Increasing availability of palatable prey induces predator-dependence and increases predation on unpalatable prey

AbstractUnderstanding the factors governing predation remains a top priority in ecology. Using a dragonfly nymph-tadpole system, we experimentally varied predator density, prey density, and prey species ratio to investigate: (i) whether predator interference varies between prey types that differ in palatability, (ii) whether adding alternate prey influences the magnitude of predator interference, and (iii) whether patterns of prey selection vary according to the predictions of optimal diet theory. In single-prey foraging trials, predation of palatable leopard frog tadpoles was limited by prey availability and predator interference, whereas predation of unpalatable toad tadpoles was limited by handling time. Adding unpalatable prey did not affect the predator’s kill rate of palatable prey, but the presence of palatable prey increased the influence of predator density on the kill rate of unpalatable prey and reduced unpalatable prey handling time. Prey selection did not change with shifts in the relative abundance of prey types. Instead, predators selected easy-to-capture unpalatable prey at low total densities and harder-to-capture palatable prey at high densities. These results improve our understanding of generalist predation in communities with mobile prey, and illustrate that characteristics of the prey types involved govern the extent to which alternate prey influence the predator’s kill rate.

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Evaluation of alternative prey-, predator-, and ratio-dependent functional response models in a zooplankton microcosm

Canadian Journal of Zoology ◽

10.1139/cjz-2016-0106 ◽

2017 ◽

Vol 95 (3) ◽

pp. 177-182 ◽

Cited By ~ 3

Author(s):

Christina M. Prokopenko ◽

Katrine Turgeon ◽

John M. Fryxell

Keyword(s):

Functional Response ◽

Theoretic Approach ◽

Type Ii ◽

Predator Density ◽

Response Models ◽

Predator Interference ◽

Kill Rate ◽

Ratio Dependent ◽

Functional Response Models ◽

Rotifer Brachionus Calyciflorus

There is strenuous debate among ecologists regarding the inclusion of predator density into the originally prey-dependent functional response. We provided comprehensive empirical comparisons of alternative functional response models for the predatory ostracod Heterocypris incongruens (Ramdohr, 1808) and the rotifer Brachionus calyciflorus (Pallas, 1766) as its prey in small freshwater microcosms. Prey killed was measured at factorial combinations of four predator densities and five prey densities, and was recorded at 3 min intervals over 60 min experiments. To support the potential effect of predator interference on per capita kill rate, we recorded ostracod activity and aggression. Kill rate increased following a saturating function with increasing prey density and decreased with increasing predator density. Model evaluation using an information–theoretic approach indicated that the Arditi–Ginzburg type II ratio-dependent model performed best, followed by the Arditi–Akcakaya and Beddington–DeAngelis type II predator-dependent models, suggesting that predator interference was important in predicting kill rates. Interference among predators increased and their activity decreased with increasing predator density, providing confirmation that interference was responsible for the predator-dependent effect. By combining a microcosm experiment and behavioral observations, our results suggest that predator interference at realistic population densities influences ostracod kill rates and this form of interference was best accommodated by predator-dependent models.

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Kill rate by wolves on moose in the Yukon

Canadian Journal of Zoology ◽

10.1139/z99-187 ◽

2000 ◽

Vol 78 (1) ◽

pp. 49-59 ◽

Cited By ~ 48

Author(s):

R D Hayes ◽

A M Baer ◽

U Wotschikowsky ◽

A S Harestad

Keyword(s):

Canis Lupus ◽

Snow Depth ◽

Prey Density ◽

Large Scale ◽

Rangifer Tarandus ◽

Prey Selection ◽

Ecological Factors ◽

Predation Rate ◽

Wolf Predation ◽

Kill Rate

We studied the kill rate by wolves (Canis lupus) after a large-scale wolf removal when populations of wolves, moose (Alces alces), and woodland caribou (Rangifer tarandus caribou) were all increasing. We followed a total of 21 wolf packs for 4 winters, measuring prey selection, kill rates, and ecological factors that could influence killing behavior. Wolf predation was found to be mainly additive on both moose and caribou populations. Kill rates by individual wolves were inversely related to pack size and unrelated to prey density or snow depth. Scavenging by ravens decreased the amount of prey biomass available for wolves to consume, especially for wolves in smaller packs. The kill rate by wolves on moose calves was not related to the number of calves available each winter. Wolves did not show a strong switching response away from moose as the ratio of caribou to moose increased in winter. The predation rate by wolves on moose was best modeled by the number and size of packs wolves were organized into each winter.

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Managing Centrarchid Fisheries in Rivers and Streams

Managing Centrarchid Fisheries in Rivers and Streams ◽

10.47886/9781934874523.ch4 ◽

2019 ◽

Keyword(s):

Community Structure ◽

Stable Isotope ◽

Prey Availability ◽

Prey Selection ◽

Trophic Position ◽

Trophic Niche ◽

Smallmouth Bass ◽

Spatial Differences ◽

Stream Size ◽

Diet Analyses

<em>Abstract.</em>—Prey selection and diet are highly plastic and can vary with temporal and spatial differences in competition or prey availability. This study investigated the possibility that the trophic position of Smallmouth Bass <em> Micropterus dolomieu </em>might change in response to systematic, hierarchical variation in community structure in stream networks. We hypothesized that a shift toward increased insectivory and decreased piscivory would be observed in smaller streams, resulting in a lower trophic position of Smallmouth Bass and reflecting differences in community structure and prey availability. We applied a combination of diet analyses and stable isotope methods to compare prey selection and trophic position of Smallmouth Bass across a range of stream sizes. Stable isotope analyses indicated that Smallmouth Bass trophic position was slightly elevated in smaller watersheds, contradicting our initial hypothesis. However, differences in average trophic position in watershed size categories were small (ranging from 3.6 to 3.8) and of limited ecological significance. Isotopic niche width did not vary among stream size categories, and gut content analyses revealed no differences in frequency of occurrence of fish, crayfish, or insects (larvae and adults). Collectively these results indicate that trophic position, and perhaps trophic niche, of Smallmouth Bass are consistent across hierarchical variation in stream size and habitat.

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Long- versus short-range foraging strategies of hoary (Lasiurus cinereus) and silver-haired (Lasionycteris noctivagans) bats and the consequences for prey selection

Canadian Journal of Zoology ◽

10.1139/z85-371 ◽

1985 ◽

Vol 63 (11) ◽

pp. 2507-2515 ◽

Cited By ~ 87

Author(s):

Robert M. R. Barclay

Keyword(s):

Short Range ◽

Prey Availability ◽

Prey Selection ◽

Foraging Strategy ◽

Foraging Strategies ◽

Lasiurus Cinereus ◽

Echolocation Calls ◽

Straight Line ◽

Lasionycteris Noctivagans ◽

Selection Of

Habitat use, temporal activity, foraging behaviour, and prey selection of hoary bats (Lasiurus cinereus) and silver-haired bats (Lasionycteris noctivagans) were studied at Delta Marsh, Manitoba. Bat activity was assessed by monitoring echolocation calls with ultrasonic detectors. Prey availability was determined using sticky and Malaise traps and dietary information was obtained from fecal analysis. Both species were active all night and foraged primarily in the lee of a narrow forested ridge. Lasionycteris noctivagans foraged in a manner that indicates that it detects and pursues prey over short distances. These bats fly slowly, are highly manoeuverable, and were commonly observed feeding on swarms of insects in small clearings. They use echolocation calls that support the notion of a short-range foraging strategy and feed opportunistically on whatever insects are available. Lasiurus cinereus, on the other hand, uses a long-range prey detection and pursuit foraging strategy. They fly rapidly along straight line paths in open areas and use echolocation calls designed to detect insects at a distance. The diet consists primarily of large insects (moths, beetles, and dragonflies), but the bats nonetheless feed opportunistically. The foraging strategy likely restricts the availability and profitability of small insects as prey.

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Hunting Behavior, Prey Selection, and Energetics of Snail Kites in Guyana: Consumer Choice by a Specialist

The Auk ◽

10.1093/auk/100.1.84 ◽

1983 ◽

Vol 100 (1) ◽

pp. 84-92 ◽

Cited By ~ 26

Author(s):

Steven R. Beissinger

Keyword(s):

Consumer Choice ◽

Prey Selection ◽

Activity Patterns ◽

Caloric Intake ◽

Handling Time ◽

Time Of Day ◽

Rice Fields ◽

Hunting Behavior ◽

Time Activity ◽

Prey Handling

Abstract The hunting behavior, snail size selection, and time-activity patterns of non-breeding Snail Kites (Rostrhamus sociabilis sociabilis) were studied in Guyana rice fields. Kites spent 62% of the photoperiod perching, 19% foraging, 13% in maintenance activities, and 6% flying. As the day progressed, the percentage of daylight hours spent perching increased significantly, while foraging decreased significantly. Kites successfully captured and ingested Pomacea snails in 78% of the foraging bouts observed. The mode of hunting was evenly split between coursing (50.7%) and still-hunting (49.3%). Searching and returning times were related to time of day, as significantly more coursing hunts and still-hunts occurred in mornings and late afternoons, respectively. Prey handling time was the most time-consuming component of a foraging bout. Time spent searching for prey, returning, or handling prey was not related to snail size. The size distribution of captured snails differed significantly from that of available snails; kites selected more medium snails and fewer small snails and took large snails in equal frequency to that at which large snails were available. Kites captured the same-sized snails when coursing as when still-hunting. As rice grew, kite utilization of rice fields declined, and the frequency of still-hunting decreased while course-hunting attempts increased. The daily caloric intake of kites was estimated to be 104.2 kcal, the daily energy expenditure 85.7 kcal. Results are discussed in relation to consumer choices of specialists. The most important decision a foraging Snail Kite may make is what patch to search in and how long to search before abandoning patches.

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Intrapopulation variation in the diet of franciscana dolphin (Pontoporia blainvillei) off southern Brazil

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315421000436 ◽

2021 ◽

pp. 1-17

Author(s):

Manuela Bassoi ◽

Eduardo R. Secchi ◽

Daniel Danilewicz ◽

Ignacio B. Moreno ◽

Roberta A. Santos ◽

...

Keyword(s):

Sexual Maturity ◽

Linear Models ◽

Prey Species ◽

Prey Availability ◽

Prey Selection ◽

Feeding Habits ◽

Stomach Contents ◽

Brazilian Coast ◽

Pontoporia Blainvillei ◽

Franciscana Dolphin

Abstract The franciscana dolphin (Pontoporia blainvillei) is a coastal dolphin endemic to the western South Atlantic Ocean. The dolphin is listed as vulnerable in the IUCN Red List, with incidental catches in gillnet fisheries the greatest conservation concern for this species. Insights into the feeding habits of this dolphin are essential to understand its distribution, movements and use of habitat, which are fundamental for effective management of the species. The feeding habits of franciscana dolphins were investigated from analyses of stomach contents of animals incidentally caught by two fishing operations from southern and northern regions of the southern Brazilian coast. In this study we investigate the existence of intrapopulation (sexual maturity and sex-related) variation in the diet of the franciscana dolphin, evaluating the spatial (northern and southern geographic areas) and seasonal influences. The analyses were based on Linear and Generalized Linear Models (LM and GLM). The majority of identified prey species were bottom-dwelling teleosts and the squid Doryteuthis sanpaulensis. The most important prey differed spatially and seasonally between northern and southern regions of the study area, and our results revealed significant differences between sexes and sexual maturity stages, mainly related to prey species sizes. This variation might indicate differences in prey selection, availability or habitat use patterns among these groups. In any case, these dietary differences are likely to minimize intraspecific competition for food resources, and/or indicate spatio-temporal variation in prey availability.

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Fish Size and Prey Availability Affect Growth, Survival, Prey Selection, and Foraging Behavior of Larval Yellow Perch

Transactions of the American Fisheries Society ◽

10.1577/t03-050.1 ◽

2004 ◽

Vol 133 (3) ◽

pp. 504-514 ◽

Cited By ~ 65

Author(s):

Brian D. S. Graeb ◽

John M. Dettmers ◽

David H. Wahl ◽

Carla E. Cáceres

Keyword(s):

Foraging Behavior ◽

Yellow Perch ◽

Prey Availability ◽

Prey Selection ◽

Fish Size

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Seasonal variation in the feeding ecology of pumas (Puma concolor) in northern California

Canadian Journal of Zoology ◽

10.1139/cjz-2013-0284 ◽

2014 ◽

Vol 92 (5) ◽

pp. 397-403 ◽

Cited By ~ 19

Author(s):

M.L. Allen ◽

L.M. Elbroch ◽

D.S. Casady ◽

H.U. Wittmer

Keyword(s):

Feeding Ecology ◽

Ursus Americanus ◽

Puma Concolor ◽

Prey Availability ◽

Black Bear ◽

Handling Time ◽

Odocoileus Hemionus ◽

Odocoileus Hemionus Columbianus ◽

Gps Collars ◽

Prey System

Direct effects of predators depend upon factors that can vary across seasons, including variations in the abundance and vulnerability of migrating prey. Past studies show conflicting results of whether puma (Puma concolor (L., 1771)) feeding ecology varies among seasons. We employed GPS collars to study puma feeding ecology in a single-prey system with migratory black-tailed deer (Odocoileus hemionus columbianus (Richardson, 1829)). We hypothesized that puma feeding ecology would vary based on changes in prey abundance and spatial distribution, as well as competition with scavengers and decomposers. Our results supported these hypotheses. Kill rates in number of ungulates/week were significantly higher in summer and autumn than in winter, likely owing to the increased availability and density of black-tailed deer fawns. The handling times of black-tailed deer ≥1 year old were significantly higher in winter than in spring, summer, or autumn. We speculated that reduced handling time in summer may have been influenced by black bear (Ursus americanus Pallas, 1780) kleptoparasitism and the decomposition of kills. Pumas killed black-tailed deer at higher elevations in summer than in winter, spring, or autumn, and the elevations correlated significantly with seasonal elevations used by black-tailed deer, suggesting that pumas exhibited seasonal foraging behaviours and tracked prey availability in a system with migrating prey.

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A test of optimal foraging and the effects of predator experience in the lizards Sceloporus jarrovii and Sceloporus virgatus

Behaviour ◽

10.1163/000579510x498219 ◽

2010 ◽

Vol 147 (8) ◽

pp. 933-951 ◽

Cited By ~ 8

Author(s):

Keyword(s):

Success Rate ◽

Prey Capture ◽

Prey Availability ◽

Search Time ◽

Handling Time ◽

Foraging Efficiency ◽

Prey Choice ◽

Foraging Experience ◽

Time Optimality ◽

Sceloporus Virgatus

AbstractForaging efficiency of predators can be evaluated by using optimality or profitability models which incorporate prey choice, handling time and pursuit or search time. Optimality of a diet could vary based on the age, sex, size, predation risk, or foraging experience of the predator. This study tested the effects of a predator's age and foraging experience by observing prey capture attempts and success rate, and by calculating diet profitability for adult and neonate Sceloporus jarrovii and adult Sceloporus virgatus. Prey availability was assessed in order to determine prey preference and profitability. Neonates showed an increased number of prey capture attempts, but success rate was similar for neonates and adults of both species. Total diet profitability of neonates was lower than adults of either species, which could be a result of poor prey choice or gape limitation (although body size showed no direct effect). Overall, the diets of all three groups were less profitable than would be expected based on the types of prey in the environment, although this is likely due to low availability (from the lizard's perspective) of highly profitable items. Lizards seem to be eating prey items in the same proportion as they are found in the environment.

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