Camera Sites Research Articles

The potential and practice of arboreal camera trapping

Abstract Arboreal camera trapping is a burgeoning method providing a novel and effective technique to answer research questions across a variety of ecosystems, and it has the capacity to improve our understanding of a wide range of taxa. However, while terrestrial camera trapping has received much attention, there is little guidance for dealing with the unique challenges of working in the arboreal realm. Our review draws on the expertise of researchers from six continents and the broader literature to investigate the advantages and disadvantages of arboreal camera trapping, and challenges to consider when using this technology. We also include mini‐guides with detailed information on the current arboreal camera trap literature, mounts used to install arboreal cameras, tree climbing pointers and safety tips, methods for deploying cameras without climbing, and tips for managing interference with camera function. We find that arboreal camera traps have been most commonly used in the study of mammals in forests; however, there is potential for this method to be applied to a broad range of habitats including urban areas, and taxa such as birds, amphibians, invertebrates, and plants. Methods in arboreal camera trapping could be improved by developing a greater understanding of the factors affecting detection of species. The most common challenges of arboreal camera trapping are camera placement and camera site access. These can be overcome by understanding correct camera orientation, managing potential sources of interference in front of cameras, utilizing appropriate cameras mounts and training researchers properly. Given the benefits and opportunities presented by arboreal camera trapping, it is likely to become an ever‐more popular method of studying arboreal species and systems. The information synthesized in this review provides guidance for future studies to help direct more reliable and robust ecological inferences from arboreal camera trapping.

Arboreal camera trapping: a reliable tool to monitor plant‐frugivore interactions in the trees on large scales

AbstractAlthough arboreal camera trapping is a growing field, it has rarely been used for monitoring plant‐frugivore interactions in the trees. Frugivore foraging behavior generally occurs in trees, hence arboreal camera trapping can be a potentially useful tool for frugivory research. We developed a camera trap sampling method to monitor plant‐frugivore interactions during mature fruiting periods. We used this method to monitor 318 individuals (camera sites) of 18 fleshy‐fruit plant species on 22 subtropical land‐bridge islands in the Thousand Island Lake, China. We recorded a total of at least 52 frugivorous animals, including a ground‐foraging bird species (Lophura nycthemera) and several mammals with foraging behaviors in the trees. We also recorded 4399 independent interaction events, including 275 unique plant‐bird interactions. We proposed a framework to classify interaction types and performed a sampling completeness test. We found that a sampling strategy that covered approximately a third of the fruit maturation period when most fruits were ripe was sufficient to sample plant‐frugivore interactions. Our results demonstrated that our sampling method with camera transects is reliable to monitor plant‐frugivore interactions in a fragmented landscape. This study helps to lay the methodological foundation for building networks of plant‐frugivore interactions with arboreal camera trapping on large spatial/temporal scales. As a non‐invasive, labor‐saving, and largely unbiased sampling method, the field application of arboreal camera trapping in different regions can advance the technology of biodiversity monitoring and lead to more accurate biodiversity inventories in arboreal environments.

Poaching Threatens the Establishment of a Lynx Population, Highlighting the Need for a Centralized Judiciary Approach

Illegal hunting represents a major threat to the conservation of predators, but its impact remains difficult to assess as there are strong incentives to conceal this criminal activity. Attributing declines of carnivores to poaching is therefore an important conservation challenge. We present a case study of the Eurasian lynx (Lynx lynx) in the Swiss Alps (Valais) where the current distribution range is smaller than in the recent past and population density is by ≥80% lower than in the adjacent Swiss Prealps. We tested four hypotheses to explain this lower density: (1) a too low density of camera-traps deployed for lynx surveys in Valais compared to the Prealps (methodological artifact); (2) less favorable environmental conditions around the camera-trap sites; (3) lower densities of the main prey; and (4) poaching. We estimated lynx and ungulate densities and environmental conditions at trail camera sites and could clearly reject the first three hypotheses because: (1) the survey protocol was similarly effective; (2) environmental conditions around the trapping sites in Valais were even more favorable for lynx detection than in the Prealps; and (3) prey supply was even larger in Valais. Concerning hypothesis 4, we discovered a network of illegal lynx traps (neck snares) in the main immigration corridor into Valais from the thriving adjacent lynx population in the Prealps, suggesting intense local poaching. Our findings substantiate the suspicions of long-lasting lynx poaching as a threat to the establishment and survival of the Valais population. The fact that instances of poaching were publicly known since 1995 but remained unabated for at least two decades, until the first conviction occurred, questions the commitment of local authorities to address this case of wildlife crime. Our study demonstrates the need for inquiries about poaching of top predators to be carried out at the highest levels of jurisdiction to avoid any risk of collusion between law enforcement agents and poachers.

Increasing the effectiveness of mobile speed cameras on rural roads in Victoria based on crash reductions from operations in Queensland

Mobile speed cameras on Victoria’s rural roads are not as effective as they could be due to the site selection criteria, the limited number of sites, and the visibility and predictability of their enforcement operations. Queensland’s overt mobile speed cameras achieve substantial crash reductions up to 4 km from rural camera sites due to site selection based only on crash history and randomised scheduling of operations to those sites. New sites in Victoria should be selected as in Queensland and camera visits should be randomly-scheduled. The Victorian Government’s announcement to increase mobile speed camera hours by 75% should take the form of at least 75% increase of rural sites. The new sites should be selected on the basis of a serious crash history within 2.5 km. Mobile speed cameras operated at these new rural sites could be expected to save 22.5 fatal crashes and 172 serious injury crashes per year.

Optimisation of surveillance camera site locations and viewing angles using a novel multi-attribute, multi-objective genetic algorithm: A day/night anti-poaching application

The optimisation of surveillance and detection systems comprised of specialised cameras is a well-known problem in the operations research literature. In these problems, the aim is to locate optimal camera sites so that their combined coverage with respect to some area of interest – called a cover zone – is maximised. The standard approach is to maximise cover with respect to a single cover zone, and to consider either cameras providing rotational (360°) cover, or cameras fixed to a specific direction and with visibility limited to within the camera's field-of-view. The Rhino Pride Foundation in South Africa required the optimisation of a camera surveillance system for a new protected area. Their coverage requirements were, however, beyond what has been previously encountered in the literature. Four covering objectives over three separate cover zones were to be maximised, while the system was to be optimised for rotational cover during the day, and some cameras would be required to be fixed towards a high-risk zone at night and limited to their field-of-view. A novel multi-attribute genetic algorithm based on the popular NSGA-II was developed for this purpose. Various solutions were provided to and considered by the Rhino Pride Foundation, and the final selected solution resulted in camera site locations providing high-quality cover with respect to all the covering objectives, while requiring fewer cameras than initially expected – resulting in significant cost savings and reduced future maintenance and upgrade requirements. The solution approach presented here may be applied to other site-selection problems with similar coverage requirements, including military radar and weapon systems, and wildfire detection systems.

Combining cameras and citizen science to define the distribution and behaviour of dingoes and foxes in New South Wales

We used two survey methods - citizen science for private land and cameras for protected areas - to map the distribution of dingoes/wild dogs and foxes in NSW. Dingo/wild dog records were mostly confined to the east coast and ranges, with scattered locations in western NSW. This contrasts to the distribution of foxes, in which occupancy was high across most of the state. Data from 200 WildCount camera sites within protected areas also showed marked differences in the distribution of the two canid species. At the scale of the state, dingoes/wild dogs are uncommon, with the greatest concentration being in the north-east of the state, as well as a marked presence in the south-east. Foxes are common and widespread within protected areas, but less common in the north-east of the state. The camera data also indicated that feral cats are widespread within protected areas. The second aim of our study was to examine the WildCount data for behavioural patterns of the canid species. Foxes and dingoes/wild dogs significantly separated within two sub-formations of dry sclerophyll forest based on the Keith (2004) classification of NSW vegetation. From species pairwise interactions at sites, we found only limited evidence for significant interactions, and then only for the co-occurrence of fox-rabbit and fox-swamp wallaby, but no avoidance for any of the predators with each other. Camera records of the time of day of being active showed little effect of the presence of dingoes/wild dogs on the times of activity of foxes, but foxes curtailed the activity times of dingoes/wild dogs. From the analysis of inter-animal times at sites where both canids were recorded, there was little difference between the time since the other species was present. Thus, there was no evidence that dingoes/wild dogs or foxes inhibit the other from being at a site. We concluded that at the landscape level, both vegetation type and land tenure play a role in the interactions between dingoes/wild dogs and foxes. We also concluded that citizen science and cameras are complementary, not alternative techniques, especially as they sample different land tenures, and that cameras in protected areas and occupancy from citizen science have produced higher resolution maps and behaviour patterns than have been previously available. We can confirm that foxes are a ubiquitous threat throughout NSW, whereas dingoes/wild dogs are concentrated into a much smaller area of eastern, particularly north-eastern, NSW.

Effects of free-ranging livestock on sympatric herbivores at fine spatiotemporal scales

Livestock grazing is one of the most widespread types of anthropogenic land use, even occurs in many protected areas and has become a threat to wildlife worldwide. Understanding livestock-wildlife interactions is crucial for rare large carnivores conservation. In China, free-ranging cattle within forests degrade the habitat of the tigers (Panthera tigris) and leopards (Panthera pardus), but quantitative assessments of how livestock affect the spatial and temporal use by the major ungulate prey of the two endangered felids are very limited. This study aimed to examine the interactions of several sympatric wildlife species with livestock at a fine spatiotemporal scale in a human-dominated forest landscape. Based on a large-scale camera-trapping data across the China-Russia border, we used N-mixture models, two-species occupancy models and activity pattern overlap to understand the effects of cattle grazing on three ungulate species (sika deer Cervus nippon, wild boars Sus scrofa and roe deer Capreolus pygargus). Spatially, with cattle activity increasing, wild boar and roe deer had different degrees of decline in the intensity of habitat use. Sika deer were displaced as more cattle encroached on forest habitat. Temporally, in the presence of cattle, wild boar and sika deer decreased their activities in the day. In addition, three wild ungulates trend to exhibit lower spatiotemporal overlap with cattle at shared camera sites. Our study shows that wildlife species may reduce the probability of habitat use by spatial avoidance and changing the daily activity patterns. We underscore that fine-scale (i.e. camera-site level) spatiotemporal avoidance is likely a key component of co-occurrence between livestock and the sympatry of competing ungulates inhabiting forest ecosystems. Given prey were depressed, efforts to minimize the livestock disturbance on these species need to be considered to ensure their sustained recoveries.

Assessing population structure and body condition to inform conservation strategies for a small isolated Asian elephant (Elephas maximus) population in southwest China.

The Asian elephant (Elephas maximus) population in Nangunhe National Nature Reserve in China represents a unique evolutionary branch that has been isolated for more than twenty years from neighboring populations in Myanmar. The scarcity of information on population structure, sex ratio, and body condition makes it difficult to develop effective conservation measures for this elephant population. Twelve individuals were identified from 3,860 valid elephant images obtained from February to June 2018 (5,942 sampling effort nights) at 52 camera sites. Three adult females, three adult males, one subadult male, two juvenile females, two juvenile males and one male calf were identified. The ratio of adult females to adult males was 1:1, and the ratio of reproductive ability was 1:0.67, indicating the scarcity of reproductive females as an important limiting factor to population growth. A population density of 5.32 ± 1.56 elephants/100 km2 was estimated using Spatially Explicit Capture Recapture (SECR) models. The health condition of this elephant population was assessed using an 11-point scale of Body Condition Scoring (BCS). The average BCS was 5.75 (n = 12, range 2-9), with adult females scoring lower than adult males. This isolated population is extremely small and has an inverted pyramid age structure and therefore is at a high risk of extinction. We propose three plans to improve the survival of this population: improving the quality and quantity of food resources, removing fencing and establishing corridors between the east and wet parts of Nangunhe reserve.

Co‐occurrence of high densities of brown hyena and spotted hyena in central Tuli, Botswana

AbstractLarge carnivore populations are declining worldwide due to anthropogenic causes such as habitat loss and human expansion into wild areas. Competition between large carnivores can exacerbate this decline. While brown hyena Parahyaena brunnea and spotted hyena Crocuta crocuta belong to the same family, they are rarely found in the same area or co‐occur at low densities as spotted hyena are known to exclude brown hyena. In Central Tuli, Botswana, however, brown hyena and spotted hyena are both found at high densities. We undertook a camera trap survey in this area to estimate the densities of both species, and to examine temporal overlap and co‐detection patterns of brown and spotted hyena. Estimated population densities based on spatial capture–recapture models were 10.5 ± 1.9/100 km2 for brown hyena and 14.9 ± 2.2/100 km2 for spotted hyena. These population densities are among the highest reported estimates in southern Africa. Strong temporal overlap was found between brown and spotted hyena, while there was no decrease in detection rate of brown hyena at camera sites where spotted hyena were also detected, which indicates that both hyena species did not tend to avoid encounters. Although both species compete for the same prey, we suggest as possible explanations that prey densities are high and that competition does not significantly negatively impact brown hyena, because brown hyena is a scavenger whereas spotted hyena scavenge and kill prey. With the found high densities of both carnivores, this study adds to the known variation in composition of existing large carnivore communities and suggests testable explanations for these densities.

Agonistic interactions and island biogeography as drivers of carnivore spatial and temporal activity at multiple scales

Carnivore communities can be diverse and complex, and lack of knowledge regarding intraguild interactions and alternative drivers of carnivore distributions can preclude effective conservation of co-occurring species. As such, our objectives were to evaluate the relative importance of intraguild interactions and island biogeography to carnivore community spatiotemporal activity at multiple spatial scales. We monitored the carnivore community of the Apostle Islands National Lakeshore (Wisconsin, USA) using a grid of camera traps from 2014 to 2018. We used generalized linear mixed-effects models and information-theoretic model selection to evaluate whether subordinate carnivore presence was related to dominant carnivore relative abundance (interactions) or to island biogeography at the island level and camera site level, and we calculated temporal overlap between each pair of species to determine whether subordinate carnivores were using temporal segregation. At the island level, the relative importance of interactions and island biogeography was species dependent. At the site level, relative abundance of dominant carnivores was not a significant predictor of subordinate carnivore presence, and all pairs exhibited high or neutral temporal overlap. At the island level, island biogeography and interactions may both impact species distributions; however, at finer spatial scales, the carnivore community may be using alternative segregation strategies, or the island system may preclude segregation.

Anthropogenic edge effects in habitat selection by sun bears in a protected area

Wildlife populations in southeast Asia are increasingly experiencing a broad array of anthropogenic threats, and mammalian carnivores are particularly vulnerable. Populations of the Malayan sun bear Helarctos malayanus are estimated to have declined by 30% over the last 30 years from forest conversion to industrial plantations and mortality associated with human–bear conflicts and illegal wildlife trade. However, the effects of industrial plantations on habitat selection and activity patterns of mammals that live at the protected area-plantation interface, including sun bears, are not well known. We investigated habitat selection and activity patterns of sun bears in Tabin Wildlife Reserve in Sabah, Malaysia. We deployed 83 remote camera sites to record sun bear detections during two sampling periods (2012–2013 and 2017). We used generalized linear models to examine relationships between sun bear presence and site covariates representing physical, environmental and anthropogenic elements of the landscape. Relative probability of sun bear presence was positively associated with distance to roads and elevation. Because most roads were on the reserve boundary and often associated with oil palm plantations, proximity to roads likely served as a surrogate measure of human accessibility and activity in peripheral areas of the reserve. Supporting that interpretation, sun bears close to the reserve boundary were primarily active at night, whereas daytime activity was more common for bears in the interior. Our findings indicate that sun bears alter behaviour and habitat selection likely in response to anthropogenic activities at the edges of Tabin Wildlife Reserve (112 200 ha). Because the ratio of edge to interior increases steeply with declining habitat area, smaller protected areas bordered by plantations are predicted to have greater impacts on sun bear behaviour and, potentially, population persistence. Effective conservation actions may benefit from management to improve the security of edge habitats for sun bears and other vulnerable species.

Evaluating the speed camera sites selection criteria in the UK

Introduction: Speed cameras have been implemented to improve road safety over recent decades in the UK. Although the safety impacts of the speed camera have been estimated thoroughly, the criteria for selecting camera sites have rarely been studied. This paper evaluates the current speed camera sites selection criteria in the UK based on safety performance. Method: A total of 332 speed cameras and 2,513 control sites with road traffic accident data are observed from 2002 to 2010. Propensity score matching method and empirical Bayes method are employed and compared to estimate the safety effects of speed cameras under different scenarios. Results: First, the main characteristics of speed cameras meeting and not meeting the selection criteria are identified. The results indicate that the proximity to school zones and residential neighborhoods, as well as population density, are the main considerations when selecting speed camera sites. Then the official criteria used for selecting camera sites are evaluated, including site length (a stretch of road that has a fixed speed camera or has had one in the past), previous accident history, and risk value (a numerical scale of the risk level). The results suggest that a site length of 500 m should be used to achieve the optimum safety effects of speed cameras. Furthermore, speed cameras are most effective in reducing crashes when the requirement of minimum number of historical killed and seriously injured collisions (KSIs) is met. In terms of the risk value, it is found that the speed cameras can obtain optimal effectiveness with a risk value greater than or equal to 30, rather than the recommended risk value of 22.

Baiting/Luring Improves Detection Probability and Species Identification-A Case Study of Mustelids with Camera Traps.

Simple SummaryCamera traps are now widely used in animal research because they can monitor animals continuously. Nocturnal mammals are particularly difficult to monitor, and identification without cameras would be difficult. However, camera traps can be improved. We here compared two experimental settings to increase detection and images taken of mustelids, mostly martens. Both tuna bait and glandular scents improved the detection and the number of images taken. Both methods were more successful than a control group setting without any attractants.Motion-triggered trail cameras (hereafter camera traps) are powerful tools which are increasingly used in biological research, especially for species inventories or the estimation of species activity. However, camera traps do not always reliably detect animal visits, as a target species might be too fast, too small, or too far away to trigger an image. Therefore, researchers often apply attractants, such as food or glandular scents, to increase the likelihood of capturing animals. Moreover, with attractants, individuals might remain in front of a camera trap for longer periods leading to a higher number of images and enhanced image quality, which in turn might aid in species identification. The current study compared how two commonly used attractants, bait (tuna) and glandular scent (mustelid mix), affected the detection and the number of images taken by camera traps compared to control camera sites with conventional camera traps. We used a before–after control group design, including a baseline. Attractants increased the probability of detecting the target species and number of images. Tuna experiments produced on average 7.25 times as many images per visit than control camera traps, and scent lures produced on average 18.7 times as many images per visit than the control traps.

A causal analysis of time-varying speed camera safety effects based on the propensity score method

Introduction: Speed limit enforcement cameras provide an effective approach to reduce vehicle speeds and the number of road accidents. However, it is still unclear whether the safety effects of speed cameras show durability over long periods of time. This paper analyses how the effects of speed cameras on road accidents change over time. A total number of 771 camera sites and 4787 potential control sites are observed for a period of 18 years (1999–2016) across England. Method: Covariates such as road class, crash history, speed limit, and annual average daily traffic (AADT) are included in the data set. A difference in difference (DID) based propensity score matching (PSM) method is employed to select proper control sites and estimate the treatment effects. The safety effects of speed cameras are then evaluated from a long-term perspective. The post-treatment period is divided into four equal-length periods: early, medium 1 and 2, and late. Results and Conclusions: The results show that speed cameras have significantly reduced the number of road accidents near the camera sites. However, the effects vary across different time periods. The safety effects of speed cameras experienced a sharp decrease during the medium periods after an initial period of highly reduced accidents (medium 1: −53.1%, medium 2: −40.7%) and recovered slightly during the late period. In addition, to evaluate the criteria for selecting camera sites in the UK, we further investigated whether speed cameras at high risk sites have better safety performance. The results show that while safety effects at high risk camera sites also decreased during the medium periods, the reduction was smaller (medium 1: −20.8%, medium 2: −2.1%). Practical Applications: Appropriate road traffic regulations and management, as well as proper camera sites selection criterion, are important to maintain the effectiveness of speed cameras.

Move to nocturnality not a universal trend in carnivore species on disturbed landscapes

Anthropogenic landscape change is a leading driver of biodiversity loss. Preceding dramatic changes such as wildlife population declines and range shifts, more subtle responses may signal impending larger‐scale change. For example, disturbance‐induced shifts to species’ activity patterns may disrupt temporal niche partitioning along the 24‐h time axis, compromising community structure via altered competitive interactions. We investigated the impacts of human landscape disturbance on species’ activity patterns and temporal niche partitioning in the Canadian Rocky Mountain carnivore guild using camera trap images collected across two regions encompassing a wide gradient of human footprint. Applying kernel density estimation techniques, we tested for carnivore species’ activity shifts 1) between a low versus high disturbance landscape, and 2) in relation to site‐scale disturbance. To test our hypothesis that human disturbance impacts species’ temporal niche partitioning, we modelled activity overlap between co‐occurring carnivore species in relation to natural and anthropogenic landscape features, as well as carnivore community composition. Multiple carnivore species altered activity patterns between the low versus high disturbance landscapes and camera sites, but these shifts varied considerably among species. While wolves appeared to increase nocturnal activity in relation to disturbance, coyote activity consistently trended towards cathemerality and marten increased diurnal activity. Detecting effects of landscape disturbance on activity overlap between co‐occurring species was highly sensitive to site‐level detection sample sizes, and our results suggest altered temporal niche partitioning between marten and wolverine in relation to forest cover. This study indicates that mesocarnivores may respond differently and perhaps indirectly to anthropogenic disturbance compared to apex predators. Apex predator shifts to nocturnality may facilitate a ‘behavioural release’ in mesocarnivores. This may be a likely component of mesocarnivore population release, with important management implications for ecological communities on disturbed landscapes.

Determinants of jaguar occupancy at the northern range edge

Identifying factors promoting jaguar (Panthera onca) occupancy is crucial for planning effective conservation and management actions that can contribute to long-term population viability. We used camera-trapping and modeled factors affecting detection and occupancy for jaguars in Sonora at 149 sites during August–November 2008 and 2009. We measured 24 covariates presumed to affect detection (n = 6) and occupancy (n = 18) at camera sites, including sampling period and various habitat characteristics. We obtained 29 jaguar detections at 19 sites (naive occupancy = 0.12) in 5455 trap-days of effort. Jaguar detectability (p = 0.16 ± 0.05) was negatively affected by human presence and varied by study year and sampling period. Jaguar occupancy (ψ = 0.30 ± 0.03) increased as prey richness, the abundance of calves of domestic cattle, and the proportion of subtropical vegetation increased. Jaguar occupancy was lower with increased abundance of adult cattle and peccary, and higher levels of fragmentation. Jaguar occupancy in Sonora was hence driven by a diverse combination of factors which should be considered when planning conservation actions. We suggest that managers mitigate the impact of livestock, especially on subtropical habitats, by employing appropriate fencing. Fencing may increase wildlife prey for jaguars, thereby reducing calf depredation by jaguars, while concurrently protecting habitat from overgrazing. Furthermore, providing financial support for ecotourism and compensation for depredation to offset potential jaguar impacts should be considered for jaguar conservation in Sonora.

An empirical evaluation of camera trap study design: How many, how long and when?

Abstract Camera traps deployed in grids or stratified random designs are a well‐established survey tool for wildlife but there has been little evaluation of study design parameters. We used an empirical subsampling approach involving 2,225 camera deployments run at 41 study areas around the world to evaluate three aspects of camera trap study design (number of sites, duration and season of sampling) and their influence on the estimation of three ecological metrics (species richness, occupancy and detection rate) for mammals. We found that 25–35 camera sites were needed for precise estimates of species richness, depending on scale of the study. The precision of species‐level estimates of occupancy (ψ) was highly sensitive to occupancy level, with <20 camera sites needed for precise estimates of common (ψ > 0.75) species, but more than 150 camera sites likely needed for rare (ψ < 0.25) species. Species detection rates were more difficult to estimate precisely at the grid level due to spatial heterogeneity, presumably driven by unaccounted habitat variability factors within the study area. Running a camera at a site for 2 weeks was most efficient for detecting new species, but 3–4 weeks were needed for precise estimates of local detection rate, with no gains in precision observed after 1 month. Metrics for all mammal communities were sensitive to seasonality, with 37%–50% of the species at the sites we examined fluctuating significantly in their occupancy or detection rates over the year. This effect was more pronounced in temperate sites, where seasonally sensitive species varied in relative abundance by an average factor of 4–5, and some species were completely absent in one season due to hibernation or migration. We recommend the following guidelines to efficiently obtain precise estimates of species richness, occupancy and detection rates with camera trap arrays: run each camera for 3–5 weeks across 40–60 sites per array. We recommend comparisons of detection rates be model based and include local covariates to help account for small‐scale variation. Furthermore, comparisons across study areas or times must account for seasonality, which could have strong impacts on mammal communities in both tropical and temperate sites.

Are multiple speed cameras more effective than a single one? Causal analysis of the safety impacts of multiple speed cameras

Most previous studies investigate the safety effects of a single speed camera, ignoring the potential impacts from adjacent speed cameras. The mutual influence between two or even more adjacent speed cameras is a relevant attribute worth taking into account when evaluating the safety impacts of speed cameras. This paper investigates the safety effects of two or more speed cameras observed within a specific radius which are defined as multiple speed cameras. A total of 464 speed cameras at treated sites and 3119 control sites are observed and related to road traffic accident data from 1999 to 2007. The effects of multiple speed cameras are evaluated using pairwise comparisons between treatment units with different doses based on the propensity score methods. The spatial effect of multiple speed cameras is investigated by testing various radii. There are two major findings in this study. First, sites with multiple speed cameras perform better in reducing the absolute number of road accidents than those with a single camera. Second, speed camera sites are found to be most effective with a radius of 200 m. For a radius of 200 m and 300 m, the reduction in the personal injury collisions by multiple speed cameras are 21.4 % and 13.2 % more than a single camera. Our results also suggest that multiple speed cameras are effective within a small radius (200 m and 300 m).

Use of Underwater Videography to Quantify Conditions Utilized by Endangered Moapa Dace While Spawning

AbstractAdvances in underwater camera technology provide an affordable means to quantify the environmental conditions under which fish spawn. This information is important for investigating spawning ecology, managing habitat, or providing information for captive breeding programs. We deployed 12 modified security cameras underwater to identify environmental conditions related to the spawning behavior of the critically endangered Moapa Dace Moapa coriacea, a Mojave Desert stream‐dwelling cyprinid that had never been observed spawning and that had fallen to a low of 459 individual fish 4 years prior to this study. Camera sites were selected systematically along the stream to represent the variety of conditions available. We divided the field of view in front of each camera into a grid, and we estimated both the available environment and the habitat over which Moapa Dace showed spawning behavior. From over 4,000 10‐min video clips that were randomly selected for analysis, 13 spawning events were identified. Using nonparametric contingency table analyses, we found that Moapa Dace selected depths between 30 and 34 cm, water velocities between 0.11 and 0.17 m/s, cobble substrate, and overhead instream cover. Although the recorded sample size of spawning events was small (13), our sample represents a large proportion of events given that the world's entire population of Moapa Dace at the time was approximately 650 fish distributed over multiple kilometers of stream length. Environmental conditions identified by this study were replicated in laboratory facilities to successfully propagate Moapa Dace for the first time in captivity. These propagation methods are now used in a management setting by the Nevada Department of Wildlife to maintain a captive population of this rare fish. Camera methods can be effective in helping to identify spawning conditions where water clarity is sufficient.

Uncertainty of Vegetation Green-Up Date Estimated from Vegetation Indices Due to Snowmelt at Northern Middle and High Latitudes

Vegetation green-up date (GUD), an important phenological characteristic, is usually estimated from time-series of satellite-based normalized difference vegetation index (NDVI) data at regional and global scales. However, GUD estimates in seasonally snow-covered areas suffer from the effect of spring snowmelt on the NDVI signal, hampering our realistic understanding of phenological responses to climate change. Recently, two snow-free vegetation indices were developed for GUD detection: the normalized difference phenology index (NDPI) and normalized difference greenness index (NDGI). Both were found to improve GUD detection in the presence of spring snowmelt. However, these indices were tested at several field phenological camera sites and carbon flux sites, and a detailed evaluation on their performances at the large spatial scale is still lacking, which limits their applications globally. In this study, we employed NDVI, NDPI, and NDGI to estimate GUD at northern middle and high latitudes (north of 40° N) and quantified the snowmelt-induced uncertainty of GUD estimations from the three vegetation indices (VIs) by considering the changes in VI values caused by snowmelt. Results showed that compared with NDVI, both NDPI and NDGI improve the accuracy of GUD estimation with smaller GUD uncertainty in the areas below 55° N, but at higher latitudes (55°N-70° N), all three indices exhibit substantially larger GUD uncertainty. Furthermore, selecting which vegetation index to use for GUD estimation depends on vegetation types. All three indices performed much better for deciduous forests, and NDPI performed especially well (5.1 days for GUD uncertainty). In the arid and semi-arid grasslands, GUD estimations from NDGI are more reliable (i.e., smaller uncertainty) than NDP-based GUD (e.g., GUD uncertainty values for NDGI vs. NDPI are 4.3 d vs. 7.2 d in Mongolia grassland and 6.7 d vs. 9.8 d in Central Asia grassland), whereas in American prairie, NDPI performs slightly better than NDGI (GUD uncertainty for NDPI vs. NDGI is 3.8 d vs. 4.7 d). In central and western Europe, reliable GUD estimations from NDPI and NDGI were acquired only in those years without snowfall before green-up. This study provides important insights into the application of, and uncertainty in, snow-free vegetation indices for GUD estimation at large spatial scales, particularly in areas with seasonal snow cover.