|
Coming Up Next: ICOET 2009 in Minnesota!
Abstracts: Wildlife & Terrestrial Ecosystems
Construction of a Highway Section Within a White-Tailed Deer Winter Yard Near Quebec City, Quebec, Canada: Mitigation Measures, Monitoring, and Preliminary Results
- Yves Leblanc, Tecsult Inc., Québec City, Québec, Canada, Phone: 418-871-2452.
- Jacques Bélanger, Direction Chaudière-Appalaches, Ministère des Transports du Québec, Canada, Phone: 418-839-7978.
- Sylvie Desjardins, Ministère des Ressources Naturelles et de la Faune du Québec, Québec City, Québec, Canada, Phone: 418-832-7222.
The construction of a new 10.4 km (6.5 mi) section of HWY Robert-Cliche (73) south of Québec City, Canada, integrated an unprecedented number of mitigation measures to maintain connectivity between a bisected white-tailed deer winter yard and minimize apprehended deer-vehicle collisions. In this paper we present mitigation measures planned and complete as well as the monitoring approach to document deer use and movements in the winter yard before, during and after the construction. Some preliminary results regarding the impact of this project on the deer winter use of the project area also will be presented and briefly discussed.
We conducted 4 years (1999-2002) of winter track surveys along the projected centerline of the new highway section and aerial surveys done in mid-winter of 2003 and 2004 to document movements and to delineate boundaries of the Calway deeryard. Mitigation measures were then proposed and integrated in the project design for the bisected deeryard. It included wildlife fencing for more than half (6.2 km or 3.9 mi) of the new highway section and combining it with 5 underpasses: one concrete box culvert, two open-span bridges over two major rivers and 2 open-span bridges over 2 rural roads. Before and during construction deer were captured each year in January and fitted with radio-collars. Yearly aerial surveys were also conducted to determine spatial use in relation with the construction phases. Around 20 deer were radio-collared each winter and telemetry data showed that about one-third of deer were long distance migrants (> 10 km) between their winter and summer home range, another one-third were short distance migrants (1 to 10 km), whereas the remaining were yearly residents of their winter range. All radio-collared deer monitored for more than a year consistently traveled between the same winter and summer home ranges. However some marked deer moved elsewhere to winter.
Two primary deer crossing structures were located at the Doyon Creek and Calway River and three secondary ones were available to deer. The design and specifications of three required underpasses were modified to facilitate use by deer. As of October 2006, four underpasses were completed, as well as 5.1 km (3.2 mi) of wildlife fencing and 21 jump-outs. An additional 6 escape ramps will be built before construction ends to allow trapped deer to escape from the fenced rights-of-way (ROW). Motorists were not yet allowed to use paved sections but they will be after project completion in fall 2007.
During the 2006 spring migration, about twenty deer were trapped within the 1.6 km (1.0 mi) fenced section and did not find the hole at the jump-outs. Adjustments were made on existing ramps to allow the deer to see the opening and not be reluctant to jump out to the adjacent forest. Also, new drawings and specifications were made to eliminate fence angles and reduce the height and slope of the ramp for the remaining one to build. Weekly visits from January to March 2007 showed that numerous deer were using both primary and secondary deer crossing structures to access both sides of the deeryard. Data from the aerial survey showed that the fenced highway section induced a light shift in the spatial use of the deeryard during the 2007 winter. Telemetry data provided evidence that deer with split winter home ranges continued to use both sides of the new section of highway despite a 5.1 km stretch of deer-proof fencing.
Using Site-Level Factors to Model Areas at High Risk of Deer-Vehicle Collisions on Arkansas Highways
- Philip Tappe, Univ. of Arkansas at Monticello, Monticello, AR, Phone: 870-460-1352.
- Donald I.M. Enderle, Arkansas Forest Resources Center and School of Forest Resources, Univ. of Arkansas, Monticello, AR, Phone: 770-270-7678.
Deer-vehicle collisions (DVCs) are increasing across the United States, including Arkansas. These collisions involve risk of human injury and fatality, property damage, and loss of wildlife. The annual number of DVCs in Arkansas may be as great as 18,000 (13.6% of the reported legal deer harvest in 2005) with an estimated property damage of $35 million. Numerous studies have examined the impacts and causes of DVCs; however, few studies have utilized a state-wide approach to increase understanding of the factors involved.
We evaluated the influence of site-level factors on the number of DVCs reported during 1998-2001 along all state and federal highways in Arkansas. Site-level factors included landcover patterns, landcover characteristics, and number of stream/highway intersections within 400, 800, and 1200 m of collision sites; landcover crossing types and maximum topographic relief within 100 m of collision sites; and distances to nearest forest and to nearest water. A total of 3,170 DVC locations were compared with an equal number of randomly-chosen highway locations based upon proportions of DVCs within each physiographic region of Arkansas. Logistic regression analysis was used to develop and test a state-wide model and six physiographic region models to identify high risk areas along highways. Akaike information criterion values were used to select the best model for the entire state and for each physiographic region. We randomly selected 25% of the DVC sites and randomly-located highway sites to exclude from model development in order to test the predictive ability of each model.
Over 1,000 variables were considered prior to model development. However, exclusion of intercorrelated variables and variables that did not differ between collision and random sites reduced the variable set to 31. These 31 variables revealed a variety of differences between known DVC locations and randomly-selected locations. Twenty-six variables were more associated with known DVC locations than with random locations. Five variables were more associated with randomly selected highway locations than with known DVC locations. The state-wide model had an overall correct classification rate of 62%. Most models developed for individual physiographic regions performed as well or better than the state-wide model: Arkansas River Valley (62%), Boston Mountains (69%), Gulf Coastal Plain (59%), Mississippi River Delta (70%), Ouachita Mountains (67%), and Ozark Mountains (60%). Almost all variables included in the state model were also included in at least one physiographic region model, and most variables of each physiographic region model were also found in the state model. Five groups of factors that were strongly correlated with DVC locations were apparent in all models: (1) the presence and amount of water in terms of distance to the nearest source, number of streams intersecting within 400 m, and amount of water within 1200 m; (2) the presence of a diverse association of land cover types in close proximity to a highway; (3) the amount and size of urban area within 1200 m; (4) forested area (deciduous and/or coniferous) in close proximity to a highway, particularly in terms of higher density of coniferous forest and greater size and irregularity of deciduous forest patches; and (5) the density of pasture and crop patches, and the density of pasture edge in particular, within 1200 m of a highway.
These results and models may be used to produce maps indicating potential segments of highways at high risk for the occurrence of DVCs. Additionally, they may aid in planning and road construction. Finally, these results provide a foundation for future research in examining more specific deer-vehicle interactions, and can aid in the evaluation of appropriateness and effectiveness of proposed methods to reduce DVCs in Arkansas.
Behavioral Responses of White-Tailed Deer to Vehicle-Mounted, Sound-Producing Devices
- Sharon Valitzski, Warnell School of Forestry and Natural Resources, Univ. of Georgia, Athens, GA, USA, Phone: 706-296-9048.
- Gino D'Angelo, Warnell School of Forestry and Natural Resources, Univ. of Georgia, Athens, GA.
- George Gallagher, Professor of Animal Science; Director, Rollins Ruminant Center; Berry College, Mount Berry, GA.
- David Osborn, Research Coordinator, Univ. of Georgia, Warnell School of Forestry and Natural Resources, Athens, GA.
- Karl Miller, Professor, Wildlife Ecology and Management, Univ. of Georgia, Warnell School of Forestry and Natural Resources, Athens, GA.
- Robert J. Warren, Interim Dean, Meigs Professor, Wildlife Ecology and Management; Univ. of Georgia; Warnell School of Forestry and Natural Resources, Athens, GA.
Deer-vehicle collisions are on the rise and are a costly side-effect of increasing deer populations and expanding transportation systems. We evaluated the efficacy of sound as a deterrent for reducing deer-vehicle collisions by observing the behavioral response of captive and free-ranging white-tailed deer (Odocoileus virginianus) to 5 pure-tone sound treatments: 0.28 kHz, 1 kHz, 8 kHz, 15 kHz, and 28 kHz. We conducted preliminary trials with semi-tame deer at the University of Georgia Captive Deer Research Facility. We exposed 8 deer in a 0.25-ha outside paddock and 5 deer in individual stalls (2.7 m x 4.8 m) to the various treatments at >70 dB Sound Pressure Level. We recorded 406 observations and determined that the behavior of captive deer did not change when presented with any of the 5 pure-tone sound treatments. We also conducted field trials at Berry College Wildlife Refuge, Georgia and gathered 319 behavioral observations of free-ranging deer relative to a moving automobile (56.45 kph). The automobile was fitted with a sound-producing device and speakers that emitted one of the pure-tone sound treatments or no sound treatment as a control. For the 1 kHz, 8 kHz, 15 kHz, and 28 kHz sound treatments, we observed no change in deer behavior relative to the control. When exposed to the 0.28 kHz treatment, deer reacted in a manner more likely to cause deer-vehicle collisions. Our results indicate that deer within 10 m of roadways did not alter their behavior in response to the pure-tone sound treatments we tested in a manner that would prevent deer-vehicle collisions. Commercially available wildlife warning whistles (aka deer whistles) are purported to emit similar consistent, continuous sounds as pure tones at various frequencies within the range of those presented in this study. Our data suggests that deer-whistles, as they are purported to operate, are likely not effective in preventing deer-vehicle collisions.
Evolution of Wildlife Exclusion Systems on Highways in British Columbia
- Leonard Sielecki, British Columbia Ministry of Transportation, Victoria, BC, Canada, Phone: 250-356-2255.
Since the mid-1980s, the British Columbia Ministry of Transportation (BCMoT) has been addressing the issue of motor vehicle-related wildlife collisions on Provincial highways with engineered wildlife exclusion systems. As a result of this initiative, the British Columbia has one of the most extensive networks of wildlife exclusion systems, designed to reduce and prevent motor-vehicle-related mortality of terrestrial mammals, in North America.
Typically, wildlife exclusion systems are incorporated as an integral part of new highway development after the potential of wildlife mortality has been identified during highway planning stages. The systems are designed to protect wildlife from motor vehicles and ensure wildlife habitat connectivity. They have been constructed primarily on limited-access, high-speed highways and expressways and designed to protect specific species of wildlife, primarily large ungulates, such as deer, elk, moose and mountain sheep. The systems comprise of specialized fencing and related structures, such as one-way gates, ungulate guards, and crossing structures, designed to safely and effectively protect wildlife by recognizing species-specific behavioral, physical and anatomical characteristics. To date, BCMoT has installed over 470 km of wildlife fencing, incorporating over 100 crossing structures and hundreds of one-way gates.
While the wildlife exclusion systems have been shown to reduce the potential for motor vehicle-related wildlife mortality, BCMoT is continually reviewing the designs of the components of these systems in an ongoing effort to improve them. With each successive project, as the interactions of wildlife with these systems become better understood, BCMoT has refined its fence and crossing structure designs and standards to increase their efficiency, effectiveness and safety for wildlife. BCMoT has also focused its attention on material quality, manufacturing processes and construction techniques to offset the challenges of climate, topography, vegetation and human activity to maximize the effective functional lifespans of wildlife exclusion systems.
Top of page
Wildlife Mitigation and Human Safety for Sterling Highway Milepost 58-79, Kenai Peninsula, Alaska
- Richard Ernst, Wildlife Biologist/Pilot, U.S. Fish and Wildlife Service, Kenai National Wildlife Refuge, Soldotna, Alaska (AK), Phone: 907-262-7021.
- Jeff Selinger, Area Wildlife Biologist, Alaska Dept. of Fish and Game, Soldotna, Alaska (AK), Phone: 907-260-2905.
- Jim Childers, Project Manager, Alaska Dept. of Transportation and Public Facilities, Anchorage, AK, Phone: 907-269-0544.
- Dale Lewis, Central Region Liaison Engineer, Federal Highway Administration, Alaska Division, Juneau, AK, Phone: 907-586-7429.
- Gary Olson, President, Alaska Moose Federation, Anchorage, AK, Phone: 907-336-6673.
- Lt. Steve Bear, Detachment Commander, Alaska Dept. of Public Safety, Wildlife Troopers, Soldotna, AK, Phone: 907-262-4453.
The Sterling Highway is a paved two-lane road which links Alaska’s western Kenai Peninsula, to the Seward Highway and Anchorage, the state’s largest city. The Kenai National Wildlife Refuge is bisected by the Sterling Highway, which has one of the highest moose (Alces alces) vehicle collision rates for a rural highway in the state. The Alaska Department of Transportation and Public Facilities is planning to reconstruct a section of the Sterling Highway between MPs 58 and 79, occurring mostly within the Refuge. A working group was formed in 2005 to collect data on moose movements and review wildlife-vehicle collisions (WVC). The group consists of representatives from the Federal Highway Administration; the Alaska Departments of Transportation and Public Facilities, Fish and Game, and Public Safety; the Alaska Moose Federation (non-profit); and the U.S. Fish and Wildlife Service. The purpose of this cooperative effort is to reduce wildlife-vehicle collisions along the Sterling Highway corridor through the Kenai National Wildlife Refuge while maintaining permeability and enhancing habitat connectivity. In this paper, we describe our study design and provide interim results from 2005-06.
Role of Fencing in Promoting Wildlife Underpass Use and Highway Permeability
- Norris Dodd, Wildlife Research Biologist, Arizona Game and Fish Dept., Research Branch, Pinetop, AZ, Phone: 928-368-3017.
- Jeffrey Gagnon, Susan Boe, Raymond Schweinsburg, Arizona Game and Fish Dept., Research Branch, Phoenix, AZ.
Ungulate-proof fencing has been used successfully to mitigate the incidence of wildlife-vehicle collisions on highways throughout North America. And while fencing is often regarded as an integral component of effective wildlife passage structures, limited information or guidelines exist for the application of fencing in conjunction with wildlife passages. Fencing itself may limit wildlife permeability across highways and exacerbate the barrier effect of highways on wildlife populations. An 8-km section of highway reconstructed from a two- to four-lane divided highway in central Arizona was opened to traffic six months before ungulate-proof fencing was erected linking four wildlife underpasses (UP) and three bridges. To assess the role of strategically placed fencing along 49% of the section, we compared before and after fencing Rocky Mountain elk (Cervus elaphus nelsoni)-vehicle collision incidence, wildlife use of UP, and elk highway permeability. From 2002–2006, we documented 110 elk-vehicle collisions. The incidence of collisions increased over three fold after highway reconstruction was completed but before fencing was erected. After fencing, the incidence of elk collisions declined 87%. We employed video camera surveillance systems at two UP to compare wildlife use for nine months before and 11 months after fencing was erected. Before fencing, we recorded 500 elk and deer (Odocoileus spp.) at the UP, of which only 12% successfully passed through the UP; 81% of animals continued to cross the highway at grade. After fencing, of 595 elk and deer recorded, 56% crossed successfully and no animals crossed the highway at grade. The probability of an approaching animal crossing through an UP increased from 0.09 to 0.56 with fencing, and the combined odds of a crossing through the UP after fencing was 13.6:1 compared to before fencing. We used Global Positioning System (GPS) telemetry to assess highway permeability and crossing patterns. We instrumented 22 elk (16 female, 6 male) with GPS receiver collars April 2004–October 2005, during which time our collars accrued 87,745 GPS fixes. The elk highway passage rate, our measure of permeability, after the highway was opened to traffic but before fencing was erected (0.54 crossings/approach) was 32% lower than the level determined from a previous study for the section during reconstruction (0.79 crossings/approach). Once fencing was erected, the passage rate increased 52% to 0.82 crossings/approach. The proportion of elk crossings that occurred along fenced highway stretches declined 50% while the proportion of crossings along unfenced highway increased 40%. Fencing plays an important role in reducing the incidence of wildlife-vehicle collisions and increasing the effectiveness of wildlife passage structures. Furthermore, fencing in combination with a relatively high density of passages (1 structure/1.1 km) promoted elk highway permeability by funneling animals toward the UP where resistance to crossing was lower than that associated with crossings at grade.
Effects of Traffic Volume on Elk Distribution and Crossing Patterns Along an Arizona Highway
- Jeff Gagnon, Wildlife Specialist, Arizona Game and Fish Dept., Phoenix, Arizona, Phone: 928-522-8164.
- Norris L. Dodd, Wildlife Research Biologist, Arizona Game and Fish Dept., Research Branch, Pinetop, AZ, Phone: 928-368-3017.
- Raymond E. Schweinsburg, Arizona Game and Fish Dept., Research Branch, Phoenix, AZ.
Roads have been recognized as a threat to wildlife species for over 80 years. Studies on the effects of roads on ungulates species did not begin till the 1970’s. We identified 53 literature sources that suggested or examined traffic levels or road types and their effects on ungulate-vehicle collisions, ungulate distribution and roadway permeability. Seventy-one percent of these suggested an effect of traffic level on ungulates. Only 47% of the papers suggested deer (Odocoileus spp.) were affected by traffic while in contrast studies on elk (Cervus elaphus) and moose (Alces alces) were at 84% and 82%, respectively. In studies that suggested no effect of traffic, other factors such as ungulate populations, ungulate behavior, driver behavior, and landscape variables were generally considered reasons for fluctuations in collisions. Although several studies examined ungulate distribution along roads, very few adequately looked at fluctuating traffic levels along highways. Highways have a greater potential for ungulate-vehicle collisions and are more likely to provide a barrier to ungulates than low traffic roads. Our further understanding of ungulate movements and behavior in relationship to highways may be important in helping to mitigate ungulate-vehicle collisions and ungulate habitat fragmentation. Our State Route 260 project in central Arizona has provided a unique opportunity to examine elk movements in relation to traffic along a highway. We documented distinct shifts in distribution associated with fluctuating traffic levels as well as reductions in probabilities of at-grade crossings during increasing traffic levels. During the same study we found that increased traffic levels did not alter elk use of wildlife underpasses. Overall, properly designed wildlife underpasses and adequate funnel fencing adequately reduced elk-vehicle collisions while simultaneously promoting highway permeability during increasing traffic levels. Further research is needed to determine if these trends hold true for other ungulate species. Currently, research of fluctuating hourly traffic levels on ungulate behavior associated with highways is underway in Arizona, including American pronghorn (Antilocapra americana), mule deer (O. hemionus), Coues’ white-tailed deer (O. virginianus couseii) and further research on elk along highways with different geographical areas and traffic level ranges.
Transportation Corridors in Arizona and Mexico and Pronghorn: Case Studies
- Richard Ockenfels, Wildlife Program Supervisor, Phone: 602-789-3379; James deVos, Jr., Research Branch (Retired); and John J. Hervert, Yuma Region; Arizona Game and Fish Dept., Phoenix, AZ.
Review of case studies in Arizona and Mexico of effects of transportation corridors on pronghorn.
We reviewed 13 case studies from Arizona and Sonora, Mexico on the effects of transportation corridors on pronghorn (Antiocapra americana). What do we know and what can we do about it? Since the mid-1900s, naturalists/biologists have known that transportation corridors such as highway and railroad rights-of-way can affect pronghorn populations. Beginning in 1983, we have radiomarked ~250 adult pronghorn across Arizona and northern Sonora, Mexico to assess the effects of transportation corridors on various populations. During this over 20-year period, we conducted 3 studies, 1 in Sonora, Mexico, on the endangered Sonoran pronghorn (A. a. sonoriensis) and 10 studies in central and northern Arizona on other subspecies. With >34,000 radio locations, we report on the documented effects of transportation corridors from these 13 case studies. Transportation corridor effects varied by type of corridor (number of lanes, fenced vs. unfenced, and presumably by traffic volume). Pronghorn readily crossed paved, unfenced roadways with low traffic volume, occasionally crossed paved, fenced 2-lane highways, but only in certain situations, but did not cross high-volume highways or divided interstates. Railroad rights-of-way also isolated pronghorn herds and fragmented habitat. Six mitigation ideas are presented and discussed that could improve the likelihood of pronghorn crossings. The current "wildlife missing linkages" project in Arizona is attempting to identify fragmentation of habitat across the state due to transportation corridors and plan for remedies to lessen the impact of transportation on many species of wildlife, including pronghorn. We conclude that additional research on mitigation features is warranted.
Top of page
Management Considerations for Designing Carnivore Highway Crossings
- Bill Ruediger, Wildlife Biologist, Wildlife Consulting Resources, Missoula, MT, Phone: 406-721-4868.
Many agencies are contemplating building wildlife crossings to reduce wildlife mortality, to improve habitat connectivity, and to reduce vehicle collisions. For this to occur without problems and interagency disagreements, relationships between agencies and key individuals must be well-developed. Once relationships are in-place highway improvements and wildlife habitat objectives are more easily integrated. The second step in coordinating wildlife issues with transportation is development of interagency statewide, regional or highway specific wildlife habitat linkage plans. These determine a number of critical factors necessary to locate wildlife crossings, prioritize opportunities and focus funding and personnel. To be effective, transportation, wildlife management and land management agencies must be involved in these plans. The third step involves choosing the appropriate location, structure type and structure size for target species. This process must take into consideration more than biological criteria and includes cost factors and construction feasibility issues born by highway agencies. Last, monitoring will help improve future wildlife crossing efforts and help all agencies and the public gain confidence in their effectiveness.
Patterns of Carnivore Road Casualties in Southern Portugal
- Clara Grilo, Faculdade de Ciências da Universidade de Lisboa, Lisboa, Portugal, Phone: 00351-966079307.
- Carla Baltazar, Margarida Santos-Reis: Centro de Biologia Ambiental, Departamento de Biologia Animal, Faculdade de Ciências, Universidade de Lisboa, Portugal.
- Clara Silva, Luis Gomes: Unidade de Biologia da Conservação, Departamento de Biologia, Universidade de Évora, Portugal.
- John Bissonette, Professor/Leader, USGS Utah Cooperative Fish and Wildlife Research Unit, Dept. of Wildland Resources, College of Natural Resources, Utah State Univ., Phone: 435-797-2511.
We examined spatial patterns of carnivore casualties by counting the number of animals killed on 574 km of national roads and highways in southern Portugal. We surveyed six national roads twice a month from July 2003 to December 2006. Highway casualty data were collected by Brisa Auto-Estradas de Portugal, S. A., a private concession. A total of 801 carnivores representing eight carnivore species were killed. We found an average of 47 road-killed individuals per 100km per year; foxes were most numerous with the 20 individuals killed per 100km per year. The distribution of carnivore road kills was clustered except fox casualties. We calculate the mean road kill rate on different classes of variables that may influence road mortality and compare among them to identify the level of risk posed by each class of variable. Casualties were more likely to occur near to suitable habitats preferred by carnivores, in high traffic volume areas, and close to streams. Livestock exclusion fences, the type of road, and the number of passages did not influence mortality. To improve the cost-effectiveness of mitigation measures for new and existing roads, the priority should be given to the road segments crossed by streams in a cork oak woodlands matrix. Short sections of buried fences near culvert openings (100m on each side) should reduce the number of casualties considerably. Habitats connectivity is a serious issue where high volume traffic discourages carnivores from crossing roads at-grade. Connectivity is enabled by appropriately-designed passages.
Major Roads: A Filter to the Movement of the Squirrel Glider Petaurus norfolcensis
- Silvana Cesarini, Monash University, Biological Sciences, Clayton, Melbourne, Victoria, Australia, Phone: +011 61399055680.
Quantifying the filter effect of major roads on the movement and dispersal of the squirrel glider Petaurus norfolcensis
An understanding of the ecological effects of roads and related traffic in highly fragmented landscapes is critical because the viability of wildlife that persist through the adverse impact of habitat loss and fragmentation, due to causes such as agriculture or urban land-uses, may be further impaired by the presence of roads. The potential barrier effect can increase the level of population isolation, especially if traffic volume increases and roads are widened. This is particularly the case in landscapes where a large proportion of the habitat occurs in linear strips, such as in hedgerows or along roadsides or watercourses. Much of eastern Australia has been cleared and many threatened species occur in habitat adjacent to roads. Thus, management must minimise the negative effects of roads while maximising their value for conservation.
Gaps in habitat may result in impeded mobility of wildlife and potentially isolate populations, with subsequent consequences for population persistence. The squirrel glider Petaurus norfolcensis can be considered a model species for investigating the impact of roads on connectivity. A native arboreal marsupial, the squirrel glider has a very efficient way of locomotion which consists of gliding between trees, with very rare ventures on the ground, where the risk of predation is higher. Glider movement within home ranges and during dispersal is expected to occur along continuous vegetation, while cleared areas wider than the maximum gliding distance achievable could act as barriers. In this study we evaluated the filter effect of major roads on the squirrel glider in central Victoria (south-eastern Australia) using a combination of radiotracking and genetic techniques. We asked two important questions. First, does a major road act as a barrier or filter to the movement of gliders and if so, does the presence of tall trees between the carriageways facilitate their crossing.
A total of 58 adult individuals were radiotracked at six sites along the Hume Freeway (central Victoria), and at two control sites (minor roads with low traffic volume and small or non-existent gap in canopy cover) over a period of six months. The six sites consisted of small roads lined with old growth trees and dissected by the freeway. Three of these sites also had tall trees present in the median section of the freeway. The percentage of animals crossing at sites with vegetated median was similar to that at control sites, with 70% and 79% of all animals observed on the opposite side of the road or the centre median at least once, respectively. In contrast, only one male glider (10% of all animals) was observed crossing at sites with non-vegetated median. Overall, females were less inclined to cross roads, even at control sites and the intensity of crossing was also higher for males than females. The presence of trees in the median of the freeway was thus demonstrated to be a very efficient method of improving connectivity for gliders.
Data on dispersal collected via direct methods can be highly informative but also requires intense efforts in field work and usually long term studies. Genetic techniques are a useful alternative to infer dispersal events, through the use of spatial autocorrelation and relatedness/parentage analysis. These methods will be implemented to consolidate the preliminary results and estimate the net effect of observed crossings on gene flow.
Mitigation structures consisting of rope bridges and poles are being constructed to improve mobility of gliders as well as a number of other arboreal species and their effectiveness will be monitored using a combination of techniques. These will include motion-detecting infrared cameras, implantable transponders and radiotracking. Data will be compared on a pre- post-mitigation basis and at treatment and control sites.
Roads and Desert Small Mammal Communities: Positive Interaction?
Several indirect effects of roads on wildlife communities have been reported such as habitat quality alteration, loss in landscape connectivity, and barrier effects (Forman et al., 2003; Jaeger et al., 2005). An effect zone of up to 100m on either side of the road has been described as causing measurable impacts on ecological communities (Underhill and Anglod, 2000).
Roads can impact small mammal communities by: 1) creating an edge with different habitat characteristics (Garland and Bradley, 1984; Tyser and Worley, 1992); 2) promoting the introduction of exotic species (Getz et al., 1978; Vermeulen and Opdam, 1995; Underhill and Anglod, 2000); 3) increasing stress and reducing survival (Benedict and Billeter, 2004) through disturbance and contamination (Jefferies and French, 1972; Williamson and Evans, 1972; Quarles et al., 1974); 4) blocking movement thus causing genetic barriers and home range rearrangements (Oxley et al., 1974; Garland and Bradley, 1984; Mader, 1984; Swihart and Slade, 1984; Merriam et al., 1989; Gerlach and Musolf, 2000); and finally 5) causing direct road mortality (Wilkins and Schmidly, 1980; Ashley and Robinson, 1996; Mallick et al., 1998).
While the main focus of studies on the impact of roads on small mammals has been on road barrier effects, less attention has been given to the effect of roads on density and diversity of local communities.
Further analysis on the effect of roads on natural habitats is needed. Our objective was to assess and compare density estimators and diversity of small mammal communities in areas influenced by roads with areas having no road influence.
Top of page
|
