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The fencing of protected areas is increasing worldwide. However, the implementation of fences for conservation has outpaced scientific assessment of their effectiveness, non-target impacts, and long-term costs. We assessed landscape predictors of fence crossing sites and employed camera traps over a one-year period to investigate wildlife responses to a conservation fence around Lake Nakuru National Park, Kenya. Specifically, we measured the impact of the fence on wild mammal movement, and the temporal impacts of fence maintenance on wildlife crossings and behavior. Cameras captured more than 65,000 detections of animals approaching fences, with 3626 observed crossings over 2818 trap nights at 19 sites. Using these data, we developed a guide to classifying fence-specific mammal behaviors. Thirty-eight wild mammal species approached known weak points in the fence, and 27 species were recorded crossing the fence. No single environmental variable predicted detection or fence crossing points for all species, but seasonality, human activity, habitat visibility, and proximity to an adjacent protected area were each correlated with species-specific crossing locations. Additionally, breaches of repaired fence-crossing locations occurred within days of maintenance. We conclude that popular, ‘one-size-fits-all’, conservation fence designs may be ineffective and costly for restraining movement of many wildlife species. We recommend that those deploying conservation fences start with clearly articulated management goals, that fence maintenance be informed by taxa-specific tendencies to breach fences, and that managers consider the strategic creation of wildlife corridors, overpasses, or ungulate-proof fences to link fenced protected areas with surrounding habitat.

Author(s): McInturff, A; Xu, W; Wilkinson, CE; Dejid, N; Brashares, JS | Abstract: Investigations of the links between human infrastructure and ecological change have provided eye-opening insights into humanity's environmental impacts and contributed to global environmental policies. Fences are globally ubiquitous, yet they are often omitted from discussions of anthropogenic impacts. In the present article, we address this gap through a systematic literature review on the ecological effects of fences. Our overview provides five major takeaways: 1) an operational definition of fencing to structure future research, 2) an estimate of fence densities in the western United States to emphasize the challenges of accounting for fences in human-footprint mapping, 3) a framework exhibiting the ecological winners and losers that fences produce, 4) a typology of fence effects across ecological scales to guide research, and 5) a summary of research trends and biases that suggest that fence effects have been underestimated. Through highlighting past research and offering frameworks for the future, we aim with this work to formalize the nascent field of fence ecology.

Author(s): Jensen, Alex J.; Perrine, John D.; Siepel, Nancy; Robertson, Morgan | Abstract: Highways can fragment habitat and be a significant mortality source for mammals. Wildlife exclusion fencing has been shown to reduce wildlife-vehicle collisions, but can also prevent animals from escaping the highway corridor if they enter at access roads or at fence ends. Earthen escape ramps, or “jumpouts,” have been proposed as a possible solution but remain relatively untested. From 2012-2014, we used wildlife cameras to continuously document wildlife use of four jumpout ramps constructed as part of a 2.5-mile wildlife exclusion fence project along Highway 101 near San Luis Obispo, California. Mule deer occasionally used the jumpouts, but quantifying the rate of utilization was confounded by repeated visits by the same individuals. Male and female deer appeared to have different responses to the jumpouts, which warrants deeper investigation using additional data collected from further monitoring through mid-2017. The longer dataset will also better document how individual deer learn to use the jumpouts. Fenced highways can also reduce connectivity unless there is sufficient use of crossing structures. We documented mountain lion, bobcat, black bear, and mule deer used culverts and underpasses in and adjacent to the wildlife fence zone from 2012-2014. Mule deer used the large underpasses almost exclusively, and rarely if ever used culverts. Bear used a wider variety of structures, and bobcats were detected at almost every site and at a higher rate than the other taxa. Mountain lion detections were quite rare, likely due to lower population density in the study area. We propose a deeper multivariate analysis of the factors influencing these species’ use of culverts including culvert dimensionality, nearby habitat, and proximity to cover, based on an expanded dataset of up to five years of continual monitoring at certain sites. The goal of these analyses is to provide information that will help reduce wildlife-vehicle collisions while facilitating regional wildlife connectivity.

Context Roads are a pernicious form of habitat loss for many wildlife populations because their effects often extend far beyond the roads themselves, giving rise to reduced wildlife abundance in road-effect zones. Quantifying the extent of road-effect zones more accurately portrays their impact on populations and the true extent to which habitat is lost for many species. Aim The purpose of the present study was to evaluate ways of determining the extent of road-effect zones for a model study species to better quantify the effect of roads on habitat loss. Methods We conducted road-side surveys for signs of Mojave desert tortoises (Gopherus agassizii) 0, 200, 400, 800 and 1600 m from county roads and interstates, two of the most common road types in critical habitat of this threatened species. Using data from these road-side surveys, we estimated the extent of road-effect zones using piecewise regression and modified von Bertalanffy models. Key results We found reduced abundances of tortoise sign along both county roads and interstates. Reductions extended farther from the large, high-traffic interstate than from the smaller, lower-traffic county roads (306 m versus 230 m). The increase in the abundance of tortoise signs with distance from roads approximated a negative exponential curve. Conclusions Interstate and county roads both contribute to habitat loss in road-side areas by making these habitats unsuitable to desert tortoises, presumably by removing animals via mortality from collisions with vehicles. Larger roads with greater traffic have more extensive effects. Implications Roadside mitigation fencing has been proposed as one way to reduce mortality of desert tortoises and to reclaim habitat by allowing tortoises to recolonise currently depauperate road-effect zones. Immediate mortality is more likely to be prevented by fencing county roads where tortoises occur closer to roads and are more likely to be struck by vehicles and killed. However, fencing interstate should yield more reclaimed habitat than that obtained from fencing county roads. Managers must consider balancing these goals along with other concerns when deciding where to place roadside fencing.

© 2015, © The Author(s) 2015. Few scientific experiments have influenced more land than one conducted in the Wallowa Mountains of eastern Oregon by the US Department of Agriculture’s Bureau of Plant Industry and US Forest Service in 1907–1909. Four square miles of land were enclosed with a “coyote-proof fence,” guarded by a hunter, and stocked with an untended band of sheep. Data were collected on vegetation and sheep performance inside and outside the fence, and two years later success was declared. By 1910, the Forest Service had wrested range research from the Bureau of Plant Industry, subordinating the emerging field to timber production and fire suppression for decades to come. The young scientist who conducted the experiment, James Jardine, was promoted to Inspector of Grazing for the fledgling Forest Service, while his Wallowa collaborator, Arthur Sampson, went on to become “the father” of range science. The model of range management that they pioneered was applied across the US West and, later, on many rangelands in the developing world. Fencing and predator control are now generally viewed as unrelated management practices, but in the Forest Service model they were intimately connected. A critical physical geography of the Wallowa experiment reveals that the institutional context in which it occurred was more important than the findings themselves, and that although the results appeared to be scientifically rigorous and ecological, the methods were weak and the real criteria for “success” were economic. The high costs of fencing could be justified only if they were offset by a reduction in labor costs for herders. But without herders to guard the livestock, predators would have to be eliminated. Enormous public subsidies were required to implement the model, which continues to affect rangelands around the world.

Author(s): Atwill, Edward R.; Jay-Russell, Michele; Li, Xunde; Vivas, Eduardo; Kilonzo, Christopher; Mandrell, Robert | Abstract: Outbreaks of foodborne illness associated with the consumption of leafy green produce from California and across the United States have heightened the need to identify vertebrate sources of these microbial hazards. Concern has focused on wildlife species that have direct access to the produce production environment and irrigation water supplies. Recent fecal surveys of California wildlife, feral animals, and livestock and companion animals are allowing regulators to compare the food safety risks of such pathogens as E. coli O157:H7 and Salmonella from these various animal species. In order to make valid food safety risk comparisons between wildlife, livestock, and companion animals, a variety of methodological and epidemiological issues need to be addressed in order to avoid substantial biases. For example, the amount of feces tested per animal can vary up to a 1000-fold, substantially biasing the probability of testing positive for large fecal contributors (e.g., cattle) compared to smaller wildlife (e.g., deer mice). Many wildlife species intrude and forage as a group in fields of produce, which can lead to in-field defecation, substantially, elevating the risk of microbial contamination compared to many larger animal species that do not have direct access to produce fields due to fencing. This paper highlights the technical challenges of making valid quantitative comparisons of microbial food safety risks from wildlife compared to other domestic animals.

Author(s): Statham, Helen L.; Statham, Mick; Dawson, John K. | Abstract: Compound 1080 (sodium monofluoroacetate) has been used in Tasmania for control of introduced rabbits since the early 1950s and for the native Bennett’s wallaby, Tasmanian pademelon, and brushtail possum for almost as long. Recently, public pressure has resulted in a target to phase out the use of 1080 by 2015. In 2005, the Australian and Tasmanian Governments announced funding for a program to assist in the development of alternatives to 1080. Following an initial independent review in 2006, research and demonstrations focussed on fencing and barriers; shooting, trapping and behavioural research; alternative toxins and delivery mechanisms; repellents; and damage / control relationships. The most positive outcomes from the program were increased understanding of the complexity of the Tasmanian browsing damage problem and the need to measure and address the damage, rather than count the numbers of animals culled. For those agricultural producers who had used it, wallaby-proof fencing was thought to be the most effective long-term control option, despite the increased costs of materials and maintenance. Fencing is not suitable for all situations, including most forest production areas; it is not a stand-alone control option, as it must be accompanied by culling at construction and over time. Shooting is the second-most-important method of control, and there is scope for improvements in effectiveness through better practices and equipment. Trapping can be useful in some areas but it is expensive, and current traps will not catch Bennett’s wallabies. Repellents have not proven to be effective, and further developmental work is required before Feratox® can be recommended for safe use in Tasmania.

Author(s): Ellis, Tracy; Sartain, Autumn; Miller, Ryan; Wilen, Cheryl; Salmon, Terrell P. | Abstract: Cottontail rabbits are a serious problem in Southern California. Of particular concern is the damage they do to ornamental plant and tree nurseries. Rabbit browsing reduces plant quality, kills containerized plants, and damages irrigation systems. Although anticoagulant baiting for cottontail rabbits is legal in California, growers should also consider multiple integrated tactics for rabbit damage control. This project employed GPS mapping technology to locate the occurrence of rabbit damage and correlate it with irrigation type, container, planting density, canopy width, and canopy height. GPS was also used to monitor the impact of experimental strategies to reduce rabbit damage. Strategies to reduce rabbit damage included the use of protective covers on irrigation tubing, exclusionary fencing, and trapping. Radiotelemetry was used to confirm the location of suspected rabbit harborages within the nursery. GPS results indicate that 1.27 to 1.9-cm (½ to ¾-in)-diameter irrigation line covers were effective in reducing rabbit damage to the irrigation system. Exclusionary fencing using erosion-control silt fencing acted as an excellent temporary barrier to protect individual growing areas and groups of planting beds, but it was found to be impractical for many nursery situations. Rabbit catch rates increased when traps were used in conjunction with drift fences. General tactics recommended to container nurseries based on these study results include: protecting and modifying irrigation systems, use of exclusionary fencing, trapping in conjunction with drift fencing, and modifying known rabbit harborages where possible.

Author(s): Jacob, Jens; Brown, Peter R.; Aplin, Ken P.; Singleton, Grant R. | Abstract: About 70% of the current energy intake of the human population in southeast Asia is met by rice. Rats, especially the ricefield rat, Rattus argentiventer, cause significant pre- and post-harvest losses in rice-based agro-ecosystems of southeast Asia and therefore require appropriate management. Current management practices focus on culling animals when populations are high and after significant damage has already occurred. The use of legal and illegal poisons poses a considerable threat to non-target species and humans. This is of particular concern in regions where rats are often consumed by humans to provide an important protein supplement to their diet. During the last seven years, CSIRO’s rodent research group has tested and refined several methods aimed at decreasing pre-harvest rodent damage in cooperation with the Indonesian Research Institute for Rice and the Vietnamese National Institute for Plant Protection. These methods include exclusion of rats by fencing and physical control by trap-barrier systems with lure crops. The effects of these technologies were investigated regarding the regulation of rat numbers (physical control), damage (exclusion, physical control) and yield (physical control). The results are promising, indicating yield increase, of up to 20% in some cases. Integration of these methods with improved field sanitation, crop synchronisation and more efficient timing of other physical methods of control should result in pronounced increases in yield and improved cost effectiveness. Our approach is contingent on a strong understanding of the ecology of specific rodent pests. Measures of success besides decrease in rat numbers and damage are an increase in farmers’ net income through yield increase and a decrease in the use of chemicals. Pros and cons of these methods in different economic and cultural environments are discussed.

Author(s): Shuler, Jim | Abstract: Northeastern California contains several extensive areas of natural and man-made wetland and marsh type habitats. These areas were void of muskrat (Ondatra zibethicus) until the early 1930s when deliberate introductions were made. Once a valuable renewable resource before the sharp decline in pelt prices and strict regulations on trapping, the muskrat has become a nuisance pest species for resource managers. Muskrats have caused extensive damage to water delivery systems, levees, dikes, stream and river banks. Other damage includes impacts on pasture, crops, livestock, property, fencing, fisheries, endangered species, and human health and safety. This paper will look at the types of damage caused by the muskrat and some of the management approaches being taken to reduce or alleviate this damage.

Author(s): Fleming, Peter J. S. | Abstract: Dingoes and other wild dogs cause substantial damage and control expense in many Australian environments. The main methods of control are exclusion fencing, poisoning with 1080, and trapping. Strategies to mitigate livestock predation by wild dogs include; enterprise substitution, the reduction of wild dog populations, and baited buffer zones between wild dog country and sheep country. Damage functions show significant positive relationships between density indices and the losses caused by predation for both sheep and cattle enterprises. However, descriptive and explanatory models fitted the data poorly. A strategic approach to the management of wild dogs that aims to reduce predation on livestock while allowing the conservation of wild living dingoes is also outlined.

Author(s): Connolly, Guy; Wagner, Bruce | Abstract: The USDA National Agricultural Statistics Service (NASS) surveyed U.S. sheep producers to determine the kinds of non-lethal (NL) predator control measures they used in 1994. An analysis of responses from 8,451 sheep producers showed that 34% of the nation’s sheep producers used fencing, 25% used husbandry, 20% used guard animals, 4% used frightening tactics, 0.3% used aversion, and 3% used other methods. Because NL methods tended to be used more in large sheep operations than on small farms, the percentages of sheep protected by each NL control method were higher than the percentages of sheep producers using the method. Approximately 33% of all sheep in the U.S. were protected by fencing, 40% by husbandry, 39% by guard animals, 12% by frightening tactics, 2% by aversion, and 5% by other methods. Overall, 55% of U.S. sheep producers used one or more NL predator control methods in 1974, and 70% of the nation’s sheep were protected by one or more NL methods.