Predator-Prey Dynamics

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Gape size influences seasonal patterns of piscivore diets in three Neotropical rivers

Gape size influences seasonal patterns of piscivore diets in three Neotropical rivers

Predation mortality is very high in tropical floodplain systems (Rodriguez & Lewis, 1997), and thus predators likely induce changes in the fish community (Jepsen et al., 1997; Jepsen & Winemiller, 1999; Hoeinghaus et al., 2006), which in turn results in a shift in predator-prey interactions (Winemiller, 1989; Gratwicke & Marshal, 2001). Although prey selection by piscivores is a function of many factors, including species- specific traits and spatial variability (e.g., differential predator and prey densities in patchy habitats), there nonetheless are general patterns of predation that provide a foundation for predicting predator-prey dynamics in species-rich tropical food webs. Our study highlights the importance of size relationships between piscivores and their prey over a seasonal hydrological cycle, which may help to predict prey- predator interactions.
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Modelling landscape-level numerical responses of predators to prey: the case of cats and rabbits.

Modelling landscape-level numerical responses of predators to prey: the case of cats and rabbits.

Predator-prey systems can extend over large geographical areas but empirical modelling of predator-prey dynamics has been largely limited to localised scales. This is due partly to difficulties in estimating predator and prey abundances over large areas. Collection of data at suitably large scales has been a major problem in previous studies of European rabbits (Oryctolagus cuniculus) and their predators. This applies in Western Europe, where conserving rabbits and predators such as Iberian lynx (Lynx pardinus) is important, and in other parts of the world where rabbits are an invasive species supporting populations of introduced, and sometimes native, predators. In pastoral regions of New Zealand, rabbits are the primary prey of feral cats (Felis catus) that threaten native fauna. We estimate the seasonal numerical response of cats to fluctuations in rabbit numbers in grassland–shrubland habitat across the Otago and Mackenzie regions of the South Island of New Zealand. We use spotlight counts over 1645 km of transects to estimate rabbit and cat abundances with a novel modelling approach that accounts simultaneously for environmental stochasticity, density dependence and varying detection probability. Our model suggests that cat abundance is related consistently to rabbit abundance in spring and summer, possibly through increased rabbit numbers improving the fecundity and juvenile survival of cats. Maintaining rabbits at low abundance should therefore suppress cat numbers, relieving predation pressure on native prey. Our approach provided estimates of the abundance of cats and rabbits over a large geographical area. This was made possible by repeated sampling within each season, which allows estimation of detection probabilities. A similar approach could be applied to predator-prey systems elsewhere, and could be adapted to any method of direct observation in which there is no double- counting of individuals. Reliable estimates of numerical responses are essential for managing both invasive and threatened predators and prey.
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T HEL OTKA -V OLTERRAE QUATIONS INF

T HEL OTKA -V OLTERRAE QUATIONS INF

The derivation of dynamical models based on bank profit were first proposed in 2008 by Petersen and Shoeman [5], who analyzed the Return-on-Assets and the Return-on-Equity of a bank. Later that year, the economic aspects of the stochastic dynamics model of a bank’s assets and liabilities were presented on [6]. In 2012, Comes proposed a three dimensional dynamical model to describe the interaction be- tween levels of the banking system [7] and used the results on the work of Apreutesei [8][9] to study its stability. In 2013, the first dynamical system of deposit and loan volumes based on the Lotka-Volterra predator-prey dynamics [10] was presented, and in 2014 Sumarti, Nurfitriyana and Nurwenda studied the equilibria of this type of dynamical systems [11].
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On the Dynamics of a General Predator-Prey System

On the Dynamics of a General Predator-Prey System

The aim of this study is to discuss the qualitative properties of the general predator-prey system (1). We discuss the existence and stability of equilibria and nonexistence criteria for limit cycles. We explore the uniqueness of limit cycles using Kuang and Freedmann approach (Moghadas and Corbett, 2008) and some applications. It is natural due to biological considerations to expect that the solutions of (1) must to be positive and bounded. So we give the following result which is a partial extension of those of (Freedman and So, 1985) and (Saha and Bandyopadhyay, 2005).The paper end with a brief discussion.
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Braz. J. Phys.  vol.38 número1

Braz. J. Phys. vol.38 número1

The same behavior is observed for other spatial models [8]: coexistence with time oscillations resulting from Hopf bifur- cations provided by mean-field approaches, and local oscil- lations with pattern formation when the spatial structure of the model is indeed considered. From these results we could infer that population cycles observed in nature and in experi- ments may be synchronized at subregions of the habitat. How- ever, we must be careful with these results, since, usually, the predator-prey lattice models are still to crude to be directly compared with data obtained from experiments and from col- lected data for population cycles in nature. We can drawn some analogies and try to capture the fundamental proper- ties of prey-predator systems. For example, the ST model [9], exhibits for a given range of the model parameters, pro- nounceable predator and prey oscillations [10] which seem to be qualitatively similar to the hare-linx population cycles. However, until now, it was not included in this model the in- herent features, as intrinsic population growth rates, which al- lows us to make direct relationships between the theoretical description and the observed population cycles.
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ECOLOGY, BEHAVIOR AND BIONOMICS

ECOLOGY, BEHAVIOR AND BIONOMICS

Recent studies have revealed that the prevalence of Wolbachia in arthropods is attributable not only to its vertical transmission, but also to its horizontal transfer. In order to assess the horizontal transmission of Wolbachia between predator and prey, arthropods belonging to 11 spider families and six insect families were collected in the same ield of rice. The distribution of Wolbachia in these arthropods was detected by diagnostic PCR ampli ication of the wsp (Wolbachia outer surface protein gene) and 16S rDNA genes. Nurscia albofasciata Strand (Araneae: Titanoecidae), Propylea japonica Thunberg (Coleoptera: Coccinellidae), Paederus fuscipes Curtis (Coleoptera: Staphylinidae), and Nilaparvata lugens Stal (Homoptera: Delphacidae) were infected with Wolbachia. This is the irst report of infection of N. albofasciata and P. fuscipes by Wolbachia. No direct evidence indicated the existence of horizontal transmission of Wolbachia between predator and prey.
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Fish predation by semi-aquatic spiders: a global pattern.

Fish predation by semi-aquatic spiders: a global pattern.

ratio of 1.6260.03 (i.e., 42 times larger) and in this respect, the disparity in size of fish catching spiders and their prey is especially notworthy. It must be added that the caloric value of fish and insect tissue do not differ significantly (,20–24 kJ/g dry weight; Table 4) and that fish and insect prey are both excellent sources of protein [139]. A substantial proportion of the mass of an arthropod is comprised of exoskeleton which is of no nutritional value to a spider. In contrast, the great bulk of the mass of a fish is comprised of muscle tissue. On an individual prey basis, fish are likely a more rewarding meal than an equivalently sized invertebrate, and especially energetically and nutritionally reward- ing given the size of the meal particularly where fish are easily acquired. Fish may, thus, represent a ‘big ticket item’ in the nutritional budget of semi-aqautic spiders. Feeding on fish may be particularly advantageous during the mating period when the elevated energy and protein requirements of gravid female spiders require increased food intake [13] or at times of limited availability of invertebrate prey when feeding frequency is otherwise depressed and cannibalism elevated [100–101]. Complete piscivory is probably rare and restricted to those occasions when semi-aquatic spiders gain easy access to small fish kept at high density in artificial rearing ponds or aquaria [18,131] or in small shallow waterbodies (see references above pertaining to Ancylometes). Additional research will be needed to reveal the extent and nutritional importance of fish in the diet of these spiders.
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Sba Controle & Automação  vol.16 número2

Sba Controle & Automação vol.16 número2

Models of virus dynamics (Nowak e May, 2000) are very similar to the predator-prey models studied in this paper. There is great current interest in systematically finding “pro- tocols"(controls) that are capable of stabilizing virus popula- tions at low levels (Wein et al., 1997) and, once again, desir- able methods must have most of the characteristics stipulated in Section 2. We expect that the control design proposed in this paper will be applicable to this class of problems as well. Finally, there has been recent interest in applying bifurca- tion analysis to planar population dynamics models, and pre- liminary work of this kind can be found in Kuznetsov et al. (2003), Cunha et al. (2003), Moreno et al. (2003).
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Functional Response of the Predator Eriopis connexa (Coleoptera: Coccinellidae) to Different Prey Types

Functional Response of the Predator Eriopis connexa (Coleoptera: Coccinellidae) to Different Prey Types

This work evaluated the functional response of adult females of Eriopis connexa to different densities of Macrosiphum euphorbiae and Tetranychus evansi. When preying upon aphids, E. connexa presented a sigmoidal functional response (Type III). This behavior, however, changed drastically to an exponential (Type II) functional response, when mites (T. evansi), rather than aphids, were offered to E. connexa. Such different patterns showed that this coccinellid needed to adopt distinct strategies according to the kind of prey available. Since predators were believed to be able to regulate prey populations only when adopting Type III functional response. E. connexa would be a good candidate for a biological control agent of M. euphorbiae, but would not suppress a growing population of T. evansi.
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Physiological responses of anti-predation in prey fish to the threat of piscivorous fish in different underwater visibility conditions

Physiological responses of anti-predation in prey fish to the threat of piscivorous fish in different underwater visibility conditions

Plasma cortisol levels significantly differed according to the predator regime (H 2,33 = 18.55; P<0.01). When faced with piscivorous fish, regardless of their hunter strategy, plasma cortisol levels in A. bimaculatus shoal members increased by 90% on average, from 28.2 ng/ml in the absence of predators to 51.2 ng/ml with predators present (grouping the data from both predation treatments). We observed that the sit-and-wait piscivore (H. aff. malabaricus) remained motionless for most of the experimental period, causing the prey fish shoal members to remain on the opposite side of the tank in a surveillance state, largely immobile. In contrast, A. crassipinnis moved frequently around the aquarium, causing the shoal of prey to swim in the opposite direction, keeping as far as possible from the predator. Despite these differences in predator activity, post-hoc comparisons did not evidence significant differences between the two hunting strategy treatments: with H. aff malabaricus (‘Mean’ 51.9 ± ‘Standard Deviation’ 12.1 ng/ ml) and with A. crassipinnis (50.4 ± 10.6 ng/ml) (Fig. 1).
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Energetic conditions promoting top-down control of prey by predators.

Energetic conditions promoting top-down control of prey by predators.

Simple models can build intuition about the relationships between observed phenomena and the processes that lead to them. By ignoring many of the details of biological reality and focusing on three species, we explicitly described relationships between energetic processes, top-down control, and equilibrium stability. Further, processes captured in our model (e.g. consumption of multiple prey and recruitment) were flexible enough to reasonably describe important processes for many species and systems. Biological realities often serve to reduce direct effects and dampen oscillations, and diffuse effects are a common characteristic of many systems [21,29,30]. Therefore, some of the equilibria predicted by our models to be unstable may indeed be stable when taken in the context of their larger food web. In this way, we see the model predictions as an initial, rather than final, step in exploring the possibility of top-down control in any given system. Whether our heuristic model’s predictions can accurately predict top-down control remains to be seen. Because no standard exists for reporting interaction strengths, conducting a complete meta-analysis is difficult – however, we can do a retrospective analysis of well-studied systems and ask whether our model is consistent with observed interaction strengths, given some energetic information about the predator-prey pair. We describe three particularly well-known predator-prey systems and how our simple predictions apply to them: bass in temperate lakes, grey wolves on Isle Royale National Park, and cod in the Atlantic.
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Predator-prey interactions between shell-boring beetle larvae and rock-dwelling land snails.

Predator-prey interactions between shell-boring beetle larvae and rock-dwelling land snails.

To understand better the predatory behavior of Drilus, we obtained three live pseudopupae (an immobile resting stage) from field-collected Albinaria shells, as well as live Albinaria, and used these for observations in the laboratory. Of these three, one remained in pseudopupal state. The other two (both Drilus ‘‘L’’) molted into active larvae. One (obtained from an A. edmundi) entered an Albinaria edmundi via the aperture and killed it. It remained inside for 28 days, bored a hole in the shell wall to exit, but then died while emerging. However, the third one (obtained from an A. discolor) stayed alive and active for almost two years, and during that time consumed eight adult prey individuals. In all eight predation events (which took place under dark conditions in a box with several loose Albinaria individuals, i.e., not adhering to any substrate), the larva entered the snail via the aperture (after having inspected several potential prey), never boring a hole in the shell wall nor into the clausilium (Video S2). After entering a snail, it apparently attacked and ate (part of) the snail immediately, because it moved fragments of dried, undigested snail tissue outside of the aperture within three days. In total, it would remain in a shell for 22–32 days, except for one very lengthy stay inside a prey shell that lasted from September 19 th until May 1 st , and possibly indicated hibernation. Each time the larva exited from an empty prey shell, it left behind an exuvia, meaning that the number of larval stages may be much larger than the three to four that had been suspected previously [15–16]. In all cases except one, the larva did bore a hole from within the prey shell to exit. Boring was done with the jaws and a copious amount of (possibly acidic) saliva and, based on the one occasion when it was observed from start to finish (Video S1; fig. 4) took seven hours.
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Stability analysis of a fractional-order HBV infection model

Stability analysis of a fractional-order HBV infection model

[6] E. Ahmed, A. M. A. El-Sayed, H. A. A. El-Saka, On some Routh-Hurwitz conditions for fractional order differential equations and their applications in Lorenz, R ¨ o ssler, Chua and Chen systems, Physics Letters A 358(1) (2006) 1-4. [7] E. Ahmed, A. M. A. El-Sayed, H. A. A. El-Saka, Equilibrium points, stability and numerical solutions of fractional order predator-prey and rabies models, Journal of Mathematical Analysis and Applications 325 (2007) 542-553. [8] E. Demirci, A. Unal, N. ¨ O zalp, A fractional order SEIR model with density dependent death rate, Hacettepe

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Diet composition and feeding strategy of the southern pipefish

Diet composition and feeding strategy of the southern pipefish

The feeding strategy and niche breadth analyses sug- gested a marked between-gender variation in the diet of south- ern pipefish. Females had a more diverse diet both in terms of prey richness and prey size range, whereas males seemed to concentrate mainly on smaller prey, mainly the isopod U. peterseni and copepods. Such differences suggest females are more mobile and active within the Widgeon grass bed than males. Although pipefish species, in general, show low activity levels, some authors (Roelke & Sogard, 1993) have demonstrated in laboratory settings that females are more active than males. These authors hypothesized that a dis- tended brood pouch with developing young may hinder the swimming ability of males, limiting their activity levels. In fact, Svensson (1988) observed that reproductively active females had an increased activity level and a higher intake of large prey compared with reproductively active males, who were less active and fed mainly on small prey. Field and laboratory experiments would be necessary to test the hy- pothesis that differential activity levels related to parental care in the southern pipefish S. folletti could be correlated with gender differences in diet composition and feeding strategy.
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Prey detection and prey capture in copepod nauplii.

Prey detection and prey capture in copepod nauplii.

According to the descriptions above, copepod nauplii are thus either ambush feeders or they produce a feeding current. It is unclear, however, whether and how feeding-current feeding nauplii can perceive prey remotely. There is a lower size-limit for chemical detection since chemical signals leaking from small cells dissipate almost instantaneously due to molecular diffusion. Empirical evidence suggests a size threshold of about 10 m m [12], but nauplii may feed on much smaller prey [13]. Prey cells arriving in the feeding current may also generate a hydromechanical signal, but the size-threshold for hydromechanical detection is of the order 50 m m [14]. Ambush feeding nauplii may detect motile prey hydrodynamically in much the same way as has been demonstrated for copepodites [15], but it is unclear how the prey can be captured. Attack jumps in calanoid and cyclopoid nauplii were described by [10] using video recordings at 25 Hz. However, such attack jumps should be theoretically ineffective due to the thick viscous boundary layer surrounding the attacking nauplius at these low Reynolds numbers: prey cells will simply be pushed away as the nauplius lunges forward [16].
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Alcides Eduardo dos Reis Peron Rafael de Brito Dias

Alcides Eduardo dos Reis Peron Rafael de Brito Dias

This shows how technology was used not only to improve the Predator itself, but also to address the economic, social and political problems and dynamics surrounding American military involvement in the Middle East and elsewhere. Persistent presence, surveillance and destruction could only be achieved if the operations were conducted from the USA, not only because this would preserve the lives of its soldiers, but mainly because it obviated the USA having to answer to any other nation or organisation for its techniques and practices. Given this, the US strategy could be summarised as distancing itself in physical and perceptual terms from the conflicts in question, mainly due to the use of drones and the mediation of information, thereby rupturing the reciprocity that charac- terises conventional warfare. Given its singular and unprecedented nature, growing num- bers of scholars and other analysts have sought to analyse and theorise this development.
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Assessing the contribution of marine protected areas to the trophic functioning of ecosystems: a model for the Banc d'Arguin and the Mauritanian shelf.

Assessing the contribution of marine protected areas to the trophic functioning of ecosystems: a model for the Banc d'Arguin and the Mauritanian shelf.

The rapid increase in exploitation rates for high TLs over the last two decades resulted in a decrease in catch and biomass highlighting the overexploitation of these species. Such results confirm and generalize the diagnoses already established for several Mauritanian fish stocks, based on more usual stock assessment methods [35]. The increase in biomass of prey fish, while the biomass of top predators is decreasing, suggests a release in predation that might results from a top-down effect. Of course, the predictions concerning small pelagics are unsatisfactory at this stage as they are also driven by other factors (e.g. upwelling conditions) happening at a larger scale than the study area, and thus, it would be premature to consider that all ecological processes involved have been understood. The decline in mean TL coupled with signs of overexploitation of high TL species, and a decrease in their biomass and catch, is characteristic of a fishing down the food web process [53]. Since the catches on high TL species were not maintained at higher levels and there was no major change in target species (Figure 6a), the results do not suggest a fishing through the food web process [54].
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Time correlation function in systems with two coexisting biological species

Time correlation function in systems with two coexisting biological species

The explicit diffusion enhances the species coexistence and the oscillatory behavior. The introduction of the diffu- sion process promotes the increase of the average species densities as can be seen in Fig. 2. Even a small value of D suffices to entail this behavior as shown by the rapid increase FIG. 5. 共Color online兲 共a兲 Densities of prey 共lower curve兲 and predator 共upper curve兲 as a function of time for p=0.3, c=0.03, and D = 0.9. 共b兲 Cross-correlation function between prey and predator. 共c兲 Time autocorrelation function for prey. 共d兲 Power spectral density for prey. The largest peak occurs at ␻ = 0.0057 which gives a period T = 1.10⫻ 10 3 . The second and the third peaks occur at ␻ = 0.0112 and
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Cost of living dictates what whales, dolphins and porpoises eat: the importance of prey quality on predator foraging strategies.

Cost of living dictates what whales, dolphins and porpoises eat: the importance of prey quality on predator foraging strategies.

Diets were determined from stomach content analysis reported in 32 studies for 3585 individual cetaceans feeding on 127 different prey species. We compiled the diet composition from published stomach content analyses for 11 species of cetaceans in the Northeast Atlantic belonging to 6 families (Balaenopteridae, Phocoenidae, Delphinidae, Ziphiidae, Physeteridae and Kogii- dae): minke whale (Balaenoptera acutorostrata), fin whale (Balaenoptera physalus), harbour porpoise (Phocoena phocoena), common dolphin (Delphinus delphis), striped dolphin (Stenella coeruleoalba), bottlenose dolphin (Tursiops truncatus), long-finned pilot whale (Globicephala melas), Cuvier’s beaked whale (Ziphius cavirostris), Mesoplodon beaked whale (Mesoplodon spp.), sperm whale (Physeter macrocephalus) and pygmy sperm whale (Kogia breviceps) [20–46]. Dietary data from stomach content analysis included prey species, and their numbers and mass, following standard analytical methods [30,43,47]. We obtained energy densities for 99 of the 127 prey species from proximate analyses. Energy densities were compiled for a wide range of marine forage species, including mesopelagic fish from the northeast Atlantic Ocean [48]. Additional data on energy densities for oceanic cephalopods were also used [49]. We then multiplied the ingested biomass by the energy density (kJNg 21 wet
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Selection of prey to improve biological parameters of the predator Podisus nigrispinus (Dallas, 1851) (Hemiptera: Pentatomidae) in laboratory conditions

Selection of prey to improve biological parameters of the predator Podisus nigrispinus (Dallas, 1851) (Hemiptera: Pentatomidae) in laboratory conditions

PIRES, E.M., AZEVEDO, D.O., LIMA, E.R., PELUZIO, R.J.E., SERRÃO, J.E. and ZANUNCIO, J.C., 2009. Desenvolvimento, reprodução e performance predatória do percevejo zoofitófago Podisus distinctus (Hemiptera: Pentatomidae) alimentado com larvas de Musca domestica (Diptera: Muscidae) imobilizadas ou soltas. Revista Brasileira de Biociências, vol. 7, no. 3, pp. 280-284. SAAVEDRA, J.L., ZANUNCIO, D., ZANUNCIO, T.V. and GUEDES, R.N.C., 1997. Prey captured ability of Podisus nigrispinus (Dallas) (Het., Pentatomidae) reared for successive generations on a meridic diet. Journal of Applied Entomology, vol. 121, no. 1-5, pp. 327-330. http://dx.doi.org/10.1111/j.1439-0418.1997.tb01414.x. SILVA, R.B., CORRÊA, A.S., DELLA LUCIA, T.M.C., PEREIRA, A.I.A., CRUZ, I. and ZANUNCIO, J.C., 2012. Does the aggressiveness of the prey modify the attack behavior of the predator Supputius cincticeps (Stål) (Hemiptera, Pentatomidae)? Revista Brasileira de Entomologia, vol. 56, no. 2, pp. 244-248. http://dx.doi.org/10.1590/S0085-56262012005000031. STROHMEYER, H.H., STAMP, N., JARZOMSKI, C.M. and BOWERS, D.M., 1998. Prey species and prey diet affect growth of invertebrate predators. Ecological Entomology, vol. 23, no. 1, pp. 68-79. http://dx.doi.org/10.1046/j.1365-2311.1998.00101.x. TORRES, J.B., PRATISSOLI, D. and ZANUNCIO, J.C., 1997. Exigências térmicas e potencial de desenvolvimento dos parasitoides Telenomus podisi Ashmead e Trissolcus brochymenae (Ashmead) em ovos do percevejo predador Podisus nigrispinus (Dallas). Anais da Sociedade Entomológica do Brasil, vol. 26, no. 3, pp. 445-453. http://dx.doi.org/10.1590/S0301-80591997000300006. TORRES, J.B., ZANUNCIO, J.C. and MOURA, M.A., 2006. The predatory stinkbug Podisus nigrispinus: biology, ecology and
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