Non-lethal Effects Of Predators Research Articles

A diabetes-like biochemical and behavioural phenotype of Drosophila induced by predator stress.

Predation can have both lethal and non-lethal effects on prey. The non-lethal effects of predation can instil changes in prey life history, behaviour, morphology and physiology, causing adaptive evolution. The chronic stress caused by sustained predation on prey is comparable to chronic stress conditions in humans. Conditions like anxiety, depression, and post-traumatic stress syndrome have also been implicated in the development of metabolic disorders such as obesity and diabetes. In this study, we found that predator stress induced during larval development in fruit flies Drosophila melanogaster impairs carbohydrate metabolism by systemic inhibition of Akt protein kinase, which is a central regulator of glucose uptake. However, Drosophila grown with predators survived better under direct spider predation in the adult phase. Administration of metformin and 5-hydroxytryptophan (5-HTP), a precursor of the neurotransmitter serotonin, reversed these effects. Our results demonstrate a direct link between predator stress and metabolic impairment, suggesting that a diabetes-like biochemical phenotype may be adaptive in terms of survival and reproductive success. We provide a novel animal model to explore the mechanisms responsible for the onset of these metabolic disorders, which are highly prevalent in human populations.

Nonlethal Effects of Predation: The Presence of Insectivorous Birds (Parus major) Affects The Behavior and Level of Stress in Locusts (Schistocerca gregaria)

Insect exposure to their predators can affect individuals and community processes, through direct consumption or nonlethal effects. However, the links between behavioral and physiological responses and stimuli needed for the development of predator avoidance are not clear. We subjected desert locusts (Schistocerca gregaria) to three nonlethal treatments, using great tits (Parus major) as a predator. The treatments included: (1) bird—presence of a great tit and its calls, (2) call—great tit calls only, (3) control—absence of a great tit and its calls. In the first behavioral laboratory experiment, locusts were offered food and shelter in an open space. The duration of hiding versus feeding indicated predator responses. In the second laboratory experiment, locusts were subjected to the same three treatments, and adipokinetic hormone (AKH) levels were measured in the central nervous system (CNS) and hemolymph. In the third experiment in an outdoor aviary, birds were allowed to fly freely over locusts before we measured physiological response. During the first experiment, locusts hid for a significantly longer amount of time and fed for a significantly shorter amount of time when the bird was present and calls were played, compared to when only calls were played or compared to the control treatment. The proximity of birds to locusts in the laboratory experiment elicited a significant increase in AKH levels in the CNS and hemolymph compared to the call/control treatment. The physical proximity of the great tits affected both the behavioral and physiological responses of the locusts.

High incidence of leg autotomy in urban crickets

Abstract Predation is an important selection pressure affecting animals. Predation has both consumptive and non-lethal effects. Because it is often difficult to estimate the extent to which non-lethal effects occur, we focused on autotomy as an indicator of non-lethal effects occurring in urban habitats. Autotomy is expected to indicate that individuals have escaped from predators. The incidence of leg autotomy in the cricket Dianemobius nigrofasciatus was compared between urban and rural habitats. The incidence of autotomy was higher in urban than in rural habitats. Failure to moult and conspecific aggressive interactions were not the main factors contributing to the incidence of autotomy in these crickets. The ease of autotomy and risk-taking tendencies did not differ among habitats. These results indicate that the incidence of autotomy reflects predation failure, and the non-lethal effects of predation are more likely to occur in urban habitats.

Immediate predation risk alters the relationship between potential and realised selection on male traits in the Trinidad guppy Poecilia reticulata.

Imminent predation risk affects mating behaviours in prey individuals in a multitude of ways that can theoretically impact the strength of sexual selection, as well as its operation on traits. However, empirical studies of the effects of imminent predation risk on sexual selection dynamics are still scarce. Here we explore how perceived predation affects: (1) the relationship between the opportunity for selection and the actual strength of selection on male traits; and (2) which traits contribute to male fitness and the shape of selection on these traits. We simulate two consecutive reproductive episodes, under control conditions and perceived predation risk using experimental populations of Trinidad guppies. The opportunity for selection is higher under predation risk compared to the control condition, but realised selection on traits remains unaffected. Pre- and postcopulatory traits follow complex patterns of nonlinear selection in both conditions. Differences in selection gradients deviate from predictions based on evolutionary and non-lethal effects of predation, the most notable being strong disruptive selection on courtship rate under predation risk. Our results demonstrate that sexual selection is sensitive to imminent predation risk perception and reinforce the notion that both trait-based and variance-based metrics should be employed for an informative quantification.

Mosquito responses to lethal and nonlethal effects of predation and an insect growth regulator

AbstractLethal and nonlethal effects of predation are likely to impact phenotypic traits of potential prey that elude capture. Nonlethal effects of predation on prey can include alterations in behavior or morphology in response to predation risk which may impair prey growth and fitness. The application of pesticide in mosquito control during aquatic stages can interact with predation stress and alter density and phenotypic traits of prey. Insect growth regulator (IGR) pyriproxyfen is a pesticide that mainly prevents pupal‐adult metamorphosis by mimicking juvenile hormone, whereas the larval stage is not targeted. The use of IGR can therefore act in conjunction with natural aquatic predators that target the larval stage to affect population of prey. In this study, we assessed the invasive mosquito prey Aedes aegypti responses to lethal and nonlethal effects of a combination of IGR and predatory mosquito larvae of Toxorhynchites rutilus. The combination of IGR and Tx. rutilus heavily lowered Ae. aegypti metamorphosis to adulthood more than the independent effects of IGR or Tx. rutilus. Exposing Ae. aegypti larvae to the combination shortened life span of adults after metamorphosis for both males and females, whereas control and numerical density reduction “removals” treatments lengthened life span. Our results show strong lethal and nonlethal outcomes of the combination on Ae. aegypti. These findings suggest an additional benefit, decreases adult life span, of the use of an IGR when combined with a natural predator of mosquitoes that may be exploited to improve mosquito control strategies to reduce the risk of disease transmission.

Non-lethal effects of the predator Meganyctiphanes norvegica and influence of seasonal photoperiod and food availability on the diel feeding behaviour of the copepod Centropages typicus.

Predators can induce changes in the diel activity patterns of marine copepods. Besides vertical migration, diel feeding rhythms have been suggested as an antipredator phenotypic response. We conducted experiments to assess the non-lethal direct effects of the predator Meganyctiphanes norvegica (northern krill) on the diel feeding patterns of the calanoid copepod Centropages typicus. We also analysed the influence of seasonal photoperiod and prey availability on the intensity of copepod feeding rhythms. We did not detect any large effect of krill presence on the diel feeding behaviour of copepods, either in day-night differences or total daily ingestions. Seasonal photoperiod and prey availability, however, significantly affected the magnitude of copepod feeding cycles, with larger diel differences in shorter days and at lower prey concentrations. Therefore, the role of non-lethal direct effects of predators on the diel feeding activity of marine copepods remain debatable and might not be as relevant as in freshwater zooplankton.

An escape theory model for directionally moving prey and an experimental test in juvenile Chinook salmon.

Prey evaluate risk and make decisions based on the balance between the costs of predation and those of engaging in antipredator behaviour. Economic escape theory has been valuable in understanding the responses of stationary prey under predation risk; however, current models are not applicable for directionally moving prey.Here we present an extension of existing escape theory that predicts how much predation risk is perceived by directionally moving prey. Perceived risk is measured by the extent antipredator behaviour causes a change in travel speed (the distance to a destination divided by the total time to reach that destination). Cryptic or cautious antipredator behaviour slows travel speed, while prey may also speed up to reduce predator–prey overlap. Next, we applied the sensitization hypothesis to our model, which predicts that prey with more predator experience should engage in more antipredator behaviour, which leads to a larger change in travel speed under predation risk. We then compared the qualitative predictions of our model to the results of a behavioural assay with juvenile Chinook salmon Oncorhynchus tshawytscha that varied in their past predator experience.We timed salmon swimming downstream through a mesh enclosure in the river with and without predator cues present to measure their reaction to a predator. Hatchery salmon had the least predator experience, followed by wild salmon captured upstream (wild‐upstream) and wild‐salmon captured downstream (wild‐downstream).Both wild salmon groups slowed down in response to predator cues, whereas hatchery salmon did not change travel speed. The magnitude of reaction to predator cues by salmon group followed the gradient of previous predator experience, supporting the sensitization hypothesis.Moving animals are conspicuous and vulnerable to predators. Here we provide a novel conceptual framework for understanding how directionally moving prey perceive risk and make antipredator decisions. Our study extends the scope of economic escape theory and improves general understanding of non‐lethal effects of predators on moving prey.

Ocean acidification may alter predator-prey relationships and weaken nonlethal interactions between gastropods and crabs

Predator–prey interactions often drive ecological patterns and are governed by factors including predator feeding rates, prey behavioral avoidance, and prey structural defenses. Invasive species can also play a large ecological role by disrupting food webs, driving local extinctions, and influencing evolutionary changes in prey defense mechanisms. This study documents a substantial reduction in the behavioral and morphological responses of multiple gastropod species (Nucella lapillus, N. ostrina, Urosalpinx cinerea) to an invasive predatory crab (green crab Carcinus maenas) under ocean acidification conditions. These results suggest that climate-related changes in ocean chemistry may diminish non-lethal effects of predators on prey responses including behavioral avoidance. While snails with varying shell mineralogies were similarly successful at deterring predation, those with primarily aragonitic shells were more susceptible to dissolution and erosion under high CO2 conditions. The varying susceptibility to predation among species with similar ecological roles could indicate that the impacts of invasive species like green crabs could be modulated by the ability of native and invasive prey to withstand ocean acidification conditions.

Predation decreases cohort foraging activity and growth, yet increases individual size variation in prey

There is increasing evidence that size variability within a cohort can have important consequences on community ecology and evolution. It is commonly assumed that the threat of predation can influence cohort size variability by homogenizing foraging behavior among members. We combined predictions of growth–defense models with those from models of genesis of size variation to test the non-lethal effects of size-selective newt and gape-unconstrained aeshnid dragonfly larva predators on the size structure of Rhacophorus arboreus tadpoles in a controlled laboratory experiment. We hypothesized that the predators would induce differential growth and behavioral responses in the tadpoles, and would decrease cohort size variation. The tadpoles reduced activity levels in the presence of the predators, but the responses were generally stronger in the presence of dragonfly larvae. Growth costs were commensurate with the levels of behavioral defense investments in the tadpoles. Despite strong reductions in activity levels and growth, cohort size variation increased in the presence of predators, contrasting current models on relationship between foraging rates, growth, and cohort size variation in prey. The underlying mechanisms are unclear, but it is possible that reduced rates of movement limited access to food for some cohort members or that predation risk enhanced the expression of behavioral variation among individuals.

How Do Trait-Mediated Non-lethal Effects of Predation Affect Population-Level Performance of Mosquitoes?

Non-lethal, trait-mediated effects of predation impact prey behavior and life-history traits. Studying how these effects in turn influence prey demography is crucial to understand prey life-history evolution. Mosquitoes are important vectors that claim several million lives every year worldwide by transmitting a range of pathogens. Several ecological factors affect life-history traits of both larval and adult mosquitoes, creating effects that cascade to population-level consequences. Few studies have comprehensively explored the non-lethal effects of predation and its interactions with resources and competition on larval, adult, and population traits of mosquitoes. Understanding these interactions is important because the effects of predation are hypothesized to rescue prey populations from the effects of density-dependence resulting from larval competition. Aedes aegypti larvae reared at two different larval densities and subjected to three non-lethal predator treatments were monitored for survival, development time, and adult size through the larval stages to adult eclosion, and adult females were monitored for survival and reproduction through their first gonotrophic cycle. Intraspecific competition increased larval development time, yielded small-bodied adults, and reduced fecundity in individuals exposed to predatory chemical cues as larvae. Exposure to cues from a living predator affected both body size and latency to blood feed in females. Analysis of life-table traits revealed significant effects of competition on net reproductive rate (R 0) of mosquitoes. The interaction between competition and predator treatments significantly affected the cohort rate of increase (r) and the index of performance (r'). The index of performance, which estimates rate of population change based on the size-fecundity relationship, was significantly and positively correlated with r, but overestimated r slightly. Lack of significant effect of predator treatments and larval density on cohort generation time (T c) further suggests that the observed effects of treatments on r and r' were largely a consequence of the effects on R 0. Also, the significant effects of treatment combinations on larval development time, adult body size and fecundity were ultimately manifested as effects on life-table traits estimated from adult survival and reproduction.

Predation risk affects egg mass but not egg steroid hormone concentrations in yellow-legged gulls.

Predators have both direct, consumptive effects on their prey and non-lethal effects on physiology and behavior, including reproductive decisions, with cascading effects on prey ecology and evolution. Here, we experimentally tested such non-lethal effects of exposure to increased predation risk on clutch size, egg mass, and the concentration of yolk steroid hormones in the yellow-legged gull Larus michahellis. We simulated increased predation risk by displaying stuffed predators (adult fox Vulpes vulpes, and adult buzzard Buteo buteo) to breeding adults before egg laying. The concentration of corticosterone, which has been shown to increase under exposure to maternal predation risk in other species, and of testosterone did not differ between eggs from mothers exposed to the predators and eggs from control mothers (i.e., eggs exposed to a novel object of similar size and position to the stuffed predators). The concentration of the two hormones negatively covaried. Clutch size did not vary according to experimental treatment, whereas egg mass was markedly larger in clutches from nests exposed to predators than in clutches from control nests. By increasing egg mass, mothers may reduce the risk of cooling of the eggs when incubation is impeded by predators, boost energy reserves, reduce post-natal detectability caused by food solicitation, and/or enhance development at hatching, thus increasing the chances of offspring survival. In general, our results are inconsistent with most of the few previous studies on similar non-lethal predator effects and suggest that such effects may vary among species according to ecological conditions, social behavior, and developmental mode.

Lethal and non-lethal effects of predation by native fish and an invasive crayfish on hatchery-reared age-0 lake sturgeon (Acipenser fulvescens Rafinesque, 1817)

Lethal and non-lethal effects of predation by native fish and an invasive crayfish on hatchery-reared age-0 lake sturgeon (<i>Acipenser fulvescens</i> Rafinesque, 1817)

Cues from a common predator cause survival-linked behavioral adjustments in Mojave Desert tortoises (Gopherus agassizii)

Animals are expected to engage in behavioral decision-making that minimizes their risk of predation; these decisions can cause non-lethal predator effects to behavior and spatial use. Our goal was to determine whether non-lethal effects of a common predator, coyotes (Canis latrans), could affect the behavior of a declining reptile, the Mojave Desert tortoise (Gopherus agassizii), hereafter tortoise. We exposed captive tortoises to olfactory and visual cues of coyotes and measured their resulting foraging behavior, burrow use, and other antipredator behaviors. We also measured risk of coyote predation in wild tortoises based on burrow use. Willingness to feed and time spent feeding were unaffected by the presence of coyote urine, but higher air temperatures at the start of feeding caused a decrease in time spent at their food dish. Captive tortoises chronically exposed to coyote urine did, however, spend more time in their burrows than when exposed to rabbit urine. When exposed to a coyote decoy, captive tortoises showed more general antipredator behaviors than those exposed to a control stimulus (deer decoy). Wild tortoises were less likely to be depredated by coyotes, if they were encountered in burrows more frequently. Predator olfactory and visual cues exerted non-lethal effects on captive tortoises through behavioral adjustments to their refuge-seeking behavior, which was a behavior linked to decreased coyote predation risk for wild tortoises. Human-subsidized predator populations may negatively affect declining species, including reptiles, as a result of behavioral modifications in response to predator cues. Predators can affect behavior of animals through olfactory and visual cues, which can have measurable effects on prey populations. Changes in prey behavior in response to predator presence can occur at the expense of opportunities to forage or reproduce, leading to decreased survival and reproduction. We tested behavioral responses of captive Mojave Desert tortoises to olfactory and visual cues of coyotes, which are a common predator in the Mojave Desert and subsidized by human food sources. Foraging behavior of captive tortoises was strongly affected by air temperatures at the start of feeding, but not coyote cues. Captive tortoises did, however, increase the amount of time they spent in burrows when coyote urine was present and showed greater fearfulness at the presentation of coyote urine combined with coyote models. Increased burrow use was associated with lower risk of coyote predation in wild tortoises, which suggested an advantage to increased refuge use when coyotes were detectable. Responses by tortoises suggest that coyote cues on the landscape affect tortoises through behavioral pathways that result in increased refuge use.

Human risk induced behavioral shifts in refuge use by elk in an agricultural matrix

ABSTRACTScientists increasingly acknowledge the influence that nonlethal effects of predation have on structuring wildlife‐landscape interactions. In landscapes dominated by human activities, wildlife can respond to human disturbance in a similar fashion to the risk of predation. Further, the risk allocation hypothesis suggests that individuals respond most strongly to risk when it is spatially and temporally predictable. We predict that individuals in agriculturally dominated landscapes will respond to potential risk from humans during hunting season by shifting their behavior to avoid agricultural areas during the day, instead retreating to refuge habitat. We predict that this shift to more nocturnal behavior will be strongest for elk (Cervus elaphus) adult female–calf pairs and will be influenced by the level of moon illumination. Using motion‐sensing cameras, we studied the response of elk moving between the Wainwright Dunes Ecological Reserve (a hunting refuge) and surrounding agriculturally dominated landscape in east‐central Alberta, Canada, to human disturbance in relation to sunrise and sunset. Elk became increasingly nocturnal with the onset of hunting, leaving the refuge following sunset and returning to the refuge earlier before sunrise. Further, elk became increasingly nocturnal in response to greater levels of moon illumination. Lastly, we found that adult female–calf pairs perceived greater risks associated with diurnal activity and exhibited the most nocturnal behavior relative to other demographic classes. Our results suggest that ungulate management based on traditional hunting seasons and times may be problematic as it creates strong cues for resident elk, allowing them to minimize risk by avoiding risky places at risky times in accordance with the risk allocation hypothesis. © 2017 The Wildlife Society.

Individual-level behavioral responses of immature green turtles to snorkeler disturbance.

Despite many positive benefits of ecotourism, increased human encounters with wildlife may have detrimental effects on wild animals. As charismatic megafauna, nesting and foraging sea turtles are increasingly the focus of ecotourism activities. The purpose of our study was to quantify the behavioral responses of immature green turtles (Chelonia mydas) to disturbance by snorkelers, and to investigate whether turtles have individual-level responses to snorkeler disturbance. Using a standardized disturbance stimulus in the field, we recorded turtle behaviors pre- and post-disturbance by snorkelers. Ninety percent of turtles disturbed by snorkeler (n=192) initiated their flights at distances of ≤3m. Using principal component analysis, we identified two distinct turtle personality types, 'bold' and 'timid', based upon 145 encounters of 19 individually identified turtles and five disturbance response variables. There was significant intra-individual repeatability in behavioral responses to disturbance, but bolder turtles had more behavioral plasticity and less consistent responses than more timid individuals. Bolder individuals with reduced evasion responses might be at a higher risk of shark predation, while more timid turtles might have greater energetic consequences due to non-lethal predator effects and repeated snorkeler disturbance. Over the longer term, a turtle population with a mix of bold and timid individuals may promote more resilient populations. We recommend that snorkelers maintain >3m distance from immature green turtles when snorkeling, and that ecotourism activities be temporally and spatially stratified. Further, turtle watching guidelines need to be communicated to both tour operators and independent snorkelers to reduce the disturbance of turtles.

Nonlethal predator effects on the turn-over of wild bird flocks.

Nonlethal predator effects arise when individuals of a prey species adjust their behaviour due to the presence of predators. Non-lethal predator effects have been shown to affect social group structure and social behaviour as well as individual fitness of the prey. In this experimental study, we used model sparrowhawks to launch attacks on flocks of wild great tits and blue tits whilst monitoring their social dynamics. We show that nonlethal attacks caused instantaneous turn-over and mixing of group composition within foraging flocks. A single experimental ‘attack’ lasting on average less than three seconds, caused the amount of turn-over expected over three hours (2.0–3.8 hours) of undisturbed foraging. This suggests that nonlethal predator effects can greatly alter group composition within populations, with potential implications for social behaviour by increasing the number of potential interaction partners, as well as longer-term consequences for pair formation and emergent effects determined by social structure such as information and disease transmission. We provide the first evidence, to our knowledge, based on in depth monitoring of a social network to comprehensively support the hypothesis that predators influence the social structure of groups, which offers new perspectives on the key drivers of social behaviour in wild populations.

Predator presence decreases food consumption in juvenile Xenopus laevis

Predators impact prey in direct (lethal) and indirect (non-lethal) manners. Predator-avoidance models capitalize on the non-lethal effects of predators to study how predator-induced fear impacts prey behavior and physiology. Here, we aimed to develop a predator avoidance model to determine how predators alter feeding and anxiety-like behavior in the African clawed frog (Xenopus laevis). We determined (1) the repeatability of frog behavior over time, (2) the effect of a stimulus (nothing, a size-matched or a large conspecific [potential predator]) on frog behavior, and (3) the effect of a stimulus on frog behavior in the presence of food. Twelve juvenile experimental frogs were exposed to all three stimulus conditions over 1 week. We predicted that (1) frog baseline behavior would be repeatable, and that (2) the presence of the large frog, but not size-matched frog, would increase fear and anxiety-like behaviors (hiding and inactivity) and would decrease food consumption and the number of air gulps. In the presence of both food and stimulus, experimental frogs ate significantly less when exposed to a large (potential predator) vs. a size-matched and no frog and took more time to first contact the food. Time spent inactive and number of air gulps did not differ across conditions. Few frogs hid during the behavioral trials. Time spent exploring and inactive and tank locations were repeatable over time. Overall, our paradigm is a viable model for studying the effects of predators on prey behavior, especially as it relates to feeding. Predators can induce fear and anxiety in prey and can alter prey behavior. We sought to develop a predator-avoidance model to study prey anxiety and feeding behavior in African clawed frogs. We determined (1) the repeatability of baseline behavior over time, (2) the effect of a stimulus (no, a size-matched, or a large [predatory] frog) on frog behavior, and (3) the effect of a stimulus on behavior in the presence of food. The presence of a potential predator alone did not significantly alter prey behavior. With predator + food, experimental frogs took longer to contact food, ate less, and spent less time feeding. Most activity and location behaviors were repeatable over time. This paradigm is a viable model for studying the effects of predators on prey feeding behavior.

Potential lethal and non-lethal effects of predators on dispersal of spider mites.

Predators can affect prey dispersal lethally by direct consumption or non-lethally by making prey hesitate to disperse. These lethal and non-lethal effects are detectable only in systems where prey can disperse between multiple patches. However, most studies have drawn their conclusions concerning the ability of predatory mites to suppress spider mites based on observations of their interactions on a single patch or on heavily infested host plants where spider mites could hardly disperse toward intact patches. In these systems, specialist predatory mites that penetrate protective webs produced by spider mites quickly suppress the spider mites, whereas generalist predators that cannot penetrate the webs were ineffective. By using a connected patch system, we revealed that a generalist ant, Pristomyrmex punctatus Mayr (Hymenoptera: Formicidae), effectively prevented dispersal of spider mites, Tetranychus kanzawai Kishida (Acari: Tetranychidae), by directly consuming dispersing individuals. We also revealed that a generalist predatory mite, Euseius sojaensis Ehara (Acari: Phytoseiidae), prevented between-patch dispersal of T. kanzawai by making them hesitate to disperse. In contrast, a specialist phytoseiid predatory mite, Neoseiulus womersleyi Schicha, allowed spider mites to escape an initial patch, increasing the number of colonized patches within the system. Our results suggest that ants and generalist predatory mites can effectively suppress Tetranychus species under some conditions, and should receive more attention as agents for conservation biological control in agroecosystems.

Effects of predation on diel activity and habitat use of the coral-reef shrimp Cinetorhynchus hendersoni (Rhynchocinetidae)

Nonlethal effects of predators on prey behaviour are still poorly understood, although they may have cascading effects through food webs. Underwater observations and experiments were conducted on a shallow fringing coral reef in Malaysia to examine whether predation risks affect diel activity, habitat use, and survival of the rhynchocinetid shrimp Cinetorhynchus hendersoni. The study site was within a protected area where predatory fish were abundant. Visual surveys and tethering experiments were conducted in April–May 2010 to compare the abundance of shrimps and predatory fishes and the relative predation intensity on shrimps during day and night. Shrimps were not seen during the day but came out of refuges at night, when the risk of being eaten was reduced. Shrimp preferences for substrata of different complexities and types were examined at night when they could be seen on the reef; complex substrata were preferred, while simple substrata were avoided. Shrimps were abundant on high-complexity columnar–foliate Porites rus, but tended to make little use of branching Acropora spp. Subsequent tethering experiments, conducted during daytime in June 2013, compared the relative mortality of shrimps on simple (sand–rubble, massive Porites spp.) and complex (P. rus, branching Acropora spp.) substrata under different predation risk scenarios (i.e., different tether lengths and exposure durations). The mortality of shrimps with short tethers (high risk) was high on all substrata while, under low and intermediate predation risks (long tethers), shrimp mortality was reduced on complex corals relative to that on sand–rubble or massive Porites spp. Overall, mortality was lowest on P. rus. Our study indicates that predation risks constrain shrimp activity and habitat choice, forcing them to hide deep inside complex substrata during the day. Such behavioural responses to predation risks and their consequences for the trophic role of invertebrate mesoconsumers warrant further investigation, especially in areas where predatory fishes have been overexploited.

Hunting for fear: innovating management of human–wildlife conflicts

Summary There is a growing theoretical basis for the role of predation risk as a driver of trophic interactions, conceptualized as the ‘ecology of fear’. However, current ungulate management ignores the role of nonlethal risk effects of predation. We introduce the concept of ‘hunting for fear’ as an extension of the more classical ‘hunting to kill’ that is typically used in large herbivore management. Hunting for fear aims to induce a behavioural response in ungulates, for example, as a way of diverting them from areas where their impact is undesired. Synthesis and applications. Hunting for fear asks for novel, potentially controversial, ways of hunting to induce strong enough risk effects, including more hunting on foot and with dogs, extended hunting seasons (ideally year‐round) and increased hunting of calves. Hunting for fear may offer novel opportunities to help manage the growing human–wildlife conflicts that we experience globally.