Prey Survival Rates Research Articles

Threshold behavior of a stochastic predator–prey system with prey refuge and fear effect

In this paper, we investigate the threshold behavior of a stochastic predator–prey system with prey refuge, fear effect and non-constant mortality rate. First, we obtain thresholds which can determine the extinction and persistence in the mean of prey and predator. Then we establish the threshold for the existence of a unique ergodic stationary distribution via constructing suitable Lyapunov functions. We can draw conclusions: (1) the survival rate of prey can be improved by increasing the strength of refuge, decreasing the cost of fear or reducing the intensity of white noise; (2) the survival rate of predator can be improved by weakening the strength of refuge, increasing the cost of fear or reducing the intensity of white noise.

Confined System Analysis of a Predator-Prey Minimalistic Model

In nature exists a properly defined food chain- an order of hunting and getting hunted. One such hunter-hunted pair is considered in this context and coordinated escape manoeuvres in response to predation is studied in case of a rarely examined confined system. Both the predator agent and prey agents are considered to be self-propelled particles moving in a viscous fluid. The state of motility when alive and passivity on death has been accounted for. A novel individual-based combination of Vicsek model and Boids flocking model is used for defining the self-propelling action and inter-agent interactions. The regimes observed at differing levels of co-ordination segregated by quantification of global order parameter are found to be in agreement with the extant literature. This study strives to understand the penalty on the collective motion due to the restraints employed by the rigid walls of the confinement and the predator’s hunting tactics. The success of any escape manoeuvre is dependent on the rate of information transfer and the strength of the agitation at the source of the manoeuvre. The rate of information transfer is studied as a function of co-ordination and the size of the influence zone and the source strength is studied as a function of escape acceleration activated on the agitated prey. The role of these factors in affecting survival rate of prey is given due coverage.

Habitat structure changes the relationships between predator behavior, prey behavior, and prey survival rates.

The individual behavioral traits of predators and prey sometimes determine the outcome of their interactions. Here, we examine whether changes to habitat complexity alter the effects of predator and prey behavior on their survival rates. Specifically, we test whether behavioral traits (activity level, boldness, and perch height) measured in predators and prey or multivariate behavioral volumes best predict the survival rates of both trophic levels in staged mesocosms with contrasting structural complexity. Behavioral volumes and hypervolumes are a composite group-level behavioral diversity metric built from the individual-level behavioral traits we measured in predators and prey. We stocked mesocosms with a host plant and groups of cannibalistic predators (n = 5 mantises/mesocosm) and their prey (n = 15 katydids/mesocosm), and mesocosms varied in the presence/absence of additional non-living climbing structures. We found that mantis survival rates were unrelated to any behavioral metric considered here, but were higher in structurally complex mesocosms. Unexpectedly, katydids were more likely to survive when mantis groups occupied larger behavioral volumes, indicating that more behaviorally diverse predator groups are less lethal. Katydid mortality was also increased when both predators and prey exhibited higher average perch heights, but this effect was increased by the addition of supplemental structure. This is consistent with the expectation that structural complexity increases the effect of intraspecific behavioral variation on prey survival rates. Collectively, these results convey that the effects of predator and prey behavior on prey survival could depend highly on the environment in which they are evaluated.

Personality variation in two predator species does not impact prey species survival or plant damage in staged mesocosms

Mounting evidence suggests that consistent individual differences in behavior, better known as animal personality, can shape aspects of population and community ecology. Yet, the potential for animal personality to affect more complex and non-linear food webs, like those seen in nature, remains understudied. Here, we explore the degree to which the aggregate behaviors of two predator species simultaneously interact to alter prey survival rates and the presence and magnitude of trophic cascades. We set up mesocosms in an old-field habitat containing four different insect prey species and either two Phidippus clarus (Salticidae), two Platycryptus undatus (Salticidae), or one of each predator. Prior to initiating each mesocosm, we assayed the activity level and boldness of each individual predator and included these metrics in our models predicting prey survival and plant damage. We then compared the number of surviving prey and plant damage under each of these conditions and tested for associations between each of these response variables and predator behavior. We found no significant effect of predator community composition or predators’ behavior on prey survival or plant damage. These results suggest that the effects of predator personality on prey survival may be subtle or absent in complex species interaction modules. Although much research suggests that animal personality can influence broader scale ecological phenomena, the ability of animal personality to alter complex species interaction modules remains unresolved. We tested whether pairs of predators of different personality types differentially impacted prey survival rates and plant damage in a tritrophic system, and whether these effects varied based on predator community composition. We recovered no evidence that predator personality types influenced prey survival or plant damage regardless of the predator composition considered. These results suggest that the effects of personality may be absent or undetectable in more complex, realistic ecological settings. The majority of laboratory-based personality studies published to date evaluate only dyadic species interactions in simplified environments. Our findings therefore raise concerns that such studies are prone to overestimate the effects of animal personality.

Behavioral Hypervolumes of Predator Groups and Predator-Predator Interactions Shape Prey Survival Rates and Selection on Prey Behavior.

Predator-prey interactions often vary on the basis of the traits of the individual predators and prey involved. Here we examine whether the multidimensional behavioral diversity of predator groups shapes prey mortality rates and selection on prey behavior. We ran individual sea stars (Pisaster ochraceus) through three behavioral assays to characterize individuals' behavioral phenotype along three axes. We then created groups that varied in the volume of behavioral space that they occupied. We further manipulated the ability of predators to interact with one another physically via the addition of barriers. Prey snails (Chlorostome funebralis) were also run through an assay to evaluate their predator avoidance behavior before their use in mesocosm experiments. We then subjected pools of prey to predator groups and recorded the number of prey consumed and their behavioral phenotypes. We found that predator-predator interactions changed survival selection on prey traits: when predators were prevented from interacting, more fearful snails had higher survival rates, whereas prey fearfulness had no effect on survival when predators were free to interact. We also found that groups of predators that occupied a larger volume in behavioral trait space consumed 35% more prey snails than homogeneous predator groups. Finally, we found that behavioral hypervolumes were better predictors of prey survival rates than single behavioral traits or other multivariate statistics (i.e., principal component analysis). Taken together, predator-predator interactions and multidimensional behavioral diversity determine prey survival rates and selection on prey traits in this system.

Prey Survival and Vulnerability of Juvenile Rhynchocypris oxycephalus in Juvenile Fish Shelters under Predation by Korean Native Piscivorous Fish (Coreoperca herzi)

The aim of this study was to evaluate the newly-developed juvenile fish shelter (JFS) for its ability to increase prey survival and to improve species diversity in a freshwater ecosystem. An experiment was performed in an outdoor large-scale mesocosm three times from 2011 to 2012 by comparing the responses to adjustment as a function of the volume of JFS in the control and experimental groups. Analysis results of the environmental monitoring over three periods indicated only minor differences in the physicochemical characteristics of the water quality and phyto- and zoo-plankton biomass, thereby enabling a comparative analysis of the feeding ecology. However, the water temperature exhibited large fluctuations, ranging from 16.4 to 27.6 °C, and high water temperature conditions (Period 1, 25.6 ± 2.0 °C) enhanced the predation activity of the piscivorous fish Coreoperca herzi (C. herzi, size 89 ± 4 mm). Statistically, the survival rates of the prey fish, Rhynchocypris oxycephalus (R. oxycephalus, size 29 ± 1 mm), with JFSs were greater by 35.9%–46.7%, and improved as the patch volume of JFS increased. Based on both experimental observations and statistical analysis, the JFS developed in this study could reduce the chances of predator–prey encounters, minimize prey vulnerability, and thereby increase prey survival rates.

Autotomy and its Effects on Wolf Spider Foraging Success

AbstractFew studies have attempted to determine how physical injury affects predators. One of the ways that physical injury can be expressed is by autotomy or the voluntary loss of a body part. Here, we examined whether the loss of specific legs affects the foraging success of the wolf spider Rabidosa santrita (predator) on another species, Pardosa valens (prey). We also wanted to identify whether the loss of legs in both the predator and prey would impact the outcome of a predation event. Both predator and prey were collected from a creek bed at Portal, AZ, in 2012. Predators were randomly assigned groups where all prey items were intact or all prey had one randomly chosen leg IV removed. Within these groups, predators were organized into a control, leg I autotomy, or leg IV autotomy treatment. All predators had their pre‐ and post‐foraging running speed determined. Predators were introduced into chambers with five prey items and allowed to forage for 1 h. The leg position autotomized or the comparison of pre‐ and post‐foraging trials had no effect on predator running speed. Additionally, there was no significant effect of either predator or prey leg treatment on the total proportion of prey items captured by the end of the foraging trials. Survival analyses indicated that intact prey items tended to have a higher survival rate when predators were missing a leg IV than when predators were intact. When both the predator and prey were missing legs, no significant difference in prey survival rates was detected. We suggest that for predators that inhabit complex, heterogeneous habitats and are classified as ambush predators, the loss of a limb may affect prey capture success, especially when the prey is intact, but that increased sample size is necessary to determine whether this trend is significant.

Stem stiffness plays a role in determining the foraging success of predators

The presence of macrophytes in the littoral zone provide prey animals with protection from predators. Two macrophyte characters, stem density and branching, are known to hinder predator foraging in macrophyte beds. Stem stiffness is a character that allows the macrophyte to withstand current power in the intertidal zone, but its effect on predator movements in macrophyte beds has not been studied to date. In this study I examined whether the foraging success of predators is constrained by stem stiffness, as well as stem density and the presence of branches. Artificial macrophytes were constructed using two types of rubber that differed in stiffness. The newt Cynops ensicauda popei and larvae of the damselfly Paracercion melanotum were used as predator and prey, respectively, in this model system. The results revealed that all three plant characters studied influenced the survival rate of prey. Stiff stems consistently increased the survival rate compared with flexible stems. Stem density had the highest positive influence on survival rate. The direct effect of branches was negative and minute, but it altered the dependency on stem density. Although stiffness did have an effect on the survival rate of prey, its magnitude was relatively low. The effect of stiffness in other settings should be examined in future studies.

Increased habitat structure does not always provide increased refuge from predation

Submerged aquatic vegetation (SAV) usually hosts higher numbers of both inverte- brates and fish than do unvegetated substrates. In addition, based on prior laboratory experiments predation risk is thought to decrease with increasing SAV biomass or stem/shoot density, resulting in higher abundance and diversity of potential prey species in dense vegetation. However, all previous tests of the effects of vegetation on prey capture have been similar: constant numbers of predators and prey have been tested at different vegetation densities. Because sampling has repeatedly shown that the abundance of both predators and prey increases with increasing SAV density, an experiment that tests the effects of increasing SAV density on prey capture would mirror reality more closely than would the design of prior experiments and would also allow predator and prey numbers to increase. Thus, in laboratory trials we increased the number of predators (pinfish Lagodon rhomboides (Linnaeus)) and prey (grass shrimp Palaemonetes pugio Hulthuis) in proportion to increases in SAV shoot density to re-evaluate whether increasing SAV density altered prey survival rates under these more realistic conditions. Treatments included an unvegetated substrate and 3 different densities (400, 2000 and 4000 leaves m -2 of artificial SAV (mimicking turtlegrass Thalassia testudinum Banks and Sol). Our results conflicted with those of prior experiments and showed no significant differences in grass shrimp survival among the different SAV densities (although there was greater grass shrimp survival in SAV than on unvegetated substrate), and indicated that increasing vegetation density will not consistently lead to proportionally greater prey survival rates.