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Do wildlife passages act as prey-traps?
Abstract
A number of studies have proposed that wildlife passages beneath roads and railway lines might be exploited by mammalian predators as ‘prey-traps’ with prey-species being effectively funnelled into areas of high concentration. This proposition has raised the possibility that use of passages by predators may reduce the effectiveness of passages in conserving other forms of wildlife. We review the literature and conclude that evidence for the existence of prey-traps is scant, largely anecdotal and tends to indicate infrequent opportunism rather than the establishment of patterns of recurring predation. Most passage studies record no evidence of predation in or around passages. Conversely, there is some evidence that predator species use different passages than their prey.
... Predation has long been considered a variable that can affect the efficacy of wildlife crossing structures (Little et al., 2002). Studies of patterns of temporal overlap among predators and prey on wildlife crossing structures or quantification of predation attempts at the structure (Little et al., 2002;Martinig et al., 2020;Soanes et al., 2015;Ford and Clevenger, 2010) reject the hypothesis that wildlife passages (in general) act as prey traps. ...
... Predation has long been considered a variable that can affect the efficacy of wildlife crossing structures (Little et al., 2002). Studies of patterns of temporal overlap among predators and prey on wildlife crossing structures or quantification of predation attempts at the structure (Little et al., 2002;Martinig et al., 2020;Soanes et al., 2015;Ford and Clevenger, 2010) reject the hypothesis that wildlife passages (in general) act as prey traps. However, predation could still be a factor affecting usage of these structures through specific attraction-avoidance relationships among predators and prey (Mata et al., 2020). ...
One of the negative effects of linear infrastructures is the formation of barriers to the movements for arboreal wildlife resulting in the reduction in connectivity between populations and thus increasing the risk of extinction. One of the most widely used ways to mitigate these barrier effects is canopy bridges. There is a lack of knowledge about how behavioral differences between species may affect the efficacy of canopy bridges. The purpose of this study was to evaluate the hypothesis that Leontopithecus rosalia (an endangered endemic species) and Callithrix spp. hybrids (introduced invasive species) perceive canopy bridges as sites with risk of predation. We compared the behavior of these species during attempts to cross four canopy bridges installed over oil and gas pipeline right-of-way strips, and another 4 bridges installed inside the forest near the pipeline bridges. The behavior was recorded from 30-second videos obtained from two camera traps installed at each end of the bridges. Of the 1917 crossing events identified, 356 events were randomly chosen for behavioral data collection. Of these, 173 were social group crossing events and 183 individual crossing events. There were few crossings (7.9%) with the two species present. The differences between the species were more quantitative than qualitative and may be related to interspecific differences in vulnerability to predation and anti-predatory tactics. Both species exhibited significantly more behaviors related to perception of risk of predation (vigilance, hesitation, rapid passage) in the pipeline bridges than in the forest bridges. One vigilance measure showed higher occurrence during the first months after installation of the cameras, especially for Callithrix spp., but in general there was little waning of the risk-assessment response. Alarm calls, scent marking and social and feeding behaviors were rare or absent. Low-cost simple canopy bridges may be an effective strategy to overcome the barrier effect of right-of-way strips over gas and oil pipelines. However, the results on perceived risk of predation raise the hypothesis that there may be a cost-benefit ratio between distance to be traveled and risk perception that would lead to a reduction in effectiveness of bridges in greater distance. We discuss the implications for conservation of an endangered species and management of an invasive species.
... Restoration efforts to create migration corridors for terrestrial animals may seem helpful to facilitate movement and connectivity, but these may also act as predation hotspots (Ohms et al. 2022). Wildlife corridors across roads and railways have frequently been found to be used by a range of terrestrial predators, to their advantage over their prey species that are attracted to such structures by the habitat created for them there by humans (Little et al. 2002). Fish passage structures in rivers that similarly provide upstream passage at dams may also become areas where predators can hide and ambush fish attempting to pass (Agostinho et al. 2012;Boulêtreau et al. 2018). ...
Habitat is a powerful force in ecosystems, and the quantity and quality of habitat can shape ecosystem structure and function. Among the many important roles that habitat plays is as a mediator of ecological interactions, including predator–prey dynamics. In the context of ecosystem restoration, there is great potential to better understand how predator–prey dynamics are influenced by habitat and whether this has implications for how ecosystems are managed. We consider the ways in which habitat serves as an important mediator of interactions between predators and their prey and present four ways in which habitat acts as an intermediary that enhances or diminishes this relationship. We found that habitat provides refuge from predators and shapes the physical traits of prey as they use their surroundings to protect themselves. We also discuss how habitat creates physical resistance and sets the cost of predation for predators and how habitat facilitates apparent competition within a community context. These roles of habitat are well established in ecology, but we believe they are underdeveloped from an applied perspective. We conclude that habitat must be appropriately considered in the context of how it mediates predation. Given the ways that habitat influences predation, restoration efforts should consider if and how physical measures may positively or negatively affect species interactions and whether this could lead to success or failure of overall programs.
... Fences can benefit populations in urbanized areas by funnelling individuals towards safe road crossing structures (Aresco, 2005b) and protecting turtles and nests from introduced predators, including red foxes (Vulpes vulpes; Streeting et al., 2023). However, fences can also kill turtles through entanglement and overheating (Ferronato et al., 2014) or indirectly through prey funnelling, leading to predation (Little et al., 2002). Additionally, linear barriers dissuade turtles from moving between seasonal habitats and may alter movement routes and increase metabolic costs while reducing available resources (Paterson et al., 2019). ...
Anthropogenic landscape change due to urbanization, agriculture, and resource extraction results in barriers within the landscape. Artificial structures such as roads, fences, levees, and dams limit the movement of some species and further fragment residual habitat. In this study, we investigated the ability of Eastern long‐necked turtles (Chelodina longicollis) to cross various terrestrial obstacles commonly encountered throughout their habitat. We tested two types of fences (chicken wire and hinged joint exclusion fencing) commonly used in agricultural systems and three sizes of rocks (gravel, cobbles, and boulders) often used for road construction, erosion control, and waterway stabilization. We examined the success rates of turtles in crossing obstacles, the effect of fatigue on crossing attempts, and the impact of individual boldness on movement behaviour. Turtles had high success rates in crossing gravel (85.4%), cobbles (86%), boulders (73.3%) and hinged joint exclusion fencing (94.7%). Turtles did not successfully cross chicken wire fencing (0%) despite 276 attempts. A significant fatigue effect occurred throughout the experiment, with turtles making an average of 3.94 (±1.42 SE) fewer attempts at the end of the experiment (day 18) than on day 1. Bolder turtles were faster at crossing obstacles, but boldness had no influence on obstacle‐crossing success. Our results highlight the need for thoughtful selection of waterway, wetland, and riparian bordering infrastructure and the fatiguing impact of constant exposure to anthropogenic barriers for wildlife.
... It is unclear what structure attributes contribute to the higher rate of success observed for the horizontal v-shape fence-end treatment for amphibians; however, we observed amphibians were more likely to turn around after becoming trapped in the corner created by the sharper angle, which may significantly decrease the fence-end effect but could also act as a prey-trap (Baxter-Gilbert et al., 2015). With few exceptions (Ford and Clevenger, 2010), little attention has been paid to examining predation events along fences; however, several studies evaluated the prey-trap hypothesis in eco-passage have largely found this risk to be minimal (Little et al., 2002;Ford and Clevenger, 2010). Furthermore, it is unclear if the angle of the fence-end treatment is the important factor influencing amphibian response compared to other potential structure attributes, such as the length of the fence-end treatment or if a rounded corner like the j-shape would perform better than the horizontal v-shape. ...
Migratory amphibians require movements to complete their biphasic life cycle, often across altered landscapes fragmented by roadways, which can have severe consequences on their populations. To manage this threat, transportation agencies have begun to implement exclusion fencing to separate natural areas from the roadway to prevent wildlife-vehicle collisions. Although fences are an effective conservation tool, the tendency of animals to access the road by circumventing the fence ends, known as the fence-end effect, threatens to jeopardize management efforts to reduce road associated mortality. One strategy to lessen the impacts of the fence-end effect is to construct fence-end treatments to block amphibian movement and guide the animals to safe crossing locations. By using experimental fence arenas, we examined how nine amphibian species responded to two alternative fence-end structures: horizontal v-shape and perpendicular fence-end treatments. Using a generalized linear model framework, we found both fence-end treatments to be an effective strategy to reduce the impacts of the fence-end effect, with our predictor variable, fence-end treatment, explaining most of the variation in amphibian response. Structure effectiveness also started to improve by 20% with each 7°C increase in temperature, however, this was not significant. Despite these promising findings, we also found for each additional 312 s an amphibians spent attempting to navigate around the experimental fence resulted in a 25% decline in structure effectiveness, suggesting longer fences are not an adequate protection measure to combat the fence-end effect for amphibians. In addition, Anaxyrus americanus was not found to differ in their response, performing equally well to both experimental fence-end treatments. In contrast, Rana spp., Pseudacris crucifer, and Notopthalmus viridescens showed a greater response to the horizontal v-shape fence-end treatment compared to the perpendicular fence-end treatment. Variation in response for Ambystoma spp. could not be detected due to a small sample size; however, no individuals responded positively to the perpendicular fence-end treatment. Guidelines for amphibian fences should continue to incorporate fence-end treatments into the design and implementation to mitigate for the fence-end effect, and preferably angle the fence-ends inward in the horizontal v-shape pattern with the fence ends diagonal to the road for migratory amphibians.
... The prey trap hypothesis argues that prey then are conducted into predictable confined spaces where predator pressure is concentrated (see also Section III.4.c for parasitism hotspots). This hypothesis has been tested several times and a literature review (Little, Harcourt & Clevenger, 2002) concluded that there was little supporting evidence. Alcott, Long & Castro-Santos (2020) described how culverts at road-stream crossings can increase fish density by reducing stream width and fish movement, which can be exploited by predators such as the snapping turtle (Chelydra serpentina) to improve their hunting success on migratory river herring (Alosa spp.). ...
Roads have pervasive impacts on wildlife, including habitat loss and fragmentation, road mortality, habitat pollution and increased human use of habitats surrounding them. However, the effects of roads on interspecific interactions are less understood. Here we provide a synthesis of the existing literature on how species interactions may be disrupted by roads, identify knowledge gaps, and suggest avenues for future research and conservation management. We conducted a systematic search using the Web of Science database for each species interaction (predation, competition, mutualism, par-asitism, commensalism and amensalism). These searches yielded 2144 articles, of which 195 were relevant to our topic. Most of these studies focused on predation (50%) or competition (24%), and less frequently on mutualism (17%) or, par-asitism (9%). We found no studies on commensalism or amensalism. Studies were biased towards mammals from high-income countries, with most conducted in the USA (34%) or Canada (18%). Our literature review identified several patterns. First, roads disrupt predator-prey relationships, usually with negative impacts on prey populations. Second, new disturbed habitats created in road corridors often benefit more competitive species, such as invasive species, although some native or endangered species can also thrive there. Third, roads degrade mutualistic interactions like seed dispersal and pollination. Fourth, roads can increase parasitism rates, although the intensity of the alteration is species specific. To reduce the negative impacts of roads on interspecific interactions, we suggest the following management actions: (i) verges should be as wide and heterogenous as possible, as this increases microhabitat diversity, thus enhancing ecosystem services like pollination and seed dispersal; (ii) combining different mowing regimes can increase the complexity of the habitat corridor, enabling it to act as a habitat for more species; (iii) the use of de-icing salts should be gradually reduced and replaced with less harmful products or maintenance practices; (iv) wildlife passes should be implemented in groups to reduce animal concentrations inside them; (v) periodic removal of carcasses from the road to reduce the use of this resource by wildlife; and (vi) implementation of traffic-calming schemes could enhance interspecific interactions like pollination and avoid disruption of predator-prey relationships.
... While there is potential for predators to exploit the use of an underpass by prey animals, there is little evidence for this occurring (Little et al. 2002;Martinig et al. 2020). Underpasses could provide shade and shelter with the correct design enabling free access, and enables safe moving of livestock from one side of the track to the other (James 2020). ...
The proximity of rail corridors to livestock production enterprises poses potential risks to welfare and production. The association between these factors and production have been extensively investigated. This review aims to assess the potential impact on the basis of existing data in a livestock production context. Due to expansion of freight rail networks through agricultural land, there is a need to investigate potential impacts of rail (including train and track) noise, vibration and visual disturbance on the physiology and behaviour of the livestock and subsequent production traits. Additionally, the factors influencing the impact on animals were characterised broadly as noise, vibration, and visual and spatial disturbance. This information was used to develop conceptual frameworks around the contribution of rail impact on allostatic load, animal welfare and production. Placing rail noise in the context of other, known, noise impacts showed that proximity to the rail line will determine the impact of noise on the behaviour and physiology of the animal. Thresholds for noise levels should be determined on the basis of known noise thresholds, taking into account the impact of noise on allostatic load. Further research is recommended to investigate the behavioural, physiological and production impacts on livestock from proximity to rail corridors. Current literature suggests that the allostatic load will vary depending on the proximity of the animal to the source of stimulus, the type, size or level of stimuli, habituation and the individual animal variation in response to the stimuli.
... Purpose-built wildlife crossing structures have been installed on new roads since the mid-1900s (Bond & Jones, 2008;Goldingay & Taylor, 2017a;Taylor & Goldingay, 2010;Taylor & Goldingay, 2012), a trend which is increasing, particularly in North America and Europe (Bond & Jones, 2008;Little et al., 2002). These include under-road structures such as drainage pipes, box drainage culverts, and dry passage bridges; and overroad structures such as dedicated wildlife land bridges, combined wildlife-vehicle overpasses, pole/rope/canopy bridges, and glide poles (Goldingay & Taylor, 2017b;Taylor & Goldingay, 2010). ...
Wildlife‐vehicle collisions are increasing with road expansion. This problem could be minimised if the use of existing infrastructure to cross roads could be enhanced. We aimed to determine whether common terrestrial vertebrates used drainage culverts to cross roads, relative to rates of surface crossings. Camera traps were deployed on road verges at 30 locations in southeast Queensland, Australia for 2 weeks each over a 3‐month period. Of 1671 independent animal observations, 397 were direct observations of road crossings, either over‐road (365) or under‐road via culverts (32). Native species and small species were found more commonly at roadsides than culverts and where vegetation density was lower. Our data showed that animals used culverts only about 6% of the time. Management such as funnel fencing or vegetation manipulation could encourage wildlife to use culverts, but this would require a substantial investment given the propensity for animals to cross via the road surface.
(1) Objective
With the help of a Geographical Information System (GIS), the fragmentation of Germany's habitat networks and the nationally significant axes of the biotope network by railway lines was assessed in order to identify defragmentation priorities. For this purpose, relevant knowledge on the barrier effect was to be compiled as a basis for evaluation and the use of habitat networks or the consideration of habitat fragmentation in current planning procedures was questioned.
(2) Assessment background
1.: Planning studies show that, contrary to legal requirements and societal goals, concerns of the biotope network and the protection of ecological corridors are insufficiently taken into account even in the new construction of railway lines. Ecological corridors and migration routes across railway lines are insufficiently protected and the railway verges and side areas are often designed counterproductively to the goals of the biotope network or nature protection at all.
2.: The barrier effect of different types of railway lines and of bundling railways with roads was assessed. Therefore
2.1 Nineteen 19 barrier-impacting features were identified and, because the barrier features have a different impact depending on the species group or ecological guild affected, their effectiveness was assessed on a guild-specific basis,
2.2: the results of 56 publications on the importance of railways as habitats, 29 on the importance as habitat corridors and 38 on the importance as barriers were compiled (see researchgate.net/publication/357164850),
2.3: several field studies about the barrier strength (a) of single and double-track railway lines and curbs for ground beetles as representatives of sensitive small animals and (b) of long underpasses for butterflies, grasshoppers and ground beetles were carried out, furthermore (c) train drivers and hunters (separately in each case) were interviewed with regard to the use or crossings of different railway types (number of tracks, speed) by larger mammals and
2.4: the different types of retaining or protection walls were described in detail.
3.: For woodland ground beetles (as particularly sensitive indicators), a significant barrier effect of single and double-track railway lines could be determined, but no significant prevention of exchange processes (i.e. no strong barrier consequence is to be expected), as long as no additional separating elements such as protective walls and the like are present.
4.: Curbs are significant barriers for small animals.
5.: Narrow and long underpasses are hardly usable for heliophilic and xerophilic small animals and the necessary minimum dimensions for effective mitigation by fauna underpasses are still insufficiently definable.
6.: Larger mammals no longer regularly cross 3-track lines and only very rarely cross 4-track lines or railways bundled with roads; wildlife accidents occur disproportionately often at high speeds (> 120 km/h).
7.: Placing rails to roads creates ecologically significant barriers when closely bundled. If high-quality habitats could be designed in the interstitial space the bundling effect could be overcome; however, the necessary minimum distance to safeguard the biotope network (without the need for very large fauna passages spanning both modes of transport), can only be defined roughly. In general, there is a particular need for research on bundling effects (in addition to disproportionately higher barrier effects, disproportionately higher land consumption and disproportionately higher requirements for the dimension and number of accompanying structures such as bridges, underpasses, protective walls, maintenance paths, etc. can be assumed).
8.: Overall, the interactions of railway lines and biotope networks have only been marginally investigated, and the need for research is still very high.
(3) Analyses using GIS
1.: A nationwide data set was generated for the railway features "number of tracks", "train frequency", "noise screens", "retaining structures" and "bundling with roads".
2.: Routes with more than two parallel tracks, routes with more than 360 trains per day, noise screens, retaining walls with a height of more than 120 cm and a close bundling with busy roads (> 5,000 cars/day) were identified as particularly strong barriers, resulting in about 6,000 potential conflict areas with habitat networks.
3.: 78 conflict areas concern nationally significant axes of the biotope network and/or large habitat networks. At these sites, the local conditions must be analyzed in detail and, depending on the results, defragmentation measures must be implemented as a matter of priority.
(4) Priority conflict areas
For the priority areas sections between the railway network and the national habitat network, maps have been drawn up showing the local situation.
In just the last few years, behavioral ecologists have begun to address issues in conservation biology. This volume is the first attempt to link these disciplines formally. Here leading researchers explore current topics in conservation biology and discuss how behavioral ecology can contribute to a greater understanding of conservation problems and conservation intervention programs. In each chapter, the authors identify a conservation issue, review the ways it has been addressed, review behavioral ecological data related to it, including their own, evaluate the strengths and weaknesses of the behavioral ecological approach, and put forward specific conservation recommendations. The chapters juxtapose different studies on a wide variety of taxonomic groups. A number of common themes emerge, including the ways in which animal mating systems affect population persistence, the roles of dispersal and inbreeding avoidance for topics such as reserve design and effective population size, the key role of humans in conservation issues, and the importance of baseline data for conservation monitoring and modeling attempts. Each chapter sheds new light on conservation problems, generates innovative avenues of interdisciplinary research, and shows how conservation-minded behavioral ecologists can apply their expertise to some of the most important questions we face today.
We describe an automated system that uses passive integrated transponder (PIT) tags to track movements of animals past specific locations. The system was designed to operate maintenance free for several months, be secure from vandalism and environmental damage, and record the identity, date, and time of passage of animals past a 2.4-m wide area. We used the system to monitor effectively the movements of 172 desert tortoises (Gopherus agassizii) through 2 storm drain culverts that pass beneath a state highway in the Mojave Desert, California. Four tortoises entered or passed through the culverts on 60 occasions. The system can be easily adapted to other species.
The Dutch Second Transport Structure Plan (Ministry of Transport 1990) is an example of an approach to integrate environmental aspects into a policy document for which an environmental impact assessment was not compulsory.
Both common black-hawks Buteogallus anthracinus and crocodiles Crocodylus acutus preyed on adult herons in Panama. Solitary herons were at greater risk than flocked foragers. White (immature) little blue herons Egretta caerula were attacked more frequently by hawks than were the blue adults of their species. Dark herons gave more alarms than white herons. Although flock size decreased in years of heavy predation and after attacks, mixed-flock composition remained the same. When flocks re-formed after hawk attacks, their members showed decreased foraging rates and increased interindividual distances. After repeated attacks, herons foraged in poorer habitats, under unfavourable climatic conditions, and under thermoregulatory stress. Results suggest that predation could be a potent force in maintaining color dimorphism in ardeids.-from Author
Road reserves provide habitat for wildlife. Roadside vegetation has greatest value as a wildlife habitat when it comprises remnant or regenerated strips of indigenous vegetation. Road, roadside habitats and the aerial space above roads can facilitate the movement of animals along the direction of the road reserve. Road reserves can act as a filter or barrier to the movements of wildlife through the landscape, thus dividing and isolating populations to varying extents. Roads are a source of mortality for wildlife. For some species, particularly those that are large, rare, or are regularly brought into contact with busy roads, road-kills can have a significant effect on conservation status. Road systems are a source of biotic and abiotic effects on the surrounding landscape. -from Author