Wildlife and Roads

2.2.1

2.2.1 Fast Track Overview of Placement of Crossings

• 2.2.1.1 Coarse Scale
• 2.2.1.2 Fine Scale

The following URLs provide important information that can be informative concerning the need for and the placement of mitigation structures. We suggest a coarse scale approach to frame the problem and a finer scale follow-up to adjust the mitigation to the specific sites. This step is intended as an initial minimal-time precursor to a more in-depth approach which follows in steps 2.2.2 - 2.2.4.

2.2.1.1 Coarse Scale

State Wildlife Action Plans for priority species locations and important habitat

Connectivity analyses

Connectivity analyses identify critical wildlife linkage areas and areas where roads bisect them. They can be developed through consensus building meetings or GIS modeling, or a combination of both. Connectivity analyses are sometimes called Green Infrastructure, particularly in the eastern states, as shown below. *Note: It is critical that if a connectivity analysis exists, it be included at this stage of planning. If there is none, expert opinion from knowledgeable wildlife ecologists may be the second best source about connectivity corridors.

The Conservation Fund's Green Infrastructure Map

This site shows Strategic Conservation Projects in every region of the United States where local people have come together through consensus building to delineate areas for conservation and areas for development. Most plans include maps of sensitive and protected or to be protected areas.

The Nature Conservancy's Page for Ecoregional Assessments

This site provides a vision for conservation priorities for ecosystems, natural communities and species representative of an ecoregion, and establish priorities for resource allocation. There are a limited number of these assessments.

The sis site provides a portal called Gap Serve to help users identify land cover and potential species present across the United States through land cover and species distribution maps.

State Natural Heritage Database or Provincial Conservation Data Centre database
State Natural Heritage Programs
State and Provincial Heritage Programs (scroll to page 5 for Canadian provinces)

Wetlands Data Geobase

California DOT — Caltrans Fish Passage Designs for Road Crossings

State Natural Resource Agency Links

These coarse scale resources provide a starting point in the planning process to identify general zones of conflict where wildlife occur near a road or rail way. These are the areas to concentrate efforts of mitigation placement or avoidance measures.

Back to Top

2.2.1.2 Finer Scale

The following internet sites provide sources of information that will be helpful in identifying potential locations of mitigation structures. This part of the analysis takes additional time to specifically address where crossings are needed for targeted species. Each of the following suggestions for the finer scale approach is hyperlinked to sections on this site with more detail.

Topographic maps for Identification of Movement Corridors (e.g., low lying areas and ridges, where wildlife may prefer to move) (link to information below).
National Map Viewer

Data Sources of Landownership
To identify areas of wildlife movement with different levels of protection (link to information below).

Species' Needs for Movement
This broad category includes scientific approaches to understanding where animals are moving over the landscape in relation to roads. This section includes placement of invertebrate (aquatic and terrestrial) crossings, amphibian and aquatic reptile crossings, terrestrial reptile crossings, and more ground dwelling birds and mammal crossings. Methods described include: review of past studies and data, location of wetlands near roadways, transect approaches to tracks, pellets, and species locations, cameras, snow and sand bed tracking, and radio and GPS collars tracking. These areas of interest are briefly described and then hyper-linked to the specific section (link to information below).

Wildlife-Vehicle Collisions and Road Kill Carcasses Data
Data on wildlife vehicle collisions and the resulting carcasses can be mapped, leading to a first step in the identification of hot spot areas in need of mitigation. Cautionary note, these areas are general areas where wildlife are not successfully crossing the road. These may not be linkage zones but rather killing zones. If mitigation is placed solely based on these locations, driver safety may be enhanced but wildlife linkages may not. Additional information about where animals first approach the road right of way is needed to assess the presence of movement corridors. Crash data from nine states are available on the Highway Safety Information System (HSIS) site; check this URL to see if you may be able to easily and quickly access your state's crash data: http://www.hsisinfo.org/. Otherwise, you may need to check with the Safety Division/Department of your state Department of Transportation (link to information below).

Allometric Scaling
Knowledge of home range sizes and dispersal distances can help identify the species' movement dynamics and the spacing of crossings. This method uses the scaling properties of species movement to determine the maximum distance between crossings in order to assure permeability of the area for the target species. Most species have surprisingly short daily movement distances, suggesting relative short inter-crossing spacing. See: Bissonette, J.A., and W. Adair. 2007. Restoring habitat permeability to roaded landscapes with isometrically-scaled wildlife crossings. Biological Conservation, 141:482-488 (link to information below).

See the site for details OR, click here for article: More information is given below.

Predictive models
These models have been created with GIS and modeling exercises to help determine where certain species have a tendency to cross roadways, thus helping to determine preferred passage locations (link to information below).

Engineering and Geologic Constraints
Wildlife crossing placement depends on the engineering feasibility of an area. If the soils are unstable, if there are water courses and wetlands to consider, if there are human concerns, then these need to be considered in wildlife crossing placement. (link to information below).

2.2.2

2.2.2 Review of Literature on Placement of Passages

The next section covers many of the areas of consideration when deciding where wildlife prefers to cross roads which are not covered in detail in the general text of these steps.

Wildlife crossings should be considered in the context of the landscape they are placed. Protection and often restoration of wildlife movement areas may be required to ensure that the habitat supporting the wildlife using the crossings is not rendered unusable by development and that the agency investment in wildlife crossings are maximized to the extent possible and retained over time.

Back to Top

2.2.2.1 Literature Review

Click on a title to view annotated notes

Back to Top

2.2.3

2.2.3 In-Depth Coarse Scale Approach

This section is a more detailed approach to determining wildlife passage placement through both a coarse scale and fine scale approach. The below sections include the steps that were presented in the Fast Track approach, as well as much more additional information.

Wildlife Presence and Movement Patterns

Wildlife presence can first be defined on a fast track coarse scale by consulting existing resources, listed above in Step 2.2.2 and also below. These data sources offer maps, both hard copy and electronic, where planning efforts can be directed in order to fairly rapidly perform a cursory analysis of what is known to be in an area, where the critical habitat is, where the protected lands lie in relation to the road/rail way, and topographic concerns.

• State Wildlife Action Plans for priority species locations and important habitat
  
• Connectivity analyses
  Connectivity analyses identify critical wildlife linkage areas and areas where roads bisect them. They can be developed through consensus building meetings or GIS modeling, or a combination of both. Connectivity analyses are sometimes called Green Infrastructure, particularly in the eastern states, as shown below. To review connectivity analyses, click here to visit step 1.2.
  *Note: It is critical that if a connectivity analysis exists, it be included at this stage of planning. If there is none, expert opinion from knowledgeable wildlife ecologists may be the second best source about connectivity corridors.
• The Conservation Fund's Green Infrastructure Map
  This site shows Strategic Conservation Projects in every region of the United States where local people have come together through consensus building to delineate areas for conservation and areas for development. Most plans include maps of sensitive and protected or to be protected areas.
• The Nature Conservancy's Page for Ecoregional Assessments
  provides a vision for conservation priorities for ecosystems, natural communities and species representative of an ecoregion, and establish priorities for resource allocation. There are a limited number of these assessements.
  
• The sis site provides a portal called Gap Serve to help users identify land cover and potential species present across the United States through land cover and species distribution maps.
  
• State Natural Heritage Database or Provincial Conservation Data Centre database
  State Natural Heritage Programs
  State and Provincial Heritage Programs (scroll to page 5 for Canadian provinces)
• National Wetlands Inventory GIS database
  
• California DOT   Caltrans Fish Passage Designs for Road Crossings
• Discussions with state/provincial and federal agency wildlife biologists knowledgeable about local conditions (url to all state wildlife agency numbers)
  

These coarse scale resources can inform the planning process with general zones of conflict where wildlife of concern such as sensitive species and ungulate herds occur near a road or rail way. These are the most obvious areas to concentrate efforts for mitigation placement. Wildlife presence and movement in an area can begin to be understood during a field site visit. Animal paths, droppings, dens and nests, and suitable microhabitat in an area can begin to show high use and critical areas for wildlife near a road project.

Landscape Linkages

Landscape linkages can be defined as areas where humans believe wildlife are moving over large distances (measured typically in miles or kilometers). These areas are typically identified in either a workshop of stakeholders built on consensus of wildlife movement areas, a GIS based model, or a combination of the two processes.

Figure 2.2.1 Attendees of the I-70 Wildlife Linkages Workshop in Utah, identifying potential places for wildlife passage. May 2007. Photo Credit: P. Cramer.

Back to Top

2.2.4

2.2.4 In-Depth Fine Scale Approach

Topography, Land Use, and Land Ownership

Often topography, land use, and ownership limit the placement of passages. Understanding the lay of the land and ownership it is a necessary preliminary step in passage placement. The following list of resources is taken from step 2.2.1, Fast Track Fine Scale Analyses

• Topographic maps for Identification of Movement Corridors (e.g., low lying areas and ridges, where wildlife may prefer to move).
  National Map Viewer
• Data Sources of Landownership
  To identify areas of wildlife movement with different levels of protection. This may involve using county and other local sources for land owner information, or a more coarse scale analysis through above mapping tools on line
• Species' Needs for Movement
  This broad category includes scientific approaches to understanding where animals are moving over the landscape in relation to roads. This section includes placement of invertebrate (aquatic and terrestrial) crossings, amphibian and aquatic reptile crossings, terrestrial reptile crossings, and more ground dwelling birds and mammal crossings. Methods described include: review of past studies and data, location of wetlands near roadways, transect approaches to tracks, pellets, and species locations, cameras, snow and sand bed tracking, and radio and GPS collars tracking. These areas of interest are briefly described and then hyper-linked to the specific section (link to information below).
  
• Wildlife-Vehicle Collisions and Road Kill Carcasses Data
  Data on wildlife vehicle collisions and the resulting carcasses can be mapped, leading to a first step in the identification of hot spot areas in need of mitigation. Cautionary note, these areas are general areas where wildlife are not successfully crossing the road. These may not be linkage zones but rather killing zones. If mitigation is placed solely based on these locations, driver safety may be enhanced but wildlife linkages may not. Additional information about where animals first approach the road right of way is needed to assess the presence of movement corridors. Crash data from nine states are available on the Highway Safety Information System (HSIS) site; check this url to see if you may be able to easily and quickly access your state's crash data: http://www.hsisinfo.org/. Otherwise, you may need to check with the Safety Division/Department of your state Department of Transportation (link to information below).
  
• Allometric Scaling
  Knowledge of home range sizes and dispersal distances can help identify the species' movement dynamics and the spacing of crossings. This method uses the scaling properties of species movement to determine the maximum distance between crossings in order to assure permeability of the area for the target species. Most species have surprisingly short daily movement distances, suggesting relative short inter-crossing spacing. See: Bissonette, J.A., Adair, W., Restoring habitat permeability to roaded landscapes with isometrically-scaled wildlife crossings ..., Biol. Conserv. (2007), doi:10.1016/j.biocon.2007.10.019 for details (link to information below).
• Predictive models
  These models have been created with GIS and modeling exercises to help determine where certain species have a tendency to cross roadways, thus helping to determine preferred passage locations (link to information below).
• Engineering and Geologic Constraints
  Wildlife crossing placement depends on the engineering feasibility of an area. If the soils are unstable, if there are water courses and wetlands to consider, if there are human concerns, then these need to be considered in wildlife crossing placement (link to information below).

Species' Needs for Movement and Field Research

Wildlife of different sizes and mobilities need to move across roaded areas, and an assessment of the local and migratory species that could potentially be moving across a roaded area or project should entail an analysis of the different species. This includes examining the logical hazardous wildlife such as deer, moose, and elk, to the smaller amphibians, reptiles, and insects. Even insects that are endangered or economically vital to pollinating crops have been addressed by mitigation in transportation projects across the United States and the world. For example, the United Kingdom has published a butterfly and roads handbook to help mitigate roads for these insects, and in the U.S. there have been efforts to protect pollinating bees (see below).

In the effort to correctly place wildlife crossings, on-the- ground field research or site visits to an area are essential. Barnum (2003) studied wildlife tracks in the snow in Colorado to determine areas where wildlife most often crossed the roadway, and found these were not the same as areas of highest wildlife-vehicle collisions. Alexander and co-authors (1999, 2004) snow-tracked wildlife in Alberta and analyzed data in a GIS format and found that species less tolerant of humans such as lynx (Lynx canadensis) and wolf (Canis lupus) were crossing the Trans Canada highway in areas that were not identified for the future wildlife crossings along that highway. It is critical to learn how the target species in a specific area may be moving across the road way. As the road project is being planned, an assessment of wildlife use of the area is possible and valuable. Such an analysis will help inform the placement of mitigation. Placement of wildlife crossing is a very site-specific action. To accurately place a crossing and ensure its success most often requires knowledge of local conditions, the opinion of local biologists, and state or province-wide data available from state-provincial wildlife agencies in site selection decisions. Inclusion of planning for the placement of crossings at early stages in the transportation development process allows for a more rigorous scientific research program that can help insure that passages would have the best chance of succeeding. Monitoring research with the objective of finding where wildlife move in the landscape may entail examination of tracks in snow, sand or track plates, scent stations with track beds, the use of remote cameras (still and video), GIS-based habitat suitability modeling, and radio or Global Positioning System (GPS) telemetry collar monitoring of the populations of concern. These methods are further described below.

Placement of Invertebrate Crossings

Invertebrates have not been traditionally considered in long range plans for transportation, but are becoming increasingly part of environmental considerations mainly due to species with special status, such as those that are endangered. These include aquatic (mussels) and airborne (insects) invertebrates. In the case of freshwater mussels, there are a growing number of transportation projects that accommodate these species. While the vast majority of recent efforts to improve aquatic passage focus on fish species, it is the ability of mussel populations to re-populate their former ranges that is also receiving focus. Jackson (2003) reported that over 70% of the 297 species of freshwater mussels in the U.S. and Canada are either endangered, threatened or of special concern. The adult mussels typical are immobile, but the larvae attach themselves to fish and salamanders that move up and down streams. Several states have mentioned mussel species as a reason to install and improve aquatic passage. The placement of these passages is dependent on identification of specific streams necessary to population persistence and restoration, which is typically within the realm of the federal Fish and Wildlife Agency, and the state wildlife agency biologists, whom should be contacted.

Invertebrates that fly over the land are also being considered in transportation planning and over existing roads. There are areas where endangered species of butterflies attempt to move across the road, from where they hatch to the places where they breed. Areas of potential remediation are typically known by the biologists and conservationists in an area.

Figure 2.2.2. Purple Milkweed butterfly of Taiwan. Photo courtesy of BBC news.

For example, a Taiwanese butterfly, the purple milkweed butterfly, migrates in numbers upwards of over one million over 600 meters of highway in Taiwan. In 2006 three actions were undertaken at the specific site where the majority of butterflies were being killed. One lane of the road was closed to traffic, a protective net was erected over the side of the highway from where the butterflies were approaching, and ultra-violet light was used to encourage butterflies to fly under an elevated section of the road. These actions were done over a short period of days to weeks. See it here.

England has created the Butterfly Handbook which helps describe how to maintain habitat along roadways that help butterflies, and other mitigation methods (link to be activated at a later time).

There are many areas where crop pollinating bees cross roads and highways and are killed in large enough numbers that their low population numbers are affecting crop yields. This can be a very serious problem, if mortality is additive to the general decline currently under way with pollinators across the U.S. Local agricultural experts are aware of this situation and can help to identify areas where reduced speeds and wind deflectance may reduce road mortality of these populations. An excellent example can be found in eastern Washington where local alfalfa seed growers were successful in convincing county officials to reduce speeds along county roads where the alfalfa crops are grown, in an effort to reduce Alkali bee mortality (see picture).

Figure 2.2.3. Alfalfa farmers were successful in a request to have county road speed limits reduced in areas where Alkali bees were crossing the road and pollinating crops, but were becoming vehicle collision causalities. Photo credit: J. Cane.

Amphibians and Reptile Passage Placement

Amphibians and reptiles may need road crossing mitigation in places where they are moving to in relation to breeding and ecological changes such as drought and flooding. Interestingly, while reptiles that live in the water need dry land to lay their eggs, amphibians need to return to water to lay theirs. It is often the roads that lie between wetland in the upland area or between breeding ponds that pose the greatest hazards for these species. A coarse scale analysis should help to define areas of streams, ponds, and lakes within several hundred meters of a road. Amphibians and reptiles typically, but not always, move within several hundred meters of these natural features. If any type of wetland is identified within this zone, it is prudent to learn more about species' movement needs to identify where the salamanders, frogs, snakes, turtles, and alligators may need to move. Passages placed in these areas can be as simple as culverts or pipes.

Scott Jackson of the University of Massachusetts Amherst is a national expert on turtle and salamander crossings. His informative papers on design and placement considerations for amphibian, reptile, and aquatic crossings can be found at: http://www.umass.edu/nrec/onlinedocs.html.

Placement recommendations for sufficient number of passages for these smaller animals may be hard to obtain, since these animals do not typically travel distances greater than a few dozen or hundred meters. A single passage for a population of animals in most situations may be insufficient. Several passages, placed close together appear to be a better solution to achieve permeability for a population; Jackson recommends amphibian and reptile tunnels be no more than 61 meters (200 feet) apart, although some species can travel greater distances (http://www.umass.edu/nrec/pdf_files/herp_tunnels.pdf).

The Paynes Prairie Example

Figure 2.2.4. Paynes Prairie State Preserve, Gainesville, Florida. Herpitle wall is present just behind sign. First culvert is just to the left of the sign. Photo credit: P. Cramer.

A well known system of passages and a barrier wall to prevent access to a highway and provide passage for amphibians and reptiles is the Paynes Prairie Ecopassages in Gainesville, Florida. The Paynes Prairie State Preserve just south of Gainesville in Central Florida has a wet prairie bisected by both a state four lane highway and Interstate 75. Thousands of individual alligators, snakes, turtles, frogs, birds, and mammals were killed along a 2 mile (3.2km) stretch of the state highway each year. A coalition of naturalists and biologists assisted the Florida DOT in designing and installing a wall that prevents the wildlife from getting on to the state highway, and four box culverts in addition to four existing box culverts to assist in terrestrial and aquatic movement of all kinds of animals across the prairie. The wall was a critical component to wildlife passages because it also guided the animals to the crossings. Placement of specific crossings was not a major consideration because over the two mile stretch, there were already 4 box culverts for passage. The additional four new culverts, brought the total passages to eight over the two mile (3.2 km) stretch, for an average of a passage every 1/4 mile or 400 meters. A post-construction study found that the number of road kill carcasses was reduced by over 90% (Dodd et al 2004).

Figure 2.2.5. Paynes Prairie wall and passage. Wall is one meter high above the ground surface, with a 13 cm lip that points backward toward the prairie area so that snakes and other species able to scale the wall find it very difficult to crawl over. Photo credit: P. Cramer.

Figure2.2.6. Alligator using Paynes Prairie box culvert passage. Photo credit: J. Barichivich.

More information on the Paynes Prairie Ecopassages can be found here.

Reptiles that are more terrestrial in nature such as snakes and tortoises have movement needs that are not as easily identified as those tied to wetlands.

Tortoises and more terrestrial reptiles

Identification of more terrestrial reptile movement pathways may involve detailed studies of local movements, due to the tortoise and more terrestrial reptiles' specific habitat requirements. Tracking surveys, radio tracking, and species specific methods are typically used to examine the most precise placement locations for passages. A knowledge of the animals' natural history is also required, in order to understand how the animals move and where they would prefer to go.

Utah's Red Cliff Desert Reserve and Placement of Desert Tortoise Passages: A Reptile Example

In the southwestern corner of Utah lies the Red Cliff Desert Reserve which is approximately 62,000 acres and contains over 38,000 acres of Mojave Desert tortoise habitat. There is a highly threatened population of tortoises on the reserve. The Utah Division of Wildlife Resources worked with Utah Department of Transportation to install tortoise fencing along local, county, and interstate roads that bisect the reserve. These tortoise-proof fences were constructed to prevent tortoises from accessing the roadway and to guide tortoises to existing culverts. Three culverts were installed to specifically facilitate tortoise movement along the Tuacahn Road within the Reserve. For the second phase of tortoise research, which included additional tortoise culvert placement as well as estimates of distribution, density, and abundance, biologists, led by Ann McLuckie of Utah's Division of Wildlife, designed research to help map tortoise distribution and density. Tortoise densities are monitored every other year through a series of random transects throughout the Reserve. The Rand-Between Function in the software program Excel was used to enter the most easting and most westing UTM coordinates of the Reserve. The program selected over 150 random points across the entire Reserve. From those points, 2 km transects were created which are surveyed by a field crew every other year during the spring. The data are combined with maps depicting the natural drainages in the areas where flash floods move through the landscape and which are used during dry times by tortoises. Biologists were able to identify areas including drainages (known as washes) with high tortoise use that were bisected by roads. The three existing culverts are monitored for tortoise use and have proved to be successful in assisting tortoise movement (see Figure 2.2.7). The map below illustrates the placement of the existing crossings. These crossings are over a 0.5 mile (0.8km) span. In this ecosystem, the biologist recommends crossings be placed no more than 1 mile (1.6 km) apart. The distance between crossings depends on the density of animals, the number of washes, and other factors. It was recommended for this area that a culvert be installed for every major wash. Major washes are dry washes that have physical features that clearly indicate a wash - such as greater than 20 degree slope, perennial plants associated with washes, often rocky substrate and water carries runoff during the majority of storm events. Minor washes are just a minor indent on the landscape - one would barely be able to discern them from a map or when looking out across the landscape. Minor washes carry runoff infrequently and only during major storm events.

Figure 2.2.7. Desert tortoise using Red Cliff Desert Reserve tortoise passage, Utah. Photo credit, A. McLuckie.

Figure 2.2.8. Red Cliffs Desert Reserve in Southwestern Utah, outside of St. George, placement of existing desert tortoise crossings along local road. Map/photo credit: A. McLuckie.

A general guideline for placing amphibian and reptile crossings is to use home range distances and placement to inform how expansive and where the daily movements are. For slow moving creatures, it may be prudent to plot weekly movement distances. The critical segment of time to examine is dependent on knowing how long it takes a tortoise to cover its home range. If this time segment is known, than we can better estimate the distance between crossings. See the Allometric Scaling section below. As a general rule, shorter distances between crossings are better than longer distances.

Mammal and Bird Passage Placement

Identifying places along a transportation corridor where wildlife prefer to move takes a knowledge of the species' life history traits (e.g., if they prefer cover or open areas) and the characteristics of local populations. This step depends on data-based knowledge. It is prudent to combine the following methods in order to obtain a better understanding of wildlife movements and needs. The relevant steps involve analyses that seek to identify where animal-vehicle collisions are occurring with larger ungulates, where animals are approaching the road, and how wildlife prefer to move in the landscape near the road. In order to correctly place crossings it is also important to identify natural ecosystems or habitats within 1 kilometer (0.6 miles) of the roadway, to better understand where the species of concern moves for its basic needs. Seasonal movement requirements are important as well. The following methods to place crossings specific to mammals and ground dwelling birds are presented with their benefits, shortcomings, and time constraints.

Mapping road kill or collision sites are recordings of where wildlife is not successfully crossing roads and rails. Hotspots of wildlife mortality on the road are killing zones and may not be where the animals enter the right-of-way, i.e., a linkage zone. If mitigation is placed at hotspot zones, driver safety may be enhanced, but wildlife linkages may not be optimally established across the roads. Data collection methods vary between collision recordings and where wildlife road kill carcasses are collected. They are often inaccurate, typically estimated to the nearest mile marker. Mapping these areas can help to identify the highest priority road areas to concentrate mitigation efforts, state or province-wide. Benefits include a quick assessment of necessary crossing placement areas with available data. Shortcomings include inaccurate data and resulting maps, and a very coarse scale identification of a problem that would be an initial step in a more detailed analysis of the situation. Collision and carcass locations are typically collected only for large ungulates; rarely do they include anything smaller than a deer. Time considerations vary from a cursory mapping procedure that can take less than a week, or one that may take several months depending on if the mile markers are geo-referenced for the state/province. Further details are provided in the next section.

Snow tracking and sand bends placed along the road right of way or in structures wildlife use to cross under the road are an excellent, inexpensive, but often a time consumptive way to determine where wildlife are approaching and attempting to cross the road. If only the locations of where wildlife cross the road, and not where they first entered the road area-right of way are recorded, the study may not adequately represent potential crossing corridors where animals first come onto the highway. The locations where wildlife first approach the Right-of-Way are ecologically the most appropriate places for passages, as these are their preferred approach sites. Once animals enter the road Right-of-Way, they may react to vehicles, or maneuver around barrier rails or median barriers. It is important to know where they approach. Methods for tracking are described in Barnum's, Alexander's, and van Manen's work, above in Literature Review (2.2.1). Snow and sand tracking are also described in: "Evaluation of wildlife crossing structures and fencing on US Highway 93 Evaro to Polson Phase I: Preconstruction data collection and finalization of evaluation plan."

Pellet Counts can be used to detect wildlife presence near a road area. These involve transects near the road that are examined to ascertain the areas where deer, elk, moose, rabbits, and others are spending the most time in the area, indicated by piles of pellets or scat. Scat piles are recorded spatially and over time. Pellet counts may not necessarily indicate where wildlife first enter or approach the road Right-Of-Way.

Precautions on the use of tracks and pellet counts
Habitat usage is an important factor to determine areas where wildlife of interest prefers to approach a road. If the study only examines areas near the road, and does not conduct studies of use distant from the road as Alexander did, a more general understanding of habitat usage may not be possible. If there is a need to identify linkages and to determine what areas wildlife are using in proportion to what is out there, assessing general habitat use will provide important data. Habitat use helps to identify linkages where tracks may not have been identified during a track count. A habitat use analysis of the areas away from the road places landscape and habitat use into context and can be used in conjunction with modeling efforts (see below).

If tracking is conducted in the winter, then only wildlife use of the road area in winter is recorded. If wildlife is killed on roads during the spring or summer, seasonal movements would be an additional important component to understand.

If the number of animals crossing the road via their tracks or visual spotting is not recorded, then one event is treated like a multiple event. The ability to quantify crossings is important if areas are to be prioritized for mitigation.

Studies of animal movement may provide the best data to ascertain what animals are doing in relation to a road or where a future road may be placed. For mammals and birds, GPS and other radio-tracking collar surveys are most helpful to understand what general areas wildlife is using, and where wildlife are crossing roads. Many state DOT's are helping to support general wildlife movement studies which are often conducted in conjunction with state wildlife agencies. An examination of the literature also reveals that the type of home range estimator program used can influence results. A review of several studies is suggested.

The Payson Arizona SR 260 Elk Crossings Study

The Arizona Game and Fish Department has worked in conjunction with the Arizona Department of Transportation to place, design, and monitor 17 wildlife crossings along State Route 260 near Payson, in the Tonto National Forest. Members of the local herd of elk were fitted with radio-GPS collars to learn of the population's and individuals' movements in relation to the road after construction of elk-specific wildlife crossings. Dodd et al. (2006) (scroll to page 534) report specific individual and herd movements in relation to the road, crossings, and fences placed to facilitate elk movement under the roadway. The data obtained helped in the design and placement of crossings and underscored the need for fencing in conjunction with crossings.

The North Carolina US 64 Black Bear Crossings Study

The series of studies under Dr. Frank van Manen of the University of Tennessee, Knoxville is one of the best designed and documented pre and post construction studies of wildlife crossings in North America. The North Carolina DOT built a new portion of US Highway 64 in north-central North Carolina through a wild area with black bear and many other wildlife species. Biologists suspected the road would have lasting effects on the black bear population in the area, and for potential animal-vehicle collisions. North Carolina DOT helped sponsor several studies to see where three new wildlife underpasses should be placed in the new 4 lane highway and its potential population effects. Dr. van Manen directed several studies that examined black bear populations in the area to be affected by the highway, as well as a control area; a study to look at black bear genetics before and after the highway; and the initial study in 1999-2000 to examine where wildlife was moving on the landscape and where the wildlife passages should be placed. The initial 1999 determined areas of highest wildlife use based on surveys of track counts, ditch crossings, and remote cameras. The results were used in conjunction with GIS mapping to determine wildlife travel corridors. Sites for the future crossings were chosen based largely on this study. The ICOET 2001 paper describes the study design and the efforts to study black bear and other wildlife prior to the 2001 building of the new highway. Since completion of the study (and the others described in the paper), the highway and underpasses were completed in 2005, and a second phase of research was begun to determine if the mitigation was successful. As of 2007, the passages have allowed white-tailed deer, black bear, and other wildlife to pass.

Camera recordings of wildlife use of existing structures can assist in seeing where wildlife is moving and what types of structures they use. An analysis of type of existing crossings and landscape variables can help ascertain what factors are important in passage placement. Trail cameras can be mounted along the road Right-Of-Way (the cleared area between the road and accompanying fencing) to determine wildlife approaches and placed inside structures to determine wildlife use. Cameras allow for an in-depth analysis of time of day and year, number, types and gender of animals, and direction of movement. If cameras are placed both near the passage entrance and inside, it is possible to calculate a potential repel rate if animals approach an area and then retreat. Cameras also record human use of potential passages, which is a consideration in placement as well.

Allometric Scaling

In our research we also developed an allometric scaling model based on home range data for specific species. The Median Dispersal Distance (MedDD) of a species as well as its Linear Home Range Distance (LHRD) is calculated its mean home range area size. It is possible to use MedDD (7 * √ Home Range) as the upper bound, and a LHRD (√Home Range) as the lower bound to develop alternative domains of scale for groups of animals to guide the placement and number of wildlife crossings. In other words, these equations can be used along with home range values and dispersal distance values to determine the maximum distance between crossings, for the target species. The analysis in this research found that 70% of all mammals need wildlife crossings placed less than one mile (1.6km) apart. The following is the abstract from the paper: Bissonette, J.A., and W. Adair. 2007. Restoring habitat permeability to roaded landscapes with isometrically-scaled wildlife crossings.

Biological Conservation

Globally, human activities impact from one-third to one-half of the earth's land surface; a major component of development involves the construction of roads. In the US and Europe, road networks fragment normal animal movement patterns, reduce landscape permeability, and increase wildlife-vehicle collisions, often with serious wildlife population and human health consequences. Critically, the placement of wildlife crossing structures to restore landscape connectivity and reduce the number of wildlife-vehicle collisions has been a hit-or-miss proposition with little ecological underpinning, however recent important developments in allometric scaling laws can be used to guide their placement. In this paper, the authors used cluster analysis to develop domains of scale for mammalian species groups having similar vagility and developed metrics that reflect realistic species movement dynamics. They identified six home range area domains; ¾ of 102 species clustered in the three smallest domains. We used HR0.5 to represent a daily movement metric; when individual species movements were plotted against road mile markers, 71.2% of 72 species found in North America were included at distances of 61 mi. The placement of wildlife crossings based on the HR0.5 metric, along with appropriate auxiliary mitigation, will re-establish landscape permeability by facilitating wildlife movement across the roaded landscape and significantly improve road safety by reducing wildlife vehicle collisions.

Figure 2.2.9. This graph demonstrates the predominance of small (less than 70 hectares) home range sizes of mammals. From: Bissonette, J.A., and W. Adair. 2007. Restoring habitat permeability to roaded landscapes with isometrically-scaled wildlife crossings. Biological Conservation. doi:10.1016/j.biocon.2007.10.019 for details.

Figure 2.2.10. Two wildlife passage bridges under Arizona's SR 260 on the Tonto National Forest. These passages are within a quarter of a mile (1.6km) apart. They allow elk to access the wet meadow at the bottom of the picture. Photo courtesy of Arizona Game and Fish.

Wildlife-Vehicle Collision and Road Kill Carcass Data

If safety and wildlife-vehicle collisions are potential issues in a project, then an analysis of collision/carcass data and the sites of those collisions could be applied to identify the most collision prone areas. Safety analyses would typically entail processes such as those described above during the consideration step (Step 1.2.5), which include:

• GIS Mapping and Analyses
• Database Spreadsheet Analyses
• Cluster Analyses
• Discussions with Local Agency Personnel
• Use of Safety Performance Functions
• These analyses are better described in Step 1.2 of the Decision Guide.

While these and other types of safety analyses are helpful, Barnum (2003) cautions that areas of wildlife-vehicle collisions may not be the best places for wildlife to cross roadways, but rather are indicative of where wildlife are not succeeding in crossing. This data should be combined with ecological resources and professional opinions in siting wildlife passages.

Predictive Models to Identify Mitigation Locations

Predictive GIS models are sometimes used to help place wildlife crossings. These models typically take data on wildlife movements in the area combine them with landscape data and expert opinion to model the pathways that would be most likely used by the species of interest. There are GIS based models, such as that used for carnivores in Washington http://www.fs.fed.us/pnw/sciencef/scifi79.pdf, expert predictive models such as those used in Montana (Ruediger et al. 2004) and models using both methods (Clevenger et al. 2002). The objective of these models was to determine the specific locations where wildlife would most often want to cross a road area within a movement linkage area. These are more site specific than the typical state-wide connectivity analyses that are becoming available in many states and some provinces.

Predictive models can also be based on past wildlife-vehicle collision data. A detailed modeling procedure such as that developed by Clevenger et al. (Final report 2007) in this research could be used to predict where wildlife-vehicle collisions might occur, and thus general zones are needed to allow wildlife to pass under or over the road through mitigation. Clevenger et al. modeled landscape and road variables at very accurate (within 3 meters) road carcass locations along the Trans Canada Highway in Banff National Park. Such an analysis would require a spatially accurate database, and the gathering of field generated data on the road, lines of vision from the collision location, and the landscape, combined with GIS analyses. Using univariate tests and logistic regression analysis, potential characteristics of the road and landscape can be identified for high collision areas, thereby helping to predict future collisions in the analyzed areas as well as other road segments. Clevenger et al. also developed GIS clustering techniques to identify hotspots where wildlife-vehicle collisions occur. Clustering techniques such as Ripley's K-statistic of road associated kills, nearest neighbor measurements, and density measures can be applied to identify wildlife-vehicle collision hotspots at different scales of application from project level to state/provincial level analysis. Future links to these papers will be forthcoming.

Citizen Scientists

Citizens concerned about wildlife can become involved in identifying areas where wildlife are on the road alive and are found as road kill. In several instances, citizens have been recording road kill and live animals via their own spreadsheets and with on-line interactive programs with GIS interfaces. See: http://www.ecologyandsociety.org/vol11/iss1/art11/
for an example of how citizens are helping to identify placement of wildlife passages in Alberta, Canada. In Colorado, citizens are helping with remote trail cameras to see wildlife movement near Interstate 70 through the mountains and where the best placement of passages would be. See: http://www.restoretherockies.org/citizen_science.html.

Engineering and Geologic Constraints

There are engineering and geologic constraints to the placement of wildlife passages. Placement is dependent on the grade of highway, the slope, curves, and other topographic concerns, landscape features such as rivers, wetlands, rock outcrops, and geologic concerns such as unstable soils that may slump or be unable to support the highway corridor infrastructure. The volume of soil excavated is a financial concern, especially if this involves rock excavation. To reduce the volume of excavation, underpasses are best located in the fill sections of the roadway. These fill sections are often areas of drainages, or low areas. If a passage is placed in these areas, it may reduce the amount of fill necessary for the road bed, as well as provide wildlife and water movement. If there is a day light area in the median to allow light into the crossings, this too could reduce the amount of fill needed. These concerns vary by locality, monetary constraints, building materials, and land ownership. A field visit to prospective wildlife crossing sites with engineers and geologists responsible for road building could greatly assist in incorporating these constraints in mitigation plans.

When working with highway engineers and planners in determining the preferred location for a crossing, it is important to be as flexible as possible. Small adjustments in the location may greatly reduce the cost of the crossings and still meet the needs of the target species. Departments of Transportation are often financially constrained and the more economical crossings are the more they can be justified from an economic analysis.

Back to Top

2.2.5

2.2.5. Final Map of Potential Wildlife Mitigation Locations

When the above coarse scale and fine scale analyses and work begins to come together, a map of potential wildlife crossing locations can be created. This map could have many of the above attributes on it, from the landscape and road variables to the animal-vehicle collision locations, animal tracking hotspots, landownership attributes, and other data. Once this map product is drafted, it can begin a review process by stakeholders who wish to finalize the plans. In cases across North America, these wildlife crossing locations are becoming the catalysts for conservation actions in the areas outside the road Right-of -Way. Once a Department of Transportation begins to commit to constructing crossing(s), state, county and local officials and citizens can then begin to plan for protecting the lands on either side so the wildlife can use these places in perpetuity. There are instances where county commissioners have committed funds to buy conservation easements, and private citizens have donated lands that the crossings are meant to connect. The placement of crossings can become the beginning of a community collaborative conservation effort.

Back to Top

2.2.6

2.2.6 Literature Cited

Alexander, S. M. and N. M. Waters. 1999. Decision support applications for evaluating placement requisites and effectiveness of wildlife crossing structures. Pages 237-252 in Evink, G.L. et al. (eds), Proceedings of the Third International Conference on Wildlife Ecology and Transportation (ICOWET, FL-ER-7399. Florida Department of Transportation, Florida.

Alexander, S. M., N. M. Waters, and P. C. Paquet. 2004. A probability-based GIS model for identifying focal species linkage zones across highways in the Canadian Rocky Mountains. Pages 233-255 in, G. Clarke and J. Stillwell, editors. Applied GIS and Spatial Modeling. John Wiley and Sones, Ltd, and the University of Leeds, United Kingdom.

Barnum, S. 2003. Identifying the best locations along highways to provide safe crossing opportunities for wildlife. A report to the Colorado Department of Transportation Research Branch. Report No. CDOT-DTD-UCD-2003-9. Final Report. CDOT, Denver, Colorado, U.S.A.

Clevenger, A.P., J. Wierzchowski, B. Chruszcz, and K. Gunson. 2002. GIS-generated, expert-based models for identifying wildlife habitat linkages and planning for mitigation passages. Conservation Biology 16:503-514

Dodd, N.L., J.W. Gagnon, S. Boe, and R.E. Schweinsburg. 2006. Characteristics of elk-vehicle collisions and comparisons to GPS-determined highway crossing patterns. Pages 461-477 in C. L. Irwin, P. Garrett, and K.P. McDermott, editors. Proceedings of the 2005 International Conference on Ecology and Transportation, Center for Transportation and the Environment, North Carolina State University, Raleigh, North Carolina (scroll to page 534).

Jackson, S. D. 2003. Proposed design and considerations for use of amphibian and reptile tunnels in New England. University of Massachusetts, Amherst.

Lee, T., M. S. Quinn, and D. Duke. 2006. Citizen, science, highways, and wildlife: using a web-based GIS to engage citizens in collecting wildlife information. Ecology and Society 11(1): 11.

Ruediger, B, Basting, P., Becker, D., Bustick, J., Cavill, P., Claar, J., Foresman, K., Hieinz, G., Kaley, D., Kratville, S., Lloyd, J., Lucas, M., McDonald, S., Stockstad, G., Vore, J., Wall, K., Wall, R. 2004. An assessment of wildlife and fish linkages on Highway 93 - western Montana. USDA Forest Service, USDI Fish and Wildlife Service, confederated Salish and Kootenai Tribe, Rocky Mountain Elk Foundation, Montana Fish, Wildlife and Parks, Montana Department of Transportation, Geodata Services, The University of Montana, Forest Service Publications #R1-04-81, Missoula, MT. 41 pp.

Tischendorf, L. and L. Fahrig. 2000. On the usage and measurement of landscape connectivity. Oikos 90:7-19.

van Manen, F. T., J. D. Jones, J. L. Kindall, L. M. Thompson, and B. K. Scheick. 2001. Determining the potential mitigation effects of wildlife passageways on black bears. Pages 435-446 in C. L. Irwin, P. Garrett, and K.P. McDermott, editors. Proceedings of the 2001 International Conference on Ecology and Transportation, Center for Transportation and the Environment, North Carolina State University, Raleigh, North Carolina.

Back to Top