Too important to tamper with Walters, Benjamin T.; Cheng, Tin Nok Natalie; Doyle, Justin ...
Functional ecology,
07/2017, Letnik:
31, Številka:
7
Journal Article
Recenzirano
Odprti dostop
Summary
Escaping from a predator is a matter of life or death, and prey are expected to adaptively alter their physiology under chronic predation risk in ways that may affect escape. Theoretical ...models assume that escape performance is mass dependent, whereby scared prey strategically maintain an optimal body mass to enhance escape. Experiments testing the mass‐dependent predation risk hypothesis have demonstrated that prior experience of predation risk can affect body mass, and the behavioural decisions about evasive actions to take. Other studies on natural changes in body mass indicate that mass can affect escape. No single experiment has tested if all of these components are indeed linked, which is a critical necessary condition underpinning the mass‐dependent predation risk hypothesis.
We tested all components of the mass‐dependent predation risk hypothesis in a repeated measures experiment by presenting predator and non‐predator cues to brown‐headed cowbirds housed in semi‐natural conditions. Exposure to predator cues affected body mass, fat, pectoral muscle thickness and evasive actions (take‐off angle and speed), but not the physiological capacity to escape, as measured by flying ability. Examining individual variation revealed that flying ability was unrelated to mass loss in either sex, unrelated to mass gain in males, and only females that gained a very large amount of mass flew poorly.
We next conducted a body mass manipulation in the laboratory to rigorously test whether small to large perturbations in mass can ever affect flying ability. We induced either no change in mass (control), a moderate reduction of <10% or a more extreme reduction of >10% which the literature suggests should enhance flight. Flying ability was maintained regardless of treatment. Examining individual variation revealed the same precise patterns as in the first experiment.
We conclude that prey may alter their mass and evasive actions in response to predation risk, but their escape ability remains robust and inelastic, presumably because disabling oneself is likely to lead to disastrous consequences. We suggest that animals may only face a mass‐dependent predation risk trade‐off in a narrow set of circumstances linked to life‐history stages that require large amounts of mass gain, for example, parturition and migration.
A lay summary is available for this article.
Lay Summary
1. For large predators living in seasonal environments, patterns of prédation are likely to vary among seasons because of related changes in prey vulnerability. Variation in prey vulnerability ...underlies the influence of predators on prey populations and the response of predators to seasonal variation in rates of biomass acquisition. Despite its importance, seasonal variation in prédation is poorly understood. 2. We assessed seasonal variation in prey composition and kill rate for wolves Canis lupus living on the Northern Range (NR) of Yellowstone National Park. Our assessment was based on data collected over 14 winters (1995-2009) and five spring-summers between 2004 and 2009. 3. The species composition of wolf-killed prey and the age and sex composition of wolf-killed elk Cervus elaphus (the primary prey for NR wolves) varied among seasons. 4. One's understanding of prédation depends critically on the metric used to quantify kill rate. For example, kill rate was greatest in summer when quantified as the number of ungulates acquired per wolf per day, and least during summer when kill rate was quantified as the biomass acquired per wolf per day. This finding contradicts previous research that suggests that rates of biomass acquisition for large terrestrial carnivores tend not to vary among seasons. 5. Kill rates were not well correlated among seasons. For example, knowing that early-winter kill rate is higher than average (compared with other early winters) provides little basis for anticipating whether kill rates a few months later during late winter will be higher or lower than average (compared with other late winters). This observation indicates how observing, for example, higherthan-average kill rates throughout any particular season is an unreliable basis for inferring that the year-round average kill rate would be higher than average. 6. Our work shows how a large carnivore living in a seasonal environment displays marked seasonal variation in prédation because of changes in prey vulnerability. Patterns of wolf prédation were influenced by the nutritional condition of adult elk and the availability of smaller prey (i.e. elk calves, deer). We discuss how these patterns affect our overall understanding of predator and prey population dynamics.
This study aimed to identify the insects which consumes Eugenia involucrata seeds and to evaluate the potential for damage to the seeds as well as the food substrate consumed by the attack. To obtain ...the data, a collection of fruits was carried out at the Forestry Research Center (FEPAGRO / Florestas) in the municipality of Santa Maria, RS, being conducted at the UFSM crop protection department. After seed processing were separated into healthy seeds and damaged seeds (those that contained an emergence hole for the insect). As for the analyzed seeds, there were a total of 3287 seeds, of which 1998 were healthy (60.08%), 1289 damaged seeds (39.2%) and a loss of substrate consumed of 7.65 g per seed, corresponding to a damage level of 39.98% of the food mass. It was found a high rate of predation in the seeds, which became unsuitable for the propagation of the plant. In this study, Atractomerus pitangae, associated with the predation of Eugenia involucrata seeds, was registered for the first time in southern Brazil.
Celotno besedilo
Dostopno za:
CEKLJ, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Summary
Post‐dispersal seed predators contribute substantially to seed loss across many ecosystems. Most research has focused on understanding sources of variation in seed loss, without appreciating ...the implications of seed predation for plant coexistence, community assembly and broader community theory. Meanwhile, research aimed at understanding coexistence and community assembly processes in plant communities has focused on axes of dispersal and resource competition and the traits influencing these processes, without accounting for the role of generalist seed predators.
We review the unique features of post‐dispersal seed predation and assess the implications of seed loss on three critical components of plant community organization – coexistence, community structure and plant invasions – pointing to both important gaps in theory and empirical knowledge. We highlight how understanding fundamental controls on plant recruitment is central to determining how seed predation affects plant recruitment and coexistence. We discuss how accounting for seed predator foraging strategies may shift trait‐based inferences of community assembly.
Synthesis. We argue that seed predation by generalist consumers, which is pervasive in temperate communities, should be better incorporated into plant community theory. Experiments that specifically incorporate the presence and attributes of the seed predator community and that follow seed fate would fill important knowledge gaps. Particularly needed are studies focused on strengthening the connections between seed removal and plant establishment and linking selective and density‐dependent foraging strategies to plant traits. Advancing our understanding of the processes regulating plant coexistence and community assembly requires that future research not only acknowledge but also incorporate generalist consumers’ effects on plant communities.
A lay summary is available for this article.
Lay Summary
To grow, survive and reproduce under anthropogenic-induced changes, individuals must respond quickly and favourably to the surrounding environment. A species that feeds on a wide variety of prey ...types (i.e. generalist diet) may be comprised of generalist individuals, specialist individuals that feed on different prey types, or a combination of the two. If individuals within a population respond differently to an environmental change, population-level responses may not be detectable. By tracking foraging movements of great black-backed gulls (Larus marinus), a generalist species, we compared group-level and individual-level responses to an increase in prey biomass (capelin; Mallotus villosus) during the breeding season in coastal Newfoundland, Canada. As hypothesized, shifts in prey availability resulted in significantly different individual responses in foraging behaviour and space use, which was not detectable when data from individuals were combined. Some individuals maintained similar foraging areas, foraging trip characteristics (e.g., trip length, duration) and habitat use with increased capelin availability, while others shifted foraging areas and habitats resulting in either increased or decreased trip characteristics. We show that individual specialization can be non-contextual in some gulls, whereby these individuals continuously use the same feeding strategy despite significant change in prey availability conditions. Findings also indicate high response diversity among individuals to shifting prey conditions that a population- or group-level study would not have detected, emphasizing the importance of examining individual-level strategies for future diet and foraging studies on generalist species.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Predation risk, the probability that a prey animal will be killed by a predator, is fundamental to theoretical and applied ecology. Predation risk varies with animal behavior and environmental ...conditions, yet attempts to understand predation risk in natural systems often ignore important ecological and environmental complexities, relying instead on proxies for actual risk such as predator–prey spatial overlap. Here we detail the ecological and environmental complexities driving disconnects between three stages of the predation sequence that are often assumed to be tightly linked: spatial overlap, encounters and prey capture. Our review highlights several major sources of variability in natural predator–prey systems that lead to the decoupling of spatial overlap estimates from actual encounter rates (e.g. temporal activity patterns, predator and prey movement capacity, resource limitations) and that affect the probability of prey capture given encounter (e.g. predator hunger levels, temporal, topographic and other environmental influences on capture success). Emerging technologies and statistical methods are facilitating a transition to a more spatiotemporally detailed, mechanistic understanding of predator–prey interactions, allowing for the concurrent examination of multiple stages of the predation sequence in mobile, free‐ranging animals. We describe crucial applications of this new understanding to fundamental and applied ecology, highlighting opportunities to better integrate ecological contingencies into dynamic predator–prey models and to harness a mechanistic understanding of predator–prey interactions to improve targeting and effectiveness of conservation interventions.
The nocturnal feeding behavior and zoogeographical habitat of cookiecutter sharks Isistius brasiliensis and Isistius plutodus (Isistius spp.) greatly reduces interaction of this species with live ...humans. Attacks on live humans are exceedingly rare with 7 cases reported worldwide, 6 of them in Hawai?i, and 5 of these occuring among channel swimmers. Published research suggests that periods of bright moonlight may increase Isistius spp. contact with live humans and does not otherwise identify significant trends or risk factors. Yet 5 of the 6 Isistius spp. bites on live humans in Hawai?ian waters occurred with the moon set and after nautical twilight end and before nautical twilight start. From 1961-2023 in Hawai?i, 129 successful solo channel crosses and 5 Isistius spp. related injuries in the habitat of cookiecutter sharks were analyzed across two groups: one where both the moon and sun were set (dark group) and one where the moon and/or sun was in the sky (light group). There was a significant difference for swimmers bitten by Isistius spp. in the dark 4 (12%) versus light groups 1 (1%), p = 0.012, RR 12.6 (95% confidence interval: 1.5-108.9). Swim start time and year was also significant (Pearson correlation 0.566, p <0.001). Swimmer gender and use of shark deterrent devices and artificial illumination were not significant. The growing popularity of channel swimming in Hawai?i and swim start times have contributed to an increasing likelihood of live human and Isistius spp. contact and a moonless night sky is a significant risk factor for this interaction.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Predation risk and prey responses exhibit fluctuations in space and time. Seasonal ecological disturbances can alter landscape structure and permeability to influence predator activity and efficacy, ...creating predictable patterns of risk for prey (seasonal risk landscapes). This may create corresponding seasonal shifts in antipredator behaviour, mediated by species ecology and trade-offs between risk and resources. Yet, how human recreation interacts with seasonal risk landscapes and antipredator behaviour remains understudied. In South Florida, we investigated the impact of a seasonal ecological disturbance, specifically flooding, which is inversely related to human activity, on interactions between Florida panthers (Puma concolor coryi) and white-tailed deer (Odocoileus virginianus). We hypothesized that human activity and ecological disturbances would interact with panther-deer ecology, resulting in the emergence of two distinct seasonal landscapes of predation risk and the corresponding antipredator responses. We conducted camera trap surveys across southwestern Florida to collect detection data on humans, panthers and deer. We analysed the influence of human site use and flooding on deer and panther detection probability, co-occurrence and diel activity during the flooded and dry seasons. Flooding led to decreased panther detections and increased deer detections, resulting in reduced deer-panther co-occurrence during the flooded season. Panthers exhibited increased nocturnality and reduced diel activity overlap with deer in areas with higher human activity. Supporting our hypothesis, panthers' avoidance of human recreation and flooding created distinct risk schedules for deer, driving their antipredator behaviour. Deer utilized flooded areas to spatially offset predation risk during the flooded season while increasing diurnal activity in response to human recreation during the dry season. We highlight the importance of understanding how competing risks and ecological disturbances influence predator and prey behaviour, leading to the generation of seasonal risk landscapes and antipredator responses. We emphasize the role of cyclical ecological disturbances in shaping dynamic predator-prey interactions. Furthermore, we highlight how human recreation may function as a 'temporal human shield,' altering seasonal risk landscapes and antipredator responses to reduce encounter rates between predators and prey.
Culling of overabundant and invasive species to manage their ecological impacts on target species is widely practised but outcomes are unpredictable and monitoring of effectiveness often poor. ...Culling must improve ecosystem function, so clear, measurable goals, such as improved breeding potential of target species, are necessary. Many overabundant and invasive species are also nest predators and nest predation is the principal cause of breeding failure of many birds of conservation concern. It is important for managers to know the likely effects on nest predation when culling one species among a suite of nest predatory species.
We tested the effect of culling a hyperaggressive, overabundant bird and known nesting disruptor, the noisy miner (Manorina melanocephala), on artificial nest predation rates in remnant eucalypt woodlands in a highly fragmented agricultural landscape of eastern Australia. Culling of noisy miners is already practised to manage this key threatening process, but evidence of improved breeding outcomes for target species is lacking.
We found no significant change in artificial nest predation rates following the treatment, despite a 28% reduction in noisy miner abundance in treatment compared to control sites. We identified five other nest predatory bird species, the noisy miner being responsible for 18.3% of total predation.
Our findings suggest a compensatory nest predation model, which is problematic for management. It means that, where culling is done with a view to improving breeding potential of target species by reducing nest predation, removing one nest predatory species may not result in a commensurate reduction in nest predation.
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•Culling noisy miners did not reduce artificial nest predation rates.•Noisy miners were responsible for 18% of artificial nest predation.•Five other bird species were recorded predating nests.•Compensatory nest predation seems to be operating in this landscape.•Culling noisy miners may not improve breeding potential of target species.
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