1985). In both of these studies, predators had a type II functional response on small prey and no functional response on larger prey.…”

Section: The Functional Response Of Rock Crabssupporting

confidence: 77%

“…Prey size is a factor that has previously been shown to affect the functional response of predators (Spitze 1985;Eggleston 1990a;Fritz et al 2001). Although we did not directly compare the effect of prey size in our study, rock crabs showed very different responses in experiments 1 and 2, which used different sized prey.…”

Section: The Functional Response Of Rock Crabsmentioning

confidence: 99%

“…The size of prey seeded may also influence a predator's functional response since certain sized prey may be easier for predators to handle (Barbeau and Scheibling 1994b), and thus be consumed in higher amounts (Spitze 1985). Different substrates and prey sizes may change the type of functional response (Lipcius and Hines 1986), or certain characteristics such as plateau level or length of density dependence (Hildrew and Townsend 1977;Spitze 1985;Fritz et al 2001;Wong et al in press).…”

Section: Introductionmentioning

confidence: 95%

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Rock crab predation of juvenile sea scallops: the functional response and its implications for bottom culture

Wong

Barbeau

2006

Aquacult Int

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The functional response describes how consumption rate of individual predators changes as prey density changes, and can have important implications for the bottom culture of scallops. We examined (i) the functional response of rock crabs (Cancer irroratus) preying on juvenile sea scallops (Placopecten magellanicus); (ii) the effect of substrate type and scallop size on the functional response; and (iii) the underlying behavioural mechanisms of observed functional responses. Specifically, we quantified predation rate and behaviours, such as the proportion of time spent searching for prey, encounter rate between predators and prey and the outcomes of encounters, when individual rock crabs were offered a range of scallop density (2-50 or 11-111 scallops m )2 ) and two size classes of scallops ($25 and $35 mm shell height) on two different substrate types (''glass-bottom'' and ''granule''). We found that crab predation rate on small juvenile scallops increased at a decelerating rate with prey density to a plateau at high prey density on both substrates, indicating a hyperbolic (type II) functional response. Crab predation rate on large juvenile scallops was independent of prey density (i.e., no functional response evident), suggesting that crabs were at their satiation level. Prey density did not influence any behaviour except encounter rate on small juvenile scallops, which increased as prey density increased. Substrate type influenced crab predation: maximum predation rate of crabs on small juvenile scallops and encounter rate with either size of juvenile scallops was lower on granule than on glass-bottom. Our results in the laboratory suggest that crabs could potentially be swamped if scallops are seeded at a high density in the field. However, many factors in the field may influence the functional response. For example, the presence of multiple prey types may lead to sigmoid functional responses, while the presence of many crab individuals may lead to aggregation of crabs in areas of high prey density.

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Section: The Functional Response Of Rock Crabssupporting

confidence: 77%

Section: The Functional Response Of Rock Crabsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 95%

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Rock crab predation of juvenile sea scallops: the functional response and its implications for bottom culture

Wong

Barbeau

2006

Aquacult Int

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“…Karasov and Martinez del Rio (2007) also proposed that secondary metabolites, common in foods of plant origin, including many fleshy fruits, may also elevate the bird's water requirements. Other food processing and dietary constraints specifically related to a fruit-based diet, such as gut capacity and mechanical function (Kersten and Visser 1996;Karasov and McWilliams 2005) and food handling and swallowing (Fritz et al 2001;Jeschke et al 2002;Durant et al 2003), may also be affected by water intake. The effects of these mechanisms may be entwined and hard to separate.…”

Section: Discussionmentioning

confidence: 98%

Drinking water boosts food intake rate, body mass increase and fat accumulation in migratory blackcaps (Sylvia atricapilla)

et al. 2008

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Fat accumulation by blackcaps (Sylvia atricapilla) is a prerequisite for successful migratory flight in the autumn and has recently been determined to be constrained by availability of drinking water. Birds staging in a fruit-rich Pistacia atlantica plantation that had access to water increased their body mass and fat reserves both faster and to a greater extent than birds deprived of water. We conducted a series of laboratory experiments on birds captured during the autumn migration period in which we tested the hypotheses that drinking water increases food use by easing limitations on the birds' dietary choices and, consequently, feeding and food processing rates, and that the availability of drinking water leads to improved digestion and, therefore, to higher apparent metabolizable energy. Blackcaps were trapped in autumn in the Northern Negev Desert, Israel and transferred to individual cages in the laboratory. Birds were provided with P. atlantica fruit and mealworms, and had either free access to water (controls) or were water-deprived. In experiment 1, in which mealworm availability was restricted, water-deprived birds had a fourfold lower fruit and energy intake rates and, consequently, gained less fat and total mass than control birds. Water availability did not affect food metabolizability. In experiment 2, in which mealworms were provided ad libitum, water availability influenced the birds' diet: water-restricted birds ate more mealworms, while control birds consumed mainly P. atlantica fruit. Further, in experiment 2, fat and mass gain did not differ between the two treatment groups. We conclude that water availability may have important consequences for fat accumulation in migrating birds while they fatten at stopover sites, especially when water-rich food is scarce. Restricted water availability may also impede the blackcap's dietary shift from insectivory to frugivory, a shift probably necessary for successful pre-migratory fattening.

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“…In several studies, ANOVAs with proportional mortality have been employed (Lipcius & Hines 1986, Eggleston 1990a, Sponaugle & Lawton 1990. However, high inherent variability between individuals (as in this study; see also Eggleston 1990b, Fritz et al 2001, Juliano 2001) often makes it difficult for post-hoc comparisons to locate differences. Other studies have used logistic regression of proportional mortality and prey density (Trexler et al 1988, Juliano 2001, but many data sets (such as ours) do not easily fit into this framework.…”

Section: Discussionmentioning

confidence: 99%

Behavioural mechanisms underlying functional response of sea stars Asterias vulgaris preying on juvenile sea scallops Placopecten magellanicus

Wong¹,

Barbeau²,

Dowd³

et al. 2006

Mar. Ecol. Prog. Ser.

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The functional response characterises the relationship between prey density and the consumption rate of individual predators. Typically, it is studied by fitting a model to observations of predation rate at different prey densities. The behavioural mechanisms underlying a functional response are not well understood, and estimates of model parameters seldom conform to observations of behaviour. We have developed a mechanistic approach that directly incorporates behavioural observations into characterisation of the functional response. Laboratory experiments were used to record predation rates and observe foraging behaviour of sea stars Asterias vulgaris preying on juvenile sea scallops Placopecten magellanicus at different densities. Experiments were conducted in tanks with no sediment and tanks with sediment. Behavioural data from the experiments were used to calculate parameters of functional response models T h (handling time per prey) and a (rate of successful search). On both substrates, T h remained constant across prey density, while a was densitydependent. An inverse quadratic was used to describe a and was incorporated into a functional response model. Estimates of a were also obtained by fitting the functional response model to the predation rate data using regression analysis. These estimates of a were highly consistent with the estimates calculated from behavioural data. On both substrates, sea stars preying on scallops had a Type III sigmoid-shaped functional response; on sediment, predation rate decreased at high prey densities. Sea star ability to capture attacked prey was probably the mechanism underlying the observed responses. In general, behavioural information can lead to better understanding of observed functional responses.

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Shape and sources of variations of the functional response of wildfowl: an experiment with mallards, Anas platyrhynchos

Cited by 29 publications

References 34 publications

Rock crab predation of juvenile sea scallops: the functional response and its implications for bottom culture

Rock crab predation of juvenile sea scallops: the functional response and its implications for bottom culture

Drinking water boosts food intake rate, body mass increase and fat accumulation in migratory blackcaps (Sylvia atricapilla)

Behavioural mechanisms underlying functional response of sea stars Asterias vulgaris preying on juvenile sea scallops Placopecten magellanicus

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