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1.
We exposed naive Siberain polecats (Mustela eversmanni) (aged 2, 3, and 4 months) to a swooping stuffed great horned owl (Buho virginianus) and a stuffed badger (Taxidae taxus) mounted on a remote control toy automobile frame. The first introduction to each was harmless, the second was accompanied by a mild aversive stimulus, the third (1 day after attack) was harmless, and the fourth (30 days after attack) was harmless. Alert behavior increased after a single attack by either predator model. Escape responses of naive polecats did not differ between ages when exposed to the badger, but 4 month old polecats reduced their escape times after a single badger attack. When exposed to the swooping owl, naive 4 month old polecats redponded more quickly than the other two age groups, and 3 and 4 month old polecats reduced escape times after a single owl attack. This indicates an innate escape response to the owl model at 4 months of age, and a short-tert ability to remember a single mild aversive encounter with the badger and owl models at 3 or 4 months of age.  相似文献   

2.
Predation plays an important role in ecological communities by affecting prey behavior such as foraging and by physical removal of individual prey. In regard to foraging, animals such as desert rodents often balance conflicting demands for food and safety. This has been studied in the field by indirectly manipulating predatory risk through the alteration of cues associated with increased risk such as cover or illumination. It has also been studied by directly manipulating the presence of predators in aviaries. Here, we report on experiments in which we directly manipulated actual predatory risk to desert rodents in the field. We conducted a series of experiments in the field using a trained barn owl (Tyto alba) to investigate how two species of coexisting gerbils (Gerbillus allenbyi and G. pyramidum) respond to various cues of predatory risk in their natural environment. The gerbils responded to risk of predation, in the form of owl flights and owl hunger calls, by reducing their activity in the risky plot relative to the control plot. The strongest response was to owl flights and the weakest to recorded hunger calls of owls. Furthermore, when risk of predation was relatively high, as in the case with barn owl flights, both gerbil species mostly limited their activity to the safer bush microhabitat. The response of the gerbils to risk of predation disappeared very quickly following removal of the treatment, and the gerbils returned to normal levels of activity within the same night. The gerbils did not respond to experimental cues (alarm clock), the presence of the investigators, the presence of a quiet owl, and recorded white noise. Using trained barn owls, we were able to effectively manipulate actual risk of predation to gerbils in natural habitats and to quantify how gerbils alter their behavior in order to balance conflicting demands of food and safety. The method allows assessment of aspects of behavior, population interactions, and community characteristics involving predation in natural habitats.  相似文献   

3.
When facing a predator, animals need to perform an appropriate antipredator behavior such as escaping or mobbing to prevent predation. Many bird species exhibit distinct mobbing behaviors and vocalizations once a predator has been detected. In some species, mobbing calls transmit information about predator type, size, and threat, which can be assessed by conspecifics. We recently found that great tits (Parus major) produce longer D calls with more elements and longer intervals between elements when confronted with a sparrowhawk, a high‐threat predator, in comparison to calls produced in front of a less‐threatening tawny owl. In the present study, we conducted a playback experiment to investigate if these differences in mobbing calls elicit different behavioral responses in adult great tits. We found tits to have a longer latency time and to keep a greater distance to the speaker when sparrowhawk mobbing calls were broadcast. This suggests that tits are capable of decoding information about predator threat in conspecific mobbing calls. We further found a tendency for males to approach faster and closer than females, which indicates that males are willing to take higher risks in a mobbing context than females.  相似文献   

4.
Barred owls (Strix varia) are forest-dwelling owls, native to eastern North America, with populations that expanded westward into the range of the spotted owl (Strix occidentalis). Barred owls exert an overwhelmingly negative influence on spotted owls, thereby threatening spotted owl population viability where the species co-occur. In this review, we provide an overview of the barred owl's range expansion and detail and synthesize previously published literature on spotted and barred owls within the range of the spotted owl as related to potential future outcomes for the northern spotted owl (S. o. caurina). We include research on diet, habitat use and selection, effects of barred owls on spotted owl demography and behavior, hybridization with spotted owls, parasites, contemporary management, and future research needs for spotted owl populations given continued barred owl expansion throughout western North America. Our literature review and synthesis should provide managers with the information necessary to develop strategies that mitigate deleterious effects of barred owls at local and landscape scales. © 2019 The Wildlife Society.  相似文献   

5.
During a field study in northeastern Peru, the reactions of a group ofSaguinus mystax on Padre Isla and of a mixed-species troop ofS. mystax andSaguinus fuscicollis at the Río Blanco to raptorial and other birds were observed. Alarms that are specific to flying stimuli were elicited by birds of prey, but other birds that do not represent a threat to the tamarins also caused alarm calls. Alarm events (i.e., instances when one or more alarm calls were given) were observed at rates of 0.3/hr (Padre Isla) and 0.5/hr (Río Blanco). Rates of alarm events significantly increased after the birth of an infant in the Padre Isla group and after the attack of an ornate hawk-eagle (Spizaetus ornatus) on the Río Blanco group. Reactions to alarming stimuli/alarm calls ranged from looking up to falling down from trees. The modification of the tamarins' behavior by the potential presence of aerial predators indicates that raptors represent an important predatory threat to tamarins.  相似文献   

6.
Many mammal and bird species respond to predator encounters with alarm vocalizations that generate risk‐appropriate responses in listeners. Two conceptual frameworks are typically applied to the information encoded in alarm calls and to associated anti‐predator behaviors. ‘Functionally referential’ alarm systems encode nominal classes or categories of risk in distinct call types that refer to distinct predation‐risk situations. ‘Risk‐based’ alarms encode graded or ranked threat‐levels by varying the production patterns of the same call types as the urgency of predation threat changes. Recent work suggests that viewing alarm‐response interactions as either referential or risk‐based may oversimplify how animals use information in decision‐making. Specifically, we explore whether graded alarm cues may be useful in classifying risks, supporting a referential decision‐making framework. We presented predator (hawk, owl, cat, snake) and control treatments to captive adult tufted titmice Baeolophus bicolor and recorded their vocalizations, which included ‘chick‐a‐dee’ mobbing calls (composed of chick and D notes), ‘seet’ notes, two types of contact notes (‘chip’, ‘chink’), and song. No single call type was uniquely associated with any treatment and the majority of acoustic measures varied significantly among treatments (46 of 60). The strongest models (ANOVA and classification tree analysis) grouped hawk with cat and owl, and control with snake, and were based on the number or proportion of a) chick and D notes per chick‐a‐dee call, b) chip versus chink notes produced following treatment exposure, and c) the frequency metrics of other note types. We conclude that (1) the predation‐threat information available in complex titmouse alarm calls was largely encoded in graded acoustic measures that were (2) numerous and variable across treatments and (3) could be used singly or in combinations for either ranking or classification of threats. We call attention to the potential use of mixed threat identification strategies, where risk‐based signal information may be used in referential decision‐making contexts.  相似文献   

7.
The range expansion by barred owls (Strix varia) into western North America has raised considerable concern regarding their potential effects on declining northern spotted owl (Strix occidentalis caurina) populations, yet most information on the occurrence of barred owls in the region is limited to incidental detections during surveys for spotted owls. To address this shortcoming we investigated response behavior, detection probabilities, and landscape occupancy patterns of barred owls in western Oregon, USA, during conspecific versus spotted owl call-broadcast surveys. Subtle differences in barred owl response behavior to conspecific versus spotted owl vocalizations combined with minor procedural differences between species-specific survey protocols led to a sizeable difference in estimated detection probabilities during conspecific (0.66, 95% CI = 0.61–0.71) versus spotted owl (0.48, 95% CI = 0.39–0.56) surveys. We identified 61 territorial pairs of barred owls during repeated surveys of a multi-ownership study area with the probability of occupancy being highest in the structurally diverse mixture of mature and old forests that occurred almost entirely on public lands. Our findings suggest that research and management strategies to address potential competitive interactions between spotted owls and barred owls will require carefully designed, species-specific survey methods that account for erratic response behaviors and imperfect detection of both species. Our sampling methods can be used by forest managers to determine the occurrence and distribution of barred owls with high confidence. © 2011 The Wildlife Society.  相似文献   

8.
The spotted owl (Strix occidentalis) is a threatened species in many areas of its western North American range. Concomitant with its decline has been a rapid invasion of its range and habitat by barred owls (Strix varia), a native species that was restricted, until relatively recently, to eastern North America. We assess the theoretical potential for negative interactions between these two owls by examining size dimorphism and ecological relationships within various owl assemblages throughout the world. We then review the anecdotal, natural history, modeling, and experimental evidence that suggest barred owls may negatively affect spotted owls with at least a potential for the competitive exclusion of spotted owls by barred owls throughout all or part of the former’2019;s range. While it is widely accepted that barred owls are either causing or exacerbating declines of spotted owl populations, there are confounding factors, such as habitat loss and bad weather that also may contribute to declines of spotted owls. Both theory and empirical information suggest that barred owls are likely to have negative effects on spotted owl range and density, but the degree of the impact is not predictable. There is a conservation conundrum here, in that the barred owl is a native species that has expanded its range westwards, either naturally or with a degree of human facilitation, and now constitutes a major threat to the viability of another native species, the threatened spotted owl. We propose that only through carefully designed experiments involving removal of barred owls will we be able to determine if recent declines in spotted owl populations are caused by barred owls or by other factors. It is rare in conservation science that replicate study areas exist for which we also have long-standing demographic information, as is the case with the spotted owl. Removal experiments would take advantage of the wealth of data on spotted owls, and allow ecologists to assess formally the impacts of an invasive species on a threatened species, as well as to suggest mitigation measures.  相似文献   

9.
Predation risk is an environmental stressor that can induce changes in prey behavior and physiology. Perception of predation risk may indirectly affect offspring traits and future fitness prospects via impacts on the condition of parents. Females may influence the survival of their offspring via maternal effects, especially when breeding in stressful conditions. We investigated the effects of continuous predation risk perceived by mothers on the maternal allocation of immune factors and carotenoids in eggs of the pied flycatcher Ficedula hypoleuca. We collected eggs from wild pied flycatchers that bred in the vicinity of a predator nest (pygmy owl Glaucidium passerinum), were exposed to cues of a mammalian nest predator (urine of least weasel Mustela nivalis), or received appropriate controls for these two groups. Pied flycatchers transferred more immunoglobulin in eggs under high predation risk in both owl and mammalian predator treatments. The presence of owl nests also lowered the level of lysozyme transferred in the eggs in one of the two study years. Predation risk did not modify egg size or overall carotenoid levels. Our results show that continuous predation risk perceived by females during egg‐laying affects egg composition. This different allocation of maternal immune factors may be an adaptive response evolved to increase the probability of offspring survival.  相似文献   

10.
Urban animals often take more risk toward humans than their non‐urban conspecifics do, but it is unclear how urbanization affects behavior toward non‐human predators. Responses to humans and non‐human predators may covary due to common mechanisms enforcing a phenotypic correlation. However, while increased tolerance toward humans may be advantageous for urban animals, reduced vigilance toward non‐human predators that can pose actual threat may be costly. Therefore, urban animals may benefit from showing specific responses to different threat levels, such as humans versus non‐human predators, or hostile versus non‐hostile humans. To test these alternatives, we compared responses (latencies to return to nest) of urban and forest‐breeding great tits (Parus major) to familiar hostile and unfamiliar humans as well as one of their common predators, the sparrowhawk (Accipiter nisus). We found that urban birds were more risk‐taking toward both humans and sparrowhawk than forest birds. However, responses to sparrowhawk did not correlate with responses to humans either within or across habitats. This suggests that higher risk‐taking of urban compared to forest‐dwelling great tits toward sparrowhawk may be threat‐specific response to lower predation risk rather than a spillover effect of increased tolerance to humans. Furthermore, birds responded similarly to unfamiliar and familiar (potentially dangerous) humans in both habitats, suggesting that great tits may not adjust their risk‐taking to the threat represented by individual humans. These findings indicate that urban birds may flexibly adjust their risk‐taking to certain, but not all, types of threat.  相似文献   

11.
We surveyed male survival and reproductive performances associated with dimorphism in the Japanese horned beetleAllomyrina dichotoma L. in a secondary forest in 1996. Morphological comparisons between living marked and prey individuals indicated that the larger horned males suffered higher predatory pressure than the smaller ones. The dominant predators of the beetles were suspected to be 2 crow species. The small-horned males showed lower recapture rates than the large-horned ones. This suggested that the former was more sensitive to disturbance, and/or dispersed more than the latter. Fighting behavior was rarely seen because of the low population density of the beetles in the study area. These results suggested that the large-horned males suffer not only the injury risk of intrasexual competition but also more predatory risk than the small-horned ones.  相似文献   

12.
We developed 37 great gray owl (Strix nebulosa) microsatellite primers from CA and TAGA enriched genomic libraries. Primers were tested in 15 great gray owls from California, USA and Alberta, Canada as well as two other Strix species, spotted owl (S. occidentalis) and barred owl (S. varia). These markers will have broad application in investigations of Strix population structure and genetic diversity.  相似文献   

13.
Developing strategies that reduce the impacts of climate change on biodiversity will require projections of the future status of species under alternative climate change scenarios. Demographic models based on empirical data that link temporal variation in climate with vital rates can improve the accuracy of such predictions and help guide conservation efforts. Here, we characterized how population dynamics and extinction risk might be affected by climate change for three spotted owl (Strix occidentalis) populations in the Southwestern United States over the next century. Specifically, we used stochastic, stage‐based matrix models parameterized with vital rates linked to annual variation in temperature and precipitation to project owl populations forward in time under three IPCC emissions scenarios relative to contemporary climate. Owl populations in Arizona and New Mexico were predicted to decline rapidly over the next century and had a much greater probability of extinction under all three emissions scenarios than under current climate conditions. In contrast, owl population dynamics in Southern California were relatively insensitive to predicted changes in climate, and extinction risk was low for this population under all scenarios. The difference in predicted climate change impacts between these areas was due to negative associations between warm, dry conditions and owl vital rates in Arizona and New Mexico, whereas cold, wet springs reduced reproduction in Southern California. Predicted changes in population growth rates were mediated more by weather‐induced changes in fecundity than survival, and were generally more sensitive to increases in temperature than declines in precipitation. Our results indicate that spotted owls in arid environments may be highly vulnerable to climate change, even in core parts of the owl's range. More broadly, contrasting responses to climate change among populations highlight the need to tailor conservation strategies regionally, and modeling efforts such as ours can help prioritize the allocation of resources in this regard.  相似文献   

14.
The northern spotted owl (Strix occidentalis caurina) is one of the most controversial threatened subspecies ever listed under the US Endangered Species Act. Despite protection of its remaining forest habitat, recent field studies show continued declines of northern spotted owls. One potential threat to northern spotted owls which has not yet been shown is loss of genetic variation from population bottlenecks. Bottlenecks can increase the probability of mating among related individuals, potentially causing inbreeding depression, and can decrease adaptive potential. Here we report evidence for recent bottlenecks in northern spotted owls using a large genetic dataset (352 individuals and 10 microsatellite loci). The signature of bottlenecks was strongest in the Washington Cascade Mountains, in agreement with field data. Our results provide independent evidence that northern spotted owls have recently declined, and suggest that loss of genetic variation is an emerging threat to the subspecies’ persistence. Reduced effective population size (N e) shown here in addition to field evidence for demographic decline highlights the increasing vulnerability of this bird to extinction.  相似文献   

15.
Breeding close to top predators is a widespread reproductive strategy. Breeding animals may gain indirect benefits if proximity to top predators results in a reduction of predation due to suppression of mesopredators. We tested if passerine birds gain protection from mesopredators by nesting within territories of a top predator, the Ural owl (Strix uralensis). We placed nest boxes for pied flycatchers (Ficedula hypoleuca) in Ural owl nest sites and in control sites (currently unoccupied by owls). The nest boxes were designed so that nest predation risk could be altered (experimentally increased) after flycatcher settlement; we considered predation rate as a proxy of mesopredator abundance. Overall, we found higher nest predation rates in treatment than in control sites. Flycatcher laying date did not differ between sites, but smaller clutches were laid in treatment sites compared to controls, suggesting a response to perceived predation risk. Relative nest predation rate varied between years, being higher in owl nest sites in 2 years but similar in another; this variation might be indirectly influenced by vole abundance. Proximity to Ural owl nests might represent a risky habitat for passerines. High predation rates within owl territories could be because small mesopredators that do not directly threaten owl nests are attracted to owl nest sites. This could be explained if some mesopredators use owl territories to gain protection from their own predators, or if top predators and mesopredators independently seek similar habitats.  相似文献   

16.
Selection of receptors is a key element of ecological risk and natural resource damage assessments. The great horned owl (Bubo virginianus; GHO) has advantages as a tertiary terrestrial receptor and integrated measure of exposure to chemical residues in a multiple-lines-of-evidence approach that includes elucidation of contaminant exposure by measured (tissue-based) and predicted (dietary) methodologies, and population-level measures of potential adverse effects (i.e., productivity, abundance). Methods described herein exploited attributes of GHO behavior, including its propensity to nest in artificial nesting platforms. This approach allowed better control of experimental conditions, minimized uncertainty in assessment endpoints, and maximized data utility for testing hypotheses. During 5 years, 54 GHO nests (14 active territories) along 38 km of river floodplain were monitored at the Kalamazoo River Superfund Site (Kalamazoo/Allegan Counties, Michigan). Concentrations of polychlorinated biphenyls (PCBs) and otho-, para-substituted isomers of dichlorodiphenyltrichloroethane (DDT), including DDD/DDE (Σ DDTs), were measured in 24 eggs and 16 samples of nestling blood plasma. Dietary PCB exposure was predicted by determining site-specific dietary composition and sampling and quantifying PCB concentrations in 171 prey items collected within active GHO territories. The convergence of exposure and effects assessments improved confidence in resulting predictions of minimal risk to resident GHO populations (Hazard Quotients ≤1.5). Repeated GHO use of nesting platforms minimized temporal and spatial variability.  相似文献   

17.
The non‐linearity and fear hypothesis predicts that certain non‐linear sounds are one way to evoke antipredator responses in both birds and mammals. This hypothesis, however, has not been studied in non‐vocal species or in reptiles. Such a study would be important because if non‐linear sounds are evocative even in a species that does not produce sounds, then there may be generally salient cues of risk in these sounds. We asked whether non‐vocal lizards, white‐bellied copper‐striped skinks (Emoia cyanura), respond to experimentally broadcast non‐linearities. This species is ideal to ask the question in because prior research has shown that they respond to predator sounds and alarm calls of other species even though they are not vocal. We conducted playback experiments with three computer‐generated simulated non‐linearities to assess whether or not skinks increased antipredator behavior after hearing them. We controlled for novelty by broadcasting a 3‐kHz, 500‐ms pure tone and tropical kingbird (Tyrannus melancholicus) song. Our treatments consisted of a 3‐kHz, 400‐ms pure tone followed by a frequency shift up to 5‐kHz for 100‐ms, a 3‐kHz, 400‐ms pure tone to frequency shift down to 1‐kHz for 100‐ms, and a pure tone followed by 100‐ms of white noise. Following a total of 222 playbacks, we categorized responses into looking, locomotion, and high locomotion, focusing on how skinks changed their rates of time allocation from baseline. We examined 95% confidence intervals to identify whether skinks responded to playbacks and fitted general linear models followed by pairwise comparisons to ask whether skinks discriminated between broadcast stimuli. We found that skinks were especially responsive to frequency downshifts: They significantly increased looking and locomotion, consistent with our predictions based on the non‐linearity and fear hypothesis. Surprisingly, they decreased rates of looking behavior after hearing frequency upshifts, possibly suggesting an increase in relaxed behavior. While skinks responded to noise by increasing their rate of locomotion, this response was not significantly different from controls. We conclude that skinks increase antipredator behavior after hearing downshifts more than any other type of non‐linearity. This provides some support for the non‐linearity and fear hypothesis; even non‐vocal species may respond fearfully to specific types of non‐linear sounds.  相似文献   

18.
Human-dominated environments often include ecological traps for wildlife, such as airports that may be perceived as suitable habitat by grassland birds but reduce fitness because of collisions with aircraft. Birds of prey are often attracted to airports where collisions with aircraft (i.e., bird strikes) are usually fatal for the birds and are a significant threat to flight safety. The snowy owl (Bubo scandiacus) is known for its nomadism, exhibiting unpredictable and highly variable movements during the nonbreeding season, including being a common visitor to airports, which often have high small-mammal populations and mimic flat, open habitats used naturally by owls. Since 2009, the Federal Aviation Administration reported an average of 22 snowy owl deaths annually due to aircraft collisions throughout 55 North American airports. To aid in active management of owls at airports, we assessed relocation data of 42 telemetry-tracked snowy owls from 2000–2020 in the United States and Canada. Owls that returned to the airport after relocation (33%) frequently crisscrossed and perched near runways where they were at risk of strikes. Adult females and immature males were more likely to return than the other sex and age classes, and returns were less likely to occur as the distance between the release site and the airport increased. Owls relocated in open habitats with a greater proportion of wetland and cropland (including grasslands and pasture) land cover classes were also less likely to return. We conclude that inclusion of multiple factors to limit return rates of relocated snowy owls from airport facilities can unspring the ecological trap presented by airports to these owls.  相似文献   

19.
Kenneth A. Schmidt 《Oikos》2006,113(1):82-90
Non-lethal effects of predators on prey are initiated in the form of responses to direct and indirect cues of predation risk. Like their lethal equivalents, non-lethal effects may affect species further down the food web initiating a behaviorally-driven trophic cascade. I presented a direct cue of predation risk, owl vocalizations, to white-footed mice ( Peromyscus leucopus ) during either a new or full moon (indirect cue). Mice reduced their activity in space by nearly two-thirds in response to playbacks of owl vocalizations during a full moon. However, neither moonlight (full vs new) nor the presence/absence of owl calls had an effect on space use when each cue varied singly. Previous studies have demonstrated a tight correlation between spatial activity in mice as used in the current experiment and nest predation rates on ground-nesting birds. Because moonlight is a ubiquitous deterrent of activity in nocturnal rodents I used of long-term nesting records the veery ( Catharus fuscescens ) to test whether nest predation rates were correlated negatively with moonlight. For half the lunar cycle (∼full moon to new moon) predation rates decreased with moonlight as predicted. During the second half of the lunar cycle predation and moonlight did not correlate as expected, but this was likely due to the depletion of vulnerable nests after a period of in which predation rates were at their maximum near the full moon. These studies suggest that the non-lethal effects of predatory risk on mice (i.e. changes in space use) cascade to affect their prey. Through the mechanism of reduced space use by rodents, perceived predation risk has the potential to significantly and indirectly affect songbird nest predation rates.  相似文献   

20.
Apex predators are integral parts of every ecosystem, having top‐down roles in food web maintenance. Understanding the environmental and habitat characteristics associated with predator occurrence is paramount to conservation efforts. However, detecting top order predators can be difficult due to small population sizes and cryptic behaviour. The endangered Tasmanian masked owl (Tyto novaehollandiae castanops) is a nocturnal predator with a distribution understood to be associated with high mature forest cover at broad scales. With the aim to gather monitoring data to inform future conservation effort, we trialled an occupancy survey design to model masked owl occurrence across ~800 km2 in the Tasmanian Southern Forests. We conducted 662 visits to assess masked owl occupancy at 160 sites during July–September 2018. Masked owl site occupancy was 12%, and estimated detectability was 0.26 (±0.06 SE). Cumulative detection probability of masked owls over four visits was 0.7. Occupancy modelling suggested owls were more likely to be detected when mean prey count was higher. However, low detection rates hindered the development of confident occupancy predictions. To inform effective conservation of the endangered Tasmanian masked owl, there is a need to develop novel survey techniques that better account for the ecology of this rare, wide‐ranging and cryptic predator. We discuss the potential to combine novel census approaches that exploit different aspects of masked owl ecology to obtain more robust and detailed data.  相似文献   

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