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1.
Ecological theory predicts that the diffuse risk cues generated by wide‐ranging, active predators should induce prey behavioural responses but not major, population‐ or community‐level consequences. We evaluated the non‐consumptive effects (NCEs) of an active predator, the grey wolf (Canis lupus), by simultaneously tracking wolves and the behaviour, body fat, and pregnancy of elk (Cervus elaphus), their primary prey in the Greater Yellowstone Ecosystem. When wolves approached within 1 km, elk increased their rates of movement, displacement and vigilance. Even in high‐risk areas, however, these encounters occurred only once every 9 days. Ultimately, despite 20‐fold variation in the frequency of encounters between wolves and individual elk, the risk of predation was not associated with elk body fat or pregnancy. Our findings suggest that the ecological consequences of actively hunting large carnivores, such as the wolf, are more likely transmitted by consumptive effects on prey survival than NCEs on prey behaviour.  相似文献   

2.
Predators play integral roles in shaping ecosystems through cascading effects to prey and vegetation. Such effects occur when prey species alter their behavior to avoid predators, a phenomenon called the risk effects of predators. Risk effects of wild predators such as wolves are well documented for wild prey, but not for free ranging domestic animals such as cattle despite their importance for ecosystem function and conservation. We compared risk effects of satellite‐collared wolves (n = 16) on habitat selection by global‐positioning‐system‐collared elk (n = 10) and cattle (n = 31). We calculated resource selection functions (RSFs) in periods before, during and after wolf visits in elk home ranges or cattle pastures. The habitat variables tested included: distance to roads and trails, terrain ruggedness, food‐quality and distance to forest. When wolves were present, elk stayed closer to forest cover and selected less for high‐quality‐food habitat. Thus, the risk effects of wolf presence on elk produced a change in the tradeoff between food and cover selection. Cattle responded by avoiding high‐quality‐food habitat and selecting areas closer to roads and trails (where people likely provided security), but these effects manifested only after wolves had left. Artificial selection in cattle may have attenuated natural anti‐predator behaviors. The effects of predators on ecosystems are likely different when mediated through risk effects on domestic compared to wild animals. Furthermore, predator control in response to livestock predation, an important conservation issue, may produce broad ecosystem effects triggered by decrease of an important predator species. Conservation planners should consider these effects where domestic herbivores are dominant species in the ecosystem.  相似文献   

3.
Abstract: Numerous studies have documented how prey may use antipredator strategies to reduce the risk of predation from a single predator. However, when a recolonizing predator enters an already complex predator—prey system, specific antipredator behaviors may conflict and avoidance of one predator may enhance vulnerability to another. We studied the patterns of prey selection by recolonizing wolves (Canis lupus) and cougars (Puma concolor) in response to prey resource selection in the northern Madison Range, Montana, USA. Elk (Cervus elaphus) were the primary prey for wolves, and mule deer (Odocoileus hemionus) were the primary prey for cougars, but elk made up an increasingly greater proportion of cougar kills annually. Although both predators preyed disproportionately on male elk, wolves were most likely to prey on males in poor physical condition. Although we found that the predators partitioned hunting habitats, structural complexity at wolf kill sites increased over time, whereas complexity of cougar kill sites decreased. We concluded that shifts by prey to structurally complex refugia were attempts by formerly naïve prey to lessen predation risk from wolves; nevertheless, shifting to more structurally complex refugia might have made prey more vulnerable to cougars. After a change in predator exposure, use of refugia may represent a compromise to minimize overall risk. As agencies formulate management strategies relative to wolf recolonization, the potential for interactive predation effects (i.e., facilitation or antagonism) should be considered.  相似文献   

4.
Characteristics of spatio-temporal clusters of locations from global positioning system (GPS)-collars have been used to distinguish kill sites of various predators. We deployed GPS collars on 9 grey wolves (Canis lupus) in the southwest area of Prince Albert National Park in central Saskatchewan, Canada, and used a GPS location clustering algorithm to identify kill sites of ungulate and other large-bodied prey during winter, December 2013–March 2017. We used logistic regression in a model-selection framework to determine if spatio-temporal and habitat characteristics of grey wolf GPS clusters could be used to reliably identify sites where wolves had killed prey. Global positioning system clusters were more likely to be wolf kill sites when they had a higher number of location fixes, did not begin within 300 m and 30 days of a previous cluster, did not begin within 1 km and 4 days of a previous cluster, began in the evening, had a high percentage of fixes occurring during the day, occurred farther from open habitat, and had both a high number of location fixes and a high percentage of fixes occurring during the day. Our results highlight the limits of using spatio-temporal clusters with a fix rate of 1/hour to discriminate wolf kill sites in systems dominated by deer (Odocoileus spp.) because of the associated short handling time with these prey.  相似文献   

5.
Abstract: Global Positioning System (GPS) telemetry is used extensively to study animal distribution and resource selection patterns but is susceptible to biases resulting from data omission and spatial inaccuracies. These data errors may cause misinterpretation of wildlife habitat selection or spatial use patterns. We used both stationary test collars and collared free-ranging American black bears (Ursus americanus) to quantify systemic data loss and location error of GPS telemetry in mountainous, old-growth temperate forests of Olympic National Park, Washington, USA. We developed predictive models of environmental factors that influence the probability of obtaining GPS locations and evaluated the ability of weighting factors derived from these models to mitigate data omission biases from collared bears. We also examined the effects of microhabitat on collar fix success rate and examined collar accuracy as related to elevation changes between successive fixes. The probability of collars successfully obtaining location fixes was positively associated with elevation and unobstructed satellite view and was negatively affected by the interaction of overstory canopy and satellite view. Test collars were 33% more successful at acquiring fixes than those on bears. Fix success rates of collared bears varied seasonally and diurnally. Application of weighting factors to individual collared bear fixes recouped only 6% of lost data and failed to reduce seasonal or diurnal variation in fix success, suggesting that variables not included in our model contributed to data loss. Test collars placed to mimic bear bedding sites received 16% fewer fixes than randomly placed collars, indicating that microhabitat selection may contribute to data loss for wildlife equipped with GPS collars. Horizontal collar errors of >800 m occurred when elevation changes between successive fixes were >400 m. We conclude that significant limitations remain in accounting for data loss and error inherent in using GPS telemetry in coniferous forest ecosystems and that, at present, resource selection patterns of large mammals derived from GPS telemetry should be interpreted cautiously.  相似文献   

6.
Over 6,000 GPS fixes from two wolves (Canis lupus) and 30,000 GPS fixes from five moose (Alces alces) in a wolf territory in southern Scandinavia were used to assess the static and dynamic interactions between predator and prey individuals. Our results showed that wolves were closer to some of the moose when inside their home ranges than expected if they had moved independently of each other, and we also found a higher number of close encounters (<500 m) than expected. This suggests that the wolves were actively seeking the individual moose within their territory. Furthermore, the wolves showed a preference for moving on gravel forest roads, which may be used as convenient travel routes when patrolling the territory and seeking areas where the moose are. However, due to the particularly large size of the wolf territory combined with relatively high moose densities, the wolves generally spent a very small proportion of their time inside the home range of each individual moose, and the frequency of encounters between the wolves and any particular moose was very low. We suggest that the high moose:wolf ratio in this large Scandinavian wolf territory compared to that typically occurring in North America, results in a relatively low encounter frequency and a low predation risk for individual moose, as the predation pressure is spread over a high number of prey individuals.  相似文献   

7.
In a predator–prey system, prey species may adapt to the presence of predators with behavioral changes such as increased vigilance, shifting habitats, or changes in their mobility. In North America, moose (Alces alces) have shown behavioral adaptations to presence of predators, but such antipredator behavioral responses have not yet been found in Scandinavian moose in response to the recolonization of wolves (Canis lupus). We studied travel speed and direction of movement of GPS‐collared female moose (n = 26) in relation to spatiotemporal differences in wolf predation risk, reproductive status, and time of year. Travel speed was highest during the calving (May–July) and postcalving (August–October) seasons and was lower for females with calves than females without calves. Similarly, time of year and reproductive status affected the direction of movement, as more concentrated movement was observed for females with calves at heel, during the calving season. We did not find support for that wolf predation risk was an important factor affecting moose travel speed or direction of movement. Likely causal factors for the weak effect of wolf predation risk on mobility of moose include high moose‐to‐wolf ratio and intensive hunter harvest of the moose population during the past century.  相似文献   

8.
ABSTRACT Prey behavioral responses to predation risk in wolf-ungulate-plant systems are of interest to wildlife managers. Using Global Positioning System data collected from telemetry-collared elk (Cervus elaphus) and wolves (Canis lupus), we evaluated elk behavioral responses to spatial and temporal variation in wolf- and human-predation risk on a winter range in the Greater Yellowstone Area, USA. We found elk changed grouping patterns and increased movement rates as predation risk increased and that these behavioral changes were habitat dependent. Elk behavioral responses to wolf- and human-predation risk were similar; however, responses to human-predation risk were stronger than responses to wolf-predation risk. These results suggest that predation risk from wolves or human hunters may result in elk spending more time on private rangelands away from public-land winter ranges, which may exacerbate problems of landowner tolerance of elk on livestock pastures. However, increased movement and changing grouping patterns on winter ranges may also disperse elk grazing impacts and lessen elk impacts on any one area.  相似文献   

9.
An intriguing aspect of social foraging behaviour is that large groups are often no better at capturing prey than are small groups, a pattern that has been attributed to diminished cooperation (i.e., free riding) in large groups. Although this suggests the formation of large groups is unrelated to prey capture, little is known about cooperation in large groups that hunt hard-to-catch prey. Here, we used direct observations of Yellowstone wolves (Canis lupus) hunting their most formidable prey, bison (Bison bison), to test the hypothesis that large groups are more cooperative when hunting difficult prey. We quantified the relationship between capture success and wolf group size, and compared it to previously reported results for Yellowstone wolves hunting elk (Cervus elaphus), a prey that was, on average, 3 times easier to capture than bison. Whereas improvement in elk capture success levelled off at 2–6 wolves, bison capture success levelled off at 9–13 wolves with evidence that it continued to increase beyond 13 wolves. These results are consistent with the hypothesis that hunters in large groups are more cooperative when hunting more formidable prey. Improved ability to capture formidable prey could therefore promote the formation and maintenance of large predator groups, particularly among predators that specialize on such prey.  相似文献   

10.
The strong impact of non‐native predators in aquatic systems is thought to relate to the evolutionary naiveté of prey. Due to isolation and limited dispersal, this naiveté may be relatively high in freshwater systems. In this study, we tested this notion by examining the antipredator response of native mosquitofish, Gambusia holbrooki, to two non‐native predators found in the Everglades, the African jewelfish, Hemichromis letourneuxi, and the Mayan cichlid, Cichlasoma urophthalmus. We manipulated prey naiveté by using two mosquitofish populations that varied in their experience with the recent invader, the African jewelfish, but had similar levels of experience with the longer‐established Mayan cichlid. Specifically, we tested these predictions: (1) predator hunting modes differed between the two predators, (2) predation rates would be higher by the novel jewelfish predator, (3) particularly on the naive population living where jewelfish have not invaded yet, (4) antipredator responses would be stronger to Mayan cichlids due to greater experience and weaker and/or ineffective to jewelfish, and (5) especially weakest by the naive population. We assayed prey and predator behavior, and prey mortality in lab aquaria where both predators and prey were free‐ranging. Predator hunting modes and habitat domains differed, with jewelfish being more active search predators that used slightly higher parts of the water column and less of the habitat structure relative to Mayan cichlids. In disagreement with our predictions, predation rates were similar between the two predators, antipredator responses were stronger to African jewelfish (except for predator inspections), and there was no difference in response between jewelfish‐savvy and jewelfish‐naive populations. These results suggest that despite the novelty of introduced predators, prey may be able to respond appropriately if non‐native predator archetypes are similar enough to those of native predators, if prey rely on general antipredator responses or predation cues, and/or show neophobic responses.  相似文献   

11.
Male and female predators are often assumed to have the same effects on prey. Because of differences in body size and behavior, however, male and female predators may use different species, sexes, and ages of prey, which could have important implications for wildlife conservation and management. We tested for differential prey use by male and female cougars (Puma concolor) from 2003 to 2008 in Washington State. We predicted that male cougars would kill a greater proportion of larger and older prey (i.e., adult elk [Cervus elaphus]), whereas females would kill smaller and younger prey (i.e., elk calves, mule deer [Odocoileus hemionus]). We marked cougars with Global Positioning System (GPS) radio collars and investigated 436 predation sites. We located prey remains at 345 sites from 9 male and 9 female cougars. We detected 184 mule deer, 142 elk, and 17 remains from 4 other species. We used log-linear modeling to detect differences in species and age of prey killed among cougar reproductive classes. Solitary females and females with dependent offspring killed more mule deer than elk (143 vs. 83, P < 0.01), whereas males killed more elk than mule deer (59 vs. 41, P < 0.01). Proportionately, males killed 4 times more adult elk than did females (24% vs. 6% of kills) and females killed 2 times more adult mule deer than did males (26% vs. 15% of kills). Managers should consider the effects of sex of predator in conservation and management of ungulates, particularly when managing for sensitive species. © 2011 The Wildlife Society.  相似文献   

12.
As the value of Global Positioning System (GPS) technology in addressing primatological questions becomes more obvious, more studies will include capturing and collaring primates, with concomitant increased risk of adverse consequences to primate subjects. Here we detail our experiences in capturing, immobilizing, and placing GPS collars on six olive baboons (Papio anubis) in four groups and 12 vervet monkeys (Chlorocebus pygerythrus) in five groups in Kenya. We captured baboons with cage traps and vervets with box traps, immobilized them, and attached GPS collars that were to be worn for 1 year. Adverse consequences from the trapping effort included incidental death of two nonsubjects (an adult female and her dependent infant), temporary rectal prolapse in one baboon, superficial wounds on the crown of the head in two vervets, and failure to recapture/remove collars from two baboons and two vervets. Obvious negative effects from wearing collars were limited to abrasions around the neck of one vervet. A possible, and if so, serious, adverse effect was greater mortality for collared adult female vervets compared with known uncollared adult female vervets, largely due to leopard (Panthera pardus) predation. Collared animals could be more vulnerable to predation because trapping favors bolder individuals, who may also be more vulnerable to predation, or because collars could slow them down or make them more noticeable to predators. Along with recommendations made by others, we suggest that future studies diversify trapping bait to minimize the risk of rectal prolapse, avoid capturing the first individuals to enter traps, test the movement speeds of collared versus noncollared animals, include a release system on the collars to avoid retrapping failure, and publish both positive and negative effects of capturing, immobilizing, and collaring.  相似文献   

13.
The spatiotemporal game between predators and prey is a fundamental process governing their distribution dynamics. Players may adopt different tactics as the associated costs and benefits change through time. Yet few studies have investigated the potentially simultaneous and dynamic nature of movement tactics used by both players. It is particularly unclear to what extent perceived predation risk mediates the fine‐scale distribution of large and dangerous prey, which are mostly driven by bottom–up, resource‐related processes. We built habitat use and movement models based on 10 years of monitoring GPS‐collared grey wolves Canis lupus and plains bison Bison bison bison in Prince Albert National Park, Canada, to investigate the predator–large prey game in a multi‐prey system. Bison did not underuse patches of high‐quality vegetation at any time during the seasonal cycle even though wolves were selectively patrolling these areas. Rather, in at least one season, bison engaged in complex tactics comprised of proactive responses to the long‐term distribution (risky places) and reactive responses to the immediate proximity (risky times) of their opponent. In summer–autumn, bison reduced the time spent in food‐rich patches as both the long‐term use and the immediate proximity of wolves increased. By demonstrating that wolf distribution triggers patch abandonment by bison, we provide a key element in support of the shell game hypothesis – where prey move constantly to avoid predators attempting to anticipate their location. In winter, a season of relatively high energetic stress, bison no longer abandoned food‐rich patches as predation risk increased, while no bison responses to wolves were observed in spring–summer. Our work demonstrates the highly dynamic and complex nature of the predator–large prey spatiotemporal game, a key trait‐mediated mechanism by which trophic interactions structure ecological communities.  相似文献   

14.
Prey respond to predation risk with a range of behavioral tactics that can vary based on space use and hunting mode of the predator. Unlike other predators, human hunters are often more spatially and temporally restricted, which creates a period of short-duration, high-intensity predation risk for prey. Consequently, identifying the roles different hunting modes (i.e., archery and rifle), hunts for targeted and non-targeted species, and landscape features play in altering spatial and temporal responses of prey to predation risk by humans is important for effective management of harvested populations. From 2009 to 2016, we used a large-scale experiment including 50 animal-years of location data from 38 unique male elk (Cervus canadensis) to quantify changes in movement and resource selection in response to hunters during 3 separate 5-day controlled hunts for antlered males (elk archery, deer [Odocoileus spp.] rifle, and elk rifle) at the Starkey Experimental Forest and Range in northeast Oregon, USA. We evaluated competing hypotheses regarding elk responses to varying levels of prey risk posed by the different hunt types. We predicted that the strength of elk behavioral responses would increase with perceived hunter lethality (i.e., weak response to elk archery but similar response to elk and deer rifle hunts) and that prey response would be closely associated with hunter activity within the diel cycle (greater during diurnal than nocturnal hours) and across hunting seasons. Elk responses were strongest during diurnal hours when hunters were active on the landscape and were generally more pronounced during both rifle hunts than during the archery hunt (supporting our perceived lethality hypothesis). Male elk avoided open roads across all periods except during nocturnal hours of the breeding season and alternated between avoidance of areas with high canopy cover during nocturnal hours and selection during diurnal hours. In combination these patterns led to distinct distributional changes of male elk from pre-hunt to hunt periods. Patterns of male elk selection highlight the importance of managing for heterogeneous landscapes to meet a variety of habitat, harvest, hunter satisfaction, and escapement objectives.  相似文献   

15.
It is well established in the scientific literature that animal prey species reduce their activity at times of high predation risk. In the case of nocturnal animals this occurs when there is a full moon; however, the response of predators to the changes in their prey behaviour is relatively unknown. Two responses are possible: (1) increase in search effort to maintain food intake; or (2) decrease in distance travelled due to either: (a) an effort to conserve energy or (b) increased kill efficiency. Using GPS tracking collars we monitored the distances travelled (which is representative of search effort) by three maned wolves during the night of the full and new moon for five lunar cycles (during the dry season). A Wilcoxon matched-paired test showed that the maned wolves travelled significantly less during the full compared to the new moon (p < 0.05). On average, during the 10 h of darkness during a full moon maned wolves travelled 1.88 km less than on a new moon. These data suggest that maned wolves respond to temporally reduced prey availability by reducing their distance travelled.  相似文献   

16.
Many ecosystems contain sympatric predator species that hunt in different places and times. We tested whether this provides vacant hunting domains, places and times where and when predators are least active, that prey use to minimize threats from multiple predators simultaneously. We measured how northern Yellowstone elk (Cervus elaphus) responded to wolves (Canis lupus) and cougars (Puma concolor), and found that elk selected for areas outside the high‐risk domains of both predators consistent with the vacant domain hypothesis. This enabled elk to avoid one predator without necessarily increasing its exposure to the other. Our results demonstrate how the diel cycle can serve as a key axis of the predator hunting domain that prey exploit to manage predation risk from multiple sources. We argue that a multi‐predator, spatiotemporal framework is vital to understand the causes and consequences of prey spatial response to predation risk in environments with more than one predator.  相似文献   

17.
Predation threat-associated behavioral response was studied in Rana temporalis tadpoles to discover the importance of predators’ visual and chemical cues (kairomones and diet-derived metabolites of consumed prey) in evoking antipredator behavior. The caged predators (dragonfly larvae) fed on prey tadpoles or insects (Notonecta spp.) and water conditioned with the predators provided the threat stimuli to the tadpole prey. The predators’ visual cues were ineffective in evoking antipredator behaviors in the tadpole prey. However, exposure to caged tadpole-fed predators or water conditioned with tadpole-fed predators elicited predator avoidance behavior in the tadpoles; they stayed away from the predators, significantly reduced swimming activity (swimming time and distance traveled), and increased burst speed. Interestingly, exposure to water conditioned with starved predators did not elicit any antipredator behavior in the prey. Further, the antipredator responses of predator-experienced tadpoles were significantly greater than those exhibited by predator-na?ve tadpoles. The study shows that R. temporalis tadpoles assess predation threat based exclusively on chemical cues emanating from the predators’ dietary metabolites and that the inclusion of conspecific prey items in the diet of the predators is perceived as a threat. The study also shows that antipredator behavior in these tadpoles is innate and is enhanced during subsequent encounters with the predators.  相似文献   

18.
There are limitations imposed by current methodologies to detect and quantify insect predation. However, there has been relatively little effort to experimentally document the sources of biases associated with the various methodologies. In this study, we examined how predation estimates in the field using predator exclusion cages may be biased when one fails to account for antipredator behavioral responses. To do this, we did the usual comparison of the number of insects missing from plants where predators were allowed access to the number missing from plants where predators were excluded, but also determined how many of the missing insects reacted to predators by dropping from plants and how many were actually preyed upon. Our results provide evidence that estimates of insect mortality in the field are significantly reduced if prey antipredator behavior is taken into account. As it is commonly assumed that prey missing in the field are predated, documenting the incidence of predator‐mediated ‘disappearance’ and capturing insect prey before they escape can provide with a relevant estimate of bias.  相似文献   

19.
ABSTRACT Using clusters of locations obtained from Global Positioning System (GPS) telemetry collars to identify predation events may allow more efficient estimation of behavioral predation parameters for the study and management of large carnivore predator-prey systems. Applications of field- and model-based GPS telemetry cluster techniques, however, have met with mixed success. To further evaluate and refine these techniques for cougars (Puma concolor), we used data from visits to 1,735 GPS telemetry clusters, 637 of which were locations where cougars killed prey >8 kg in a multi-prey system in west-central Alberta. We tested 1) whether clusters were reliably created at kill locations, 2) the ability of logistic regression models to identify kill occurrence (prey >8 kg) and multinomial regression models to identify the prey species at a kill cluster, and 3) the duration of monitoring required to accurately estimate kill rate and prey composition. We found that GPS collars programmed to attempt location fixes every 3 hours consistently identified locations where prey >8 kg were handled, and cluster creation was robust to GPS location acquisition failures (poor collar fix success). The logistic regression model was capable of estimating cougar kill rate with a mean 5-fold cross validation error of <10%, provided the appropriate probability cutoff distinguishing kill clusters from non-kill clusters was selected. Logistic models also can be used to direct visits to clusters, reducing field efforts by as much as 25%, while still locating >95% of all kills. The multinomial model overpredicted occurrence of primary prey (deer) in the diet and underpredicted consumption of alternate prey (e.g., elk and moose) by as much as 100%. We conclude that a purely model-based approach should be used cautiously and that field visitation is required to obtain reliable information on species, sex, age, or condition of prey. Ultimately, we recommend a combined approach that involves using models to direct field visitation when estimating behavioral predation parameters. Regardless of the monitoring approach, long continuous monitoring periods (i.e., >100 days of a 180-day period) were necessary to reduce bias and imprecision in kill rate and prey composition estimates.  相似文献   

20.
Effective management of infectious disease relies upon understanding mechanisms of pathogen transmission. In particular, while models of disease dynamics usually assume transmission through direct contact, transmission through environmental contamination can cause different dynamics. We used Global Positioning System (GPS) collars and proximity‐sensing contact‐collars to explore opportunities for transmission of Mycobacterium bovis [causal agent of bovine tuberculosis] between cattle and badgers (Meles meles). Cattle pasture was badgers’ most preferred habitat. Nevertheless, although collared cattle spent 2914 collar‐nights in the home ranges of contact‐collared badgers, and 5380 collar‐nights in the home ranges of GPS‐collared badgers, we detected no direct contacts between the two species. Simultaneous GPS‐tracking revealed that badgers preferred land > 50 m from cattle. Very infrequent direct contact indicates that badger‐to‐cattle and cattle‐to‐badger M. bovis transmission may typically occur through contamination of the two species’ shared environment. This information should help to inform tuberculosis control by guiding both modelling and farm management.  相似文献   

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