Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “predation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 217 records · Page 12Linked to original sources
PubMed2004

Habitat structural complexity mediates the foraging success of multiple predator species.

We investigated the role of freshwater macrophytes as refuge by testing the hypothesis that predators capture fewer prey in more dense and structurally complex habitats. We also tested the hypothesis that habitat structure not only affects the prey-capture success of a single predator in isolation, but also the effectiveness of two predators combined, particularly if it mediates interactions between the predators. We conducted a fully crossed four-factorial laboratory experiment using artificial plants to determine the separate quantitative (density) and qualitative (shape) components of macrophyte structure on the prey-capture success of a predatory damselfly, Ischnura heterosticta tasmanica, and the southern pygmy perch, Nannoperca australis. Contrary to our expectations, macrophyte density had no effect on the prey-capture success of either predator, but both predators were significantly less effective in the structurally complex Myriophyllum analogue than in the structurally simpler Triglochin and Eleocharis analogues. Furthermore, the greater structural complexity of Myriophyllum amplified the impact of the negative interaction between the predators on prey numbers; the habitat use by damselfly larvae in response to the presence of southern pygmy perch meant they captured less prey in Myriophyllum. These results demonstrate habitat structure can influence multiple predator effects, and support the mechanism of increased prey refuge in more structurally complex macrophytes.

Analysis of Variance↗
PubMed2004

Predation by sparrowhawks decreases with increased breeding density in a songbird, the great tit.

Predators may regulate prey populations if predation rate increases with prey density. Alternatively, if space-limited (e.g. territorial) predators become 'satiated' when prey exceed a certain density, increased prey abundance may lead to reduced predation rate. These alternatives have been difficult to test experimentally for mobile prey in the wild. We present such a test, manipulating the density of great tits (Parus major) by adding nest boxes in territories of sparrowhawks (Accipiter nisus). Predation rate was measured for young tits after they left the nests. Although the great tit is an important prey, there was no evidence for regulation during the breeding season: the rate of hawk predation declined with increasing density of tits. This result was not confounded by changes in breeding density of alternative prey species (other songbirds). Hawk predation can therefore favour dense breeding in a territorial (solitary) bird, and conspecific attraction and aggregation reported in several territorial species may partly result from predation pressure. This result also has potential implications for conservation work.

Animals↗
PubMed2004

Dynamics of demographically open mutualists: immigration, intraspecific competition, and predation impact goby populations.

Although it is now recognized that mutualistic species are common and can have stable populations, the forces controlling their persistence are poorly understood. To better understand the mechanisms that impact the stability of obligate mutualists, I conducted several field experiments within a sandy coral reef lagoon in Moorea, French Polynesia that manipulated densities of fish (gobies) that interact mutualistically with shrimp. Obligate, mutualistic partnerships of gobies and shrimp are common on Indo-Pacific coral reefs and have been shown previously to interact as follows: shrimp construct burrows in which both species reside, and gobies warn shrimp of predators through tactile communication. Augmentation of gobies by up to 100% above ambient densities within 9 m2 plots produced no change in overall density of gobies or shrimp because gobies competed intraspecifically for a limited number of shrimp burrows and smaller gobies were outcompeted by larger individuals. I used predators to assess the impact of goby removal on the stability of goby and shrimp populations. First, although surveys taken throughout the lagoon revealed no relationship between goby and predator densities, predators correlated negatively with the proportion of adult gobies and positively with the proportion of small gobies paired with large shrimp. Second, experimental augmentation of predators resulted in a dramatic reduction of adult gobies within predator-addition plots, but had no impact on overall densities as immigrants rapidly replaced the missing adult gobies. Furthermore, goby turnover resulted in an increase in the proportion of small gobies paired with large shrimp because body sizes of gobies and shrimp in a burrow were similar prior to predator introduction, and predators apparently had a greater impact on gobies than shrimp. The mechanisms that prevent expansion (intraspecific competition) and collapse (immigration) of goby-shrimp populations likely contribute to local-scale stability of mutualistic populations in other terrestrial and aquatic environments.

Animals↗
PubMed2006

Detecting emergent effects of multiple predator species.

When foraging together, multiple predator species that share a single prey often cause prey mortality that cannot be predicted based on knowledge of predation by each species separately. Modeling and managing the effects of multiple predator species depend on accurately assessing these combined effects. Two methods are currently used to experimentally examine combined predation by multiple predator species: the additive and substitutive experimental designs. I simultaneously employed both experimental designs to examine predation by two crab species on shared mussel prey. I show that the two methods yield results that disagree both quantitatively and qualitatively, leading to very different conclusions about the way that predator species combine to affect prey mortality. This discrepancy occurred because the two methods examine complimentary, but not interchangeable questions. I advocate using an experimental design that incorporates both additive and substitutive designs to achieve a more complete understanding of the combined effects of multiple predator species.

Animals↗
PubMed2006

The effects of resource enrichment, dispersal, and predation on local and metacommunity structure.

Community structure is the observable outcome of numerous processes. We conducted a laboratory experiment using a microbial model system to disentangle effects of nutrient enrichment, dispersal, and predation on prey species richness and predator abundance at local and metacommunity scales. Prey species included: Chilomonas sp., Colpidium striatum, Colpoda cucullus, Paramecium tetraurelia, P. caudatum, Philodina sp., Spirostomum sp., Tetrahymena thermophila, and Uronema sp., and Stentor coeruleus was the predator used. We hypothesized that: (1) increased basal resources should maintain greater species richness and higher predator abundance; (2) dispersal should maintain greater species richness; and (3) predation should reduce species richness, especially in the high resource treatments relative to no-predator treatments. Our results support all three hypotheses. Further, we show that dispersal affects richness at the local community scale but not at the metacommunity scale. However, predation seems to have major effects at both the local and metacommunity scale. Overall, our results show that effects of resource enrichment, dispersal, and predation were mostly additive rather than interactive, indicating that it may be sometimes easier to understand their effects than generally thought due to complex interactive effects.

Analysis of Variance↗
PubMed2006

Predators induce egg retention in prey.

To prevent predation on their eggs, prey often avoid patches occupied by predators. As a result, they need to delay oviposition until they reach predator-free patches. Because many species allocate energy to egg production in a continuous fashion, it is not clear what kind of mechanism prey use to delay oviposition. We used females of the phytoseiid mite Neoseiulus cucumeris to study these mechanisms. Females were placed in patches with pollen, a food source they use for egg production, and they were exposed to another phytoseiid mite, Iphiseius degenerans, which is an intraguild predator of N. cucumeris juveniles. We found that the oviposition of N. cucumeris females on patches with the predator was lower than on patches without the predator. Cues left by the intraguild predator were not sufficient to elicit such behaviour. Females of N. cucumeris reduced oviposition when exposed to the predator by retaining the egg inside their body, resulting in a lower developmental rate once these eggs were laid. Hence, females are capable of retaining eggs, but the development of these eggs continues inside the mother's body. In this way, females gain some time to search for less risky oviposition sites.

Animals↗
PubMed1994

Parasite infection attenuates nonopioid mediated predator-induced analgesia in mice.

Parasites have been shown to have a broad range of effects on host behavior, including alterations of host responses to predators. Response to the threat of predation consist of a number of defensive behaviors, including a reduction in pain sensitivity and the induction of analgesia. The present study examined the relationships between subclinical (i.e., nonpathological) infection with the naturally occurring, enteric, sporozoan (coccidian) parasite, Eimeria vermiformis, predator exposure, and nociceptive responses in male mice. Brief (30 s) exposure of nonparasitized mice to a predator (a cat) induced marked, relatively short-lived analgesia that was insensitive to naloxone and blocked by the serotonin-1A (5-HT1A) agonist, 8-OH-DPAT. In contrast, mice acutely infected for 6 days with E. vermiformis, failed to show a predator-induced analgesia. The parasitized mice did display a naloxone-sensitive hypoalgesia or analgesia. However, restraint-stressed mice, which displayed a naloxone-sensitive hypoalgesia similar in amplitude to that of the infected mice, still exhibited a nonopioid mediated, predator-induced analgesia. These observations indicate that parasite infection attenuates 5-HT1A-sensitive predator-induced analgesia and likely reduces the accompanying fear and anxiety related anticipatory defense reactions of the host to the predator.

Animals↗
PubMed2004

Impact of spatial heterogeneity on a predator-prey system dynamics.

This paper deals with the study of a predator-prey model in a patchy environment. Prey individuals moves on two patches, one is a refuge and the second one contains predator individuals. The movements are assumed to be faster than growth and predator-prey interaction processes. Each patch is assumed to be homogeneous. The spatial heterogeneity is obtained by assuming that the demographic parameters (growth rates, predation rates and mortality rates) depend on the patches. On the predation patch, we use a Lotka-Volterra model. Since the movements are faster that the other processes, we may assume that the frequency of prey and predators become constant and we would get a global predator-prey model, which is shown to be a Lotka-Volterra one. However, this simplified model at the population level does not match the dynamics obtained with the complete initial model. We explain this phenomenom and we continue the analysis in order to give a two-dimensional predator-prey model that gives the same dynamics as that provided by the complete initial one. We use this simplified model to study the impact of spatial heterogeneity and movements on the system stability. This analysis shows that there is a globally asymptotically stable equilibrium in the positive quadrant, i.e. the spatial heterogeneity stabilizes the equilibrium.

Animals↗
PubMed2000

Evaluating the impact of predation by fish on the assemblage structure of fishes associated with seagrass (Heterozostera tasmanica) (Martens ex Ascherson) den Hartog, and unvegetated sand habitats.

The role of fish predation in structuring assemblages of fish over unvegetated sand and seagrass was examined using enclosure and exclusion cages to manipulate the abundance of predatory fish from November 1998 to January 1999. In our exclusion experiment, piscivorous fish were excluded from patches of unvegetated sand and seagrass to measure how they altered abundances of small fishes, i.e., fish <10 cm in length. Habitats from which piscivorous fish were excluded contained more small fish than those with partial cages, which in turn contained more fish than uncaged areas. These patterns were consistent between unvegetated sand and seagrass areas, although the relative differences between predator treatments varied with habitat. Overall, small fish were more abundant in unvegetated sand than seagrass. Atherinids and syngnathids were the numerically dominant families of small fish and varied in complex ways amongst habitats and cage treatments. The abundance of atherinids varied inconsistently between cage treatments through time. Only during the final two sampling times did the abundance of atherinids vary significantly across cage treatments. Syngnathids were strongly associated with seagrass and were significantly more abundant in caged than uncaged habitats. In our enclosure experiment, five individuals of a single species of transient piscivorous fish, Western Australian salmon (Arripidae: Arripis truttacea Cuvier), were enclosed in cages to provide an estimate of the potential for this species to impact on small fish. The abundance of small fish varied significantly between cage treatments. Small fish were more abundant in enclosure cages and exclusion cages than uncaged areas; however, there was no difference in the abundance of small fish in enclosure cages and partial cages, and no difference between exclusion cages and partial cages. These patterns were consistent amongst habitats. Atherinids and syngnathids were again the numerically dominant families of small fish; atherinids varied more with cage structure while syngnathids did not vary statistically between cages, blocks (locations within which a single replicate of each cage treatment was applied) or habitats. Dietary analysis of caged A. truttacea demonstrated the potential for this species to influence the assemblage structure of small fish through predation - atherinids were consumed more frequently in unvegetated sand than seagrass, and syngnathids were consumed only in seagrass, where they are most abundant. Observations of significant cage or predation effects depended strongly on the time at which sampling was undertaken. In the case of the atherinids, no predation or cage effects were observed during the first two sampling times, but cage effects and predation effects strongly influenced abundances of fish during the third and fourth sampling times, respectively. Our study suggests that transient piscivorous fish may be important in structuring assemblages of small fish in seagrass and unvegetated sand, and seagrass beds may provide a refuge to fishes. But the importance of habitat complexity and predation, in relation to the potentially confounding effects of cage structure, depends strongly on the time at which treatments are sampled, and the periodicity and multiplicity of sampling should be considered in future predation studies.

Journal Article↗
PubMed1997

Harvesting in discrete-time predator-prey systems.

Fisheries for assemblages of interacting species with seasonal recruitment occur throughout temperate and boreal regions of the world ocean. Such systems are conveniently modeled within a difference-equation framework. Here, we examine the dynamic behavior of discrete-time models for an exploited predator-prey system. We contrast the dynamic properties of an aggregate production model and an age-structured model in which recruitment and mortality are explicitly considered. The joint effects of harvesting and interspecific interactions on the stability of the system are defined and contrasted with results for single species systems. We demonstrate that harvesting is a potentially stabilizing factor in the production model and in an age-structured model in which juveniles are harvested and that the relative magnitude of the interaction between predator and prey strongly affects the exploitation levels at which stabilization occurs. In contrast, harvesting is potentially destabilizing (i.e., results in complex dynamics) in an age-structured model with harvesting of adults only; again, the magnitude of the interaction determines the stability boundaries, with stronger interactions leading to a broader range of stable parameter space. In both the aggregate production model and the age-structured model with harvesting of juvenile predator and prey, exploitation effectively reduces the intrinsic rate of increase of the populations; for prey, this effect is amplified by high predation mortality rates. Sustainable levels of exploitation for both predators and prey are lower for the case where juveniles are harvested. Predators and resource harvesters can be viewed as competitors for the prey, and sustainable harvest levels are directly affected by the magnitude of predation mortality. These considerations expand the scope of issues to be resolved in fishery management to include factors such as trade-offs between mean yield and the potential for intrinsic variability and the role of predator-prey interactions in shaping the dynamics of exploited systems.

Age Factors↗
PubMed2000

Do herbivore-induced plant volatiles influence predator migration and local dynamics of herbivorous and predatory mites?

If predators lack information on the prey's position, prey have more chance to escape predation and will therefore reach higher population densities. One of the many possible cues that predators may use to find their prey are herbivore-induced plant volatiles. Although their effects on the behaviour of foraging predators have been well studied, little is known about how these prey-related odours affect predator-prey dynamics on a plant. We hypothesise that herbivore-induced plant volatiles provide the major cue eliciting predator arrestment on prey-infested leaves and that the response to these volatiles ultimately leads to lower prey densities. To test this hypothesis experimentally, we created two types of odour-saturated environments: one with herbivore-induced plant volatiles (treatment), and one with green-leaf volatiles (control). An odour-free environment could not be tested because herbivores require plants for population growth. We measured the rate at which predatory mites (Phytoseiulus persimilis) immigrate, emigrate and exploit a single leaf infested by two-spotted spider mites (Tetranychus urticae). The experiments did not show a significant difference between treatment and control. At best, there was a somewhat higher rate of predator (and possibly also prey) emigration in the treatment. The lack of a pronounced difference between treatment and control indicates that at the spatial scale of the experiments random searching for prey was as effective as directional searching. Alternatively, predators were arrested in the prey patch by responding not merely to herbivore-induced plant volatiles, but also to other prey-related cues, such as web and faeces. Based on our current experience we advocate to increase the spatial scale of the experiment (> 1 m2) and we provide other suggestions for improving the set-up.

Animals↗
PubMed2002

Effect of predator diet on life history shifts of red-legged frogs, Rana aurora.

Larval red-legged frogs (Rana aurora) are known to exhibit antipredator behavior in response to both chemical alarm cues released from injured conspecifics and chemical cues of predators. In some cases, the response to predators is dependent on the predator's diet. In this experiment, we tested whether long-term exposure to predator chemical cues and alarm cues resulted in alteration of life history characteristics of red-legged frogs. We raised groups of tadpoles in the presence of chemical cues of predators that were either fed conspecifics or heterospecific caddis-fly larvae, chemical cues of injured conspecifics, or a no-cue control. Tadpoles raised in the presence of either a predator fed conspecifics or cues of injured conspecifics metamorphosed earlier and at a smaller size than those exposed to predators fed heterospecifics or the no-cue control. The result suggests that red-legged frogs exhibit a life history shift in response to predatory cues and that this response is dependent on the diet of predators.

Animals↗
PubMed2002

Field verification of predator attraction to minnow alarm substance.

Fishes such as minnows in the superorder Ostariophysi possess specialized alarm substance cells (ASC) that contain an alarm cue. Alarm substance can only be released by damage to the epidermis; thus, the release of alarm substance is a reliable indicator of predation risk. When nearby minnows detect the cue, they adopt a range of antipredator behaviors that reduce their probability of predation. Predator-predator interactions afford prey an opportunity to escape and, thus, a fitness benefit that maintains alarm substance calls over evolutionary time. Here, we present data from a simple field experiment verifying that nearby predators are attracted to minnow alarm substance because it signals an opportunity to pirate a meal. Fishing lures were baited with sponge blocks scented with either (1) water (control for sponge odor and appearance), (2) skin extract from non-ostariophysan convict cichlids (superorder Acanthopterygii, Archocentrus "Cichlasoma" nigrofasciatus) to control for general injury-released cues from fish, or (3) skin extract from fathead minnows (superorder Ostariophysi, Pimephales promelas). Predator strike frequency on each sponge type was 1, 1, and 7 for water, cichlid, and minnow cues, respectively. These data provide the first field test using fish predators of the predator-attraction hypothesis for the evolution of Ostariophysan alarm substance cells.

Adaptation, Physiological↗
PubMed2001

Seasonal occurrence of specialist and generalist insect predators of spider mites and their response to volatiles from spider-mite-infested plants in Japanese pear orchards.

In two adjacent Japanese pear orchards (orchards I and 2), we studied the seasonal occurrence of the Kanzawa spider mite. Tetranychus kanzawai, and its predators. Also the response of these predators to the volatiles from kidney bean plants infested with T kanzawai was investigated using trap boxes in orchard 1. The mite density in orchard 1 was unimodal. with one peak at the end of August. In this orchard, population development of the specialist insect predators, Scolothrips takahashii, Oligota kashmiria benefica and Stethorus japonicus was almost synchronized with that of the spider mites. These predators disappeared when the density of their prey became very low in mid-September. Both S. takahashii and O. kashmirica benefica abruptly increased in number in orchard 2 when the spider mite population in orchard 1 decreased. These results suggested that some of the predators migrated from orchard 1 to orchard 2. In this period, predator-traps with T kanzawai-infested bean plants attracted significantly more S. takahashii than traps with uninfested plants. Very few individuals of S. japonicus and O. kashimirica benefica were found in the traps, despite their abundance in orchard 1. The generalist insect predator, Orius sp., was attracted to the traps throughout the experimental period irrespective of the density of spider mites, although this predator was never observed inside the orchards.

Animals↗
PubMed2003

Effects of prey mite species on life history of the phytoseiid predators Typhlodromalus manihoti and Typhlodromalus aripo.

The effects of prey mite suitability on several demographic characteristics of phytoseiid predators and the relationship of these effects to the potential of phytoseiid predators to control herbivorous mite populations are well documented. Evidence has also accumulated in the last 20 years demonstrating that phytoseiid predators utilize herbivorous prey mite-induced plant volatiles as olfactory cues in locating their herbivorous mite prey. but less well established is the predictability of reproductive success from the ability of the predators to utilize olfactory cues to locate their prey, and how these processes are related to the success of the predators as biological control agents of the herbivorous mite. In this study, we determined in laboratory no choice experiments, the development, survivorship and fecundity of the two neotropical phytoseiid predators Typhlodromalus manihoti Moraes and T. aripo DeLeon when feeding on three herbivorous mites, including the key prey species Mononychellus tanajoa (Bondar), and the two alternative prey species Oligonychus gossypii (Zacher) and Tetranychus urticae (Koch). Intrinsic rate of increase (rm) of T. aripo was 2.1 fold higher on M. tanajoa as prey compared with T. urticae as prey, while it was almost nil on O. gossypii. For T. manihoti, rm was 2.3 fold higher on M. tanajoa as prey compared with O. gossypii as prey, while reproduction was nil on T. urticae. An independent experiment on odor-related prey preference of the two predator species (Gnanvossou et al. 2002) showed that T. manihoti and T. aripo preferred odors from M. tanajoa-infested leaves to odors from O. gossypii-infested leaves. Moreover, both predator species preferred odors from M. tanajoa-infested leaves over those from T. urticae-infested leaves. As reported here, life history of the two predatory mites matches odor-related prey preference if the key prey species is compared to the two inferior prey species. The implications of our findings for the persistence of T. manihoti and T. aripo and biological control of M. tanajoa in the cassava agroecosystem in Africa are discussed.

Analysis of Variance↗
PubMed2004

Predator diversity dampens trophic cascades.

Food web complexity is thought to weaken the strength of terrestrial trophic cascades in which strong impacts of natural enemies on herbivores cascade to influence primary production indirectly. Predator diversity can enhance food web complexity because predators may feed on each other and on shared prey. In such cases, theory suggests that the impact of predation on herbivores relaxes and cascading effects on basal resources are dampened. Despite this view, no empirical studies have explicitly investigated the role of predator diversity in mediating primary productivity in a natural terrestrial system. Here we compare, in a coastal marsh community, impacts of arthropod predators on herbivores and plant productivity between a simple food web with a single predator species and a complex food web with a diverse predator assemblage. We show that enhancing predator diversity dampens enemy effects on herbivores and weakens trophic cascades. Consequently, changes in diversity at higher trophic levels can significantly alter ecosystem function in natural systems.

Animals↗
PubMed2004

Plastic phenotypic resistance to predation by Bdellovibrio and like organisms in bacterial prey.

Predation at the lowest trophic level, i.e. between bacteria, is poorly understood, hindering efforts to assess its impact on the structure of bacterial communities. The interaction of Bdellovibrio and Bacteriovorax (Bdellovibrio and like organisms, BLOs), a group of obligate, ubiquitous predatory bacteria, with their Gram-negative bacterial prey results in the multiplication of the predator and in the lysis, but not in the eradication, of the prey. We show that the residual, surviving populations of prey cells exposed to predation stress differ from the populations before exposure, as they exhibit increased resistance to predation. This resistance was demonstrated in a number of Gram-negative prey. Moreover, predation resistance is not specific for the BLO strain experienced by the prey. The phenomenon does not stem from a mutation but is a plastic response associated with a phenotypic change, and it disappears upon removal of the predator. As resistance to predation is not total, this mechanism can ensure survival of both predator and prey.

Adaptation, Physiological↗
PubMed2006

Selective predation on Utah prairie dogs.

Predation always affects demography and population dynamics, but removal of certain types of individuals is especially consequential. Predators strike quickly and commonly avoid areas with human observers, however, and thereby make it difficult to document patterns of predation under natural conditions. At a colony of marked Utah prairie dogs (Cynomys parvidens), a high frequency of predation in 2005 provided an unusual opportunity to examine susceptibility of five types of individuals to predation by red foxes (Vulpes vulpes) and northern goshawks (Accipiter gentilis). Juveniles were more vulnerable than adults to predation by northern goshawks. Adults at the edge of the colony were more vulnerable than central adults to predation by both red foxes and northern goshawks. Recent immigrants, who were not yet familiar with the best routes for escape, were more likely than longtime residents to be captured by northern goshawks. Adult males, preoccupied with finding, impregnating, and guarding estrous females during the 17-day mating season, were easy targets for red foxes and northern goshawks. Pregnant females, who could not run quickly, were especially prone to predation by red foxes.

Animals↗