Ungulate use of non-wildlife underpasses

The Factors Influencing Wildlife to Use Existing Bridges and Culverts in Giant Panda National Park

Roads, acting as barriers, hamper wildlife movements and disrupt habitat connectivity. Bridges and culverts are common structures on roads, and some of them can function to allow wildlife passage. This study investigated the effects of traffic, the surrounding landscape, human disturbance, and bridge and culvert structures on the utilization of bridges and culverts as dedicated passages by wildlife, using motion-activated infrared camera traps along a 64 km road in Giant Panda National Park, Sichuan, China. The results show that both species richness and counts of wildlife recorded at the bridge and culvert were significantly lower than those observed at sites distant from roads. No large-sized wildlife was recorded at the bridges and culverts. Human activities and traffic volume significantly and negatively affect medium-sized wildlife utilization of bridges and culverts. We conclude that bridges and culverts serve as wildlife crossings, but their efficacy is weak. This emphasizes the necessity of retrofitting bridges and culverts via mitigation facilities such as noise and light barriers, and vegetation restoration on both sides of the roads in Giant Panda National Park.

Methodology of Wildlife Underpasses Attractiveness Assessment

The permeability of line barriers in the landscape is often a prerequisite for the survival of the wide spectrum of native species. The aim of this study is to create a methodology for assessing the attractiveness of wildlife underpasses used by animals during migrations, translocations or as a habitat. Understanding the relationship between the parameters of underpasses in the broader landscape-ecological context and their attractiveness for animals is a key aspect in spatial planning and the construction of new linear transport structures, which will significantly help mitigate the barrier effect and isolation of animal populations. The attractiveness assessment is based on the evaluation of the underpass individual parameters and its surroundings through the 8 sub-indexes (openness, substrate, anthropogenic, vegetation, landscape structure elements, ecological networks, potential and real migration/habitat).

Are several small wildlife crossing structures better than a single large? Arguments from the perspective of large wildlife conservation

Crossing structures for large wildlife are increasingly being constructed at major roads and railways in many countries and current guidelines for wildlife mitigation at linear infrastructures tend to advocate for large crossing structures sited at major movement corridors for the target species. The concept of movement corridors has, however, been challenged and pinching animal movements into bottlenecks entails risks. In this paper, I address the SLOSS dilemma of road ecology, i.e. the discussion whether a Single Large Or Several Small crossing structures along a linear barrier would produce the most benefit for wildlife, using the case of crossing structures for large wildlife in Sweden. I point out risks, ecological as well as practical, with investing in one large crossing structure and list a number of situations where it may be more beneficial to distribute the conservation efforts in the landscape by constructing several smaller crossing structures; for example, when the ecological knowledge is insufficient, when animal interactions are expected to be significant, when the landscape changes over time or when future human development cannot be controlled. I argue that such situations are often what infrastructure planning faces and that the default strategy, therefore, should be to distribute, rather than to concentrate passage opportunities along major transport infrastructures. I suggest that distributing passage opportunities over several smaller crossing structures would convey a risk diversification and that this strategy could facilitate the planning of wildlife mitigation. What to choose would however depend on, inter alia, landscape composition and ecology and on relationships amongst target species. A single large structure should be selected where it is likely that it can serve a large proportion of target animals and where the long-term functionality of the crossing structure can be guaranteed. New research is needed to support trade-offs between size and number of crossing structures. Cost-effectiveness analyses of wildlife crossing structures are currently rare and need to be further explored. Camera trapping and video surveillance of crossing structures provide opportunities to analyse details concerning, for example, any individual biases according to sex, age, status and grouping and any antagonism between species and individuals. Wildlife ecology research needs to better address questions posed by road and railway planning regarding the importance of specific movement routes and movement distances.

Co-use of existing crossing structures along roads by wildlife and humans: Wishful thinking?

This study assesses existing human-purpose underpasses below an unfenced high-traffic 4-lane highway in the Appalachian region of Quebec, Canada, as potential crossing structures for native mammal species. Eight underpasses of three types (five water culverts with minimum height and width of 1.8 m, one low-use gravel road byway, and two railroad underpasses) were continuously monitored by motion-detection infrared camera traps for time periods spanning up to 778 days (September 2016 to November 2018). We asked how the ratios of successful crossings through the structures (termed full crossings) and aversions to the structures (termed aversions) differed between species and we explored the influence of human activity levels on the use of these structures by wildlife. All monitored crossing structures had low human observations (with averages of less than 35 human activities per day). Our results provide evidence that 21 species of mammals in the study area successfully crossed through at least one of the eight observed underpasses on a minimum of one occasion. Some species were observed crossing through some of the underpasses on a regular basis, namely raccoon, red fox, and white-tailed deer. We propose a classification of mammal species into five human co-use classes (no or low co-use to very high co-use) to explore the relationship between mammal use of the structures and human presence. We found that humans and mammals were observed sharing passages for the four mammal species identified as tolerant of human co-use (high and very high co-use classes), but co-use was observed to be limited or not occurring for most other species. The strengths of this study include the length of time during which monitoring took place, as well as the placement of four cameras at each structure (two facing inward and two facing outward) to determine whether individuals successfully crossed through the structures or displayed avoidance behaviour. The results suggest select species of mammals show some co-use with humans at existing underpasses. The activity patterns of mammals documented over the two-year study can assist with future estimates of highway permeability. Further, measurements of human and mammal co-use have species-specific implications for retrofitting existing structures and constructing wildlife fences and purpose-built wildlife passages.