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opencc-by-4.0Oct 2018View details →

Fig. 1 in Physiological responses of anti-predation in prey fish to the threat of piscivorous fish in different underwater visibility conditions

Fig. 1. Mean and standard error of plasma cortisol levels for Astyanax bimaculatus (Linnaeus, 1758) shoals in treatments with clear (white box) and turbid water (striped box). Different letters above bars indicate significant differences at P<0.05 in the Kruskal Wallis test between predator types. There were no differences between plasma cortisol levels in clear and turbid water treatments.

Figure 5 in Shifts in ground-dwelling predator communities in response to changes in management intensity in Alpine meadows

Figure 5. Proportions and χ2-test results for the ecological species traits moisture, rarity and ecological tolerance of ground-dwelling predatory arthropods (Arachnida, Carabidae, Staphylinidae, Formicidae) from extensively and intensively managed hay meadows in South Tyrol, Italy.

Figure 4 in Shifts in ground-dwelling predator communities in response to changes in management intensity in Alpine meadows

Figure 4. Non-metric multidimensional scaling (NMDS) of the full species community of predatory invertebrates, including the two treatments (intensive and extensive) and the two seasons (spring and autumn). Each spot represents one pitfall trap. Spider web centres represent the weighted centroids of each management type.

Figure 3 in Shifts in ground-dwelling predator communities in response to changes in management intensity in Alpine meadows

Figure 3. Abundance based accumulation curves for predatory arthropods based on Hill numbers N0 and N1 confronting extensively and intensively used montane hay meadows in South Tyrol, Italy.

Figure 2 in Shifts in ground-dwelling predator communities in response to changes in management intensity in Alpine meadows

Figure 2. The mean (and 95 % confidence interval) activity density (individuals per sampling day), species richness, and exponential Shannon diversity of ground-dwelling predatory arthropods from montane extensively and intensively used hay meadows and two sampling seasons (spring and autumn) in South Tyrol, Italy. No significant effect of management was detected for any biodiversity index.

Figure 1 in Shifts in ground-dwelling predator communities in response to changes in management intensity in Alpine meadows

Figure 1. Maps of the distribution of the six selected hay meadows (EH = extensively used hay meadows; IH = intensively used hay meadows) located in Barbian/Barbiano in the Autonomous Province South Tyrol, Italy.

opencc-by-4.0Sep 2005View details →

Figure 1 in An investigation of predator-induced defence responses in ciliated protozoa

Figure 1. Effect of different predators on Euplotes muscorum. Results are means of three independent replicates for each treatment; ''eaten'', E. muscorum cells ingested by predators; ''cysts'', encysted E. muscorum cells; ''alive'', uningested, trophic E. muscorum cells.

opencc-by-4.0Sep 2005View details →

Figure 2 in An investigation of predator-induced defence responses in ciliated protozoa

Figure 2. Prey width distributions of Colpidium kleini from the experiment described in Table II, i.e. (a) in the absence of predators; (b) in the presence of Euplotes sp. Each distribution was calculated after 24 h and represents the mean of three replicates (n5150).

opencc-zeroOct 2022View details →

Can predators stabilize host-parasite interactions? Changes in aquatic predator identity alters amphibian responses and parasite abundance across life stages

The role of parasites can change depending on the food web community. Predators, for instance, can amplify or dilute parasite effects on their hosts. Likewise, exposure to parasites or predators at one life stage can have long-term consequences on individual performance and survival, which can influence population and disease dynamics. To understand how predators affect amphibian parasite infections across life stages, we manipulated exposure of northern leopard frog (Rana pipiens) tadpoles to three predators (crayfish [Orconectes rusticus], bluegill [Lepomis macrochirus], or mosquitofish [Gambusia affinis]) and to trematode parasites (Echinostoma spp.) in mesocosms and followed juveniles in outdoor terrestrial enclosures through overwintering. Parasites and predators both had strong impacts on metamorphosis with bluegill and parasites individually reducing metamorph survival. However, when fish were present, the negative effects of parasites on survival were not apparent, likely because fish altered community composition via increased algal food resources. Bluegill also reduced snail abundance, which could explain the reduced abundance of parasites in surviving metamorphs. Bluegill and parasite exposure increased mass at metamorphosis, which increased metamorph jumping, swimming, and feeding performance, suggesting larger frogs would experience better terrestrial survival. Effects on size at metamorphosis persisted in the terrestrial environment but did not influence overwintering survival. Based on our results, we constructed stage-structured population models to evaluate the lethal and sublethal effects of bluegill and parasites on population dynamics. Our models suggested that the positive effects of bluegill and parasites on body size may have greater effects on population growth than the direct effects of mortality. This study illustrates how predators can alter the outcome of parasitic infections and highlights the need for long-term experiments that investigate how changes in host-parasite systems alter population dynamics. We show some predators reduce parasite effects and have indirect positive effects on surviving individuals potentially increasing host population persistence.

opencc-zeroNov 2022View details →

Ungulate spatiotemporal responses to contrasting predation risk from wolves and snow leopards

Spatial responses to risk from multiple predators can precipitate emergent consequences for prey (i.e., multiple-predator effects, MPEs) and mediate indirect interactions between predators. How prey navigate risk from multiple predators may therefore have important ramifications for understanding the propagation of predation-risk effects (PREs) through ecosystems. The interaction of predator and prey traits has emerged as a potentially key driver of anti-predator behaviour but remains underexplored in large vertebrate systems, particularly where sympatric prey share multiple predators. We sought to better generalize our understanding of how predators influence their ecosystems by considering how multiple sources of contingency drive prey distribution in a multi-predator-multi-prey system. Specifically, we explored how two sympatric ungulates with different escape tactics – vertically agile, scrambling ibex (Capra sibirica) and sprinting argali (Ovis ammon) – responded to predation risk from shared predators with contrasting hunting modes – cursorial wolves (Canis lupus) and vertical-ambushing, stalking snow leopards (Panthera uncia). Contrasting risk posed by the two predators presented prey with clear trade-offs. Ibex selected for greater exposure to chronic long-term risk from snow leopards, and argali for wolves, in a nearly symmetrical manner that was predictable based on the compatibility of their respective traits. Yet, acute short-term risk from the same predator upended these long-term strategies, increasing each ungulate's exposure to risk from the alternate predator in a manner consistent with a scenario in which conflicting anti-predator behaviours precipitate risk-enhancing MPEs and mediate predator facilitation. By contrast, reactive responses to wolves led ibex to reduce their exposure to risk from both predators – a risk-reducing MPE. Evidence of a similar reactive risk-reducing effect for argali vis-à-vis snow leopards was lacking. Our results suggest that prey spatial responses and any resulting MPEs and prey-mediated interactions between predators are contingent on the interplay of hunting mode and escape tactics. Further investigation of interactions among various drivers of contingency in PREs will contribute to a more comprehensive understanding and improved forecasting of the ecological effects of predators.

opencc-zeroJun 2023View details →

Data from: Predator response to the coloured eyespots and defensive posture of Colombian four-eyed frogs

Deimatic displays, where sudden changes in prey appearance elicit aversive predator reactions, have been suggested to occur in many taxa. These (often only putative) displays frequently involve different components that may also serve antipredator functions via other mechanisms (e.g. mimicry, warning signalling, body inflation). The Colombian four-eyed frog, Pleurodema brachyops, has been suggested to gain protection against predation through putative deimatic displays where they inflate and elevate the posterior part of their body revealing eye-like colour markings. We exposed stationary artificial frogs to wild predators to test whether the two components (eyespot/colour markings, defensive posture) of their putative deimatic display, and their combination, provide protection from predation without the sudden change in appearance. We did not detect any obvious additive effect of defensive posture and eyespots/colour markings on predation risk but found a marginally-significant trend for model frogs in the resting posture to be less attacked when displaying eyespots/colour markings than when they were not, suggesting that the presence of colour markings/eyespots may provide some protection on its own. Additionally, we found that models in a resting posture were overall more frequently attacked on the head than models in a defensive posture, indicating that a defensive posture alone could help redirect predator attacks to non-vital parts of the body. The trends found in our study suggest that the different components of P. brachyops' coloration may serve different functions during a deimatic display, but further research is needed to elucidate the role of each component when accompanied by sudden prey movement.

opencc-zeroSep 2023View details →

Numerical response of predator to prey: Dynamic interactions and population cycles in Eurasian lynx and roe deer

The dynamic interactions between predators and their prey have two fundamental processes; numerical and functional responses. Numerical response is defined as predator growth rate as a function of prey density or both prey and predator densities [dP/dt = f(N, P)]. Functional response is defined as the kill rate by an individual predator being a function of prey density or prey and predator densities combined. Although there are relatively many studies on the functional response in mammalian predators, numerical response remains poorly documented. We studied numerical response of Eurasian lynx (Lynx lynx) to various densities of its primary prey species, roe deer (Capreolus capreolus), and to itself (lynx). We exploited an unusual natural situation, spanning three decades where lynx, after a period of absence in central and southern Sweden, during which roe deer populations had grown to high densities, subsequently recolonized region after region, from north to south. We divided the study area into seven regions, with increasing productivity from north to south. We found strong effects of both roe deer density and lynx density on lynx numerical response. Thus, both resources and intraspecific competition for these resources are important to understand the lynx population dynamic. We built a series of deterministic lynx–roe deer models and applied them to the seven regions. We found a very good fit between these Lotka-Volterra-type models and the data. The deterministic models produced almost cyclic dynamics or dampened cycles in five of the seven regions. Thus, we documented population cycles in this large-predator-large-herbivore system, which is rarely done. The amplitudes in the dampened cycles decreased towards the south. Thus, the dynamics between lynx and roe deer became more stable with increasing carrying capacity for roe deer, which is related to higher productivity in the environment. This increased stability could be explained by variation in predation risk, where human presence can act as prey refugia, and by a more diverse prey guild that will weaken the direct interaction between lynx and roe deer.