Data paper: FoRAGE (Functional Responses from Around the Globe in all Ecosystems) database: a compilation of functional responses for consumers and parasitoids

2020

Ecology

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157

Functional responses describe how consumer foraging rates change with resource density. Despite extensive research looking at the factors underlying foraging interactions, there remains ongoing controversy about how temperature and body size control the functional response parameters space clearance (or attack) rate and handling time. Here, we investigate the effects of temperature, consumer mass, and resource mass using the largest compilation of functional responses yet assembled. This compilation contains 2,083 functional response curves covering a wide range of foragers and prey types, environmental conditions, and habitats. After accounting for experimental arena size, dimensionality of the foraging interaction, and consumer taxon, we find that both space clearance rate and handling time are optimized at intermediate temperatures (a unimodal rather than monotonic response), suggesting that the response to global climate change depends on the location of the consumer’s current temperature relative to the optimum. We further confirm that functional responses are higher and steeper for large consumers and small resources, and models using consumer and resource masses separately outperformed models using consumer:resource mass ratios, suggesting that consumer and resource body mass act independently to set interaction strengths. Lastly, we show that the extent to which foraging is affected by temperature or mass depends on the taxonomic identity of the consumer and the dimensionality of the consumer–resource interaction. We thus argue that although overall body size and temperature effects can be identified, they are not universal, and therefore food web and community modeling approaches could be improved by considering taxonomic identity along with body size and unimodal temperature effects.

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Functional responses are maximized at intermediate temperatures

Uiterwaal

2020

Ecology

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157

“…The range of parameters considered are well within those that have been observed in traditional functional response experiments (Uiterwaal et al, 2018). Some of the parameter combinations and initial prey densities used for the simulations led to total times required to consume all prey that would be difficult to achieve experimentally (alternative experimental designs may be possible for predators in which consuming all prey is unlikely or would take too much time; see Discussion).…”

Section: Simulation Studymentioning

confidence: 83%

“…We placed a vaguely informative Cauchy prior with µ = 10 and σ = 10 truncated at zero on the space clearance rate and a vaguely informative Cauchy prior with µ = 0 and σ = 2 truncated below at zero and above at the minimum observed time between feeding events. The priors were derived from the FoRAGE database using the observed space clearance rates and handling times for invertebrate predators feeding on invertebrate prey (Uiterwaal et al, 2018). A maximum likelihood approach to estimating the spider functional responses is outlined in Online Supplementary Material 1.…”

Section: Empirical Study -Bold Jumping Spidersmentioning

confidence: 99%

“…It is no surprise then that ecologists have spent decades performing experiments to measure functional responses. For example, in a recent effort to compile a database of functional response experiments (the Functional Responses from Around the Globe in all Ecosystems or FoRAGE database), Uiterwaal et al (2018) collated over 2,000 functional response experiments from the literature. Despite this monumental effort devoted to measuring functional responses, there remain many open questions regarding functional responses that are difficult to address using the traditional 'gold standard' functional response experimental design.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Estimating predator functional responses using the times between prey captures

Coblentz

2020

Preprint

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Predator functional responses, which describe how predator feeding rates change with prey densities, are a core component of predator-prey theory. Given their importance, ecologists have measured thousands of predator functional responses. However, most of these studies have used a single standard experimental method that is ill-suited to address many current, pressing questions regarding functional responses.We derive a new experimental design and statistical analysis that quantifies the parameters of predator functional responses by using the time between a predator’s feeding events and can be used with individual predators requiring only one or a few trials. We examine the feasibility of this experimental method and analysis by using simulations to examine the ability of the statistical model to estimate the ‘true’ functional response parameters from simulated data. We also perform a proof-of-concept experiment estimating the functional responses of two individual jumping spiders feeding on midges.Our simulations show that the statistical method is capable of reliably estimating functional response parameters under a wide range of parameter values and sample sizes. Our proof-of-concept experiment illustrates that the experimental design and statistical method provided reasonable estimates of functional response parameters and good fits to the data for individual jumping spiders using only a few trials per individual.By virtue of the fewer number of trials required to measure a functional response, the method derived here promises to expand the questions that can be addressed using functional response experiments and the systems for which functional responses can be measured. For example, this method is well-poised to address questions such as intraspecific variation in predator functional response parameters and the role of predator and prey traits and abiotic conditions on shaping functional responses. We hope, therefore, that this time-between-captures method will refine our understanding of functional responses and thereby our understanding of predator-prey interactions more generally.

Estimating predator functional responses using the times between prey captures

Coblentz

2021

Ecology

Self Cite

Predator functional responses describe predator feeding rates and are central to predator-prey theory. Ecologists have measured thousands of predator functional responses using the same basic experimental method. However, this design is ill-suited to address many current questions regarding functional responses. We derive a new experimental design and statistical analysis that quantifies functional responses using the times between a predators' feeding events requiring only one or a few trials. We examine the feasibility of the experimental method and analysis using simulations to assess the ability of the statistical model to estimate functional response parameters and perform a proof-of-concept experiment estimating the functional responses of two individual jumping spiders. Our simulations show that the statistical method reliably estimates functional response parameters. Our proof-of-concept experiment illustrates that the method provides reasonable estimates of functional response parameters. By virtue of the fewer number of trials required to measure a functional response, the method derived here promises to expand the questions that can be addressed using functional response experiments and the systems in which they can be measured. Thus, we hope that our method will refine our understanding of functional responses and predator-prey interactions more generally.