This study proposes an alternative to the current use of the “openness ratio” by investigating the contribution of the acoustical and visual proprerties as a result of structure shape and size to its effectiveness for deer. Reed et al. (1975) coined the term “openness” to describe and measure a concept that mule deer (Odocoileus hemionus) prefer crossing structures with a clear view of the horizon. Since then, the concept has been extrapolated far beyond Reed’s use, for all shapes of underpasses and for many species of animals, most often with no definition beyond a simplistic height x width/length. Other problems with the current use of the concept are the inconsistent use of the units (English vs metric), different terms (ratio, index or simply openness), measurements at different points on a non-square underpass, lack of differentiation between the value of height vs width, and lack of well-designed experimental studies controlling for this variable. Yet biologists intuitively know that ungulates prefer structures with good visibility, and several studies support this even without a means to clearly differentiate the contribution of openness components. This study looks at the way that different shapes and sizes of underpasses contribute to the components of an open feeling in terms of the predator avoidance adaptations of white-tailed deer (Odocoileus virginianus). Underpass shape, size and materials determine the acoustical signature of noises resonating within a structure. For example, an arch shape within the sizes often used for wildlife crossing structures will focus sound in the approximate location of a deer’s head. As underpass size increases, resonance diminishes. Underpass length deter¬mines the amount of total light and the perception of distance to the end of the structure. White-tailed deer perceive danger through hearing, vision and smell. Their use of hearing is impaired if sounds resonating from the interior of an underpass are unknown to them and mask other normal sounds, thus causing fright and possible flight. White-tailed deer perceive movement along a horizontal plane better than focused detail, and their depth perception is lower than animals with eyes facing forward. Their vision in low light conditions is far better than humans. These factors taken together can be used to redefine the Openness concept into its important components. We propose that Openness be comprised of the following four measures. 1) Aspect Ratio measures the relationship between a structure’s length and height, measured at the approximate height of a deer’s head, or 1 meter. This measure considers the greater importance of horizontal visibility for predator detection from an ungulate’s perspective. 2) Cross-sectional Area measures the area above a horizontal line at a 1 meter. This measure takes into account that structures of varying shape produce different perceptions of openness. 3) Brightness measures the perception of distance that varies with the length of a structure. This measure takes into account the perception of apparent distance to safety and flight distance. 4) Presence of a Ledge indicates presence or absence of a horizontal ledge whose surface is not visible from an animal inside the structure. This indicator considers the intimidating effect of a possible predator attack position on the willingness of deer to pass through an enclosed structure. Thresholds for these components will be proposed as alternative measures to the current use of the “Openness Ratio” for highway crossing structures intended for white-tailed deer, and suggested as further study for other ungulates as well.
Many highways wind their way through excellent wildlife habitat. Florida’s highways slice through rare black bear habitat. Alaska struggles with moose-vehicle collisions. Grizzly bears in the northern Rockies are killed on highways or avoid crossing them, limiting them to smaller areas. Solutions are available, but the information is widely scattered. The Wildlife Crossings Toolkit gathers information in one location on proven solutions and lessons learned. Who can use the toolkit? Professional wildlife biologists, engineers, and transportation planners can use the toolkit to work together to create innovative solutions for wildlife-friendly highways and railways. Features: 1. Case Histories • Fully searchable database of case histories • Highlights projects from around the world • Provides examples of solutions used in planning or retrofitting to prevent highway-caused impacts to wildlife • Demonstrates collaboration of engineers and biologists • Includes sections on alternative approaches and suggested modifications • Includes engineered drawings and photos 2. Resources • Summary articles by experts on wildlife habitat connectivity, highway impacts, and solutions • Extensive illustrated glossary to facilitate a common lexicon between engineers and biologists • Links to other pertinent resources including ICOET proceedings and international information 3. Training and Workshops The USDA Forest Service has developed associated training sessions to complement the information in the Wildlife Crossings Toolkit.
The need for a comprehensive (yet concise) training course on the basics of highway and wildlife interactions has become more apparent as more transportation engineers and wildlife biologists are faced with demands to consider wildlife mortality and connectivity issues and to incorporate wildlife crossing structures in highway projects. The USDA Forest Service has developed an interagency, interdisciplinary two-day training session that walks engineers and biologists through the basics of habitat connectivity, impacts to wildlife from highways, effective mitigation measures, funding sources, and law and policy related to highway projects. This course, Innovative Approaches to Wildlife and Highway Interactions, has been designed to be taught by a wildlife biologist and a transportation engineer, with a target audience of mixed, mid-level professionals who are planning highway projects of various types. The course was designed to integrate disciplines so that the challenging situations we face in highway projects can be innovatively solved and networking between agencies and disciplines is facilitated. The course is modular and based on the Wildlife Crossings Toolkit (http://www.wildlifecrossings.info), also developed by the USDA Forest Service, and current scientific works. Eight sessions across the country have been completed since course development, with participants from eight state DOT’s, FHWA, NGO’s, state fish and wildlife agencies, FWS, and three federal resource agencies. Departments of transportation and resource agencies are welcome to host training sessions across the country with these training materials and instructors. Funding for the course development was provided by the Coordinated Transportation Improvement Project fund, an interagency pooled fund.
Highway 89 stretches from north to south across California, through Sierra County from Sierraville to Truckee. The highway bisects an important portion of the Loyalton-Truckee deer herd, as well as important habitat for forest carnivores, amphibians and other wildlife on the Tahoe National Forest. By 2002, several groups were working independently to investigate different aspects of animal-vehicle collisions along the highway. These independent efforts were the: • Continuation of a 20-plus year collection of carcass information on SR 89 by Caltrans • Investigation of the effects of roadside forest thinning on roadkill by University of California-Davis Agricultural Extension Service • Investigation of radio-collared deer movements across the highway by California Department of Fish and Game • Applications to study the effects of deicing salt on deer attraction by the Sierra County Fish and Game Commission • Long-term connectivity and habitat planning by the USDA Forest Service These groups and their efforts were brought together in 2002 when they were catalyzed by the USDA Forest Service into a stewardship team to work together collaboratively to improve the high wildlife mortality and increasing habitat fragmentation on the highway. Most efforts to mitigate similar highway impacts are precipitated by a department of transportation project. In the case of SR 89, no improvement for SR 89 was planned by Caltrans. Thus, instead of responding to a tight project timeline and budget, the Stewardship Team was able to proactively develop a connectivity and mitigation plan using Caltrans’ large roadkill database, the Forest Service’s large-scale habitat maps, and the other cooperators’ information. In 2004, Caltrans independently funded a $720,000 wildlife-mitigation project on SR 89, thus allowing the Stewardship Team to use its connectivity plan as the basis for decisions on prioritizing wildlife crossing structures. The Stewardship Team is using the connectivity plan to propose further mitigation to Caltrans after the initial structure is constructed. The Stewardship Team has also secured grant funding to involve the local high school in a long-term investigation of how habitat connectivity and highway impacts are related. This presentation traces the efforts of the Stewardship Team member agencies and how their diverse contributions, once coordinated, supported a grass-roots effort to mitigate highway impacts on SR 89.
Transportation planners occasionally notice a curious lack of consistency and communication between hydrologists, fisheries biologists and wildlife biologists regarding passages designed for their respective specialties. Several substantial differences in treatments between aquatic and terrestrial passages at highways masks the majority of similarities. At one end of the continuum, aquatics passages can be characterized by a total containment within a watercourse, with no need for modification of the shape or size of water conveyance structure as long as the structure maintains hydrological functionality. At the opposite end of the continuum terrestrial passages can be intentionally designed to avoid water conveyance entirely. Between these two extremes lie similarities in the need for functional streamcourses that allow passage for all age classes of fish and wildlife, as well as high water events. Our paper discusses the common mistakes made when considering only one passage category and suggests remedies designed to integrate the needs of terrestrial and aquatic organism passages. Our paper also discusses the professional basis for the occasional forgetfulness in dealing with other disciplines using lessons learned on this topic by the USDA Forest Service as an interdisciplinary land management agency.
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