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Robby Stoks - One of the best experts on this subject based on the ideXlab platform.
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Effects of pesticide exposure and Predation Risk on nutrient cycling and primary production.
The Science of the total environment, 2019Co-Authors: Marie Van Dievel, Lizanne Janssens, Robby StoksAbstract:Abstract Understanding how pesticides and natural stressors shape ecosystem functions remains a major challenge. A largely overlooked way how stressors may affect nutrient cycling and primary production is through effects on body stoichiometry and the egestion of elements. We investigated how exposure to the pesticide chlorpyrifos and to Predation Risk, an abundant natural stressor in aquatic systems, altered the stoichiometry of the bodies and the egested faecal pellets of Enallagma cyathigerum damselfly larvae and how this further cascaded into effects on primary production (algae growth). Chlorpyrifos exposure reduced egestion rates while Predation Risk had no effect. Chlorpyrifos exposure and Predation Risk affected both elemental composition of bodies and faecal pellets, and this in an additive way. Chlorpyrifos exposure increased body C(carbon), N(nitrogen), and P(phosphorous) contents, and increased the C content of the faecal pellets. Predation Risk induced an increase of the N content, resulting in a decreased C:N ratio, of both the bodies and faecal pellets. The changes in the composition of the faecal pellets caused by Predation Risk but not by chlorpyrifos exposure increased algae growth under control conditions. This indicated that algae growth was N limited. Our results provide an important proof-of-principle how a stressor may shape nutrient cycling and subsequently primary productivity.
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Additive bioenergetic responses to a pesticide and Predation Risk in an aquatic insect.
Aquatic toxicology (Amsterdam Netherlands), 2019Co-Authors: Marie Van Dievel, Lizanne Janssens, Robby StoksAbstract:Ignoring natural stressors such as Predation Risk may contribute to the failure of ecological Risk assessment of pesticides to protect freshwater biodiversity. To better understand combined effects of multiple stressors, bioenergetic responses are important as these inform about the balance between energy input and consumption, and provide a unifying mechanism to integrate the impact of multiple stressors with different modes of action. We studied in Enallagma cyathigerum damselfly larvae the single and combined effects of exposure to the pesticide chlorpyrifos and Predation Risk on life history (survival and growth rate) and bioenergetic response variables at the organismal level (assimilation and conversion efficiency) and the cellular level (cellular energy allocation CEA, energy storage Ea, and energy consumption Ec). Chlorpyrifos exposure almost halved the survival of the damselfly larvae, while Predation Risk had no effect on survival. Both exposure to the pesticide and to Predation Risk reduced larval growth rates. This was caused by a reduced conversion efficiency under chlorpyrifos exposure, and by a reduced assimilation efficiency under Predation Risk. Both chlorpyrifos and Predation Risk reduced the CEA because of a decreased Ea, and for chlorpyrifos also an increased Ec. The lower Ea was driven by reductions in the fat and glycogen contents. Effects of the pesticide and Predation Risk were consistently additive and for most variables the strongest response was detected when both stressors were present. The absence of any synergisms may be explained by the high mortality and hypometabolism caused by the pesticide. Our results indicate that CEA can be a sensitive biomarker to evaluate effects of not only contaminants but also natural stressors, such as Predation Risk, and their combined impact on organisms.
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Reinforcing effects of non-pathogenic bacteria and Predation Risk: from physiology to life history
Oecologia, 2014Co-Authors: Lizanne Janssens, Robby StoksAbstract:The important ecological role of Predation Risk in shaping populations, communities and ecosystems is becoming increasingly clear. In this context, synergistic effects between Predation Risk and other natural stressors on prey organisms are gaining attention. Although non-pathogenic bacteria can be widespread in aquatic ecosystems, their role in mediating effects of Predation Risk has been ignored. We here address the hypothesis that non-pathogenic bacteria may reinforce the negative effects of Predation Risk in larvae of the damselfly Coenagrion puella . We found synergistic effects for all three life history variables studied: mortality increased, growth reductions were magnified and bacterial load was higher when both non-lethal stressors were combined. The combined exposure to the bacterium and Predation Risk considerably impaired the two key antipredator mechanisms of the damselfly larvae: they no longer reduced their food intake under Predation Risk and showed a synergistic reduction in escape swimming speed. The reinforcing negative effects on the fitness-related traits could be explained by the observed synergistic effects on food intake, swimming muscle mass, immune function and oxidative damage. These are likely widespread consequences of energetic constraints and increased metabolic rates associated with the fight-or-flight response. We therefore hypothesize that the here documented synergistic interactions with non-pathogenic bacteria may be widespread. Our results highlight the ignored ecological role of non-pathogenic bacteria in reinforcing the negative effects of Predation Risk on prey organisms.
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Predation Risk causes oxidative damage in prey.
Biology letters, 2013Co-Authors: Lizanne Janssens, Robby StoksAbstract:While there is increasing interest in non-consumptive effects of predators on prey, physiological effects are understudied. While physiological stress responses play a crucial role in preparing escape responses, the increased metabolic rates and shunting of energy away from other body functions, including antioxidant defence, may generate costs in terms of increased oxidative stress. Here, we test whether Predation Risk increases oxidative damage in Enallagma cyathigerum damselfly larvae. Under Predation Risk, larvae showed higher lipid peroxidation, which was associated with lower levels of superoxide dismutase, a major antioxidant enzyme in insects, and higher superoxide anion concentrations, a potent reactive oxygen species. The mechanisms underlying oxidative damage are likely to be due to the shunting of energy away from antioxidant defence and to an increased metabolic rate, suggesting that the observed increased oxidative damage under Predation Risk may be widespread. Given the potentially severe fitness consequences of oxidative damage, this largely overlooked non-consumptive effect of predators may be contributing significantly to prey population dynamics.
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Predation Risk induces stress proteins and reduces antioxidant defense
Functional Ecology, 2008Co-Authors: Stefanie Slos, Robby StoksAbstract:Summary 1Despite its wide ecological relevance, we know little about the physiological mechanisms underlying the growth vs. mortality by Predation trade-off. Here, we test for two costly, potential physiological correlates of the fight-or-flight response that may contribute to the growth reduction under Predation Risk: induction of stress proteins (Hsp60 and Hsp70) and of antioxidant enzymes (superoxide dismutase, SOD and catalase, CAT), in larvae of the damselfly Enallagma cyathigerum. 2Under Predation Risk, there was a growth reduction and an increase in oxygen consumption, indicative of the fight-or-flight response. Predation Risk did not affect Hsp60 levels but induced an increase in energetically costly Hsp70 levels. 3Under Predation Risk, levels of SOD remained constant and those of CAT decreased. Together with the increase in respiration, this should inevitably result in oxidative stress. 4Our results suggest that induction of stress proteins may contribute to the partly physiologically mediated growth reduction under Predation Risk and that oxidative stress is a novel cost of Predation Risk that may have important long-term negative fitness consequences for the prey. The latter adds to the recent insight that costs of stressors and life-history trade-offs may not always directly operate through increased energy consumption and differential allocation, but, may also work through the increased production of reactive oxygen species.
Danielle L. Dixson - One of the best experts on this subject based on the ideXlab platform.
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Intertidal crustaceans use seaweed-derived chemical cues to mitigate Predation Risk
Behavioral Ecology and Sociobiology, 2017Co-Authors: Rohan M. Brooker, Danielle L. DixsonAbstract:As Predation is a primary driver of mortality, the need to minimize Predation Risk can shape prey behavior, influencing habitat selection and investment in vigilance. As structurally complex habitats can reduce Predation Risk, prey within heterogeneous environments may have evolved sensory abilities to locate them. In temperate rocky intertidal systems, fucoid seaweeds are a main source of structural complexity and can provide shelter for small organisms. This study examined the effects of Predation Risk on habitat selection in a tide pool-dwelling shrimp, Palaemon affinis , specifically testing whether Predation Risk drives preferences for fucoid seaweeds and if shrimps use chemical cues to locate fucoid-rich habitats. While tide pools with and without fucoids were equally abundant, P. affinis densities were >3 times higher in pools containing fucoids. The relationship between P. affinis and fucoids appears to be related to Predation Risk with P. affinis exhibiting a preference for fucoid microhabitats when a potential predator was present. Shrimps could distinguish between olfactory signatures from tide pools with and without fucoids and the odor of fucoids from other marine algae, suggesting that chemical cues are used to identify these structurally complex habitats. In addition to reducing Predation Risk, fucoid-rich habitats may provide better access to essential resources and reduce exposure to other biotic and abiotic stressors. This study shows that prey organisms can rapidly modify habitat use based on ambient Predation Risk, with olfactory cues used to identify the shelter characteristics of different habitats. Significance statement Predation is the major source of mortality for most animal species. For this reason, animals may have evolved ways to minimize Predation Risk by modifying their behavior. In this study, we show that small tide pool-dwelling shrimps modify their habitat use in response to predators, using chemical cues to locate and identify structurally complex habitats that could reduce Predation Risk when this Risk is high.
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Intertidal crustaceans use seaweed-derived chemical cues to mitigate Predation Risk
Behavioral Ecology and Sociobiology, 2017Co-Authors: Rohan M. Brooker, Danielle L. DixsonAbstract:As Predation is a primary driver of mortality, the need to minimize Predation Risk can shape prey behavior, influencing habitat selection and investment in vigilance. As structurally complex habitats can reduce Predation Risk, prey within heterogeneous environments may have evolved sensory abilities to locate them. In temperate rocky intertidal systems, fucoid seaweeds are a main source of structural complexity and can provide shelter for small organisms. This study examined the effects of Predation Risk on habitat selection in a tide pool-dwelling shrimp, Palaemon affinis, specifically testing whether Predation Risk drives preferences for fucoid seaweeds and if shrimps use chemical cues to locate fucoid-rich habitats. While tide pools with and without fucoids were equally abundant, P. affinis densities were >3 times higher in pools containing fucoids. The relationship between P. affinis and fucoids appears to be related to Predation Risk with P. affinis exhibiting a preference for fucoid microhabitats when a potential predator was present. Shrimps could distinguish between olfactory signatures from tide pools with and without fucoids and the odor of fucoids from other marine algae, suggesting that chemical cues are used to identify these structurally complex habitats. In addition to reducing Predation Risk, fucoid-rich habitats may provide better access to essential resources and reduce exposure to other biotic and abiotic stressors. This study shows that prey organisms can rapidly modify habitat use based on ambient Predation Risk, with olfactory cues used to identify the shelter characteristics of different habitats. Predation is the major source of mortality for most animal species. For this reason, animals may have evolved ways to minimize Predation Risk by modifying their behavior. In this study, we show that small tide pool-dwelling shrimps modify their habitat use in response to predators, using chemical cues to locate and identify structurally complex habitats that could reduce Predation Risk when this Risk is high.
Niels J Dingemanse - One of the best experts on this subject based on the ideXlab platform.
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Behavioral and morphological responses to perceived Predation Risk: a field experiment in passerines
Behavioral Ecology, 2015Co-Authors: Robin N. Abbey-lee, Kimberley J. Mathot, Niels J DingemanseAbstract:Predators can affect prey both directly (consumptive effects) and indirectly (nonconsumptive effects), with a growing body of literature showing the latter may have pronounced effects. Prey populations are comprised of individuals that differ in perception of and willingness to take Risk; therefore, studying how different types of individuals respond to Predation Risk is necessary to fully understand prey dynamics. Playbacks were used to experimentally manipulate perceived Predation Risk in nest-box populations of wild great tits (Parus major) to examine the nonconsumptive effects of avian predators on prey behavior and morphology, and to explore individual differences in prey response. Individuals responded to our treatment, and responses differed depending on both treatment and premanipulation behavioral type. Birds in areas exposed to predator playback tended to decrease in body mass more than birds exposed to nonthreatening (control) playback. Differences between treatment groups were mainly driven by initially fast exploring birds: In the control treatment, fast explorers increased in mass, whereas the initially fast exploring birds in the Predation treatment decreased in mass. Furthermore, birds exposed to predator playback decreased exploratory tendency compared with controls. These findings demonstrate that Predation Risk alters great tit behavior (exploration) and morphology (body mass) and that plasticity in response to Risk relates to an individual’s willingness to take Risks. Our findings suggest that individuals differ in susceptibility to Predation Risk, causing adaptive individual differences in responsiveness to changes in Predation Risk. Acknowledging individuality in responses to perceived Predation Risk has important consequences for understanding prey dynamics.
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perceived Predation Risk affects sleep behaviour in free living great tits parus major
Animal Behaviour, 2014Co-Authors: Erica F Stuber, M M Grobis, Robin N Abbeylee, Bart Kempenaers, Jakob C Mueller, Niels J DingemanseAbstract:Sleep is of major importance to most organisms but insights into how sleep is affected by ecological processes are largely lacking. Perceived Predation Risk constitutes a major factor that should shape adaptive phenotypic plasticity in sleep but it is unclear to what degree an individual can tailor sleep to different types of Risk. If animals base behavioural decisions on the Predation landscape then we would expect individuals to adjust their sleep behaviour when exposed to changes in Predation Risk. Here we investigated the plasticity of phenotypic sleep in wild great tits roosting in nestboxes and exposed to different types of Predation Risk. Following our prediction, when exposed to experimentally increased perceived Predation Risk from owls, Strix aluco (a bird that can prey on birds solely outside their roosting cavity), individuals increased total sleep duration. Contrary to our prediction, when exposed to experimentally increased perceived Predation Risk from martens, Martes martes (a mammal that can prey on birds inside cavities), individuals woke up less often during the night, but otherwise did not change their sleep behaviour. Birds did not alter total time spent awake during the night in response to predator exposure. Our findings demonstrate that individual great tits modify their sleep behaviour in response to changes in Predation Risk. Ecological factors including exposure to predators, resource availability and reproductive competition may act as significant constraints on natural sleep patterns and warrant further investigation with free-living individuals.
Rohan M. Brooker - One of the best experts on this subject based on the ideXlab platform.
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Intertidal crustaceans use seaweed-derived chemical cues to mitigate Predation Risk
Behavioral Ecology and Sociobiology, 2017Co-Authors: Rohan M. Brooker, Danielle L. DixsonAbstract:As Predation is a primary driver of mortality, the need to minimize Predation Risk can shape prey behavior, influencing habitat selection and investment in vigilance. As structurally complex habitats can reduce Predation Risk, prey within heterogeneous environments may have evolved sensory abilities to locate them. In temperate rocky intertidal systems, fucoid seaweeds are a main source of structural complexity and can provide shelter for small organisms. This study examined the effects of Predation Risk on habitat selection in a tide pool-dwelling shrimp, Palaemon affinis , specifically testing whether Predation Risk drives preferences for fucoid seaweeds and if shrimps use chemical cues to locate fucoid-rich habitats. While tide pools with and without fucoids were equally abundant, P. affinis densities were >3 times higher in pools containing fucoids. The relationship between P. affinis and fucoids appears to be related to Predation Risk with P. affinis exhibiting a preference for fucoid microhabitats when a potential predator was present. Shrimps could distinguish between olfactory signatures from tide pools with and without fucoids and the odor of fucoids from other marine algae, suggesting that chemical cues are used to identify these structurally complex habitats. In addition to reducing Predation Risk, fucoid-rich habitats may provide better access to essential resources and reduce exposure to other biotic and abiotic stressors. This study shows that prey organisms can rapidly modify habitat use based on ambient Predation Risk, with olfactory cues used to identify the shelter characteristics of different habitats. Significance statement Predation is the major source of mortality for most animal species. For this reason, animals may have evolved ways to minimize Predation Risk by modifying their behavior. In this study, we show that small tide pool-dwelling shrimps modify their habitat use in response to predators, using chemical cues to locate and identify structurally complex habitats that could reduce Predation Risk when this Risk is high.
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Intertidal crustaceans use seaweed-derived chemical cues to mitigate Predation Risk
Behavioral Ecology and Sociobiology, 2017Co-Authors: Rohan M. Brooker, Danielle L. DixsonAbstract:As Predation is a primary driver of mortality, the need to minimize Predation Risk can shape prey behavior, influencing habitat selection and investment in vigilance. As structurally complex habitats can reduce Predation Risk, prey within heterogeneous environments may have evolved sensory abilities to locate them. In temperate rocky intertidal systems, fucoid seaweeds are a main source of structural complexity and can provide shelter for small organisms. This study examined the effects of Predation Risk on habitat selection in a tide pool-dwelling shrimp, Palaemon affinis, specifically testing whether Predation Risk drives preferences for fucoid seaweeds and if shrimps use chemical cues to locate fucoid-rich habitats. While tide pools with and without fucoids were equally abundant, P. affinis densities were >3 times higher in pools containing fucoids. The relationship between P. affinis and fucoids appears to be related to Predation Risk with P. affinis exhibiting a preference for fucoid microhabitats when a potential predator was present. Shrimps could distinguish between olfactory signatures from tide pools with and without fucoids and the odor of fucoids from other marine algae, suggesting that chemical cues are used to identify these structurally complex habitats. In addition to reducing Predation Risk, fucoid-rich habitats may provide better access to essential resources and reduce exposure to other biotic and abiotic stressors. This study shows that prey organisms can rapidly modify habitat use based on ambient Predation Risk, with olfactory cues used to identify the shelter characteristics of different habitats. Predation is the major source of mortality for most animal species. For this reason, animals may have evolved ways to minimize Predation Risk by modifying their behavior. In this study, we show that small tide pool-dwelling shrimps modify their habitat use in response to predators, using chemical cues to locate and identify structurally complex habitats that could reduce Predation Risk when this Risk is high.
Mark Hebblewhite - One of the best experts on this subject based on the ideXlab platform.
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linking habitat selection and Predation Risk to spatial variation in survival
Journal of Animal Ecology, 2014Co-Authors: Nicholas J Decesare, Mark Hebblewhite, Mark Bradley, David Hervieux, Lalenia Neufeld, Marco MusianiAbstract:1. A central assumption underlying the study of habitat selection is that selected habitats confer enhanced fitness. Unfortunately, this assumption is rarely tested, and in some systems, gradients of Predation Risk may more accurately characterize spatial variation in vital rates than gradients described by habitat selection studies. 2. Here, we separately measured spatial patterns of both resource selection and Predation Risk and tested their relationships with a key demographic trait, adult female survival, for a threatened ungulate, woodland caribou (Rangifer tarandus caribou Gmelin). We also evaluated whether exposure to gradients in both Predation Risk and resource selection value was manifested temporally through instantaneous or seasonal effects on survival outcomes. 3. We used Cox proportional hazards spatial survival modelling to assess the relative support for 5 selection- and Risk-based definitions of habitat quality, as quantified by woodland caribou adult female survival. These hypotheses included scenarios in which selection ideally mirrored survival, Risk entirely drove survival, non-ideal selection correlated with survival but with additive Risk effects, an ecological trap with maladaptive selection and a non-spatial effect of annual variation in weather. 4. Indeed, we found positive relationships between the predicted values of a resource selection function (RSF) and survival, yet subsequently incorporating an additional negative effect of Predation Risk greatly improved models further. This revealed a positive, but non-ideal relationship between selection and survival. Gradients in these covariates were also shown to affect individual survival probability at multiple temporal scales. Exposure to increased Predation Risk had a relatively instantaneous effect on survival outcomes, whereas variation in habitat suitability predicted by an RSF had both instantaneous and longer-term seasonal effects on survival. 5. Predation Risk was an additive source of hazard beyond that detected through selection alone, and woodland caribou selection thus was shown to be non-ideal. Furthermore, by combining spatial adult female survival models with herd-specific estimates of recruitment in matrix population models, we estimated a spatially explicit landscape of population growth predictions for this endangered species.
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trade offs between Predation Risk and forage differ between migrant strategies in a migratory ungulate
Ecology, 2009Co-Authors: Mark Hebblewhite, Evelyn H. MerrillAbstract:Trade-offs between Predation Risk and forage fundamentally drive resource selection by animals. Among migratory ungulates, trade-offs can occur at large spatial scales through migration, which allows an "escape" from Predation, but trade-offs can also occur at finer spatial scales. Previous authors suggest that ungulates will avoid Predation Risk at the largest scale, although few studies have examined multi-scale trade-offs to test for the relative benefits of Risk avoidance across scales. Building on previously developed spatial models of forage and wolf Predation Risk, we tested for trade-offs at the broad landscape scale and at a finer, within-home-range scale for migratory and non-migratory resident elk (Cervus elaphus) during summer in the Canadian Rockies in Banff National Park (BNP) and adjacent Alberta, Canada. Migration reduced exposure to wolf Predation Risk by 70% relative to residents at the landscape scale; at the fine scale, migrants used areas that were, on average, 6% higher in forage digestibility. In contrast, by forgoing migration, resident elk were exposed to higher Predation Risk, but they reduced Predation Risk at fine scales to only 15% higher than migrants by using areas close to human activity, which wolves avoided. Thus, residents paid for trying to avoid Predation Risk with lower forage quality. Residents may have been able to compensate, however, by using areas of abundant forage close to human activity where they may have been able to forage more selectively while avoiding Predation Risk. Human activity effectively decoupled the positive correlation between high forage quality and wolf Predation, providing an effective alternate strategy for residents, similar to recent findings in other systems. Although ungulates appear capable of balancing Risk and forage at different spatial scales, Risk avoidance at large landscape scales may be more effective in the absence of human-caused refugia from Predation.
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Multiscale wolf Predation Risk for elk: does migration reduce Risk?
Oecologia, 2007Co-Authors: Mark Hebblewhite, Evelyn H. MerrillAbstract:While migration is hypothesized to reduce Predation Risk for ungulates, there have been few direct empirical tests of this hypothesis. Furthermore, few studies examined multiscale Predation Risk avoidance by migrant ungulates, yet recent research reveals that predator-prey interactions occur at multiple scales. We test the Predation Risk reduction hypothesis at two spatial scales in a partially migratory elk (Cervus elaphus) population by comparing exposure of migrant and resident elk to wolf (Canis lupus) Predation Risk. We used GPS and VHF telemetry data collected from 67 migrant and 44 resident elk over the summers of 2002-2004 in and adjacent to Banff National Park (BNP), Canada. We used wolf GPS and VHF telemetry data to estimate Predation Risk as a function of the relative probability of wolf occurrence weighted by a spatial density model that adjusted for varying pack sizes. We validated the Predation Risk model using independent data on wolf-killed elk, and showed that combining wolf presence and spatial density best predicted where an elk was likely to be killed. Predation Risk on summer ranges of migrant elk was reduced by 70% compared to within resident elk summer ranges. Because wolves avoided areas near high human activity, however, fine-scale selection by resident elk for areas near high human activity reduced their Predation Risk exposure to only 15% higher than migrants, a difference significant in only one of three summers. Finally, during actual migration, elk were exposed to 1.7 times more Predation Risk than residents, even though migration was rapid. Our results support the hypothesis that large-scale migrations can reduce Predation. However, we also show that where small-scale spatial variation in Predation Risk exists, nonmigratory elk may equally reduce Predation Risk as effectively as migrants under some circumstances.