Predator feeding rates may often be unsaturated under typical prey densities

Coblentz, Kyle E.; Novák, Márk; DeLong, John P.

doi:10.1101/2022.08.09.503207

Cited by 2 publications

(1 citation statement)

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“…Most relevant work has focused on the gut‐evacuation rates of prey mass in fishes, but with little focus on generalist predators' diverse prey attributes (Preston et al, 2017). In the functional‐response literature, handling and digestion times are primarily considered important only at high prey abundances, where feeding rates are limited by saturation or satiation (Coblentz et al, 2022; Jeschke et al, 2002). The potential for the effect of which Pearson (1897) warned to alter the interpretation of apparent diets for many more types of taxa indicates that more attention to detection times is warranted, and that factors to which handling and digestion times are sensitive may be more important for feeding rates than currently assumed even at prey abundances far below the point of saturation.…”

Section: Discussionmentioning

confidence: 99%

High variation in handling times confers 35‐year stability to predator feeding rates despite community change

Novák

2023

Ecology

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Historical resurveys of ecological communities are important for placing the structure of modern ecosystems in context. Rarely, however, are snapshot surveys alone sufficient for providing direct insight into the rates of the ecological processes underlying community functioning, either now or in the past. In this study, I used a statistically reasoned observational approach to estimate the feeding rates of a New Zealand intertidal predator, Haustrum haustorium, using diet surveys performed at several sites by Robert Paine in 1968-1969 and by me in 2004. Comparisons between time periods reveal a remarkable consistency in the predator's prey-specific feeding rates, which contrasts with the changes I observed in prey abundances, the predator's body-size distribution, and the prey's proportional contributions to the predator's apparent diet. Although these and additional changes in the predator's per-capita attack rates seem to show adaptive changes in its prey preferences, they do not. Rather, feeding-rate stability is an inherently statistical consequence of the predator's high among-prey variation in handling times which determine the length of time that feeding events will remain detectable to observers performing diet surveys. Though understudied, similarly high among-prey variation in handling (or digestion) times is evident in many predator species throughout the animal kingdom. The resultant disconnect between a predator's apparent diet and its actual feeding rates suggests that much of the temporal, biogeographic, and seemingly context-dependent variation that is often perceived in community structure, predator diets, and food-web topology may be of less functional consequence than assumed. Qualitative changes in ecological pattern need not represent qualitative changes in ecological process.

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Section: Discussionmentioning

confidence: 99%

High variation in handling times confers 35‐year stability to predator feeding rates despite community change

Novák

2023

Ecology

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Food web context modifies predator foraging and weakens trophic interaction strength

Lemmen,

Pennekamp

2024

Preprint

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Trophic interaction modifications (TIM) are widespread in natural systems and occur when a third species indirectly alters the strength of a trophic interaction. Past studies have focused on documenting the existence and relative magnitude of TIMs, however the underlying processes and long-term consequences often remain elusive. To address this gap, we experimentally quantified the density-dependent effect of a third species on a predator's functional response to identify the processes impacted by, and consequences of TIMs. To do so we conducted short-term experiments with two ciliate communities each composed of a predator, prey, and non-consumable 'modifier' species. In both communities, increasing modifier density weakened the trophic interaction strength, due to a negative effect on the predator's search clearance rate, however the magnitude of the effect differed with prey species identity. Using parameters estimated from our experimental observation we simulated long-term dynamics and observed quantitative differences between models that account for TIMs or include only pairwise interactions. Our study is a clear demonstration that TIMs are important to understand and predict community dynamics and highlights the need to extend past pairs of focal species to understand the consequences of species interactions in communities.

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Predator feeding rates may often be unsaturated under typical prey densities

Cited by 2 publications

References 56 publications

High variation in handling times confers 35‐year stability to predator feeding rates despite community change

High variation in handling times confers 35‐year stability to predator feeding rates despite community change

Food web context modifies predator foraging and weakens trophic interaction strength

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