Mule Deer Migrations and Highway Underpass Usage in California,USA

Roadways may pose barriers to long-distance migrators such as some ungulates. Highway underpasses mitigate wildlife-vehicle collisions and can be an important management tool for protecting migration corridors. In northern California, 3 underpasses were built on United States Route 395 (Route 395) in Hallelujah Junction Wildlife Area (HJWA) in the 1970s for a migratory mule deer (Odocoileus hemionus) herd that had been negatively affected by highway traffic. To determine whether these underpasses were still reducing mule deer mortalities >40 years after construction, we investigated deer use of the underpasses from 2006–2019 using cameras, global positioning system (GPS) collars, and roadkill records. We used occupancy models, approximations of GPS-collared mule deer movement paths, and roadkill locations to estimate the highway crossing patterns of deer. From camera data, there was higher use of the underpasses by deer during migration (spring [Mar–Jun], fall [Oct–Dec]) than in summer (Jul–Sep), when only resident deer were present. Higher underpass usage occurred in the spring compared to fall migrations. Eleven of 21 GPS-collared migrating mule deer crossed Route 395. We estimated 30% of the crossings (by 7 of the 11 deer) occurred south of the underpasses where deer could easily access the highway because of short (1-m high) and deteriorating highway fencing. Roadkill data confirmed that deer-vehicle collisions were occurring south of the underpasses and at the underpasses. This was likely due to deteriorating infrastructure at the underpasses that allows wildlife access to the highway. Overall, our study indicated that although underpasses can provide safe passage for migratory deer decades (>40 yr) after their construction, deteriorating infrastructure such as fencing and gates can lead to wildlife mortalities on highways near underpasses. © 2021 The Wildlife Society.     

Using Video Surveillance to Estimate Wildlife Use of a Highway Underpass

ABSTRACT Roads pose many threats to wildlife including wildlife-vehicle collisions, which are a danger to humans as well as wildlife. Bridges built with provisions for wildlife can function as important corridors for wildlife passage. We used video surveillance to record wildlife passage under a bridge near Durham, North Carolina, USA, to determine whether it functioned as a wildlife underpass. This is particularly important for white-tailed deer (Odocoileus virginianus) because forests associated with the bridge created a corridor between 2 natural areas. We calculated detection probabilities and estimated the number of crossings as observed crossings divided by detection probability. We observed 126 crossings by >10 species of mammals. Detection probability was 42%; therefore, an estimated 299 wildlife crossings occurred. We observed 75 deer: 17 deer approached the underpass and retreated. We estimated sighting 40% of deer crossings and 92% of deer approaches. Thus, an estimated 185 deer crossings and 18 approaches occurred. As an index of road mortality, we conducted weekly surveys of vehicle-killed animals on a 1.8-km section containing the underpass. We discovered only 5 incidences of animals killed by vehicles. The size and design of the bridge promoted wildlife use of the underpass, providing landscape connectivity between habitats on opposite sides of the highway and likely increasing motorist safety. Thus, bridges in the appropriate landscape context and with a design conducive to wildlife use, can function as a corridor to reduce the effects of fragmentation.     

Effects of US 1 Project on Florida Key Deer Mortality

ABSTRACT Approximately 26% of annual mortality for the endangered Florida Key deer (Odocoileus virginianus clavium) occurs as deer-vehicle collisions (DVCs) on the 5.6-km section of United States Highway 1 (US 1) on Big Pine Key (BPK), but extensive urban development adjacent to sections of US 1 complicates efforts to reduce DVCs. Our objective was to evaluate the effectiveness of the US 1 Project (continuous 2.6-km system of 2.4-m fencing, 2 underpasses, and 4 experimental deer guards constructed on US 1 on BPK) in reducing DVCs along US 1. Deer used the underpasses all 3 postproject years (2003–2005); however, we observed higher underpass use in 2004 and 2005 compared to 2003. Exclusion fencing reduced deer intrusions onto the fenced section of US 1 during the 3-year period (2003, n = 7 deer; 2004, n = 4; 2005, n = 12). With a reduction of deer intrusions onto this section of US 1, DVCs decreased in the fenced area by 73–100%; however, US 1 DVCs within the unfenced sections of US 1 also increased (40%) as expected. In controlling for effects of increasing deer density and traffic volume, study results suggest that highway improvements have decreased the net risk of DVCs along US 1, which indicates that use of deer fencing, deer guards, and underpasses is applicable in other urban communities experiencing unacceptable levels of DVCs.     

Wildlife Interactions within Highway Underpasses

Highway underpasses are a common management tool used to lessen wildlife-vehicle collisions on roadways. Despite their widespread use, the effects of predator-prey interactions and human disturbances on wildlife within underpasses have not been well studied. To understand the effect of species interactions and human disturbances on wildlife traveling through underpasses, we analyzed camera data from 3 underpasses in Hallelujah Junction Wildlife Area, Sierra County, California, USA, from June 2017 to December 2018. We recorded 3,589 detections, which were predominately mule deer (Odocoileus hemionus), rodents, lagomorphs, California quail (Callipepla californica), bobcats (Lynx rufus), mountain lions (Puma concolor), and coyotes (Canis latrans). We used occupancy modeling and daily activity estimates to analyze species' spatial and temporal activity within the underpasses. Predator-prey interactions and human disturbances were among the most important factors that influenced wildlife travel through the underpasses. Mule deer avoided underpasses highly used by mountain lions, and mountain lions followed mule deer daily temporal activity patterns and seasonal activity patterns. These results indicate that predator-prey interactions influenced deer and mountain lion use of the underpasses. Coyotes favored underpasses and seasons with higher rodent and lagomorph presence, suggesting that the presence of prey was also important to coyote use of the underpasses. Coyotes, mountain lions, and bobcats all exhibited either temporal or spatial avoidance of human activity within the underpasses. California quail avoided predators within the underpasses and favored underpasses and times with high human activity. Our study suggests that underpass managers need to closely monitor the effect of predator-prey interactions and human activity on wildlife within underpasses to ensure these interactions do not discourage wildlife from using them. © 2019 The Wildlife Society.     

Factors associated with use of wildlife underpasses and importance of long-term monitoring

We evaluated use of 6 wildlife underpasses (UP) using video camera surveillance along State Route 260 in Arizona, USA. We documented wildlife use and compared successful UP crossings by various species and among UP. From 2002 to 2008, we recorded visits by 15,134 animals of 21 species (16 wildlife, 5 domestic) resulting in 72.4% crossing through UP. Elk (Cervus elaphus) accounted for 68% of recorded animals, white-tailed deer (Odocoileus virginianus) and mule deer (O. hemionus) accounted for 13% and 6%, respectively. As elk and white-tailed deer were the only species adequately represented across all UP, we used logistic regression to further evaluate factors associated with successful use of UP. To evaluate habituation over time we limited this analysis to 5 UP monitored for ≥4 yr. For elk, structural attributes and placement, season, time of day, and months monitored were associated with successful elk UP crossing in year 1, however, by year 4 only structural attributes and placement were significant, suggesting that UP structure and placement likely were of primary importance for successful elk passage. By year 4, probabilities of crossing at 4 of 5 UP converged on >0.70, indicating that given sufficient time to allow habituation, most UP we evaluated appeared to be effective for elk, regardless of structural attributes or placement. For deer, only structural attribute and placement were significant, and aside from one structure did not increase in probability of a successful crossing over time. The overall number of animals and species that crossed SR 260 via UP underscores efficacy of UP in promoting multi-species permeability. Long-term monitoring allows wildlife and highway managers to evaluate adaptation to wildlife crossing structures by different species. Results from this study add to our knowledge of mitigating the impact of highways on wildlife. © 2011 The Wildlife Society.     

Highway widening and underpass effects on vertebrate road mortality

Road widening (a.k.a. road dualling) and the presence of mitigation structures may have opposing effects on the number of animal‐vehicle collisions. Their influence in tropical areas is poorly quantified, and we know little about how modifications of road structure affect fauna roadkill and mitigation. We evaluated how road widening and proximity to a wildlife underpass affect roadkill of medium and large mammals, using roadkill records from before and after the widening of 150 km of road with new and old wildlife underpasses. Roadkilled species were divided into three groups based on mobility and sensitivity to human disturbance. Four of 16 species exhibited significantly higher roadkill after widening. Roadkill near underpasses was generally higher than by chance, despite our expectation of reduction in roadkills. This result indicates that we must adopt more effective mitigation measures, such as appropriate fencing combined with underpasses.     

Assessment of Elk Highway Permeability by Using Global Positioning System Telemetry

Abstract: Highways have significant direct and indirect impact on natural ecosystems, including wildlife barrier and fragmentation effects, resulting in diminished habitat connectivity and highway permeability. We used Global Positioning System (GPS) telemetry to assess Rocky Mountain elk (Cervus elaphus nelsoni) permeability across a 30-km stretch of highway in central Arizona, USA, currently being reconstructed with 11 wildlife underpasses, 6 bridges, and associated ungulate-proof fencing. The highway was reconstructed in phases, allowing for comparison of highway crossing and passage rates during various stages of reconstruction. We instrumented 33 elk (25 F, 8 M) with GPS receiver collars May 2002 to April 2004. Our collars accrued 101,506 GPS fixes with 45% occurring within 1 km of the highway. Nearly 2 times the proportion of fixes occurred within 1 km of the highway compared with random. We think elk were attracted to the highway corridor by riparian—meadow foraging habitats that were 7 times more concentrated within the 1-km zone around the highway compared with the mean proportion within elk use areas encompassing all GPS fixes. Elk crossed the highway 3,057 times; crossing frequency and distribution along the highway were aggregated compared with random. Crossing frequency within 0.16-km highway segments was negatively associated with the distance to riparian—meadow habitats (r_s = -0.714, n = 190, P < 0.001). Mean observed crossing frequency (92.6 ± 23.5 [SE] crossings/elk) was lower than random (149.6 ± 27.6 crossings/elk). Females crossed 4.5 times as frequently as males. Highway permeability among reconstruction classes was assessed using passage rates (ratio of highway crossings to approaches); our overall mean passage rate was 0.67 ± 0.08 crossings per approach. The mean passage rate for elk crossing the highway section where reconstruction was completed (0.43 ± 0.15 crossings/approach) was half that of sections under reconstruction and control sections combined (0.86 ± 0.09 crossings/approach). Permeability was jointly influenced by the size of the widened highway and associated vehicular traffic on all lanes. Crossing frequency was used to delineate where ungulate-proof fencing yielded maximum benefit in intercepting and funneling crossing elk toward underpasses, promoting highway safety. Use of passage rates provides a quantitative measure to assess permeability, conduct future pre- and postconstruction comparisons, and to develop mitigation strategies to minimize highway impacts to wildlife.     

Assessing changes in clusters of wildlife road mortalities after the construction of wildlife mitigation structures

Collisions with vehicles can be a major threat to wildlife populations, so wildlife mitigation structures, including exclusionary fencing and wildlife crossings, are often constructed. To assess mitigation structure effectiveness, it is useful to compare wildlife road mortalities (WRMs) before, during, and after mitigation structure construction; however, differences in survey methodologies may make comparisons of counts impractical. Location‐based cluster analyses provide a means to assess how WRM spatial patterns have changed over time. We collected WRM data between 2015 and 2019 on State Highway 100 in Texas, USA. Five wildlife crossings and exclusionary fencing were installed in this area between September 2016 and May 2018 for the endangered ocelot (Leopardus pardalis) and other similarly sized mammals. Roads intersecting State Highway 100 were mitigated by gates, wildlife guards, and wing walls. However, these structures may have provided wildlife access to the highway. We combined local hot spot analysis and time series analysis to assess how WRM cluster intensity changed after mitigation structure construction at fine spatial and temporal scales and generalized linear regression to assess how gaps in fencing and land cover were related to WRM cluster intensity in the before, during, and after construction periods. Overall, WRMs/survey day decreased after mitigation structure construction and most hot spots occurred where there were more fence gaps, and, while cluster intensity increased in a few locations, these were not at fence gaps. Cluster intensity of WRMs increased when nearer to fence gaps in naturally vegetated areas, especially forested areas, and decreased nearer to fence gaps in areas with less natural vegetation. We recommend that if fence gaps are necessary in forested areas, less permeable mitigation structures, such as gates, should be used. Local hot spot analysis, coupled with time series and regression techniques, can effectively assess how WRM clustering changes over time.     

Effects of Traffic on Elk Use of Wildlife Underpasses in Arizona

ABSTRACT We used video surveillance at 4 wildlife underpasses along 27 km of Arizona State Route 260, USA, to monitor elk (Cervus elaphus) responses to traffic volume and traffic type during underpass use. Passage rates at the highest traffic category (>10–27 vehicles/min) were not lower than passage rates when no vehicles were present, whereas passage rates at low, intermittent traffic volume (>0–1 vehicles/min) were 15% lower. Once elk entered an underpass, semi-trailer trucks were 4 times more likely than passenger vehicles to cause flight behavior when traffic levels were intermittent versus when traffic was continuous. Overall, traffic volumes of >10–27 vehicles per minute did not decrease the effectiveness of wildlife underpasses as a means of mitigating elk population subdivision. However, if flight away from underpasses at intermediate traffic levels causes elk to cross the highway at other points and thereby increases the potential for costly elk-vehicle collisions, we recommend that managers consider measures to reduce traffic noise and visual stimuli, especially those caused by semi-trailer trucks.     

Does small-perimeter fencing inhibit mule deer or pronghorn use of water developments?

Wildlife water development can be an important habitat management strategy in western North America for many species, including both pronghorn (Antilocapra americana) and mule deer (Odocoileus hemionus). In many areas, water developments are fenced (often with small-perimeter fencing) to exclude domestic livestock and feral horses. Small-perimeter exclosures could limit wild ungulate use of fenced water sources, as exclosures present a barrier pronghorn and mule deer must negotiate to gain access to fenced drinking water. To evaluate the hypothesis that exclosures limit wild ungulate access to water sources, we compared use (photo counts) of fenced versus unfenced water sources for both pronghorn and mule deer between June and October 2002–2008 in western Utah. We used model selection to identify an adequate distribution and best approximating model. We selected a zero-inflated negative binomial distribution for both pronghorn and mule deer photo counts. Both pronghorn and mule deer photo counts were positively associated with sampling time and average daily maximum temperature in top models. A fence effect was present in top models for both pronghorn and mule deer, but mule deer response to small-perimeter fencing was much more pronounced than pronghorn response. For mule deer, we estimated that presence of a fence around water developments reduced photo counts by a factor of 0.25. We suggest eliminating fencing of water developments whenever possible or fencing a big enough area around water sources to avoid inhibiting mule deer. More generally, our results provide additional evidence that water development design and placement influence wildlife use. Failure to account for species-specific preferences will limit effectiveness of management actions and could compromise research results. © 2011 The Wildlife Society.     

Interchange as the main factor determining wildlife–vehicle collision hotspots on the fenced highways: spatial analysis and applications

Despite the fact that all highways in Hungary are built with fencing, there are still 5 % of traffic accidents that involve wildlife. Therefore, this study focused on the incidence of collisions along fenced roads. Wildlife–vehicle collision (WVC) hotspots were mapped, and the spatial frequencies were analysed with Poisson regression. In general, most WVCs and almost all of the roe deer fatalities occurred at highway intersections, or at interchanges. Red fox casualties also occurred at interchanges as well as at passages. Wild boar fatalities were not particularly frequent at interchanges but were recorded near railways that are parallel to highways; otter–vehicle collision hotspots were found near their habitats and migration corridors such as streams. For otter, badger and wild boar, we were able to examine the role of local population density; most WVCs happened in areas of high population density. The badger model predicted that badger kills were more likely where the fence was not buried in the soil. Most WVCs occur at interchanges because wildlife enters the right-of-way (ROW) at fence ends; or it enters at a fence gap and runs along the outside of fence and becomes funnelled onto the ROW at the interchanges. Interruption in the continuity and linearity are important factors in both cases. We concluded that the number of WVCs can be reduced significantly if animals were prevented from entering highway interchanges and proposals for mitigation were made. We also propose a tool to assist in alleviating WVCs, by mapping them in Google Maps and integrating hotspots into a car navigation system.     

The role of deer as vehicles to move ticks, Ixodes ricinus, between contrasting habitats

In Europe the most important hosts maintaining Ixodes ricinus tick populations are deer. Therefore, excluding deer by fencing or culling are potential tick management tools. Here we test the hypothesis that deer act as vehicles for moving ticks between two distinct habitats: forest and open heather moorland. We utilised an ideal “natural experiment” whereby forests were either fenced or unfenced to prevent or allow deer to move between habitats. We aimed to test the hypothesis that deer cause a net movement of ticks from high tick density areas, i.e. forests, to low tick density areas, i.e. open moorland. We recorded I. ricinus and host abundance in 10 unfenced and seven fenced forests and their respective surrounding heather moorland. We found that fenced forests had fewer deer and fewer I. ricinus nymphs than unfenced forests. However, we found no evidence that fencing forests reduced I. ricinus abundance on adjacent heather moorland. Thus there was insufficient evidence for our hypothesis that deer cause a net movement of ticks from forest onto adjacent moorland. However, we found that deer abundance generally correlates with I. ricinus abundance. We conclude that fencing can be used as a tool to reduce ticks and disease risk in forests, but that fencing forests is unlikely to reduce ticks or disease risk on adjacent moorland. Instead, reducing deer numbers could be a potential tool to reduce tick abundance with implications for disease mitigation.     

Roadkill distribution at the wildland-urban interface

The growing wildland-urban interface is a frontier of human-wildlife conflict worldwide. Where natural and developed areas meet, there is potential for negative interactions between humans and wild animals, including wildlife-vehicle collisions. Understanding the environmental and anthropogenic factors leading to these collisions can inform transportation and habitat planning, with an objective of reducing animal mortality and human costs. We investigated spatial, temporal, and species-specific patterns of roadkill on Interstate-280 (I-280) in California, USA, and examined the effects of land cover, fencing, lighting, and traffic. The highway is situated just south of San Francisco, dividing a large wildlife refuge to the west from dense residential areas to the east, and therefore presents a major barrier to wildlife movement. Areas with a higher percentage of developed land east of I-280 and areas with more open space on the west side of I-280 were associated with an increase in overall roadkill, suggesting that hard boundaries at the wildland-urban interface may be zones of high risk for dispersing animals. This pattern was especially strong for raccoons (Procyon lotor) and black-tailed deer (Odocoileus hemionus). The presence of lighting correlated with increased roadkill with the exception of coyote (Canis latrans). Contrary to our expectations, we found weak evidence that fencing increases roadkill, perhaps because animals become trapped on roadways or because fencing is not sufficient to block access to the road by wildlife. Finally, we found strong evidence for roadkill seasonality, correlated with differences in movement and dispersal across life-history stages. We highlight the value of citizen-science datasets for monitoring human-wildlife conflict and suggest potential mitigation measures to reduce the negative effects of wildlife-vehicle collisions for people and wildlife. © 2019 The Wildlife Society.     

Traffic Volume Alters Elk Distribution and Highway Crossings in Arizona

ABSTRACT We used 38,709 fixes collected from December 2003 through June 2006 from 44 elk (Cervus elaphus) fitted with Global Positioning System collars and hourly traffic data recorded along 27 km of highway in central Arizona, USA, to determine how traffic volume affected elk distribution and highway crossings. The probability of elk occurring near the highway decreased with increasing traffic volume, indicating that elk used habitat near the highway primarily when traffic volumes were low (<100 vehicles/hr). We used multiple logistic regression followed by model selection using Akaike's Information Criterion to identify factors influencing probability of elk crossings. We found that increasing traffic rates reduced the overall probability of highway crossing, but this effect depended on both season and the proximity of riparian meadow habitat. Elk crossed highways at higher traffic volumes when accessing high quality foraging areas. Our results indicate that 1) managers assessing habitat quality for elk in areas with high traffic-volume highways should consider that habitat near highways may be utilized at low traffic volumes, 2) in areas where highways potentially act as barriers to elk movement, increasing traffic volume decreases the probability of highway crossings, but the magnitude of this effect depends on both season and proximity of important resources, and 3) because some highway crossings still occurred at the high traffic volumes we recorded, increasing traffic alone will not prevent elk-vehicle collisions. Managers concerned with elk-vehicle collisions could increase the effectiveness of wildlife crossing structures by placing them near important resources, such as riparian meadow habitat.     

Effects and Mitigation of Road Impacts on Individual Movement Behavior of Wildcats

ABSTRACT Roads can affect the persistence of wildlife populations, through posing mortality risks and acting as barriers. In many countries, transportation agencies attempt to counterbalance these negative impacts. Road mortality is a major threat for European wildcats (Felis silvestris); therefore, we tested the effectiveness of a newly developed wildcat-specific fence in preventing wildcat mortality along a new motorway. We hypothesized that such a fenced motorway would at the same time be a significant barrier to wildcats and may at worst result in 2 isolated populations. We used radiotracking data of 12 wildcats, resulting in 13,000 fixes, to investigate individual movement behavior during and after construction of a new motorway in southwestern Germany. The motorway was fenced with the wildcat-specific fence and included crossing structures, not especially constructed for wildlife. Additionally we collected road kills on stretches of the same motorway with various types of fencing. A rate of 0.4 wildcat kills/km/year on the motorway, which was traveled by 10,000 vehicles/day and fenced with a regular wildlife fence, was reduced by 83% on stretches with wildcat-specific fencing. Of the available crossing structures, wildcats preferred open-span viaducts. Road underpasses were used but hold a mortality risk themselves. As opposed to our expectations, the fenced motorway (fenced with wildcat fence) posed only a moderate barrier to wildcats. Individuals were hindered in their daily routine and some stopped crossing completely but others continued crossing regularly. The adaptation of spatial and temporal behavior to traffic volume and location of crossing structures has an energetic cost. Hence, we suggest that only a small number of major roads can be tolerated within a wildcat's home range. To meet the demands of the European Habitats Directive, we recommend installing the wildcat fence in wildcat core areas along motorways to reduce wildcat mortality. We suggest that fences should incorporate safe crossing structures every 1.5-2.5 km. Our findings in terms of fencing design and crossing structures can be used by transportation agencies for an effective reduction of road mortality and barrier effect for carnivores.     

Comparison of environmental,biological and anthropogenic causes of wildlife–vehicle collisions among three large herbivore species

Wildlife–vehicle collisions are of increasing concern with regards to the continuous and accelerating anthropogenic development. Preventing and mitigating collisions with wildlife will require a better understanding of the environmental and biological drivers of collision risks. Because species of large mammals differ in terms of food requirements, habitat selection and movement behaviors we tested, at the management unit level, if the density of collisions with red deer, roe deer and wild boar differed in terms of spatial distribution and explanatory factors. From 20,275 documented collisions in France between years 1990 and 2006, we found marked differences in the most influential environmental factors accounting for the density of collisions among the three large herbivore species. The effect of road density was higher for the red deer than for the two other species and did not level off at our spatial-scale of observation. As expected, the annual hunting harvest—interpreted as a proxy of population abundance—was positively associated with the density of collisions for all species, being the strongest for red deer. While the collision density decreased with the proportion of forest in a management unit for wild boar, it increased with the fragmentation of forest for red deer that commute among forest patches between day and night. To reduce the number of wildlife–vehicle collisions, our results suggest to generalize road fencing and/or a control of abundance of large herbivore populations. Mitigation measures should target units where the collision risk is the highest for the most problematic species.     

Survey of haircoat fungal flora for the presence of dermatophytes in a population of white-tailed deer (Odocoileus virginianus) in Virginia

Before releasing rehabilitated wildlife, patients should be cured of all infectious agents that pose a risk to free-roaming wildlife or humans after release. Dermatophyte fungi, commonly known as "ringworm," have zoonotic potential and may be carried as normal flora on the haircoats of certain species. Outbreaks of ringworm are anecdotally reported to occur in white-tailed deer (Odocoileus virginianus) fawns, but no prevalence surveys have been conducted on the haircoat flora of free-roaming individuals. In November 2008, we tested 60 legally hunted white-tailed deer for dermatophyte flora by using a modified MacKenzie technique. Results indicate it is unlikely that wild, mature white-tailed deer in Virginia, USA, carry dermato-phyte fungi as normal haircoat flora. Therefore, wildlife rehabilitators and hunters are at low risk for dermatophyte infection by direct contact with this species. In addition, the RapidVet-D 3 Day Test for Veterinary Dermatophytosis was determined to have poor specificity for presence of dermatophyte fungi on asymptomatic white-tailed deer in Virginia.     

Response of Deer to Containment by a Poly-Mesh Fence for Mitigating Disease Outbreaks

Abstract: Rapidly deployable and effective methods are needed to contain free-ranging deer (Odocoileus spp.) during acute disease outbreaks. We evaluated efficacy of a 2.1-m-tall polypropylene mesh (poly-mesh) fence for containing ≥15 free-ranging white-tailed deer (O. virginianus) within a 42-ha area in eastern Nebraska, USA. We observed a 99% decrease in deer leaving the enclosure area after we installed fencing (1 deer jumped; 0.02 deer/hr) compared with prefence rates (5.26 deer/hr). However, 8 deer (53% of censused population) escaped the enclosure during a census drive after our study. Poly-mesh fencing may be effective in temporarily containing free-ranging deer during minimally disruptive deer removal actions such as trapping or sharpshooting.     

Where to invest in road mitigation? A comparison of multiscale wildlife data to inform roadway prioritization

Roads and associated traffic have significant impacts on wildlife, from direct mortality caused by vehicle collisions to indirect effects when wildlife avoid roads, restricting access to important resources. Road mitigation measures such as constructing wildlife passages over or under the road with directional fencing have proven effective at reducing wildlife vehicle collisions while also enabling wildlife to safely cross the road. Highway mitigation projects are led by transportation agencies with a primary purpose of improving motorist safety. More recently, through the discipline of road ecology, considerations have included safe wildlife passage through transportation corridors. To prioritize road sections for mitigation, data sources include animal vehicle collision data collected by transportation agencies and connectivity models generated by wildlife professionals. We used a third data source, pronghorn observations collected by citizen scientists, and demonstrated its value to prioritize potential wildlife mitigation sites. Our results clearly demonstrate a misalignment of road mitigation sites using animal-vehicle collision data and those of rarer species of interest.     

The permeability of highway in Gorski kotar (Croatia) for large mammals

The highway from Zagreb to Rijeka stretches 68.5 km through a wildlife core area in Gorski kotar (Croatia). It has 43 viaducts and tunnels, and one specifically constructed (100 m wide) green bridge (Dedin). One quarter of the total highway length consists of possible crossing structures. At Dedin green bridge, a total of 12,519 crossings have been recorded during 793 different days of active infrared monitors being in operation, or 15.8 crossings per day. Two monitored tunnel overpasses had 11.2 and 37.0 crossings per day, respectively, whilst 4.3 crossings occurred per day under one monitored viaduct. Of those crossings, 83.2% were by ungulates and 14.6% by large carnivores. Radio-tracked large carnivores, brown bear (Ursus arctos), grey wolf (Canis lupus) and Eurasian lynx (Lynx lynx), expressed strong positive selection for tunnels and viaducts, whilst avoiding small underpasses or bridges. Selection for the use of Dedin green bridge was equal to its availability. We conclude that this green bridge, constructed as a measure to mitigate the negative effects of the studied highway, served its purpose acceptably. Territorial and dispersing radio-tracked large carnivores crossed the highway 41 times, using both sides of the highway as parts of their home ranges. Overall, the highway in Gorski kotar does not seem to be a barrier. This demonstrates that it is possible to maintain habitat connectivity during the process of planning the highway route.