13Studying animal movement provides insights into how animals react to land-use changes, specifically 14 how animals can change their behaviour in agricultural areas. Recent reviews show a tendency for 15 species to reduce movements in response to increased human landscape modification, but the study of 16 movement has not been extensively explored in reptiles. We examined movements of a large reptilian 17 predator, the King Cobra (Ophiophagus hannah), in Northeast Thailand. We used a consistent regime 18 of radio-telemetry tracking to document movements across protected forest and adjacent agricultural 19 areas. We then adapted GPS-targeting analytic methods to examine the movement using metrics of site 20 reuse and dynamic Brownian Bridge Movement Model derived motion variance. Examination of 21 motion variance demonstrated that King Cobra movements increased in forested areas and tended to 22 decrease in agricultural areas. Our Integrated Step-Selection Functions indicated that when moving in 23 agricultural areas King Cobras restricted their movements, thereby remaining within vegetated semi-24 natural areas, often located along the banks of irrigation canals. Site reuse metrics of residency time and 25 number of revisits remained unaffected by distance to landscape features. Neither motion variance nor 26 reuse metrics were consistently affected by the presence of threatening landscape features (e.g. roads, 27 human settlements); suggesting that King Cobras will remain in close proximity to threats, provided 28 habitat patches are available. Although King Cobras displayed heterogeneity in their response to 29 agricultural landscapes, the overall trend suggested a reduction in movements when faced with 30 fragmented habitat patches embedded in an otherwise inhospitable land-use matrix. Reductions in 31 movements are consistent with findings for mammals and forest specialist species. 32
Home range estimators are a critical component for understanding animal spatial ecology. The choice of home range estimator in spatial ecology studies can significantly influence management and conservation actions, as different methods lead to vastly different interpretations of movement patterns, habitat selection, as well as home range requirements. Reptile studies in particular have struggled to reach a consensus on the appropriate home range estimators to use, and species with cryptic behavior make home range assessment difficult. We applied dynamic Brownian Bridge Movement Models (dBBMMs) to radio-telemetry data from Ophiophagus hannah, a wide-ranging snake species. We used two focal individuals at different life stages (one juvenile male and one adult male) and sought to identify whether the method would accurately represent both their home range and movement patterns. To assess the suitability of dBBMMs, we compared this novel method with traditional home range estimation methods: minimum convex polygons (MCP) and Kernel density estimators (KDE). Both KDE and MCP incorporated higher levels of Type I and Type II errors, which would lead to biases in our understanding of this species space-use and habitat selection. Although these methods identified some general spatial-temporal patterns, dBBMMs were more efficient at detecting movement corridors and accurately representing long-term shelters sites, showing an improvement over methods traditionally favored in reptile studies. The additional flexibility of the dBBMM approach in providing insight into movement patterns can help further improve conservation and management actions. Additionally, our results suggest that dBBMMs may be more widely applicable in studies that rely on VHF telemetry and not limited to studies employing GPS tags.
Road networks are increasing globally, and as such incur increased pressure on wildlife communities. Large‐scale road expansion and infrastructure development occurring throughout Asia (i.e. Belt and Road Initiative) will affect hundreds of threatened species, leading to an increase in wildlife‐vehicle collisions. However, only a limited number of studies have quantified road mortality within this threatened landscape. To rectify this, we monitored the spatial‐temporal patterns of vertebrate roadkill in the Dong Phayayen‐Khao Yai forest complex, an UNESCO World Heritage Site located in Thailand, considered a refuge for many globally threatened species. We ran 100 standardized road surveys between 2015 and 2017, on a 47.8‐km highway transect currently being expanded, and recorded a total of 1395 casualties from 124 species. After correcting for removal time and detection probability, we estimated an average of 9688 vertebrate mortalities per year. We observed a mortality peak during the dry season for almost all taxonomic groups, due to a combination of high bird and bat mortality events. All taxa showed significant spatial clustering, highlighting high‐risk road sections. We modelled the road and landscape features most likely to lead to higher mortality rates, disentangling small‐scale (250–500 m from road) from large‐scale effects (1000–2500 m). We recorded lower mortality rates and species diversity near forest sites in protected areas, representing either lower crossing events due to habitat quality or an already depleted environment. Spatial analyses provided information on hotspots and landscape factors, which can be used to inform future mitigations at multiple scales throughout the Southeast Asia region. Our study provides a baseline of the direct road impacts on vertebrate species in a tropical biodiversity hotspot, and we suggest that more studies be conducted to fully assess the direct road effects on the many threatened species in this landscape.
Reptiles are the most species-rich terrestrial vertebrate group with a broad diversity of life history traits. Biotelemetry is an essential methodology for studying reptiles as it compensates for several limitations when studying their natural history. We evaluated trends in terrestrial reptile spatial ecology studies focusing upon quantifying home ranges for the past twenty years. We assessed 290 English-language reptile home range studies published from 2000–2019 via a structured literature review investigating publications’ study location, taxonomic group, methodology, reporting, and analytical techniques. Substantial biases remain in both location and taxonomic groups in the literature, with nearly half of all studies (45%) originating from the USA. Snakes were most often studied, and crocodiles were least often studied, while testudines tended to have the greatest within study sample sizes. More than half of all studies lacked critical methodological details, limiting the number of studies for inclusion in future meta-analyses (55% of studies lacked information on individual tracking durations, and 51% lacked sufficient information on the number of times researchers recorded positions). Studies continue to rely on outdated methods to quantify space-use (including Minimum Convex Polygons and Kernel Density Estimators), often failing to report subtleties regarding decisions that have substantial impact on home range area estimates. Moving forward researchers can select a suite of appropriate analytical techniques tailored to their research question (dynamic Brownian Bridge Movement Models for within sample interpolation, and autocorrelated Kernel Density Estimators for beyond sample extrapolation). Only 1.4% of all evaluated studies linked to available and usable telemetry data, further hindering scientific consensus. We ultimately implore herpetologists to adopt transparent reporting practices and make liberal use of open data platforms to maximize progress in the field of reptile spatial ecology.
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