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At least 271 records · Page 15Linked to original sources
PubMed2005

Rapid habituation of scan behavior in captive marmosets following brief predator encounters.

Scan behavior in 10 captive predator-naive adult black tufted-ear marmosets (Callithrix penicillata) was investigated prior, during and following brief predator encounters (taxidermized oncilla cat -- Leopardus tigrinus) versus neutral stimulus exposures (stuffed toy). For each stimulus, three 9 min home-cage trials were conducted > or = 72 h apart. Each trial was divided into three consecutive 3 min intervals: pre-exposure baseline observation, stimulus exposure, and post-exposure observation period. Post-exposure scan duration increased during the first two predator confrontations, while scan frequency increased significantly only after the first. Scan behavior remained constant within the last predator encounter, as it also did within and between the three neutral stimulus exposures. Although marmosets scanned more often and significantly longer after encountering the predator than the neutral stimulus, this response rapidly habituated by the second trial. Therefore, black tufted-ear marmosets in a familiar environment rapidly habituate to brief repeated predator encounters, possibly minimizing anti-predation costs once the degree of a potential threat has been adequately assessed.

Animals↗
PubMed2005

Role of nutrient bound of prey on the dynamics of predator-mediated competitive-coexistence.

The coexistence of competitive species with a shared predator is well established. The effect of 'food-value' on predator-prey dynamics has also received much attention. However, the study of a nutrient bound of prey, specifically on predator-mediated competitive-coexistence has not received much attention. Here we study the effects of the caloric content or a nutrient bound of prey on the dynamics of competitive-coexistence with the shared predator in a specific model. We propose and analyze a mathematical model for exploitative competition of two prey species with a shared predator. The change of dynamic stability due to the variation of a nutrient bound of each prey on predator-mediated dynamics is studied through extensive numerical experiments. Our analytical and numerical results demonstrate that variation in a nutrient bound promotes the switching of dynamics and may be treated as a driving force for the dynamics of competitive-coexistence with the shared predator.

Animal Nutritional Physiological Phenomena↗
PubMed2004

Prophylactic and therapeutic effects of acute systemic injections of EMD 281014, a selective serotonin 2A receptor antagonist on anxiety induced by predator stress in rats.

We examined the effect of the selective serotonin 2A (5-HT(2A)) receptor antagonist 7-[4-[2-(4-fluoro-phenyl)-ethyl]-piperazine-1-carbonyl]-1H-indole-3-carbon itrile HCl (EMD 281014) [Bartoszyk, G.D., van Amsterdam, C., Bottcher, H., Seyfried, C.A., 2003. EMD 281014, a new selective serotonin 5-HT2A receptor antagonist. Eur. J. Pharmacol. 473, 229-230.] on change in affect following predator stress. Predator stress involved a 5 min unprotected exposure of rats to a domestic cat. Behavioral effects of stress were evaluated with hole board, plus maze, light/dark box and acoustic startle tests 1 week after stress. Predator stress increased anxiety-like behavior in the plus maze, light/dark box, and elevated response to acoustic startle. EMD 281014 (0.001, 0.01, 0.1, 1 or 10 mg/kg) and vehicle injection (ip) occurred either 10 min after predator stress (prophylactic testing), or 90 min prior to behavioral testing for the effects of predator stress (therapeutic testing 1 week after predator stress). In prophylactic testing, EMD 281014 prevented stress potentiation of startle in a dose dependent manner, though the most effective doses were midrange (0.01 and 0.1 mg/kg). Prophylactic administration of EMD 281014 also prevented stress-induced increase of open arm avoidance in the plus maze in a clear dose dependent manner (from 0.01 mg/kg onward). In therapeutic testing, EMD 281014 had no clear drug dependent effects on stress elevation of startle or on behavior of stressed rats in the elevated plus maze. Finally, EMD 281014 did not block the effects of stress on behavior in the light/dark box when given prophylactically or therapeutically. Findings implicate 5-HT(2A) receptors in initiation of some but not all lasting changes in anxiety-like behavior following predator stress. Potential clinical significance of findings are discussed.

Animals↗
PubMed2006

Infection with an acanthocephalan manipulates an amphipod's reaction to a fish predator's odours.

Many parasites with complex life cycles increase the chances of reaching a final host by adapting strategies to manipulate their intermediate host's appearance, condition or behaviour. The acanthocephalan parasite Pomphorhynchus laevis uses freshwater amphipods as intermediate hosts before reaching sexual maturity in predatory fish. We performed a series of choice experiments with infected and uninfected Gammarus pulex in order to distinguish between the effects of visual and olfactory predator cues on parasite-induced changes in host behaviour. When both visual and olfactory cues, as well as only olfactory cues were offered, infected and uninfected G. pulex showed significantly different preferences for the predator or the non-predator side. Uninfected individuals significantly avoided predator odours while infected individuals significantly preferred the side with predator odours. When only visual contact with a predator was allowed, infected and uninfected gammarids behaved similarly and had no significant preference. Thus, we believe we show for the first time that P. laevis increases its chance to reach a final host by olfactory-triggered manipulation of the anti-predator behaviour of its intermediate host.

Acanthocephala↗
PubMed2005

Dynamics of prey-flock escaping behavior in response to predator's attack.

The dynamic behavior of prey-flock in response to predator's attack was investigated by using molecular dynamics (MD) simulations in a two-dimensional (2D) continuum model. By locally applying interactive forces between prey individuals (e.g. attraction, repulsion, and alignment), a coherently moving state in the same direction was obtained among individuals in prey-flock. When a single predator was introduced to the prey population, the prey-flock was correspondingly deformed by the predator's continuous attacks towards the prey-flock's center. In response to the predator's attack, three regimes in the flock size (compression (Regime I), expansion (Regime II), compression (Regime III)) were revealed if the predator's attack speed (kappa) was comparatively low to the escape speed of prey-flock. If noise was added to the predator's attacking course, a higher degree of variation was observed in the patterns of compression and expansion in the prey-flock size. However, the scaling behavior in the changes in prey-flock size was present in different levels of noise with the increase in predation risk (R) when kappa takes an appropriately low value. During the procedure of escaping, order breaking in alignment (phi) of prey population was observed, while the degree of alignment was dependent upon the changes in parameters of kappa and R.

Animals↗
PubMed2004

Modeling direct positive feedback between predators and prey.

Predators can have positive impacts on their prey through such mechanisms as nutrient mineralization and prey transport. These positive feedbacks have the potential to change predictions based on food web theory, such as the assertion that enrichment is destabilizing. We present a model of a simple food web, consisting of a resource, a consumer, and its predator. We assume that the predator has a direct positive effect on the consumer, by increasing the rate at which the consumer acquires resources. We consider two cases: the feedback strength is a saturating function of predator density, or it is proportional to the encounter rate between predators and prey. In both cases, the positive feedback is stabilizing, delaying or preventing the onset of oscillations due to enrichment. Positive feedback can introduce an Allee effect for the predator population, yielding multiple stable equilibria. Strong positive feedback can yield counterintuitive results such as a transient increase in consumer density following the introduction of predators, and a decrease in the resource pool following enrichment.

Animals↗
PubMed2000

Epibenthic amphipod abundance and predation efficiency of the pink shrimp Farfantepenaeus duorarum (Burkenroad, 1939) in habitats with different physical complexity in a tropical estuarine system.

Amphipod abundance and biomass were determined in soft-bottom substrates (SBS), monospecific Thalassia testudinum patches and T. testudinum with attached macroalgae (SAV) from Términos Lagoon. Amphipods were absent in SBS, and their density and biomass were higher in SAV (3351 individualsm(-2), 1718 mg AFDWm(-2)) than in T. testudinum (1220 indm(-2), 625 mg AFDWm(-2)). Although macroalgae and seagrasses are recognised as an alternative refuge against predation for amphipods, the high abundance of amphipods in SAV suggests that macroalgae represent a habitat that provides greater food availability. Pink shrimp Farfantepenaeus duorarum (Burkenroad, 1939) consumption rate (Mo) of epibenthic amphipods was experimentally evaluated. Mo intensifies as prey density increases and varied from 0.39 to 2.39 mg AFDWh(-1). Predation efficiency of F. duorarum on epibenthic amphipods was also evaluated in four artificial habitats with different physical complexity: soft-bottom substrates (SBS), small woody debris (SWD), seagrasses with densities of 300 and 1200 shootsm(-2) (S300 and S1200, respectively), macroalgae (MA), and at two prey densities (962 and 2406 indm(-2)). Amphipod consumption rate by F. duorarum varied from 1.20 to 2.07 indh(-1) in S1200 and MA, respectively. Habitat complexity had a significant effect on consumption rate, but prey density did not. Habitat physical complexity and predation efficiency maintained an inverse and a non-linear relationship. Presumably, the decrease in predation efficiency in association with the habitat complexity is due to the differential refuge value of these habitats. However, predation efficiency may also be influenced by either the microhabitat use by amphipods, the shrimp's dependence on seagrasses, or by differences in habitat value caused by the diel behavioural distribution pattern of amphipods and shrimp. Both field and experimental results highlight the importance of evaluating the relative value of tropical estuarine habitats through the study of the relationship between habitat physical complexity and predator-prey interactions. They also emphasise that inherent biological and ethological factors of the predator and prey involved, coupled to spatial and temporal variations in the habitat, should also be considered.

Journal Article↗
PubMed2000

Experimental evidence of predation by juvenile flounder, Platichthys flesus, on a shallow water meiobenthic community.

In the northern Baltic Sea juvenile flounder, Platichthys flesus, occur in high abundances on shallow sandy bottoms in late summer and autumn. They feed mainly on meiofauna and the ontogenetic switch to macrofaunal sized food occurs at a larger size here than in other areas, exemplifying the high relative importance of meiofauna. Consequently, juvenile P. flesus in the Baltic feed for a longer period on meiofauna, and could thus be expected to have a stronger predation effect on the meiofaunal assemblages. In this study the predation effects of juvenile P. flesus on meiofaunal abundances and community structure were studied using microcosms that were sampled repeatedly over a 3-week period. Significant differences between treatment and control were found for the total number of taxa, for abundances of harpacticoids, copepod nauplii and ostracods. The nematode community was not affected, but one genus, Axonolaimus, was negatively affected by predation. The predation affected meiofaunal community structure as the major taxon diversity was significantly reduced. The results suggest that the meiofauna on shallow sandy bottoms may be structured by juvenile P. flesus, and the combined predation pressure of juvenile flounder and other epibenthic predators in the area might be considerable. Microcosms are effective in testing natural predation, especially on meiofaunal communities, but field experiments should be conducted to account for the physical characteristics of the area studied.

Journal Article↗
PubMed2003

The effect of fasting, prolonged swimming, and predator presence on energy utilization and stress in juvenile walleye (Stizostedion vitreum).

We evaluated how two diets with different lipid levels (4% vs. 10%) influenced nutrient expenditure in juvenile walleye Stizostedion vitreum subjected to starvation, prolonged swimming, and predator presence. We also determined how exercise and predator presence influenced stress indicators such as blood plasma cortisol and glucose. Groups of six fish were placed in triplicate rectangular wire cages per treatment and submerged randomly in three artificial stream compartments at a water temperature of 14 degrees C. Three treatments were established: (A) no water current and no predator, (B) water current (1.5 body lengths s(-1)) and no predator, (C) water current and predator. Six 1-year-old muskellunge (Esox masquinongy, 28.4+/-2.3 cm) were used as predators. They were allowed to swim freely outside walleye cages and were fed with walleye. To simulate poststocking period of fasting, walleyes were exposed to experimental treatments for 6 weeks and were deprived of food. Regardless of the prior diet, fish weight significantly declined in all treatments but no differences were found among them. Lipids declined in both dietary groups of fish; in turn, body moisture increased. Protein levels were only affected in fish fed with high-lipid diet prior to the experiment and subjected to current and predator presence. Plasma glucose gradually declined in fish fed with high-lipid diet prior to the study; whereas in the fish fed with low-lipid diet before the experiment, it remained low regardless of the treatment severity. Plasma cortisol concentrations never exceeded 30 ng ml(-1) indicating no signs of acute stress during the experiment. We concluded that fish fed with diet containing higher lipid levels prior to stocking would possess better potential of withstanding adverse conditions and better survival once released to the wild.

Animal Feed↗
PubMed2003

Changes in brain cholecystokinin and anxiety-like behavior following exposure of mice to predator odor.

Exposure of CD-1 mice to a familiar environment lined with clean shavings (control odor) as well as a familiar environment lined with soiled rat shavings (predator odor) induced anxiety in the light/dark box. Mice exposed to the familiar environment or predator odor displayed decreased latency to enter the dark chamber of the light/dark box and spent less time in the light portion of the apparatus relative to home-caged mice. Mice exposed to the familiar environment lined with clean shavings or predator odor displayed elevated cholecystokinin mRNA levels from the ventral tegmental area, medial and basolateral nuclei of the amygdala relative to home-caged mice. Exposure of CD-1 mice to 2, 5 or 10 min of predator odor increased acoustic startle relative to mice merely exposed to the familiar environment lined with clean shavings at protracted intervals. Mice exposed to the familiar environment lined with clean shavings did not exhibit enhanced startle relative to home-caged mice. Exaggerated startle reactivity was in evidence immediately, 24, and 48 h following a 5-min exposure of mice to predator odor. In contrast, a 10-min exposure of mice to predator odor produced an oscillating pattern of enhanced startle evident during the immediate and 48-h post-stressor intervals only. However, when the startle stimulus was withheld 1 h following odor presentation, mice exhibited enhanced startle patterns reminiscent of the 5-min exposure. The 2-min exposure of mice to predator odor produced a delayed onset of enhanced startle observed at the 168-h test interval only. Potential anxiogenic influences of mesocorticolimbic cholecystokinin availability as well as the time course and underlying neuronal substrates of long-term behavioral disturbances as a result of psychogenic stressor manipulations are discussed.

Acoustic Stimulation↗
PubMed2003

Ventilatory frequency indicates visual recognition of an allopatric predator in nai;ve Nile tilapia.

Perceiving a possible predator may promote physiological changes to support prey 'fight or flight'. In this case, an increase in ventilatory frequency (VF) may be expected, because this is a way to improve oxygen uptake for escape tasks. Therefore, changes in VF may be used as a behavioral tool to evaluate visual recognition of a predator threat. Thus, we tested the effects of predator visual exposure on VF in the fish Nile tilapia, Oreochromis niloticus. For this, we measured tilapia VF before and after the presentation of three stimuli: an aquarium with a harmless fish or a predator or water (control). Nile tilapia VF increased significantly in the group visually exposed to a predator compared with the other two, which were similar to each other. Hence, we conclude that Nile tilapia may recognize an allopatric predator; consequently VF is an effective tool to indicate visual recognition of predator threat in fish.

Journal Article↗
PubMed2003

Influence of predation pressure on the escape behaviour of Podarcis muralis lizards.

Relationships between predator avoidance behaviour and predation pressure were investigated in the wall lizard, Podarcis muralis. The wariness of lizards belonging to high (1185m) and low elevation (308m) populations under two different predation pressure levels was compared. Wall lizards belonging to the lowland population experienced greater predation pressure than those belonging to the highland population. Lizards belonging to the population under higher predation pressure had higher frequency of refuge use, and had longer flight initiation distances (i.e. the distance lizards allowed the observer to approach before fleeing). In contrast, neither the distance fled (i.e. the total distance they fled in one continuous movement from the lizard's initial position until hiding or stopping at a safe distance) nor the distance to the nearest refuge were significantly different between populations. Escape responses were independent of ambient temperature in the lowland population, but animals belonging to the highland population had longer flight initiation distances when the ambient temperatures were higher. These findings suggest that predator avoidance behaviour may vary with predation pressure.

Journal Article↗
PubMed2006

Hairworm anti-predator strategy: a study of causes and consequences.

One of the most fascinating anti-predator responses displayed by parasites is that of hairworms (Nematomorpha). Following the ingestion of the insect host by fish or frogs, the parasitic worm is able to actively exit both its host and the gut of the predator. Using as a model the hairworm, Paragordius tricuspidatus, (parasitizing the cricket Nemobius sylvestris) and the fish predator Micropterus salmoïdes, we explored, with proteomics tools, the physiological basis of this anti-predator response. By examining the proteome of the parasitic worm, we detected a differential expression of 27 protein spots in those worms able to escape the predator. Peptide Mass Fingerprints of candidate protein spots suggest the existence of an intense muscular activity in escaping worms, which functions in parallel with their distinctive biology. In a second step, we attempted to determine whether the energy expended by worms to escape the predator is traded off against its reproductive potential. Remarkably, the number of offspring produced by worms having escaped a predator was not reduced compared with controls.

Animals↗
PubMed2001

Prey preference, intraguild predation and population dynamics of an arthropod food web on plants.

The theory of intraguild predation (IGP) largely studies effects on equilibrium densities of predators and prey, while experiments mostly concern transient dynamics. We studied the effects of an intraguild (IG) predator, the bug Orius laevigatus, on the population dynamics of IG-prey, the predatory mite Phytoseiulus persimilis, and a shared prey, the phytophagous two-spotted spider mite Tetranychus urticae, as well as on the performance of cucumber plants in a greenhouse. The interaction of the predatory mite and the spider mite is highly unstable, and ends either by herbivores overexploiting the plant or predators exterminating the herbivores. We studied the effect of IGP on the transient dynamics of this system, and compared the dynamics with that predicted by a simple population-dynamical model with IGP added. Behavioural studies showed that the predatory bug and the predatory mite were both attracted to plants infested by spider mites and that the two predators did not avoid plants occupied by the other predator. Observations on foraging behaviour of the predatory bug showed that it attacks and kills large numbers of predatory mites and spider mites. The model predicts strong effects of predation and prey preference by the predatory bugs on the dynamics of predatory mites and spider mites. However, experiments in which the predatory bug was added to populations of predatory mites and spider mites had little or no effect on numbers of both mite species, and cucumber plant and fruit weight.

Animals↗
PubMed2003

Effect of conspecific and heterospecific feces on foraging and oviposition of two predatory ladybirds: role of fecal cues in predator avoidance.

Growing evidence suggests a flow of chemical information from higher to lower trophic levels that affects foraging and oviposition of 'prey' in response to potential risks from predators. This was investigated in two species of ladybird predators of aphid, Harmonia axyridis and Propylea japonica. H. axyridis is known to be the stronger intraguild predator and P. japonica to be the more frequent intraguild prey in interactions of these two species. These ladybirds share aphid prey on mugworts, hibiscus, and Italian ryegrasses in fields of northern Japan but largely avoid each other on the same plant. Fecal cues of these ladybird predators were found to contribute in their assessment of predation risk from conspecific and heterospecific competitors in common habitats. Gravid females of H. axyridis reduced rates of feeding and oviposition when exposed to feces of conspecifics, but not when exposed to feces of P. japonica. In contrast, gravid females of P. japonica reduced feeding and oviposition when exposed to feces of both H. axyridis and its own species. Females of both ladybird species exhibited similar behavior in response to water extracts of feces. For P. japonica, the influence of heterospecific feces was greater than that of conspecific feces. Our results demonstrate that feces of ladybirds contain odors that have the potential to deter the feeding and oviposition activities of conspecific as well as heterospecific ladybirds. Such deterrence allows these insects to avoid predation risk. Differences in responses of the two predators are discussed.

Animals↗
PubMed2002

Selective habituation shapes acoustic predator recognition in harbour seals.

Predation is a major force in shaping the behaviour of animals, so that precise identification of predators will confer substantial selective advantages on animals that serve as food to others. Because experience with a predator can be lethal, early researchers studying birds suggested that predator recognition does not require learning. However, a predator image that can be modified by learning and experience will be advantageous in situations where cues associated with the predator are highly variable or change over time. In this study, we investigated the response of harbour seals (Phoca vitulina) to the underwater calls of different populations of killer whales (Orcinus orca). We found that the seals responded strongly to the calls of mammal-eating killer whales and unfamiliar fish-eating killer whales but not to the familiar calls of the local fish-eating population. This demonstrates that wild harbour seals are capable of complex acoustic discrimination and that they modify their predator image by selectively habituating to the calls of harmless killer whales. Fear in these animals is therefore focused on local threats by learning and experience.

Acoustic Stimulation↗
PubMed1999

Can multiple-copy sequences of prey DNA be detected amongst the gut contents of invertebrate predators?

The first experiments to clearly demonstrate that DNA techniques might be used to detect predator-prey interactions between arthropods are reported. The accurate modelling of such interactions has depended until now upon a mixture of laboratory experiments, population monitoring and biochemical tests. The latter involve gut-content analyses, and have most recently depended upon the development of prey-specific monoclonal antibodies. Although these are excellent for detecting predation on a target prey, they are impractical for analysing the prey range of a particular predator. Molecular detection depends upon the ability of DNA to resist digestion in the predator gut and of the polymerase chain reaction (PCR) to amplify prey-specific DNA from semidigested material. As a first step, experiments using carabid beetles, Pterostichus cupreus L., as predators and mosquitoes as prey are reported. The target sequences were fully characterized multiple-copy esterase genes from two laboratory strains of Culex quinquefasciatus Say. Although DNA was extracted from homogenates of whole beetles (minus appendages), a 146 bp product could be amplified from both mosquito strains digested in the beetle gut for 28 h. The larger, 263 bp product was detectable for 28 h in one mosquito strain, but could not be amplified after 5 h from the other. Whether the beetles had eaten one mosquito or six, digested for zero or 28 h, the prey were equally detectable. Having demonstrated that shorter, multiple-copy sequences survive digestion for a considerable period in the gut of a predator, the opportunity exists to develop new detection systems for studying predation in the field.

Animals↗
PubMed2000

Induced defenses in response to an invading crab predator: an explanation of historical and geographic phenotypic change.

The expression of defensive morphologies in prey often is correlated with predator abundance or diversity over a range of temporal and spatial scales. These patterns are assumed to reflect natural selection via differential predation on genetically determined, fixed phenotypes. Phenotypic variation, however, also can reflect within-generation developmental responses to environmental cues (phenotypic plasticity). For example, water-borne effluents from predators can induce the production of defensive morphologies in many prey taxa. This phenomenon, however, has been examined only on narrow scales. Here, we demonstrate adaptive phenotypic plasticity in prey from geographically separated populations that were reared in the presence of an introduced predator. Marine snails exposed to predatory crab effluent in the field increased shell thickness rapidly compared with controls. Induced changes were comparable to (i) historical transitions in thickness previously attributed to selection by the invading predator and (ii) present-day clinal variation predicted from water temperature differences. Thus, predator-induced phenotypic plasticity may explain broad-scale geographic and temporal phenotypic variation. If inducible defenses are heritable, then selection on the reaction norm may influence coevolution between predator and prey. Trade-offs may explain why inducible rather than constitutive defenses have evolved in several gastropod species.

Adaptation, Physiological↗