Comparison of methods for estimating density and population trends for low-density Asian bears

Global Ecology and Conservation, Год журнала: 2022, Номер 35, С. e02058 - e02058

Опубликована: Фев. 15, 2022

Populations of bears in Asia are vulnerable to extinction and effective monitoring is critical measure direct conservation efforts. Population abundance (local density) or growth (λ) the most sensitive metrics change. We discuss value implementing spatially explicit capture-recapture (SCR), current gold standard for density estimation, open population SCR (OPSCR) monitor changes over time. provide guidance designing studies estimates with sufficient power detect changes. Because wide availability camera traps interest their use, we consider six estimation methods extensions developed use traps, specific consideration assumptions applications Asian bears. conducted a analysis calculate precision needed populations reference IUCN Red List criteria. performed systematic review empirical trap considered sample sizes, effort, model required achieve adequate monitoring. found OPSCR, reliant on "marked" individuals, currently only enough reliably even moderate major (20–80%) declines. Camera unmarked individuals rarely achieved large declines (80–90%), although some exceptions (e.g., situations densities, number sampling sites, inclusion ancillary local telemetry data. describe additional options including line transects, observations, age-specific survival reproductive rates, hybrid/integrated methodologies that may have potential work bear populations. conclude possible but will require collaboration among researchers broad spatial extents extensive financial investment overcome biological logistical constraints. strongly encourage practitioners study design effort meet objectives by conducting simulations, analyses, assumption checks prior efforts, reporting standardized dispersion measures such as coefficients variation allow assessment precision. Our relevant other low-density wide-ranging species.

Язык: Английский

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Limitations of invasive snake control tools in the context of a new invasion on an island with abundant prey

NeoBiota, Год журнала: 2024, Номер 90, С. 1 - 33

Опубликована: Янв. 5, 2024

In October 2020, a new population of invasive brown treesnakes ( Boiga irregularis ) was discovered on the 33-ha Cocos Island, 2.5 km off south coast Guam. Island is unique conservation resource, providing refuge for many lizards and birds, including endangered species, which were extirpated from mainland Guam by predators treesnakes. We sought to evaluate usefulness toxic baiting with acetaminophen-treated carrion baits cage trapping, common tools control Guam, as potential eradication Island. evaluated multiple bait types presentations: ground, suspended in canopy emulating aerial applications four plastic-tube station configurations intended exclude non-target species. monitored all time-lapse cameras. Despite improved exclusion non-targets design, most quickly removed particularly coconut crabs Birgus latro Mariana monitors Varanus tsukamotoi ). Monitoring 1,250 available 2,427 nights resulted no observations taking any bait. Subsequently, we tested two trap commonly used compared trapping success live versus dead mouse lures. 10,553 using lures, only captured one treesnake, lure. These rates are so low be ineffectual practical purposes. Concurrent visual searching hand capture during initial rapid response efforts demonstrates that these not result snake density. make case our assumption ineffectiveness due context extremely high abundance preferred prey, primarily large geckos birds. Our results have profound ramifications, because future island invasions likely occur within similarly prey-rich environments where methods might ineffective.

Язык: Английский

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Best practices to account for capture probability and viewable area in camera‐based abundance estimation

Remote Sensing in Ecology and Conservation, Год журнала: 2022, Номер 9(1), С. 152 - 164

Опубликована: Авг. 26, 2022

Abstract A suite of recently developed statistical methods to estimate the abundance and density unmarked animals from camera traps require accurate estimates area sampled by each camera. Although viewshed is fundamental achieving estimates, there are no established guidelines for collecting this information in field. Furthermore, while complexities detection process motion sensor photography generally acknowledged, viewable (the common factor between time lapse photography) on its own has been underemphasized. We establish a set terminology identify component parts area, contrast photographic capture measurements photography, review estimating use case study demonstrate importance estimates. Time combined with allow researchers assume that probability equals 1. Motion requires measuring distances animal fitting distance sampling curve account <1.

Язык: Английский

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A cautionary tale comparing spatial count and partial identity models for estimating densities of threatened and unmarked populations

Global Ecology and Conservation, Год журнала: 2022, Номер 38, С. e02268 - e02268

Опубликована: Авг. 18, 2022

Population monitoring is critical to wildlife conservation, but density estimation difficult for wide-ranging, unmarked species inhabiting remote habitats. Furthermore, recent investigations into with camera trap data has revealed models be potentially unreliable, prompting cautious application and continued model development. Two related approaches increasing appeal include spatial count (SC), which infer latent identities from the pattern of detections, partial identity (SPIM), additionally leverage covariates (e.g., sex, antler point count, presence GPS/radio collar). To assess performance models, we applied SC SPIM threatened boreal caribou in Canada, are declining have few rigorous estimates across their broad distribution inform conservation efforts. In particular, focused on two spatially proximate ranges northern Alberta, Canada that differ estimated demographic trends, disturbance histories, abundances predators apparent competitors. Estimates varied over a 4 year period (2016 – 2019), were higher region more stable reported growth rates less anthropogenic (mode estimates: 155 225/1000 km2 vs. 19 96/1000 km2). However, differed by modeling approach had low variable precision, hindering inferences about population status trajectories. Simulations suggest may been biased precise. likely underestimated mistaking detections neighboring individuals as recaptures single individual, although also overestimated inflating assignment probabilities non-existent individuals. Findings highlight need explore how grouping dynamics non-independent movement violate assumptions reduce ability distinguish We advocate investigation accuracy approaches, ecological sampling conditions appropriate different coordination efforts analyses improve inferences.

Язык: Английский

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Lynx in the Eye of the Camera: Presence and Activity of Eurasian Lynx (Lynx Lynx) Across Multiple Seasons and Years in the Polish Carpathian Mountains

Опубликована: Янв. 1, 2025

Over the last century, large carnivore populations in Europe were severely depleted. By 1950s, only five of Eurasian lynx (Lynx lynx) persisted isolated ranges, including L. l. carpathicus subspecies within Carpathian Mountains. Although this population today is an important source genetic diversity for reintroduction and recolonisation, little research has focused on its occurrence activity Polish Carpathians. The main objective study was to evaluate dynamic structure across space time. We conducted a continuous 5-year (2015-2019) using camera traps how detections varied (1) years between four seasons, (2) diel periods (3) their social status. recorded 2261 20 trap locations, with 89% records one solitary individual per detection 10% females cubs, remaining 1% adult pairs. While solitaries detected all families utilised 9 locations. Based generalised linear model, increased during breeding period from January till March. Additionally, number decreased at night compared daylight (p<0.001) twilight (p<0.001). Families individuals season more active day. Our results indicate that promote conservation area, wildlife managers may consider maintaining areas limited human disturbance, especially season.

Язык: Английский

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Development and evaluation of the remote passive integrated transponder tag reader for customizable monitoring of wildlife

Wildlife Society Bulletin, Год журнала: 2025, Номер unknown

Опубликована: Фев. 6, 2025

Abstract Increasing the quantity and quality of mark‐reencounter data can be important when individual identification are needed to address research or management questions. Physical recapture methods tend labor‐intensive therefore expensive, while remote detection not easily applied all taxa proprietary thus difficult customize. However, partnerships between wildlife scientists engineers have potential provide innovative solutions that improve collection reducing costs. We describe a collaborative effort on an invasive reptile, brown treesnake ( Boiga irregularis ). In laboratory trials conducted Guåhan (CHamoru; Guam in English) 2021, we assessed feasibility detecting snakes fitted with passive integrated transponder (PIT) tags using customized PIT‐tag readers (RePTaR) paired baited snake traps. evaluated differences scanning success as function traits, location PIT within snakes, distance tag from reader. successfully scanned individuals, average 529 times but ranging 3 6,436 times, during 12‐hour designed customizable RePTaR unit. Snake characteristics marking explained little variability success, reader best‐supported covariate. By building cross‐disciplinary partnerships, develop technological additional tools which challenges management.

Язык: Английский

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Smart IoT-based snake trapping device for automated snake capture and identification

Environmental Monitoring and Assessment, Год журнала: 2025, Номер 197(3)

Опубликована: Фев. 10, 2025

Язык: Английский

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Estimating animal density using the Space‐to‐Event model and bootstrap resampling with motion‐triggered camera‐trap data

Remote Sensing in Ecology and Conservation, Год журнала: 2023, Номер 10(2), С. 141 - 155

Опубликована: Июль 24, 2023

Abstract Over the past few decades, use of camera‐traps has revolutionized our ability to monitor populations wild terrestrial mammals. While methods estimate abundance from individually‐identifiable animals are well‐established, they mostly restricted species with clear natural markings or else necessitate invasive and often costly animal tagging campaigns. Estimating density unmarked remains challenging. Several models recently developed deal this issue promising, but not widely used by field ecologists. Here, we a framework for applying Space‐To‐Event (STE) model—originally designed be time‐lapse images—on motion‐triggered camera‐trap data. Our approach involves performing bootstrap resampling on photographic dataset generate multiple datasets that then as input STE model. We tested 29 datasets, including 17 ungulate eight sites, in six different countries various ecosystems. Then, conducted regression analysis evaluate how variations ecological sampling conditions across studies affected bias precision estimates. study shows information activity effective detection distances animals, model can analyze motion‐trigger provide population estimates similar those other methods. found measuring camera viewshed was critical prevent major negative biases Moreover, using 1‐s window important avoid positive results violating instantaneous‐sampling assumption. increased greater effort higher populations. Based these results, highlight several issues have applied original timelapse‐based addresses. caution model, whether timelapse relies strict assumptions. Any violations assumptions, such non‐instantaneous application angle distance provided manufacturer, cause directions may difficult differentiate.

Язык: Английский

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Evaluating sources of bias in pedigree‐based estimates of breeding population size

Ecological Applications, Год журнала: 2022, Номер 32(5)

Опубликована: Апрель 5, 2022

Abstract Applications of genetic‐based estimates population size are expanding, especially for species which traditional demographic estimation methods intractable due to the rarity adult encounters. Estimates breeding ( N S ) particularly amenable approaches as parameter can be estimated using pedigrees reconstructed from genetic data gathered discrete juvenile cohorts, therefore eliminating need sample adults in population. However, a critical evaluation how genotyping and sampling effort influence bias pedigree reconstruction, these biases subsequently , is needed evaluate efficacy approach under range scenarios. We simulated model system understand interactive effects on error program COLONY . then evaluated errors reconstruction influenced precision three different rarefaction estimators. Results indicated that minimal when adequate available, such sizes large and/or individuals genotyped at many informative loci. even cases limited, results simulation analysis magnitude sources still estimating applied federally endangered Atlantic sturgeon Acipenser oxyrinchus Delaware River, USA. Our likely orders lower compared with historic sizes, considerable advancement our understanding status River. analyses broadly applicable design interpretation studies seeking estimate help guide conservation decisions ecological uncertainty high. The utility expected grow rapid advances technologies increase popularity monitoring estimation.

Язык: Английский

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Animal reactivity to camera traps and its effects on abundance estimate using distance sampling in the Taï National Park, Côte d’Ivoire

PeerJ, Год журнала: 2022, Номер 10, С. e13510 - e13510

Опубликована: Май 27, 2022

The use of camera traps (CTs) has become an increasingly popular method studying wildlife, as CTs are able to detect rare, nocturnal, and elusive species in remote difficult-to-access areas. It thus makes them suited estimate animal density abundance, identify activity patterns new behaviours animals. However, animals can react when they see the this lead bias population estimates. While may provide many advantages, improved understanding their impacts on individual’s behaviour is necessary avoid erroneous Yet, impact detected individuals, such human odour near device environment, or infrared illumination, received relatively little attention. To date, there no clear procedure remove potential bias. Here, we trap distance sampling (CTDS) (1) quantify resulting from different responses determining (2) test if olfactory, visual auditory signals have influence animals’ reaction CTs. Between March 2019 2020, deployed at 267 locations distributed systematically over entire Taï National Park. We obtained 58,947 videos which analysed four medium- to-large-bodied (Maxwell’s duiker ( Philantomba maxwellii ), Jentink’s Cephalophus jentinki pygmy hippopotamus Choeropsis liberiensis ) Western chimpanzee Pan troglodytes verus )) displaying towards then established species-specific ethograms describing behavioural Using these responses, observed that Maxwell’s reacted weakly (about 0.11% data), contrary duiker, with high frequencies, representing 32.82%, 52.96% 16.14% data, respectively. Not taking into account artificial doubling tripling populations’ sizes. All more close distances. Besides, significantly night than during day. Finally, for olfactory signals, probability first days after installation was weak but concerned 18% video captures chimpanzees decreasing time, remained (65% 70% respectively). Careful consideration should be given animal’s response analysis field, by reducing human’s around installation.

Язык: Английский

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