Constant Predation Research Articles

A Vibrio cholerae Type IV restriction system targets glucosylated 5-hydroxymethylcytosine to protect against phage infection.

A major challenge faced by Vibrio cholerae is constant predation by bacteriophage (phage) in aquatic reservoirs and during infection of human hosts. To overcome phage predation, V. cholerae has acquired and/or evolved a myriad of phage defense systems. Although several novel defense systems have been discovered, we hypothesized that more were encoded in V. cholerae given the low diversity of phages that have been isolated, which infect this species. Using a V. cholerae genomic library, we identified a Type IV restriction system consisting of two genes within a 16-kB region of the Vibrio pathogenicity island-2, which we name TgvA and TgvB (Type I-embedded gmrSD-like system of VPI-2). We show that both TgvA and TgvB are required for defense against T2, T4, and T6 by targeting glucosylated 5-hydroxymethylcytosine (5hmC). T2 or T4 phages that lose the glucose modifications are resistant to TgvAB defense but exhibit a significant evolutionary tradeoff, becoming susceptible to other Type IV restriction systems that target unglucosylated 5hmC. We also show that the Type I restriction-modification system that embeds the tgvAB genes protects against phage T3, secΦ18, secΦ27, and λ, suggesting that this region is a phage defense island. Our study uncovers a novel Type IV restriction system in V. cholerae, increasing our understanding of the evolution and ecology of V. cholerae, while highlighting the evolutionary interplay between restriction systems and phage genome modification.IMPORTANCEBacteria are constantly being predated by bacteriophage (phage). To counteract this predation, bacteria have evolved a myriad of defense systems. Some of these systems specifically digest infecting phage by recognizing unique base modifications present on the phage DNA. In this study, we discover a Type IV restriction system encoded in V. cholerae, which we name TgvAB, and demonstrate it recognizes and restricts phage that have 5-hydroxymethylcytosine glucosylated DNA. Moreover, the evolution of resistance to TgvAB render phage susceptible to other Type IV restriction systems, demonstrating a significant evolutionary tradeoff. These results enhance our understanding of the evolution of V. cholerae and more broadly how bacteria evade phage predation.

Consequences for predator–prey dynamics caused by the presence of obstacles

In order to understand how a heterogeneous habitat affects the population dynamics of the predator–prey system, a spatially explicit lattice model consisting of predators, prey and obstacles is constructed. The model includes smart pursuit (predators to prey) and evasion (prey from predators). Both species can affect their movement by visual perception within their finite sighting range. Non-conservative processes that change the number of individuals within the population, such as breeding and physiological dying, are implemented in the model. Obstacles are represented by non-overlapping lattice shapes that are randomly placed on the lattice. In the absence of obstacles, numerical simulations reveal regular, coherent oscillations with a nearly constant predator–prey phase difference. Numerical simulations have shown that changing the probabilities for non-conservative processes can increase or decrease the period of coherent oscillations in species abundances and change the relative lag between coherent components. After introducing obstacles into the model, we observe random transitions between coherent and non-coherent oscillating regimes. In the non-coherent regime, predator and prey abundances continue to oscillate, but without a well-defined phase relationship. Our model suggests that stochasticity introduced by density fluctuations of obstacles is responsible for the reversible shift from coherent to non-coherent oscillations.

The Rosenzweig–MacArthur Graphical Criterion for a Predator-Prey Model with Variable Mortality Rate

We consider a general modified Gause type model of predation, for which the predator mortality rate can depend on the densities of both species, prey and predator. We give a graphical criterion for the stability of positive hyperbolic equilibria, which is an extension of the well-known Rosenzweig–MacArthur graphical criterion for the case of a constant predator mortality rate. We examine the occurrence of a Poincaré–Andronov–Hopf bifurcation and give an expression for the first Lyapunov coefficient. Our model generalizes several models appearing in the literature. The relevance of our results, i.e. the use of the graphical criterion and the expression for the first Lyapunov coefficient, is tested on these models. The global behavior of the system is illustrated by numerical simulations which confirm the local properties of the models near the equilibria.

Codimension-2 bifurcation in a discrete predator–prey system with constant yield predator harvesting

This work investigates the bifurcation analysis in a discrete-time Leslie–Gower predator–prey model with constant yield predator harvesting. The stability analysis for the fixed points of the discretized model is shown briefly. In this study, the model undergoes codimension-1 bifurcation such as fold bifurcation (limit point), flip bifurcation (period-doubling) and Neimark–Sacker bifurcation at a positive fixed point. Further, the model exhibits codimension-2 bifurcations, including Bogdanov–Takens bifurcation and generalized flip bifurcation at the fixed point. For each bifurcation, by using the critical normal form coefficient method, various critical states are calculated. To validate our analytical findings, the bifurcation curves of fixed points are drawn by using MATCONTM. The system exhibits interesting rich dynamics including limit cycles and chaos. Moreover, it has been shown that the predator harvesting may control the chaos in the system.

Farmers’ Perception of the Feasibility of Mithun (Bos frontalis) Farming and its Constraints in Nagaland, India

The present study was conducted on a sample of 126 mithun farmers randomly drawn from three districts of Nagaland to assess the perception of the farmers regarding the feasibility of mithun farming and its constraints that can contribute to a better understanding of the mithun production systems and its declining population in Nagaland. The farmer’s perception of the feasibility of mithun farming and its constraints was measured using a 3 and 5 point continuum Likert scale, respectively, drawing various inferences based on the respondents’ responses. A low mean perception score (MPS) of 1.06, reveals that the majority (99.21%) of the respondents are in disagreement with the statement that mithun farming is not profitable. Mithun farming according to them is very profitable which needs the right hand-holding support from financial institutions for the exploitation of its marketable potential. Due to the lack of institutional efforts in promoting mithun rearing as bankable and insured schemes, 99.21 percent of farmers held a strong perception (MPS=2.98) that mithun farming, in the long run, may not be feasible and may result in discontinuity of mithun farming in some villages. Also, the high cost of inputs for fencing (Mean value=3.91) and constant predator attack on the animal particularly the young calves (Mean value= 3.88) renders mithun farming difficult with the existing system of rearing. The findings indicate that though mithun farming is profitable, there is a strong need to promote a scientific and alternative semi-intensive method of mithun rearing and encourage the diversified use of mithun for meat, milk, hide, and draught potential to stop the slaughter of mithun for table purpose only. Therefore, considering the socio-cultural linkages of the tribes with the mithun proper strategies and policies are essential for its conservation.

Noisy waters can influence young-of-year lobsters’ substrate choice and their antipredatory responses

Offshore human activities lead to increasing amounts of underwater noise in coastal and shelf environments, which may affect commercially-important benthic invertebrate groups like the re-stocked Helgoland European lobster (Homarus gammarus) in the German Bight (North Sea). It is crucial to understand the impact tonal low-frequency noises, like maritime transport and offshore energy operations, may have on substrate choice and lobsters' behavior to assess potential benefits or bottlenecks of new hard-substrate artificial offshore environments that become available. In this study, we investigated the full factorial effect of a tonal low-frequency noise and predator presence on young-of-year (YOY) European lobsters' in a diurnal and nocturnal experiment. Rocks and European oyster shells (Ostrea edulis) were offered as substrate to YOY lobsters for 3 h. Video recordings (n = 134) allowed the identification of lobsters' initial substrate choice, diel activity and key behaviors (peeking, shelter construction, exploration and hiding). To ensure independence, YOY lobsters in the intermolt stage were randomly selected and assigned to the experimental tanks and used only once. We provide the first evidence that stressors alone, and in combination, constrain YOY lobsters' initial substrate choice towards rocks. During nighttime, the joint effect of exposure to a constant low-frequency noise and predator presence decreased antipredator behavior (i.e., hiding) and increased exploration behavior. Noise may thus interfere with YOY lobsters' attention and decision-making processes. This outcome pinpoints that added tonal low-frequency noise in the environment have the potential to influence the behavior of early-life stages of European lobsters under predator pressure and highlights the importance of including key benthic invertebrates' community relationships in anthropogenic noise risk assessments. Among others, effects of noise must be taken into consideration in plans involving the multi-use of any offshore area for decapods’ stock enhancement, aquaculture, and temporary no-take zones.

Impact of fear on a predator–prey system with prey-dependent search rate in deterministic and stochastic environment

A modified Holling type II (variable predator search rate rather than constant) predator–prey interaction has been proposed where apart from direct consumption the prey biomass is affected by the fear of predator. The goal of this work is to analyze the dynamic nature of the system when the constant search rate in the Holling type II response is replaced by a prey-dependent search rate in the presence of fear effect which raises the anti-predator behaviour of prey. Some basic properties such as positivity, uniform boundedness, and persistence have been provided. Next, we have studied the existing conditions and stability criteria of all equilibria. Then, the conditions for the occurrence of local bifurcations of co-dimension 1 are given. Furthermore, we have investigated the effects of all the combinations of delay factors (breeding and gestation delay) for which the proposed system switches its stability through supercritical Hopf bifurcation. Numerical simulations are conducted to validate analytical results. It is observed that level of fear can not only reduce predator’s growth at the interior equilibrium but also stabilize the system by excluding the existence of a limit cycle. We also discuss the similarities and differences between our proposed system and the usual Holling type II model. Lastly, the deterministic system has been extended to a stochastic model using nonlinear perturbation.

An interaction mechanism for the maintenance of fission-fusion dynamics under different individual densities.

Animals often show high consistency in their social organisation despite facing changing environmental conditions. Especially in shoaling fish, fission–fusion dynamics that describe for which periods individuals are solitary or social have been found to remain unaltered even when density changed. This compensatory ability is assumed to be an adaptation towards constant predation pressure, but the mechanism through which individuals can actively compensate for density changes is yet unknown. The aim of the current study is to identify behavioural patterns that enable this active compensation. We compared the fission–fusion dynamics of two populations of the live-bearing Atlantic molly (Poecilia mexicana) that live in adjacent habitats with very different predator regimes: cave mollies that inhabit a low-predation environment inside a sulfidic cave with a low density of predatory water bugs (Belostoma sp.), and mollies that live directly outside the cave (henceforth called “surface” mollies) in a high-predation environment. We analysed their fission–fusion dynamics under two different fish densities of 12 and 6 fish per 0.36 m2. As expected, surface mollies spent more time being social than cave mollies, and this difference in social time was a result of surface mollies being less likely to discontinue social contact (once they had a social partner) and being more likely to resume social contact (once alone) than cave mollies. Interestingly, surface mollies were also less likely to switch among social partners than cave mollies. A random walk simulation predicted each population to show reduced social encounters in the low density treatment. While cave mollies largely followed this prediction, surface mollies maintained their interaction probabilities even at low density. Surface mollies achieved this by a reduction in the size of a convex polygon formed by the group as density decreased. This may allow them to largely maintain their fission–fusion dynamics while still being able to visit large parts of the available area as a group. A slight reduction (21%) in the area visited at low densities was also observed but insufficient to explain how the fish maintained their fission–fusion dynamics. Finally, we discuss potential movement rules that could account for the reduction of polygon size and test their performance.

Hitchhiking, collapse, and contingency in phage infections of migrating bacterial populations

Natural bacterial populations are subjected to constant predation pressure by bacteriophages. Bacteria use a variety of molecular mechanisms to defend themselves from phage predation. However, since phages are nonmotile, perhaps the simplest defense against phage is for bacteria to move faster than phages. In particular, chemotaxis, the active migration of bacteria up attractant gradients, may help the bacteria escape slowly diffusing phages. Here we study phage infection dynamics in migrating bacterial populations driven by chemotaxis through low viscosity agar plates. We find that expanding phage-bacteria populations supports two moving fronts, an outermost bacterial front driven by nutrient uptake and chemotaxis and an inner phage front at which the bacterial population collapses due to phage predation. We show that with increasing adsorption rate and initial phage population, the speed of the moving phage front increases, eventually overtaking the bacterial front and driving the system across a transition from a regime where bacterial front speed exceeds that of the phage front to one where bacteria must evolve phage resistance to survive. Our data support the claim that this process requires phage to hitchhike with moving bacteria. A deterministic model recapitulates the transition under the assumption that phage virulence declines with host growth rate which we confirm experimentally. Finally, near the transition between regimes we observe macroscopic fluctuations in bacterial densities at the phage front. Our work opens a new, spatio-temporal, line of investigation into the eco-evolutionary struggle between bacteria and phage.

Continuity of chronic predation risk determines changes in prey physiology

Prey reconfigure their physiology to avoid costs of prolonged predator pressure. However, these changes might not occur under periodic predation risk, with repeating acute phases. To test the effect of predation risk continuity on changes in prey physiology, we exposed amphipods: Dikerogammarus villosus and Gammarus jazdzewskii to periodic and constant predation cue. After one week, we measured: cellular defence systems: total antioxidant status (TAS), heat shock proteins (Hsp70); intracellular damage marker: lipid peroxidation (TBARS); condition index: glycogen concentration. Predator presence reduced TAS level in G. jazdzewskii independent of its continuity and in D. villosus after periodic exposure. Amphipods showed downregulation of Hsp70 when exposed to periodic (D. villosus) or constant (G. jazdzewskii) predation risk. Exposure to predators reduced TBARS level in D. villosus (irrespective of the continuity) and G. jazdzewskii (periodic exposure). Glycogen concentration in both species was not affected by predator presence. Thus, the continuity of the predator cue shaped prey physiology reconfiguration, optimizing costs of physiological adjustments under challenging conditions. Nevertheless, the lack of negative consequences of the prolonged exposure to the predator cue, whether constant or periodic, shows that amphipods can thrive under chronic predation risk, which is a constant part of the wild environment.

Thermal squeeze will exacerbate declines in New Zealand's endemic forest birds

The effects of invasive species whose ranges are expanding in response to climate change have the potential to drive a new wave of extinctions in vulnerable species. We explore whether expansion of mammalian predators in New Zealand will lead to the thermal squeeze of a forest avifauna by investigating the mechanisms that have led to recent declines. Analysis of local occupancy across the three main islands between 1969–1979 and 1999–2004 shows that the ranges of predator-vulnerable endemic species are constrained by lowland forest loss and continued to contract to higher-elevation, colder parts of forested mountains. Species that are large, nest in tree cavities, and/or disperse poorly have undergone more rapid recent loss where temperatures are higher, consistent with higher and more constant predation in warmer forested sites being the principal mechanism of recent decline. Warming climate is likely to exacerbate local extinctions of predator-vulnerable species by reducing the extent of cool thermal refugia from continuously high predation pressure below the upper limit of forest. However, warming is unlikely to jeopardise small-bodied, non-cavity-nesting, mobile species, which have had stable or increasing populations in warm sites and largely deforested landscapes. New Zealand will share with Hawai'i the phenomenon of thermal squeeze of endemic forest bird species that is mediated by the changing range of an invasive species, rather than by native species themselves tracking their climatic niches. New Zealand will need to make substantial advances in large-scale predator management in warm forests to halt and reverse forest bird declines.

Staphylococci phages display vast genomic diversity and evolutionary relationships

BackgroundBacteriophages are the most abundant and diverse entities in the biosphere, and this diversity is driven by constant predator–prey evolutionary dynamics and horizontal gene transfer. Phage genome sequences are under-sampled and therefore present an untapped and uncharacterized source of genetic diversity, typically characterized by highly mosaic genomes and no universal genes. To better understand the diversity and relationships among phages infecting human pathogens, we have analysed the complete genome sequences of 205 phages of Staphylococcus sp.ResultsThese are predicted to encode 20,579 proteins, which can be sorted into 2139 phamilies (phams) of related sequences; 745 of these are orphams and possess only a single gene. Based on shared gene content, these phages were grouped into four clusters (A, B, C and D), 27 subclusters (A1-A2, B1-B17, C1-C6 and D1-D2) and one singleton. However, the genomes have mosaic architectures and individual genes with common ancestors are positioned in distinct genomic contexts in different clusters. The staphylococcal Cluster B siphoviridae are predicted to be temperate, and the integration cassettes are often closely-linked to genes implicated in bacterial virulence determinants. There are four unusual endolysin organization strategies found in Staphylococcus phage genomes, with endolysins predicted to be encoded as single genes, two genes spliced, two genes adjacent and as a single gene with inter-lytic-domain secondary translational start site. Comparison of the endolysins reveals multi-domain modularity, with conservation of the SH3 cell wall binding domain.ConclusionsThis study provides a high-resolution view of staphylococcal viral genetic diversity, and insights into their gene flux patterns within and across different phage groups (cluster and subclusters) providing insights into their evolution.

Indirect legacy effects of an extreme climatic event on a marine megafaunal community

AbstractWhile extreme climatic events (ECEs) are predicted to become more frequent, reliably predicting their impacts on consumers remains challenging, particularly for large consumers in marine environments. Many studies that do evaluateECEeffects focus primarily on direct effects, though indirect effects can be equally or more important. Here, we investigate the indirect impacts of the 2011 “Ningaloo Niño” marine heatwaveECEon a diverse megafaunal community in Shark Bay, Western Australia. We use an 18‐year community‐level data set before (1998–2010) and after (2012–2015) the heatwave to assess the effects of seagrass loss on the abundance of seven consumer groups: sharks, sea snakes (multiple species), Indo‐pacific bottlenose dolphins (Tursiops aduncus), dugongs (Dugong dugon), green turtles (Chelonia mydas), loggerhead turtles (Caretta caretta), and Pied Cormorants (Phalacrocoraxspp.). We then assess whether seagrass loss influences patterns of habitat use by the latter five groups, which are under risk of shark predation. Sharks catch rates were dominated by the generalist tiger shark (Galeocerdo cuvier) and changed little, resulting in constant apex predator density despite heavy seagrass degradation. Abundances of most other consumers declined markedly as food and refuge resources vanished, with the exception of generalist loggerhead turtles. Several consumer groups significantly modified their habitat use patterns in response to the die‐off, but only bottlenose dolphins did so in a manner suggestive of a change in risk‐taking behavior. We show thatECEs can have strong indirect effects on megafauna populations and habitat use patterns in the marine environment, even when direct effects are minimal. Our results also show that indirect impacts are not uniform across taxa or trophic levels and suggest that generalist marine consumers are less susceptible to indirect effects ofECEs than specialists. Such non‐uniform changes in populations and habitat use patterns have implications for community dynamics, such as the relative strength of direct predation and predation risk. Attempts to predict ecological impacts ofECEs should recognize that direct and indirect effects often operate through different pathways and that taxa can be strongly impacted by one even if resilient to the other.

Protein Inhibitors of CRISPR-Cas9.

Bacteria are under constant predation from viruses, called bacteriophages (phages). This threat has driven the evolution of multiple defense systems, including the CRISPR-Cas (clustered regularly interspaced short palindromic repeats and CRISPR associated genes) immune pathway. Phages are not passive bystanders in their CRISPR-mediated demise, however, as many have developed potent protein inhibitors of the bacterial adaptive immune system. Here, I review the work that led to the discovery of many distinct "anti-CRISPR" proteins. Furthermore, I outline how understanding their mechanisms of action has provided a suite of specific and high-affinity reagents to modulate and study CRISPR-Cas applications.

Traps and transformations influencing the financial viability of tourism on private-land conservation areas.

The ability of private conservation organizations to remain financially viable is a key factor influencing their effectiveness. One-third of financially motivated private-land conservation areas (PLCAs) surveyed in South Africa are unprofitable, raising questions about landowners' abilities to effectively adapt their business models to the socioeconomic environment. In any complex system, options for later adaptation can be constrained by starting conditions (path dependence). We tested 3 hypothesized drivers of path dependence in PLCA ecotourism and hunting business models: (H1) the initial size of a PLCA limits the number of mammalian game and thereby predators that can be sustained; (H2) initial investments in infrastructure limit the ability to introduce predators; and (H3) rainfall limits game and predator abundance. We further assessed how managing for financial stability (optimized game stocking) or ecological sustainability (allowing game to fluctuate with environmental conditions) influenced the ability to overcome path dependence. A mechanistic PLCA model based on simple ecological and financial rules was run for different initial conditions and management strategies, simulating landowner options for adapting their business model annually. Despite attempts by simulated landowners to increase profits, adopted business models after 13 years were differentiated by initial land and infrastructural assets, supporting H1 and H2. A conservation organization's initial assets can cause it to become locked into a financially vulnerable business model. In our 50-year simulation, path dependence was overcome by fewer of the landowners who facilitated natural ecological variability than those who maintained constant hunting rates and predator numbers, but the latter experienced unsustainably high game densities in low rainfall years. Management for natural variability supported long-term ecological sustainability but not shorter term socioeconomic sustainability for PLCAs. Our findings highlight trade-offs between ecological and economic sustainability and suggest a role for governmental support of the private conservation industry.

Maternally induced intraclutch cannibalism: an adaptive response to predation risk?

Theory on condition-dependent risk-taking indicates that when prey are in poor condition, their anti-predator responses should be weak. However, variation in responses resulting from differences in condition is generally considered an incidental by-product of organisms living in a heterogeneous environment. Using Leptinotarsadecemlineata beetles and stinkbug (Podisusmaculiventris) predators, we hypothesised that in response to predation risk, parents improve larval nutritional condition and expression of anti-predator responses by promoting intraclutch cannibalism. We showed that mothers experiencing predation risk increase production of unviable trophic eggs, which assures provisioning of an egg meal to the newly hatched offspring. Next, we experimentally demonstrated that egg cannibalism reduces L.decemlineata vulnerability to predation by improving larval nutritional condition and expression of anti-predator responses. Intraclutch cannibalism in herbivorous insects might be a ubiquitous strategy, aimed to overcome the dual challenge of feeding on protein-limited diets while living under constant predation threat.

Study of refuge use on a predator–prey system with a competitor for the prey

In this paper, we propose a predator–prey system with a competitor for the prey. The model incorporates a constant prey refuge and predation process follows Holling type II response function. Using the Routh–Hurwitz criterion, the sufficient conditions of locally asymptotically stable of all the equilibria are obtained. Furthermore, global stability of the positive equilibrium is investigated by constructing a suitable Lyapunov function. The occurrence of Hopf-bifurcation of the system is shown at a critical value “[Formula: see text]” and the system can be stabilized by increasing amount of prey refuge. The result includes the sufficient conditions for uniform persistence. Numerical simulations are carried out to illustrate the obtained results and the dependence of the dynamic behavior on the prey refuge.

The consequences of facultative sex in a prey adapting to predation.

A species reproductive mode, along with its associated costs and benefits, can play a significant role in its evolution and survival. Facultative sexuality, being able to reproduce both sexually and asexually, has been deemed evolutionary favourable as the benefits of either mode may be fully realized. In fact, many studies have focused on identifying the benefits of sex and/or the forces selecting for increased rates of sex using facultative sexual species. The costs of either mode, however, can also have a profound impact on a population's evolutionary trajectory. Here, we used experimental evolution and fitness assays to investigate the consequences of facultative sexuality in prey adapting to predation. Specifically, we compared the adaptive response of algal prey populations exposed to constant rotifer predation and which had alternating cycles of asexual and sexual reproduction where sexual episodes were either facultative (sexual and asexual progeny simultaneously propagated) or obligate (only sexual progeny propagated). We found that prey populations with facultative sexual episodes reached a lower final relative fitness and suffered a greater trade-off in traits under selection, that is defence and competitive ability, as compared to prey populations with obligate sexual episodes. Our results suggest that costs associated with sexual reproduction (germination time) and asexual reproduction (selection interference) were amplified in the facultative sexual prey populations, leading to a reduction in the net advantage of sexuality. Additionally, we found evidence that the cost of sex was reduced in the obligate sexual prey populations because increased selection for sex was observed via the spontaneous production of sexual cells. These results show that certain costs associated with facultative sexuality can affect an organism's evolutionary trajectory.

Interactive effects of predation risk and conspecific density on the nutrient stoichiometry of prey.

The mere presence of predators (i.e., predation risk) can alter consumer physiology by restricting food intake and inducing stress, which can ultimately affect prey-mediated ecosystem processes such as nutrient cycling. However, many environmental factors, including conspecific density, can mediate the perception of risk by prey. Prey conspecific density has been defined as a fundamental feature that modulates perceived risk. In this study, we tested the effects of predation risk on prey nutrient stoichiometry (body and excretion). Using a constant predation risk, we also tested the effects of varying conspecific densities on prey responses to predation risk. To answer these questions, we conducted a mesocosm experiment using caged predators (Belostoma sp.), and small bullfrog tadpoles (Lithobates catesbeianus) as prey. We found that L.catesbeianus tadpoles adjust their body nutrient stoichiometry in response to predation risk, which is affected by conspecific density. We also found that the prey exhibited strong morphological responses to predation risk (i.e., an increase in tail muscle mass), which were positively correlated to body nitrogen content. Thus, we pose the notion that in risky situations, adaptive phenotypic responses rather than behavioral ones might partially explain why prey might have a higher nitrogen content under predation risk. In addition, the interactive roles of conspecific density and predation risk, which might result in reduced perceived risk and physiological restrictions in prey, also affected how prey stoichiometry responded to the fear of predation.

A “death trap” in the landscape of fear

Abstract A crucial element in the “the landscape of fear” concept is that prey animals are aware of varying levels of predation risk at a spatial scale. This often leads to a negative spatial relationship between prey and predator in which prey avoid the most risky sites in the landscape. In this paper, we argue that our understanding of large carnivore-ungulate interactions is biased by studies from highly heterogeneous landscapes (e.g. the Yellowstone National Park). Due to a high availability of refuges and foraging sites in such landscapes, prey are able to reduce predation risk by showing habitat shifts. Besides the spatial heterogeneity at the landscape scale, the ungulate response to predation risk can be affected by the hunting mode (stalking vs. cursorial) of the predator. We propose that prey cannot easily avoid predation risk by moving to less risky habitats in more homogenous landscapes with concentrated food resources, especially where the large carnivores’ assemblage includes both stalking and cursorial species. No distinct refuges for prey may occur in such landscapes due to equally high accessibility to predators in all habitats, while concentrated resources make prey distribution more predictable. We discuss a model of a densely forested landscape based on a case study of the Białowieża Primeval Forest, Poland. Within this landscape, ungulates focus their foraging activity on small food-rich forest gaps, which turn out to be “death traps” as the gaps are primarily targeted by predators (stalking lynx and cursorial wolf) while hunting. No alternative of moving to low predation risk areas exist for prey due to risk from wolves in surrounding closed-canopy forest. As a result, the prey is exposed to constant high predation pressure in contrast to heterogeneous landscapes with less concentrated resources and more refuge areas. Future research should focus on explaining how ungulates are coping with predation risk in these landscapes that offer little choice of escaping predation by considering behavioural and physiological (e.g. metabolic, hormonal) responses.