Assessing habitat connectivity of rare species to inform urban conservation planning

Urbanization is commonly associated with biodiversity loss and habitat fragmentation. However, urban environments often have greenspaces that can support wildlife populations, including rare species. The challenge for conservation planners working in these systems is identifying priority habitats and corridors for protection before they are lost. In a rapidly changing urban environment, this requires prompt decisions informed by accurate spatial information. Here, we combine several approaches to map habitat and assess connectivity for a diverse set of rare species in seven urban study areas across southern Michigan, USA. We incorporated multiple connectivity tools for a comprehensive appraisal of species-habitat patterns across these urban landscapes. We observed distinct differences in connectivity by taxonomic group and site. The three turtle species (Blanding's, Eastern Box, and Spotted) consistently had more habitat predicted to be suitable per site than other evaluated species. This is promising for this at-risk taxonomic group and allows conservation efforts to focus on mitigating threats such as road mortality. Grassland and prairie-associated species (American Bumble Bee, Black and Gold Bumble Bee, and Henslow's Sparrow) had the least amount of habitat on a site-by-site basis. Kalamazoo and the northern Detroit sites had the highest levels of multi-species connectivity across the entire study area based on the least cost paths. These connectivity results have direct applications in urban planning. Kalamazoo, one of the focal urban regions, has implemented a Natural Features Protection (NFP) plan to bolster natural area protections within the city. We compared our connectivity results to the NFP area and show where this plan will have an immediate positive impact and additional areas for potential consideration in future expansions of the protection network. Our results show that conservation opportunities exist within each of the assessed urban areas for maintaining rare species, a key benefit of this multi-species and multi-site approach.

Passing rail traffic reduces bat activity

Rail transport is expanding, with a global increase in infrastructure of up to one-third predicted by 2050. Greater reliance on rail is expected to benefit the environment at a planetary level, by mitigating transport-related carbon emissions. However, smaller-scale, more direct consequences for wildlife are unclear, as unlike roads, railway impacts on animal ecology are rarely studied. As a group, bats frequently interact with transport networks due to their broad distribution and landscape-scale movements. Additionally, their nocturnality, and use of echolocation mean bats are likely to be affected by light and noise emitted by trains. To investigate whether passing trains affect bat activity levels, we monitored the two most abundant UK species using ultrasonic detectors at 12 wooded rail-side sites in southern England. Activity fell by ≥ 30-50% each time a train passed, for at least two minutes. Consequently, activity was reduced for no less than one-fifth of the time at sites with median rail traffic, and two-thirds or more of the time at the busiest site. Such activity changes imply repeated evasive action and/or exclusion from otherwise favourable environments, with potential for corresponding opportunity or energetic costs. Hence, disturbance by passing trains may disadvantage bats in most rail-side habitats.

Diversity and Abundance of Roadkilled Bats in the Brazilian Atlantic Forest

Faunal mortality from roadkill has a negative impact on global biodiversity, and bats are among the roadkilled animals. In South America, the Atlantic Forest covers southeastern Brazil, a region which sustains a large bat diversity. In this biome, the Sooretama reserves are crossed by the federal highway BR-101, one of the busiest in Brazil. We analyzed bats roadkilled along the 25 km stretch of highway that crosses the Sooretama reserves. Data were collected between the years 2010 and 2015. In total, 773 individuals distributed among 47 bat species were roadkilled during this period. The insectivorous feeding guild was the most affected, accounting for 25 species and 74% of the recorded roadkill, and those flying in the open area were the most frequently roadkilled (41.9%). Bat mortality rates did not differ between months of the year. However, the relation between rainy days and roadkill was negative. Monitoring by foot was more efficient than by car for detection of bat carcasses. Radars with a speed limit below 60 km/h reduced the rates of roadkill. The diversity of deceased bats found in this study represents 40% of the known species in the Atlantic Forest, and is the largest among current studies of species killed on highways globally. The present study raises concerns about the high diversity and abundance of roadkilled insectivorous bats and the conservation of these animals in the Neotropical region.

Fish Avoid Visually Noisy Environments Where Prey Targeting Is Reduced

AbstractThe environment contains different forms of ecological noise that can reduce the ability of animals to detect information. Here, we ask whether animals adapt their behavior to either exploit or avoid areas of their environment with increased dynamic visual noise. Three-spined sticklebacks (Gasterosteus aculeatus) were immersed in environments with a simulated form of naturally occurring visual noise-moving light bands that form on underwater substrates caused by the refraction of light through surface waves. We tested whether this form of visual noise affected fish's habitat selection, movements, and prey-targeting behavior. Fish avoided areas of the environment with increased visual noise and achieved this by increasing their activity as a function of the locally perceived noise level. Fish were less likely to respond to virtual prey in environments with increased visual noise, highlighting a potential impact that visual noise has on their perceptual abilities. Fish did not increase or decrease their refuge use in environments with increased visual noise, providing no evidence that visual noise increased either exploratory or risk-aversive behavior. Our results indicate that animals can use simple behavioral strategies to avoid visually noisy environments, thereby mitigating the impacts that these environments appear to have on their perceptual abilities.

Hit the road bat! High bat activity on the road verges in Brazilian savanna

Roads have direct and indirect impacts on animals present in the surrounding habitats. Bats have extensive foraging ranges which may include roads, and are therefore particularly affected by them. This study aimed to analyze the effects of roads on bat activity and diversity in the Brazilian savanna. Nine transects were established in protected areas in central Brazil with sampling points at 0, 500, 1,000, and 1,500 m away from roads. At each point, we recorded bat echolocation for 12 h and evaluated the influence of road type and distance from the road on bat activity, diversity, and foraging effort. Season, normalized difference vegetation index (NDVI), and distance to water also were included in the models. We found that species richness in the dry season and activity of open space insectivores were significantly higher on road verges than on areas farther from roads, while foraging effort and activity of edge space insectivores were only influenced by season. The activity of edge space insectivores also increased significantly with increasing distance to water during the rainy season. We suggest that bat individuals do not forage near roads, but rather use them as flyways or cross them to forage in sites outside the protected areas, which can increase the risk of collision with vehicles.

Insectivorous bats are less active near freeways

Traffic disturbances (i.e. pollution, light, noise, and vibrations) often extend into the area surrounding a road creating a ‘road-effect zone’. Habitat within the road-effect zone is degraded or, in severe cases, completely unsuitable for wildlife, resulting in indirect habitat loss. This can have a disproportionate impact on wildlife in highly modified landscapes, where remaining habitat is scarce or occurs predominantly along roadside reserves. In this study, we investigated the road-effect zone for insectivorous bats in highly cleared agricultural landscapes by quantifying the change in call activity with proximity to three major freeways. The activity of seven out of 10 species of bat significantly decreased with proximity to the freeway. We defined the road-effect zone to be the proximity at which call activity declined by at least 20% relative to the maximum detected activity. The overall road-effect zone for bats in this region was 307 m, varying between 123 and 890 m for individual species. Given that this road-effect zone exceeds the typical width of the roadside verges (<50 m), it is possible that much of the vegetation adjacent to freeways in this and similar landscapes provides low-quality habitat for bats. Without accounting for the road-effect zone, the amount of habitat lost or degraded due to roads is underestimated, potentially resulting in the loss of wildlife, ecosystem services and key ecosystem processes (e.g. predator-prey or plant-pollinator interactions) from the landscape. We suggest all future environmental impact assessments include quantifying the road-effect zone for sensitive wildlife, in order to best plan and mitigate the impact of roads on the environment. Mitigating the effects of new and existing roads on wildlife is essential to ensure enough high-quality habitat persists to maintain wildlife populations.

Artificial lighting reduces the effectiveness of wildlife-crossing structures for insectivorous bats

In an attempt to improve cost-effectiveness, it has become increasingly popular to adapt wildlife crossing structures to enable people to also use them for safe passage across roads. However, the required needs of humans and wildlife may conflict, resulting in a structure that does not actually provide the perceived improvement in cost-effectiveness, but instead a reduction in conservation benefits. For example, lighting within crossing structures for human safety at night may reduce use of the structure by nocturnal wildlife, thus contributing to barrier and mortality effects of roads rather than mitigating them. In this study, we experimentally evaluated the impact of artificial light at night on the rate of use of wildlife crossing structures, specifically underpasses, by ten insectivorous bat species groups in south-eastern Australia. We monitored bat activity before, during and after artificially lighting the underpasses. We found that bats tended to avoided lit underpasses, and only one species consistently showed attraction to the light. Artificial light at night in underpasses hypothetically increases the vulnerability of bats to road-mortality or to the barrier effect of roads. The most likely outcomes of lighting underpasses were 1. an increase in crossing rate above the freeway and a decrease under the underpasses, or 2. a reduction in crossing rate both above freeways and under the underpasses, when structures were lit. Our results corroborate those of studies on terrestrial mammals, and thus we recommend that underpasses intended to facilitate the movement of wildlife across roads should not be lit.

Testing bat abundance and diversity predictions by PREBAT, a connectivity-based habitat suitability model for insectivorous bats

Where large landscape modifications are planned, e.g. for infrastructure or exploitation, ecological impact assessments are required because of their potential effects on environment and species. Methods that make such assessments more standardized, efficient, and reliable are highly desirable. This paper proposes a new connectivity-based habitat model for bats (PREBAT), which could be used as a tool for impact assessments. Using data that was specifically collected for this purpose, the performance of PREBAT is critically analyzed and discussed. For this study, 50 sites within an area of 850 km2 in eastern Sweden were inventoried for four nights each using automatic ultrasound recorders to get an empiric measure of bat occurrence that could be compared with PREBAT predictions. The correlation between the predicted values from PREBAT and the observed bat activity (number of recordings) or species richness was tested using generalized linear mixed models. Predicted values of PREBAT are significantly correlated to the number of species that regularly (more than one night) occur at a given site, but not to the total number of species. PREBAT performed also much better at predicting the activity of forest-living species than overall bat activity, which makes PREBAT particularly suitable for predicting conflicts for those species. This study proposes a new habitat model for bats that takes spatial connectivity between habitat patches into account. PREBAT is shown to perform satisfyingly and has the potential to become a useful tool in assessing the ecological impact of large-scale landscape modifications.

Road effects on bat activity depend on surrounding habitat type

The effects of roads on bats are still a poorly documented issue. Most of the available research focuses on large and high-traffic highways, while low-medium-traffic roads are often assumed to have negligible impacts. However, small roads are ubiquitous in landscapes around the world. We examined the effects of these roads, as well as habitat types, on the activity of three bat guilds (short-, mid- and long-range echolocators) and the most common bat species Pipistrellus kuhlii. We performed three bat acoustic surveys between May and October 2015, with these surveys being performed along twenty transects that were each 1000 m long and perpendicular to three roads with different traffic volumes. The surveys were performed in dense Mediterranean woodland ("montado") and open agricultural field habitats, which were the two dominant land uses. At each transect, bat activity was simultaneously registered at 0, 50, 100, 200, 500 and 1000 m from the road with the use of an ultrasound recorder. According to the generalized linear mixed effects models, the overall activity of bats and of the short- and mid-range echolocators increased with increased distance from the roads and was dependent on the surrounding habitats. In contrast, the long-range echolocators and P. kuhlii were more tolerant to road. Our results also show that the activity was higher in woodland areas, however road verges seem to be a significant habitat in an open agricultural landscape. The major negative effects extended to approximately 300 m from the roads in woodlands and penetrate further into the open field (>500 m). The management of roadside vegetation, combined with the bat habitat improvement in areas that are further from the roads, may mitigate the negative effects. To make road-dominated landscapes safer for bats, the transport agencies need to balance the trade-offs between habitat management and road kill risk.

Do riparian forest strips in modified forest landscapes aid in conserving bat diversity?

Agricultural practices lead to losses of natural resources and biodiversity. Maintaining forests alongside streams (riparian forest strips) has been used as a mechanism to minimize the impact of clearing for agriculture on biodiversity. To test the contribution of riparian forest strips to conserve biodiversity in production landscapes, we selected bats as a biodiversity model system and examined two dimensions of diversity: taxonomic and functional. We compared bat diversity and composition in forest, with and without stream habitat, and in narrow forest riparian strips surrounded by areas cleared for agriculture. We tested the hypothesis that riparian forest strips provide potential conservation value by providing habitat and serving as movement corridors for forest bat species. Riparian forest strips maintained 75% of the bat species registered in forested habitats. We found assemblage in sites with riparian forest strips were dominated by a few species with high abundance and included several species with low abundance. Bat species assemblage was more similar between sites with streams than between those sites to forests without stream habitat. These results highlight the importance of stream habitat in predicting presence of bat species. We registered similar number of guilds between forest sites and riparian forest strips sites. Relative to matrix habitats, stream and edge habitats in riparian forest strips sites were functionally more diverse, supporting our hypothesis about the potential conservation value of riparian forest strips. Results from this study suggest that maintaining riparian forest strips within cleared areas for agricultural areas helps conserve the taxonomic and functional diversity of bats. Also, it provides basic data to evaluate the efficacy of maintaining these landscape features for mitigating impacts of agricultural development on biodiversity. However, we caution that riparian forest strips alone are not sufficient for biodiversity maintenance; their value depends on maintenance of larger forest areas in their vicinity.

Variation in regional and landscape effects on occupancy of temperate bats in the southeastern U.S

Habitat loss, wind energy development, and the disease white-nose syndrome are major threats contributing to declines in bat populations in North America. In the southeastern US in particular, the recent arrival of white-nose syndrome and changes in landscape composition and configuration have driven shifts in bat species populations and distributions. Effective management strategies which address these large-scale, community-level threats require landscape-scale analyses. Our objective was to model the relationship between ecoregional and landscape factors and occupancy by all bat species in South Carolina, USA, during summer. We conducted acoustic surveys from mid-May through July 2015 and 2016 and evaluated temporally dynamic occupancy models for eight bat species or species groups at the 100 km2 level. We found significant effects of landscape factors such as ecoregion and forest edge density for three species, but habitat condition effects were not statistically significant for five other species. Thus, for some species, site-use analyses may be more appropriate than larger scale occupancy analyses. However, our occupancy predictions generally matched statewide historical distributions for all species, suggesting our approach could be useful for monitoring landscape-level trends in bat species. Thus, while our scale of study was likely too coarse for assessing fine-scale habitat associations for all bat species, our findings can improve future monitoring efforts, inform conservation priorities, and guide subsequent landscape-scale studies for bat species and community-level responses to global change.

No effect of artificial light of different colors on commuting Daubenton's bats (Myotis daubentonii) in a choice experiment

Progressive illumination at night poses an increasing threat to species worldwide. Light at night is particularly problematic for bats as most species are nocturnal and often cross relatively large distances when commuting between roosts and foraging grounds. Earlier studies have shown that illumination of linear structures in the landscape disturbs commuting bats, and that the response of bats to light may strongly depend on the light spectrum. Here, we studied the impact of white, green, and red light on commuting Daubenton's bats (Myotis daubentonii). We used a unique location where commuting bats cross a road by flying through two identical, parallel culverts underneath. We illuminated the culverts with white, red, and green light, with an intensity of 5 lux at the water surface. Bats had to choose between the two culverts, each with a different lighting condition every night. We presented all paired combinations of white, green, and red light and dark control in a factorial design. Contrary to our expectations, the number of bat passes through a culvert was unaffected by the presence of light. Furthermore, bats did not show any preference for light color. These results show that the response of commuting Daubenton's bats to different colors of light at night with a realistic intensity may be limited when passing through culverts.

Timing and technique impact the effectiveness of road-based, mobile acoustic surveys of bats

Mobile acoustic surveys are a common method of surveying bat communities. However, there is a paucity of empirical studies exploring different methods for conducting mobile road surveys of bats. During 2013, we conducted acoustic mobile surveys on three routes in north‐central Indiana, U.S.A., using (1) a standard road survey, (2) a road survey where the vehicle stopped for 1 min at every half mile of the survey route (called a “start‐stop method”), and (3) a road survey with an individual using a bicycle. Linear mixed models with multiple comparison procedures revealed that when all bat passes were analyzed, using a bike to conduct mobile surveys detected significantly more bat passes per unit time compared to other methods. However, incorporating genus‐level comparisons revealed no advantage to using a bike over vehicle‐based methods. We also found that survey method had a significant effect when analyses were limited to those bat passes that could be identified to genus, with the start–stop method generally detecting more identifiable passes than the standard protocol or bike survey. Additionally, we found that significantly more identifiable bat passes (particularly those of the Eptesicus and Lasiurus genera) were detected in surveys conducted immediately following sunset. As governing agencies, particularly in North America, implement vehicle‐based bat monitoring programs, it is important for researchers to understand how variations on protocols influence the inference that can be gained from different monitoring schemes.

Sound-mapping a coniferous forest-Perspectives for biodiversity monitoring and noise mitigation

Acoustic diversity indices have been proposed as low-cost biodiversity monitoring tools. The acoustic diversity of a soundscape can be indicative of the richness of an acoustic community and the structural/vegetation characteristics of a habitat. There is a need to apply these methods to landscapes that are ecologically and/or economically important. We investigate the relationship between the acoustic properties of a coniferous forest with stand-age and structure. We sampled a 73 point grid in part of the UK’s largest man-made lowland coniferous plantation forest, covering a 320ha mosaic of different aged stands. Forest stands ranged from 0–85 years old providing an age-gradient. Short soundscape recordings were collected from each grid point on multiple mornings (between 6am-11am) to capture the dawn chorus. We repeated the study during July/August in 2014 and again in 2015. Five acoustic indices were calculated for a total of 889 two minute samples. Moderate relationships between acoustic diversity with forest stand-age and vegetation characteristics (canopy height; canopy cover) were observed. Ordinations suggest that as structural complexity and forest age increases, the higher frequency bands (4-10KHz) become more represented in the soundscape. A strong linear relationship was observed between distance to the nearest road and the ratio of anthropogenic noise to biological sounds within the soundscape. Similar acoustic patterns were observed in both years, though acoustic diversity was generally lower in 2014, which was likely due to differences in wind conditions between years. Our results suggest that developing these relatively low-cost acoustic monitoring methods to inform adaptive management of production landscapes, may lead to improved biodiversity monitoring. The methods may also prove useful for modelling road noise, landscape planning and noise mitigation.

Patterns of Bat Distribution and Foraging Activity in a Highly Urbanized Temperate Environment

Understanding how to manage biodiversity in urban areas will become increasingly important as density of humans residing in urban centers increases and urban areas expand. While considerable research has documented the shifts in biodiversity along urbanization gradients, much less work has focused on how characteristics of dense urban centers, effectively novel environments, influence behavior and biodiversity. Urban bats in San Francisco provide an opportunity to document changes in behavior and biodiversity to very high-density development. We studied (1) the distribution and abundance of bat foraging activity in natural areas; and (2) characteristics of natural areas that influence the observed patterns of distribution and foraging activity. We conducted acoustic surveys of twenty-two parks during 2008-2009. We confirmed the presence of four species of bats (Tadarida brasiliensis, Myotis yumanensis, Lasiurus blossevillii, and M. lucifugus). T. brasiliensis were found in all parks, while M. yumanensis occurred in 36% of parks. Results indicate that proximity to water, park size, and amount of forest edge best explained overall foraging activity. Proximity to water best explained species richness. M. yumanensis activity was best explained by reduced proportion of native vegetation as well as proximity to water. Activity was year round but diminished in December. We show that although bats are present even in very densely populated urban centers, there is a large reduction in species richness compared to that of outlying areas, and that most habitat factors explaining their community composition and activity patterns are similar to those documented in less urbanized environments.

Anthropogenic noise disrupts use of vocal information about predation risk

Anthropogenic noise is rapidly becoming a universal environmental feature. While the impacts of such additional noise on avian sexual signals are well documented, our understanding of its effect in other terrestrial taxa, on other vocalisations, and on receivers is more limited. Little is known, for example, about the influence of anthropogenic noise on responses to vocalisations relating to predation risk, despite the potential fitness consequences. We use playback experiments to investigate the impact of traffic noise on the responses of foraging dwarf mongooses (Helogale parvula) to surveillance calls produced by sentinels, individuals scanning for danger from a raised position whose presence usually results in reduced vigilance by foragers. Foragers exhibited a lessened response to surveillance calls in traffic-noise compared to ambient-sound playback, increasing personal vigilance. A second playback experiment, using noise playbacks without surveillance calls, suggests that the increased vigilance could arise in part from the direct influence of additional noise as there was an increase in response to traffic-noise playback alone. Acoustic masking could also play a role. Foragers maintained the ability to distinguish between sentinels of different dominance class, increasing personal vigilance when presented with subordinate surveillance calls compared to calls of a dominant groupmate in both noise treatments, suggesting complete masking was not occurring. However, an acoustic-transmission experiment showed that while surveillance calls were potentially audible during approaching traffic noise, they were probably inaudible during peak traffic intensity noise. While recent work has demonstrated detrimental effects of anthropogenic noise on defensive responses to actual predatory attacks, which are relatively rare, our results provide evidence of a potentially more widespread influence since animals should constantly assess background risk to optimise the foraging-vigilance trade-off.

Roads and bats: a meta-analysis and review of the evidence on vehicle collisions and barrier effects

Roads are a potential threat to bat conservation. In addition to the direct risk of collision of bats with vehicles, roads could pose a threat to bat populations as a result of habitat loss, degradation and fragmentation, and could act as barriers to movements of bats between habitats.

We performed a systematic review of the literature and conducted meta‐analyses to assess the threat posed by roads to bats as a result of 1) collisions between bats and vehicles and 2) roads acting as barriers to movements of bats.

Based on collated records of 1207 bat road casualties in Europe, we found that low‐flying species are more prone to collisions than high‐flying species, and that juveniles are more vulnerable to collisions than adults. In addition, meta‐analysis identified a significant bias towards male casualties. Casualties included rare species such as Barbastella barbastellus and geographically restricted species such as Rhinolophus species.

The bias towards male casualties could be indicative of greater natal philopatry or lower dispersal among females, or of sexual segregation in habitats of varying quality, i.e. females may occupy better quality habitats than males, and road density may be lower in better quality habitats.

Whether or not roads act as barriers to the movement of bats depends on a complex interplay of habitat and species‐specific behaviour. For example, the presence of favourable habitat for bats – notably woodland – was found in this review to be linked with significantly reduced barrier effects but a heightened risk of collision.

Our data suggest that roads do pose a threat to bats. Future research should assess the contribution of traffic noise and street lighting to the barrier effect of roads. Where new road schemes are monitored by ecological practitioners, it is vital that consistent protocols are employed to ensure that bat activity can be compared before and after the road is built. Evidence from such research should be used to minimize the risks for bats of any roads built in the future, and to design safe crossing points for bats.

Sensitivity of bats to urbanization: a review

In this article we review the current knowledge of the effects of urban expansion on bats and assess the potential of these mammals as bioindicators of urbanization. The response of bats to this process is highly species-specific: some species tolerate urban habitat or are even favoured by its roosting or foraging opportunities, others are affected by the loss or fragmentation of key natural habitat, or by the physical and chemical pollution associated with urbanization. Species responses generally translate into altered community structures, with few markedly dominating species. We propose different hypothetical models of bat fitness along an urbanization gradient and discuss why bat population density may not be an effective fitness proxy to assess the reactions of these mammals to urban expansion. We also suggest that urban habitat may act as an ecological trap even for apparently synurbic species. Overall, bat sensitivity to urbanization makes these mammals promising candidates to track the effects of this process of land use change on the biota, but more studies, specifically tailored to explore this role, are needed.

Large roads reduce bat activity across multiple species

Although the negative impacts of roads on many terrestrial vertebrate and bird populations are well documented, there have been few studies of the road ecology of bats. To examine the effects of large roads on bat populations, we used acoustic recorders to survey bat activity along ten 300 m transects bordering three large highways in northern California, applying a newly developed statistical classifier to identify recorded calls to the species level. Nightly counts of bat passes were analyzed with generalized linear mixed models to determine the relationship between bat activity and distance from a road. Total bat activity recorded at points adjacent to roads was found to be approximately one-half the level observed at 300 m. Statistically significant road effects were also found for the Brazilian free-tailed bat (Tadarida brasiliensis), big brown bat (Eptesicus fuscus), hoary bat (Lasiurus cinereus), and silver-haired bat (Lasionycteris noctivagans). The road effect was found to be temperature dependent, with hot days both increasing total activity at night and reducing the difference between activity levels near and far from roads. These results suggest that the environmental impacts of road construction may include degradation of bat habitat and that mitigation activities for this habitat loss may be necessary to protect bat populations.