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Snakebite envenoming is a major neglected tropical health issue. The high incidence of snakebites in tropical rural communities suggests that venomous snakes and people are often in proximity but quantitative evidence is lacking. I used radio-telemetry on a population of Russell’s vipers (Daboia russelii), one of the most medically important snakes in the world, to quantify proximity between this venomous snake and people and estimate susceptibility to snakebite envenoming in India. I observed people ≤50 m of a radio-equipped viper in ~17% of 2,066 snake relocations. People were more frequently observed in proximity to Russell’s vipers in January and July compared to March, but all other contrasts were statistically similar. This pattern indicates that snakebite incidence, which peaks in summer in the study area, is not particularly linked to the encounter frequency between people and vipers. However, consistent with epidemiological data plantation workers were the most at-risk part of the population. By integrating information about the locations of humans and snakes in space and time, this pioneering research highlights the need to include snake ecology into the study of the human–venomous-snake conflict, and provides a model approach to help mitigate the burden caused by venomous snakes in the rural Tropics

1. Information about when and where animals die is important to understand population regulation. In migratory animals, mortality might occur not only during the stationary periods (e.g. breeding and wintering) but also during the migration seasons. However, the relative importance of population limiting factors during different periods of the year remains poorly understood, and previous studies mainly relied on indirect evidence. 2. Here, we provide direct evidence about when and where migrants die by identifying cases of confirmed and probable deaths in three species of long-distance migratory raptors tracked by satellite telemetry. 3. We show that mortality rate was about six times higher during migration seasons than during stationary periods. However, total mortality was surprisingly similar between periods, which can be explained by the fact that risky migration periods are shorter than safer stationary periods. Nevertheless, more than half of the annual mortality occurred during migration. We also found spatiotemporal patterns in mortality: spring mortality occurred mainly in Africa in association with the crossing of the Sahara desert, while most mortality during autumn took place in Europe. 4. Our results strongly suggest that events during the migration seasons have an important impact on the population dynamics of long-distance migrants. We speculate that mortality during spring migration may account for short-term annual variation in survival and population sizes, while mortality during autumn migration may be more important for long-term population regulation (through density-dependent effects).

Pathogenic fungi have become a global concern to wildlife populations over the last 2 decades. However, the threat of snake fungal disease (SFD; caused by Ophidiomyces ophiodiicola) to snake populations is still largely unknown. From 2014–2016, we monitored 3 disjunct populations of the federally threated eastern massasauga (Sistrurus catenatus) in Michigan, USA. We used clinical signs of SFD, quantitative TaqMan polymerase chain reaction (qPCR), repeated sampling of individuals and sites, and single-season occupancy models to estimate site-specific prevalence of Ophidiomyces. Point estimates of Ophidiomyces prevalence in 2016 were larger at the northernmost study site (0.17, 95% CI = 0.04–0.50), where 17 of 34 snakes were implanted with radio-transmitters, and smaller at southern sites (0.03, 95% CI = 0.00–0.19). However, Ophidiomyces prevalence was not different between snakes with transmitters and snakes without transmitters. Swabbing snakes with 1 applicator resulted in a high probability of failure in detecting Ophidiomyces DNA for individuals with clinical signs of SFD and the probability was even higher for individuals without clinical signs of SFD. Repeated sampling of individuals reduced the probability of obtaining a false-negative qPCR result by 72% for snakes with clinical signs and 12% for snakes without clinical signs when we swabbed individuals with 5 applicators. We recommend resampling individuals and sites as a sampling design for estimating fine-scale, site-specific Ophidiomyces prevalence and population-level responses to SFD. If clinical signs are used as a surrogate for SFD, we recommend researchers standardize diagnosis of clinical signs of SFD by providing technicians adequate field training and educational materials, and minimize the number of observers recording clinical signs. We discourage the use of radio-telemetry methods where SFD occurs unless sterile surgical, handling, and equipment protocols can be ensured and the benefits to the population from such activities outweigh the increased health risks to individuals.

A major uncertainty in automated radio-telemetry studies of small birds is the detection range of receiving antennas. We compared simultaneous daytime detections (± 30 s) by automated and manual radio-telemetry to assess detection probability and the proportion of transmissions detected for birds on migratory stopover as a function of distance, foraging guild (Black-throated Blue Warblers, Setophaga caerulescens, and Yellow-rumped Warblers, Dendroica coronata coronata, represented mid-canopy foliage gleaners and White-throated Sparrows, Zonotrichia albicollis, represented a ground forager), habitat type, meteorological variables, tower antenna number (1-4), and the position of a bird relative to the receiving antenna's bearing (offset angle). Our study was conducted at a migratory stopover site in southern Ontario, Canada. Most detections were in dense to sparse forest, and all individuals were within 1.03 km of the automated receiving station. Daily detection probability was near 100% for both foraging guilds. However, within 30 s before and after a manual radio-telemetry location was made, detection probability and the proportion of transmissions detected by automated radio-telemetry declined with distance, was higher for warblers than sparrows, and was lowest for 90° offset angles. Our results suggest that when research goals do not require detections with high temporal frequency, e.g., estimation of departure date or daily departure probability, our study design had an effective detection range of at least 1 km. However, where temporal precision is required, e.g., to investigate movements and changes in activity levels during stopover, detection range was ~300 m for ground-foraging sparrows and 600 m for mid-canopy foraging warblers, which is much lower than the presumed detection range of antennas under optimal conditions (15 km). This corresponds to a spatial area of coverage for forest-dwelling birds of ~0.3-1.1 km² . Our results suggest that to optimally configure an automated radio-telemetry array at the regional scale, investigators should carefully consider detection range and its underlying covariates, including species type, the habitat matrix, and the orientation of antennas relative to preferred habitat. Una gran incertidumbre en los estudios automatizados de radio-telemetría en aves pequeñas es el rango de detección de las antenas receptoras. Comparamos las detecciones diurnas simultáneas (± 30 seg.) mediante radio-telemetría manual y automatizada para evaluar la probabilidad de detección y la proporción de transmisiones detectadas de aves en escala migratoria en función de la distancia, el gremio de alimentación (Setophaga caerulescens, Dendroica coronata coronata, representando a las espigadoras del follaje del dosel m y Zonotrichia albicollis, representó un buscador de alimento del suelo), tipo de hábitat, variables meteorológicas, número de antenas de la torre (1-4) y la posición de un ave en relación con el soporte de la antena receptora (ángulo de desplazamiento). Nuestro estudio se realizó en un sitio de parada migratoria en el sur de Ontario, Canadá. La mayoría de las detecciones se realizaron en bosques densos a dispersos, y todas las personas se encontraban a menos de 1.03 km de la estación receptora automática. La probabilidad de detección diaria fue cercana al 100% para ambos gremios de forrajeo. Sin embargo, dentro de los 30 segundos anteriores y posteriores a la ubicación de la radio-telemetría manual, la probabilidad de detección y la proporción de las transmisiones detectadas por la radio-telemetría automatizada disminuyeron con la distancia, fue mayor para las reinitas que para los gorriones y fue más baja para los ángulos de desplazamiento de 90°. Nuestros resultados sugieren que cuando los objetivos de la investigación no requieren detecciones con alta frecuencia temporal, por ejemplo, la estimación de la fecha de salida o la probabilidad de salida diaria, el diseño de nuestro estudio tuvo un rango de detección efectivo de al menos 1 km. Sin embargo, cuando se requiere precisión temporal, por ejemplo, para investigar los movimientos y cambios en los niveles de actividad durante la parada, el rango de detección fue de ~300 m para los gorriones que buscan alimento en el suelo y 600 m para las reinitas que buscan alimento en el dosel medio, que es mucho más bajo que la detección estimada de las antenas en condiciones óptimas (15 km). Esto corresponde a un área espacial de cobertura para aves que habitan en el bosque de ~0.3 a 1.1 km². Nuestros resultados sugieren que, para configurar de manera óptima un conjunto automatizado de radio-telemetría a escala regional, los investigadores deben considerar cuidadosamente el rango de detección y sus covariables subyacentes, incluido el tipo de especie, la matriz del hábitat y la orientación de las antenas en relación con el hábitat preferido

Detailed data on juvenile survival are rare in the literature. Although many studies estimate recruitment, if you cannot distinguish between permanent dispersal and mortality, the management implications for a population may be unclear. We estimated juvenile survival in a reintroduced North Island robin (Petroica longipes) population in a protected sanctuary surrounded by an unprotected landscape where the species is extirpated. The population has had marginal population growth due to poor recruitment so we modeled 3 types of data (resighting of fledglings, radio-telemetry of independent juveniles, resighting of adults) in an integrated framework to determine the life stages where high mortality was occurring, and to distinguish mortality from dispersal. Approximately 16% of birds that fledged (n = 109) were present at the start of the next breeding season, consistent with recruitment rates from previous years. Low survival in the first 6 weeks after fledging was the primary cause of poor recruitment. Only 50% survived to independence (4 weeks after fledging), and 18% survived to the end of the radio-tracking period (14 weeks), after which juvenile survival matched adult survival. No dispersal from the sanctuary occurred during the radio-tracking period. Juveniles moved between adjacent forest fragments within the sanctuary, but did not leave the sanctuary. This information, which demonstrates the importance of distinguishing between natal mortality and dispersal, is important for ongoing management of the site and selection of future reintroduction sites for this species.

Radio-telemetry is a commonly used scientific technique that allows researchers to collect detailed movement, habitat use, and survival data of animals; however, evidence indicates that using telemetry can affect behavior and survival. Using multiple breeding colonies and years, we investigated the effects of attached radio-transmitters on growth and survival of Forster’s tern (Sterna forsteri) chicks in San Francisco Bay, California, USA, 2010–2011. We tested these potential effects at isolated islands that allowed for high re-capture rates (typically >85%) in radio-marked and banded-only chicks. Modeled Gompertz growth curves suggested that transmitters had a small negative effect on some of the asymptotic growth parameters of tern chicks; tarsus (−1.5±0.7% [SE]), culmen (−1.7±1.2%), and wing (−4.9±2.0%) lengths were shorter for radio-marked chicks compared to banded-only chicks. In contrast, there was no difference in asymptotic mass between radio-marked chicks and banded-only chicks. Survival from hatching to fledging was lower for radio-marked chicks than banded-only chicks during 2010 (banded-only=0.313±0.162 vs. radio-marked=0.250±0.165) and 2011 (0.193±0.030 vs. 0.123±0.027). Most of the transmitter effect occurred within the first week after hatching, rather than in older chicks. Notably, the effect of transmitters on chick survival was primarily additive, indicating that the effect of transmitters on radio-marked chicks was not influenced by other ecological covariates. Given the effect radio-transmitters had on survival did not change across temporal or ecological gradients, transmitters can still be used to evaluate ecological factors affecting survival and timing of mortality and radio-marked birds can be used to make inferences to the general population.

Accurate population estimates are essential for monitoring and managing wildlife populations. Mark–recapture sampling methods have regularly been used to estimate population parameters for rare and cryptic species, including the federally listed Mojave desert tortoise (Gopherus agassizii); however, the methods employed are often plagued by violations of statistical assumptions, which have the potential to bias density estimates. By incorporating spatial information into conventional density estimation models, spatial capture–recapture (SCR) models can account for common assumption violations such as spatially heterogeneous detection probabilities and temporary emigration when animals leave plots during a survey. We conducted mark–recapture surveys at 10 1‐km2 plots in and adjacent to the Ivanpah Valley of California and Nevada from 2015 to 2019. Locality data were collected concurrently using radio‐telemetry and GPS data loggers. GPS data demonstrated that desert tortoises frequently exhibited temporary emigration outside a plot during the survey periods, thereby complicating standard approaches for closed‐model density estimation. We integrated mark–recapture survey data for subadults and adults at each plot with corresponding spatial capture locations and supplementary spatial data using a modified SCR model fitted in a Bayesian framework. We compared density estimates modeled with conventional non‐spatial methods, as well as three SCR models based on symmetrical usage areas described by various levels and types of supplementary spatial data. The conventional model consistently resulted in inflated estimates of density while the SCR models allowed us to generate spatially corrected estimates for a species where detectability and densities are low. However, we found that if not properly specified, the temporal scale of supplementary data may result in an unintended source of bias in parameter estimates. Integrating spatial data over a larger temporal scale than mark–recapture surveys were conducted resulted in higher detection probabilities and lower density estimates, due to an overestimation of space use. Our results not only demonstrate the importance of accounting for spatial information but also the value of understanding the potential for bias when integrating multiple data sets at different temporal resolutions. The methods presented can be used to enhance monitoring efforts for the Mojave desert tortoise and other species where mark–recapture methods are used.

Four freshwater eel species (Anguilla spp.) occur in southern African rivers that are increasingly anthropogenically modified. Information on movements, habitat use and overlap by African eels is needed for their conservation. We carried out a preliminary investigation of the spatial ecology of three eel species in the Thukela River, South Africa, using radio-telemetry. Nineteen yellow-stage eels were surgically implanted with radio-tags, comprising A. mossambica (n = 2), A. bengalensis (n = 9) and A. marmorata (n = 8), and tracked from October 2018 to August 2019. Tagged eels exhibited high individual variability in space use. We recorded very small home ranges in winter for all species. A lack of apparent territoriality at inter- and intra-specific levels was observed. Eel species tended to use similar mesohabitats, especially glides, but habitat preference changed across seasons, and between species, suggesting fine-scale spatial and temporal niche partitioning. Given the breadth of flow typologies used by Thukela eels across the seasons, conservation of these long-lived species indicates that management of river flows needs to be sensitive to their habitat requirements all year round, but in many water-stressed South African rivers, this may be unlikely. Maintaining good habitat connectivity for these migrant species must be prioritised.

Prescribed fire is an increasingly important management tool for eastern deciduous forests, but relativity little is known about the direct effects of fire on the eastern box turtle (Terrapene carolina carolina). We used very high frequency (VHF) transmitters to monitor mortality, movement, and spatial ecology of 118 box turtles in response to 17 prescribed fires across 4 seasons and 3 sites in east Tennessee, USA, during 2016–2018. Annual survival of box turtles that experienced a prescribed fire event was lower (0.87 ± 0.04 [SE]) than turtles that did not (0.98 ± 0.01) and was negatively correlated with fire intensity, fire temperature the turtle experienced, and litter depth. All prescribed fire-related mortalities occurred during the early (Apr–May, n = 5) or late growing season (Sep–Oct, n = 1). Fourteen percent of box turtles we captured exhibited damage to their carapace from previous fire events. Box turtles that survived prescribed fires were in microsites that did not burn, moved to unburned areas during the fire, or burrowed following ignition. Home range size was similar before and after burns and sinuosity of movements did not differ in burned or unburned areas. Our results indicate that though box turtles are susceptible to prescribed fire during their active season, they have behavioral and physical traits that reduce the direct effects of prescribed fire. Prescribed fire practitioners should be aware of the risks of fire, particularly during the active season. We suggest managers consider altering prescribed fire intensity, seasonality, and firing pattern to minimize risk of direct effects where box turtles are of concern. © 2020 The Wildlife Society.

During migration, birds require stopover habitat to rest and refuel before resuming flight. While long-distance migratory flights represent a large energy investment, stopover accounts for roughly two-thirds of a bird's total energy expenditure during migration. Therefore, birds should minimize energy expenditure while also minimizing time and predation risk during stopover. To understand activity during migration, we recorded activity patterns (i.e. fine-scale movements associated with a range of behaviors) of 3 species, Red-eyed Vireo (Vireo olivaceus), Swainson's Thrush (Catharus ustulatus), and Wood Thrush (Hylocichla mustelina), at a stopover site along the northern coast of the Gulf of Mexico during autumn migration using automated radio telemetry. We found Red-eyed Vireos to be the most active and Swainson's Thrushes the least active. For each species, we used boosted regression trees to investigate associations between activity and factors known to influence bird behavior during stopover. While species differed, day of year and temperature were important predictors of activity for all species. Vireos were active early in the season, under light winds and warmer temperatures, and on evenings when winds were more favorable. Thrushes were more active as the season progressed and when temperatures were cooler. Thrush activity also differed between years, although thrushes increased activity later in the season during all years. Our results illustrate automated radio telemetry as a unique and valuable tool for understanding fine-scale behaviors of birds during stopover.