Camera Sites Research Articles

The effect of camera-trap viewshed obstruction on wildlife detection: implications for inference

Abstract ContextCamera traps are one of the most popular tools used to study wildlife worldwide. Numerous recent studies have evaluated the efficiency and effectiveness of camera traps as a research tool. Nonetheless, important aspects of camera-trap methodology remain in need of critical investigation. One such issue relates to camera-trap viewshed visibility, which is often compromised in the field by physical obstructions (e.g. trees) or topography (e.g. steep slopes). The loss of visibility due to these obstructions could affect wildlife detection rates, with associated implications for study inference and management application. AimsWe aimed to determine the effect of camera-trap viewshed obstruction on wildlife detection rates for a suite of eight North American species that vary in terms of ecology, commonness and body size. MethodsWe deployed camera traps at 204 sites throughout an extensive semi-urban park system in Cleveland, Ohio, USA, from June to September 2016. At each site, we quantified camera-trap viewshed obstruction by using a cover-board design. We then modelled the effects of obstruction on wildlife detection rates for the eight focal species. Key resultsWe found that detection rates significantly decreased with an increasing viewshed obstruction for five of the eight species, including both larger and smaller mammal species (white-tailed deer, Odocoileus virginianus, and squirrels, Sciurus sp., respectively). The number of detections per week per camera decreased two- to three-fold as visibility at a camera site decreased from completely free of obstruction to mostly obstructed. ConclusionsThese results imply that wildlife detection rates are influenced by site-level viewshed obstruction for a variety of species, and sometimes considerably so. ImplicationsResearchers using camera traps should address the potential for this effect to ensure robust inference from wildlife image data. Accounting for viewshed obstruction is critical when interpreting detection rates as indices of abundance or habitat use because variation in detection rate could be an artefact of site-level viewshed obstruction rather than due to underlying ecological processes.

Using lorelograms to measure and model correlation in binary data: Applications to ecological studies

Abstract Tools for describing correlation structures in binary data are underrepresented in the ecological literature, and methods commonly applied to continuous data are inappropriate because of intrinsic features of binary data (e.g. variance dependent on the mean). Describing how correlation changes in time and space, or in response to different stimuli, can provide insights into the ecological processes generating observed patterns. Moreover, proper modelling of correlation structures is necessary for reliably estimating covariate effects. We introduce ecologists to the lorelogram (Heagerty & Zeger, 1998), a tool used to identify and describe dependency structures in binary data. Lorelograms can help guide data aggregation efforts to facilitate independence, or alternatively, to inform appropriate structures for modelling correlated data. We developed the r‐package, lorelogram, for estimating and plotting lorelograms and show how it can be used to identify various dependency structures using simulated data. We analyse data from the North American Breeding Bird Survey and camera trap data from a carnivore study in Minnesota to demonstrate how the lorelogram can describe spatial and temporal dependencies, respectively. In the latter case, we show how the lorelogram can identify short‐term dependencies (e.g. individuals that linger at the camera site for several minutes), longer‐term dependencies (i.e. diel activity patterns) and effects of site‐specific covariates such as attractants. We then illustrate how this information can be incorporated in a modelling framework that accounts for these correlation structures (e.g. when modelling daily activity patterns). The lorelogram is a promising tool for quantifying correlation in binary data over space or time. In addition to the applications presented in our paper, it could be used to identify independent sampling units for occupancy modelling or to quantify behavioural responses to covariates such as anthropogenic stressors or recent presence of prey, predators or competitors.

An Overall Deformation Monitoring Method of Structure Based on Tracking Deformation Contour

In structural deformation monitoring, traditional methods are mainly based on the deformation data measured at several individual points. As a result, only the discrete deformation, not the overall one, can be obtained, which hinders the researcher from a better and all-round understanding on the structural behavior. At the same time, the surrounding area around the measuring structure is usually complicated, which notably escalates the difficulty in accessing the deformation data. In dealing with the said issues, a digital image-based method is proposed for the overall structural deformation monitoring, utilizing the image perspective transformation and edge detection. Due to the limitation on camera sites, the lens is usually not orthogonal to the measuring structure. As a result, the obtained image cannot be used to extract the deformation data directly. Thus, the perspective transformation algorithm is used to obtain the orthogonal projection image of the test beam under the condition of inclined photography, which enables the direct extraction of deformation data from the original image. Meanwhile, edge detection operators are used to detect the edge of structure’s orthogonal projection image, to further characterize the key feature of structural deformation. Using the operator, the complete deformation data of structural edge are obtained by locating and calibrating the edge pixels. Based on the above, a series of load tests has been carried out using a steel–concrete composite beam to validate the proposed method, with the implementation of traditional dial deformation gauges. It has been found that the extracted edge lines have an obvious sawtooth effect due to the illumination environment. The sawtooth effect makes the extracted edge lines slightly fluctuate around the actual contour of the structure. On this end, the fitting method is applied to minimize the fluctuation and obtain the linear approximation of the actual deflection curve. The deformation data obtained by the proposed method have been compared with the one measured by the dial meters, indicating that the measurement error of the proposed method is less than 5%. However, since the overall deformation data are continuously measured by the proposed method, it can better reflect the overall deformation of the structure, and moreover the structural health state, when compared with the traditional “point” measurements.

Estimating leopard density across the highly modified human-dominated landscape of the Western Cape, South Africa

AbstractApex predators play a critical role in maintaining the health of ecosystems but are highly susceptible to habitat degradation and loss caused by land-use changes, and to anthropogenic mortality. The leopard Panthera pardus is the last free-roaming large carnivore in the Western Cape province, South Africa. During 2011–2015, we carried out a camera-trap survey across three regions covering c. 30,000 km2 of the Western Cape. Our survey comprised 151 camera sites sampling nearly 14,000 camera-trap nights, resulting in the identification of 71 individuals. We used two spatially explicit capture–recapture methods (R programmes secr and SPACECAP) to provide a comprehensive density analysis capable of incorporating environmental and anthropogenic factors. Leopard density was estimated to be 0.35 and 1.18 leopards/100 km2, using secr and SPACECAP, respectively. Leopard population size was predicted to be 102–345 individuals for our three study regions. With these estimates and the predicted available leopard habitat for the province, we extrapolated that the Western Cape supports an estimated 175–588 individuals. Providing a comprehensive baseline population density estimate is critical to understanding population dynamics across a mixed landscape and helping to determine the most appropriate conservation actions. Spatially explicit capture–recapture methods are unbiased by edge effects and superior to traditional capture–mark–recapture methods when estimating animal densities. We therefore recommend further utilization of robust spatial methods as they continue to be advanced.

Using cameras of automatic number plate recognition system for seat belt enforcement a case study of Sanliurfa (Turkey)

Purpose The purpose of this paper is to quantify the effect of the enforcement, which was carried out with ANPRs, on seat belt use. Though the Seat belt Act was enacted in 1992, it did not lead to an expected increase in seat belt use in Turkey including Sanliurfa, which is one of the immense provinces with a population of over 2m. The Sanliurfa Police Department set in an enforcement campaign, in which automatic number plate recognition (ANPR) cameras were used to facilitate an increment in using seat belts in the city center. Under the police leadership, seat belt use enforcement campaign was hugely publicized and sustained throughout the city. Design/methodology/approach The ANPRs did not have a feature to detect seat belt wearing automatically. Thus, this study tested whether automated plate recognition cameras have a deterrence effect on seat belt usage. To assess the efficacy of this enforcement project, the authors employed a pre/post-implementation design. For this study, the records of the 11 ANPR camera sites, 2 non-camera sites and 2 control sites were utilized. Findings The results of this study revealed that the seat belt use rate was around 8 percent, before camera enforcement in Sanliurfa. Overall increases were 12 percent during the warning period, 60 percent for the beginning period and 78 percent three months after enforcement began at camera sites. One-way ANOVA results suggested the differences between means of seat belt use counts were statistically significant F (3, 61,596)=15,456, p=0.000. Research limitations/implications The findings suggest that there are several reasons for the substantial increase in the seat belt use rate. The first reason for the success of the cameras was their deterrent effect on the drivers, because the drivers were aware that the traffic offense had become readily observable via camera detection in the intersections, and the drivers did not want to be penalized. Second, it is considered that a well-organized publicity of the cameras made a significant contribution to the effectiveness of the enforcement by increasing perceived detection risk. Finally, it is considered that the reason behind the sudden increase in seat belt use was the red-light cameras that had been already in use in Sanliurfa. Namely, the experience of the drivers about camera enforcement gave rise to the rapid decrease in seat belt violation rate in the warning period. Practical implications Using cameras (automatic or not) for seat belt enforcement and publicizing this enforcement can help to save resources and lives. Originality/value This study found a lot of news about similar enforcement on the internet, but no study was found in the literature that reveals if the enforcement can produce an effective result. Thus, this is the first study in Turkey, may be in the world, that evaluated if cameras of the ANPRS can generate effective seat belt enforcement. Furthermore, the study betokened that traffic violations, which cannot be automatically detected by cameras such as cell phone use and smoking in a vehicle can be effectively enforced by non-automatic cameras. Therefore, we believe that the study will contribute policing and the traffic safety literature.

Spatial and temporal relationship between native mammals and free-roaming dogs in a protected area surrounded by a metropolis

With rapid urbanization worldwide, anthropogenic impacts such as human settlements and invasive carnivores (dogs Canis familiaris, cats Felis catus) are altering spatial distributions and temporal activity patterns of native species. In this study, we focused on spatiotemporal responses of native mammals to anthropogenic impacts in a protected area surrounded by a large metropolis (i.e. Yangmingshan National Park inside Taipei-Keelung metropolis in northern Taiwan). We collected site use data of 11 mammal species (i.e. dogs, cats, nine native species) between 2012 and 2017 with a camera system comprising 121 camera sites. We quantified anthropogenic disturbances as distance to human settlements and activity levels of free-roaming dogs and cats. Species richness and occurrences of the native mammals increased with increasing distances to human settlements and decreasing activity level of dogs, with the latter having a stronger effect than the former. Diel activity overlap between native mammals and dogs was lower during April–July season, coinciding with the breeding season for several native mammals. In contrast, activity level of cats showed no relationships with species richness, occurrences or diel activities of the native mammals. This study demonstrated negative impacts of human settlements and free-roaming dogs on native mammal communities for protected areas in urban environments, and highlights dog activity as a major anthropogenic threat to wildlife.

Monitoring Landscape Dynamics in Central U.S. Grasslands with Harmonized Landsat-8 and Sentinel-2 Time Series Data

Remotely monitoring changes in central U.S. grasslands is challenging because these landscapes tend to respond quickly to disturbances and changes in weather. Such dynamic responses influence nutrient cycling, greenhouse gas contributions, habitat availability for wildlife, and other ecosystem processes and services. Traditionally, coarse-resolution satellite data acquired at daily intervals have been used for monitoring. Recently, the harmonized Landsat-8 and Sentinel-2 (HLS) data increased the temporal frequency of the data. Here we investigated if the increased data frequency provided adequate observations to characterize highly dynamic grassland processes. We evaluated HLS data available for 2016 to (1) determine if data from Sentinel-2 contributed to an improvement in characterizing landscape processes over Landsat-8 data alone, and (2) quantify how observation frequency impacted results. Specifically, we investigated into estimating annual vegetation phenology, detecting burn scars from fire, and modeling within-season wetland hydroperiod and growth of aquatic vegetation. We observed increased sensitivity to the start of the growing season (SOST) with the HLS data. Our estimates of the grassland SOST compared well with ground estimates collected at a phenological camera site. We used the Continuous Change Detection and Classification (CCDC) algorithm to assess if the HLS data improved our detection of burn scars following grassland fires and found that detection was considerably influenced by the seasonal timing of the fires. The grassland burned in early spring recovered too quickly to be detected as change events by CCDC; instead, the spectral characteristics following these fires were incorporated as part of the ongoing time-series models. In contrast, the spectral effects from late-season fires were detected both by Landsat-8 data and HLS data. For wetland-rich areas, we used a modified version of the CCDC algorithm to track within-season dynamics of water and aquatic vegetation. The addition of Sentinel-2 data provided the potential to build full time series models to better distinguish different wetland types, suggesting that the temporal density of data was sufficient for within-season characterization of wetland dynamics. Although the different data frequency, in both the spatial and temporal dimensions, could cause inconsistent model estimation or sensitivity sometimes; overall, the temporal frequency of the HLS data improved our ability to track within-season grassland dynamics and improved results for areas prone to cloud contamination. The results suggest a greater frequency of observations, such as from harmonizing data across all comparable Landsat and Sentinel sensors, is still needed. For our study areas, at least a 3-day revisit interval during the early growing season (weeks 14–17) is required to provide a >50% probability of obtaining weekly clear observations.

A Longitudinal Quasi-Experimental Study of Violence and Disorder Impacts of Urban CCTV Camera Clusters

Methodological challenges have hampered a number of previous studies into the crime reduction effectiveness of closed-circuit television (CCTV) surveillance systems. These have included the use of arbitrary fixed distances to represent estimated camera deterrence areas and a lack of control for camera sites with overlapping surveillance areas. The current article overcomes the first of these challenges by using camera view areas individually constructed by researchers viewing and manipulating cameras to determine precise camera viewsheds. The second challenge is addressed by grouping cameras into clusters of combined viewshed areas. The longitudinal crime and disorder reduction effectiveness of these clusters of overlapping CCTV cameras is tested in Philadelphia, PA. Multilevel mixed-effects models with time-varying covariates and measures from a noncomparable control area are applied to 10 years of crime data (2003–2012) within the viewsheds of 86 CCTV cameras grouped into 13 clusters. Models applied across violent street felonies and disorder incidents find no significant impact associated with the introduction of CCTV surveillance. Potential reasons for this are discussed.

A partially randomized field experiment on the effect of an acoustic gunshot detection system on police incident reports

To examine whether the introduction of an acoustic gunshot detection system (AGDS) allied to CCTV cameras increased the frequency of confirmed incidents of shots fired by bringing to notice gunfire events in public places that were not reported by the public. In a partially block-randomized experimental design, 17 acoustic sensors were co-located with CCTV cameras in a balanced design that matched the sensor camera sites with equivalent control locations. Gunshot-related incidents within 900 ft of both intervention and control sites for 8 months pre- and post-intervention were examined with multilevel negative binomial regression models. After implementation of the AGDS, gunshot incidents increased by 259%; however, there was no significant increase in the number of confirmed shootings. The AGDS did not significantly affect the number of confirmed shootings, but it did increase the workload of police attending incidents for which no evidence of a shooting was found. While awaiting technological improvements and considering the operational goals, police departments may wish to reconsider the current operational plan and objective of an AGDS.

A simple method to improve the quality of NDVI time-series data by integrating spatiotemporal information with the Savitzky-Golay filter

High-quality Normalized Difference Vegetation Index (NDVI) time-series data are important for many regional and global ecological and environmental applications. Unfortunately, residual noise in current NDVI time-series products greatly hinders their further applications. Several noise-reduction methods have been proposed during the past two decades, but two important issues remain to be resolved. First, the methods usually perform poorly for cases of continuous missing data in the NDVI time series. Second, they generally assume negatively biased noise in the NDVI time series and thus erroneously raise some local low NDVI values in certain cases (e.g., the harvest period for multi-season crops).We therefore developed a new noise-reduction algorithm called the Spatial-Temporal Savitzky-Golay (STSG) method. The new method assumes discontinuous clouds in space and employs neighboring pixels to assist in the noise reduction of the target pixel in a particular year. The relationship between the NDVI of neighboring pixels and that of the target pixel was obtained from multi-year NDVI time series thanks to the accumulation of NDVI data over many years, which would have been impossible a decade ago. We tested STSG on 16-day composite MODIS NDVI time-series data from 2001 to 2016 in regions of mainland China and 11 phenology camera sites in North American. The results showed that STSG performed significantly better compared with four previous widely used methods (i.e., the Asymmetric Gaussian, Double Logistic, Fourier-based, and Savitzky-Golay filter methods). One obvious advantage was that STSG was able to address the problem of temporally continuous NDVI gaps. STSG effectively increased local low NDVI values and simultaneously avoided overcorrecting low NDVI values during the crop harvest period. In addition, implementing STSG required only raw MODIS NDVI time-series products without any additional burden of data requirements. All of these advantages make STSG a promising noise-reduction method for generating high-quality NDVI time-series data.

Looking beyond wildlife: using remote cameras to evaluate accuracy of gridded snow data

AbstractThe use of remote cameras is widespread in wildlife ecology, yet few examples exist of their utility for collecting environmental data. We used a novel camera trap method to evaluate the accuracy of gridded snow data in a mountainous region of the northeastern US. We were specifically interested in assessing (1) how snow depth observations from remote cameras compare with gridded climate data, (2) the sources of error associated with the gridded data and (3) the influence of spatial sampling on bias. We compared daily observations recorded by remote cameras with Snow Data Assimilation System (SNODAS) gridded predictions using data from three winters (2014–2016). Snow depth observations were correlated with SNODAS predictions for sites (R2 = 0.20) and regions (R2 = 0.16), yet we detected factors associated with SNODAS bias at both scales. Specifically, SNODAS underpredicted depths at high elevations, at sites with higher solar radiation, and within conifer‐dominated forest. Depths were most underpredicted at highest elevations, up to 44 and 26 cm on average at the site and region scales, respectively. Bias was greatest when predictions were lowest, occasionally predicting snow absence when depths were >100 cm at camera sites. We also detected breakdowns in accuracy when certain environmental conditions varied within the 1 km2 SNODAS grid cells. For example, underprediction was greatest when the solar radiation values of camera stations increased relative to the mean of the SNODAS grid cells. This relationship was most prominent in mountainous regions, suggesting that factors which influence solar radiation (e.g. topographic complexity) contribute to SNODAS inaccuracy. We caution using gridded snow data for ecological studies when bias is unknown. We suggest increased sampling to adjust for errors associated with gridded data products that arise from factors, such as forest cover and topographic variability. Increasing resolution and accuracy of climate data will improve predictions of species’ responses to climate change.

Influence of biotic interactions on the distribution of Canada lynx (Lynx canadensis) at the southern edge of their range

The persistence of cold-adapted species along their equatorial range edge (i.e., southern range edge for species in the Northern Hemisphere and northern range edge for species in the Southern Hemisphere) is threatened by climate change. These species will be challenged not just by unfavorable climatic regimes, but also by changing biotic interactions, which may be more intense along equatorial edges. However, we currently have a poor understanding of the nature of biotic interactions at range edges and how climate may mediate those interactions, particularly for cold-adapted mammals. We studied the distribution of threatened Canada lynx (Lynx canadensis) at their southern range edge in northern Washington, United States from 2014 to 2016. Using data collected from 397 camera-trap stations in snow-on and snow-off seasons, and single- and 2-species occupancy models, we investigated seasonal patterns of habitat selection and spatial association of lynx with their primary prey (snowshoe hares, Lepus americanus) and potential competitors (bobcats, Lynx rufus; cougars, Puma concolor). Single-species occupancy models revealed lynx distribution was strongly associated with snowshoe hare abundance and topographic variables related to lower temperatures and increased moisture. In contrast, bobcats and cougars were more generalized in their habitat associations or displayed the reverse response to environmental variables. Spatial overlap of the 3 felid species increased during snow-off seasons. Two-species occupancy models showed a decrease in use of camera sites by lynx when bobcats were present, suggesting lynx were avoiding their warm-adapted competitor. Taken together, these results suggest that biotic interactions are partly shaping large-scale lynx distribution patterns along their southern range edge. Increasing temperatures and loss of snow may result in a combination of habitat isolation and potential for increased competitive interactions for lynx at the margins of their range.

Intercomparison of phenological transition dates derived from the PhenoCam Dataset V1.0 and MODIS satellite remote sensing

Phenology is a valuable diagnostic of ecosystem health, and has applications to environmental monitoring and management. Here, we conduct an intercomparison analysis using phenological transition dates derived from near-surface PhenoCam imagery and MODIS satellite remote sensing. We used approximately 600 site-years of data, from 128 camera sites covering a wide range of vegetation types and climate zones. During both “greenness rising” and “greenness falling” transition phases, we found generally good agreement between PhenoCam and MODIS transition dates for agricultural, deciduous forest, and grassland sites, provided that the vegetation in the camera field of view was representative of the broader landscape. The correlation between PhenoCam and MODIS transition dates was poor for evergreen forest sites. We discuss potential reasons (including sub-pixel spatial heterogeneity, flexibility of the transition date extraction method, vegetation index sensitivity in evergreen systems, and PhenoCam geolocation uncertainty) for varying agreement between time series of vegetation indices derived from PhenoCam and MODIS imagery. This analysis increases our confidence in the ability of satellite remote sensing to accurately characterize seasonal dynamics in a range of ecosystems, and provides a basis for interpreting those dynamics in the context of tangible phenological changes occurring on the ground.

High altitude ungulate communities in southwest China

Abstract In southwest China, three major rivers, the Yangtze, Mekong and Salween, flow down from the Tibetan plateau, creating a complex topography with a diverse, little-known ungulate community. We used camera traps and multi-species occupancy modeling to determine presence/absence, habitat use and estimate species richness/occupancy. At Langdu, east of the Yangtze, we had 23 camera sites in four habitats from 4000 to 4815 m asl; at Gehuaqing in the south of Baimaxueshan Nature Reserve (BNR) between Mekong and Yangtze we had 14 sites in two habitats from 3050 to 3600 m asl. At Langdu, we photographed tufted deer Elaphodus cephalophus (Milne-Edwards 1872) most often followed by serow Capricornis milneedwardsii (David 1869) and alpine musk deer Moschus chrysogaster (Hodgson 1839). At Gehuaqing, we photographed serow most often followed by tufted deer and forest musk deer Moschus berezovskii (Flerov 1929). Tufted deer were in the most habitats, and alpine musk deer were at an elevation higher than previously reported (4815 m). The only large carnivore recorded was Asian black bear Ursus thibetanus (Cuvier 1823) leopard cats Prionailurus bengalensis (Kerr 1792) were at 4579 m asl, higher than previously documented. Langdu had higher species richness than Gehuaqing, and tufted deer had the highest occupancy at both sites. We discuss differences with another site in the north of BNR.

Sympatry among Three Suid Species (Family Suidae) on the North Coast of Kenya

ABSTRACT Three species of suids occur on the broad coastal plain of Kenya east and north of the Tana River; desert warthog Phacochoerus aethiopicus, common warthog Phacochoerus africanus, and bushpig Potamochoerus larvatus. Systematic cameratrap surveys, comprising 9229 camera-trap days on grids at six study sites, were used to determine the distribution and relative abundance of these three suids in the Boni-Dodori Forest Complex (ca. 4000 km2) and in Arabuko-Sokoke Forest Reserve (416 km2) on Kenya's north and central coasts, respectively. In the Boni-Dodori Forest Complex, desert warthog was captured at one camera site, common warthog at four camera sites, and bushpig at 33 camera sites. In Arabuko-Sokoke Forest Reserve, only bushpig was captured (seven camera sites). Sympatry of desert warthog and common warthog seems limited in the Boni-Dodori Forest Complex. Here, desert warthog appears to be narrowly sympatric with bushpig whereas common warthog is broadly sympatric with bushpig. Sympatry of the th...

Coyote, fox, and bobcat response to anthropogenic and natural landscape features in a small urban area

Increasing urbanization across the southeastern United States presents unique challenges for wildlife; however certain species have learned to adapt and thrive in these environments. Coyotes (Canis latrans), bobcats (Lynx rufus), red foxes (Vulpes vulpes) and gray foxes (Urocyon cinereoargenteus) are four common medium-sized carnivores that have become closely associated with urban areas. The goal for this study was to determine how urban landscape features influence density and occurrence of these species in a small urban area and to evaluate if any effects were similar to those observed in larger urban areas. We conducted two eight-week camera surveys in the city of Nacogdoches, Texas (pop. 32,699) and immediate surrounding areas in summer and fall 2013. We evaluated single-season spatially explicit capture-recapture and occupancy models to estimate density, and occurrence, respectively, based on anthropogenic and natural features around each camera site. Coyotes (fall: 1.38 coyotes/km2) and bobcats (fall: 0.64 coyotes/km2) were associated with areas of green space, but their response to large and small green spaces changed seasonally. Conversely, red foxes (fall: 2.53 red foxes/km2) were more likely to occur near developed areas and were less detectable in areas with greater probability of coyote presence in fall only. In summer, gray foxes (fall: 0.05 gray foxes/km2) were more likely to occur in areas with lower building density and closer to buildings. This study indicates coyotes, foxes and bobcats respond to small-scale urbanization in a similar manner as large-scale urbanization.

AVERAGE SPEED ENFORCEMENT SYSTEM EFFICIENCY ASSESSMENT MODEL

Accidents are one of the leading cause of death all over the world. Speed has been identified as a factor in road accidents, influencing both the risk of accidents and the severity of the accidents. However, speeding is one of the most frequent violations of traffic rules by the road users. Many results of studies showed that the implementation of speed cameras significantly reduced the vehicle speed and the number of accidents near camera sites. One issue regarding speed enforcement by a speed camera is that a reduction in speed is obtained only on a short section of a road. The results of scientific research analysis suggest that this issue can be overcome by the employment of average speed enforcement system (hereafter system), which is a relatively new approach to traffic law enforcement. Until now, Lithuania had no methodology for selecting road sections to be installed with the system. The purpose of this paper is to develop a model for the assessment of safety impact of the system and to perform economic estimation of a system of Lithuanian main road sections selected under this model. The analysis of international practice helped to develop this model, which joins accident indicators, road and traffic parameters. A cost-benefit analysis of the system, implemented on main road sections and selected by suggested model, shows a high level of payback. The implementation of the system would pay back in one year of service.

Staying safe from top predators: patterns of co-occurrence and inter-predator interactions

Top predators often have cascading effects on mesopredator communities by driving behavioural changes. Using camera-trapping surveys, we explored the site-detection probability of sympatric predators and temporal overlap and examined behavioural patterns to explore hypotheses of carnivore guild interactions between and within large and small predators in the presence/absence of lion (Panthera leo) in open and closed habitat cover. We used single-season two-species occupancy models to test inter-predator interactions at 205 camera sites spread across five Protected Areas of the Maputaland Conservation Unit, South Africa. These data showed the respective associations between the presence of large carnivores and smaller carnivores. We observed that leopard (Panthera pardus) and hyena (Crocuta crocuta) tended to avoid interference encounters, as they were less likely co-detected at the same sites. There was a decrease in detection of leopard and hyena as a function of lion presence. Small predators such as the group honey badger (Mellivora capensis)-striped polecat (Ictonyx striatus) and the slender mongoose (Herpestes sanguineus) were detected less often at cameras where leopards were detected. Detection probabilities of the group badger-polecat and slender mongoose were much higher in the closed habitat than in open habitat where leopards were detected. At camera sites where hyenas were detected, badger-polecat and genet (Genetta tigrina) detection probability was much higher in the closed habitat than open habitat. Slender mongoose overlapped less temporally with large predators while others did not. Our study showed that large predator guilds can affect the probability of detecting subordinate mesopredators; therefore, reintroduction of large carnivores can have a cascading effect on subordinate carnivores, and it is necessary to consider this effect when planning recovery programmes for carnivore conservation. We think this study is of importance and interest as top predators often shape mesopredator communities by inducing apparent avoidance behaviour based on associations between the presence of large carnivores and smaller carnivores. As a consequence, smaller predators use closed habitat to minimize the risk of larger predators due to intraguild interference interaction. We explored behavioural patterns of sympatric predators’ site detection probability and temporal overlap and examined hypotheses about carnivore guild interactions between leopard and spotted hyena, these two and small predators with and without lion in open and closed habitat cover. Reintroduction of one carnivore population can have cascading effects on the other, and this nature of consequences needs to be accounted when planning conservation or species recovery programmes. Therefore, we extended our study to explore these important aspects. Our study is novel as there are no studies documenting species interactions between/within large and small predators from co-occurrence patterns in South Africa.

Large Mammal Use of Linear Remnant Forests in an Industrial Pulpwood Plantation in Sumatra, Indonesia

Riparian forests are often the last remaining areas of natural vegetation in agricultural and plantation forestry landscapes. Covering millions of hectares of land in Indonesia, industrial pulpwood plantations have rapidly replaced native forests. Our study aimed to better understand the conservation importance of linear remnants of riparian forest by examining their use by larger (>1 kg) mammal species. Our study site was located within an extensive acacia ( Acacia mangium) plantation adjoining Tesso Nilo National Park in Sumatra, Indonesia. Camera traps were used to detect mammals at 57 sites to assess the effects of corridor design and land cover covariates and species behavioral traits on mammal habitat use of four linear riparian forests. We recorded 17 species (including one International Union for Conservation of Nature [IUCN] Critically Endangered, two Endangered, and four Vulnerable) in riparian forests inside the plantation, including the Sumatran tiger ( Panthera tigris sumatrae), Malay tapir ( Tapirus indicus), and sun bear ( Helarctos malayanus). Some threatened species were only detected in the park buffer zone. Species varied in their responses to riparian forests, but distance to the national park, remnant width, and percent forest cover around the camera site were common predictors of remnant use. Many mammal species used riparian forests regardless of whether they were surrounded by intact acacia forests or recently cleared land. Our results indicate that linear remnant riparian forests ≤ 200 m in width can facilitate local (< 4 km) movements of many large mammal species in Sumatra, but wider riparian remnants would likely be more effective at promoting mammal movements over longer distances.

Heterogeneous treatment effects of speed cameras on road safety

This paper analyses how the effects of fixed speed cameras on road casualties vary across sites with different characteristics and evaluates the criteria for selecting camera sites. A total of 771 camera sites and 4787 potential control sites are observed for a period of 9 years across England. Site characteristics such as road class, crash history and site length are combined into a single index, referred to as a propensity score. We first estimate the average effect at each camera site using propensity score matching. The effects are then estimated as a function of propensity scores using local polynomial regression. The results show that the reduction in personal injury collisions ranges from 10% to 40% whilst the average effect is 25.9%, indicating that the effects of speed cameras are not uniform across camera sites and are dependent on site characteristics, as measured by propensity scores. We further evaluate the criteria for selecting camera sites in the UK by comparing the effects at camera sites meeting and not meeting the criteria. The results show that camera sites which meet the criteria perform better in reducing casualties, implying the current site selection criteria are rational.