Density‐dependent space use affects interpretation of camera trap detection rates

Ecology and Evolution, Год журнала: 2019, Номер 9(24), С. 14031 - 14041

Опубликована: Ноя. 22, 2019

Abstract Camera traps (CTs) are an increasingly popular tool for wildlife survey and monitoring. Estimating relative abundance in unmarked species is often done using detection rate as index of abundance, which assumes that has a positive linear relationship with true abundance. This assumption may be violated if movement behavior varies density, but the degree to density‐dependent across taxa unclear. The potential confounding population‐level indices by would depend on how regularly, what magnitude, home‐range size vary density. We conducted systematic review meta‐analysis quantify relationships between rate, size, terrestrial mammalian taxa. then simulated animal movements CT sampling test effect contrasting scenarios indices. Overall, were negatively correlated density positively one another. strength varied significantly populations. In simulations, rates related underestimated change, particularly slower moving small home ranges. situations where space use changes markedly we estimate up thirty percent change missed due movement, making trend estimation more difficult. common remains constant densities therefore wide range mammal species. When studying rates, researchers managers should explicitly consider such reflect both movement. Practitioners interpreting camera aware observed differences biased low Further information or methods do not assumptions density‐independent required make robust inferences population trends.

Язык: Английский

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Density and distribution of a brown bear (Ursus arctos) population within the Caucasus biodiversity hotspot

Journal of Mammalogy, Год журнала: 2018, Номер 99(5), С. 1249 - 1260

Опубликована: Июль 4, 2018

Population declines and extirpations of large mammalian carnivores are major concerns for global biodiversity conservation. Many vulnerable to conflict with humans attract conservation attention their flagship appeal ecological importance. Coexisting requires an understanding carnivore distribution abundance relative human activities disturbances. Such knowledge is often hindered by the rare elusive nature lack systematic surveys in biodiverse regions facing high levels threat. The Caucasus Ecoregion one such hotspot harboring several threatened mammal species which there a paucity reliable data, including brown bears (Ursus arctos). bear populations have declined significantly from historical times may be isolated disturbance development as mining, well increasing hunting pressure. To inform land-use planning Ecoregion, we conducted May–October 2015 foothills Mountains within Vayots Dzor region Armenia. We used noninvasive genetic sampling, camera trapping, statistical models that account imperfect detection estimate density population 1,000-km2 study area. Across 34 sampling sites, obtained 3,163 camera-trap photos genotyped 28 individual (7 males 21 females). Spatially explicit capture-recapture revealed unexpectedly (59.4/1,000 km2; females = 44.6, 95% confidence interval, CI 25.4–78.4; 14.8, 6.6–34.0), multi-method occupancy indicated were distributed across most area (ψ 0.85; SE 0.07). These results provide robust evidence significant persists Armenia's region, despite history habitat loss driven throughout much Ecoregion. Continued persistence this poaching, other anthropogenic pressures underscoring urgent need strategic planning, impact mitigation, expanded monitoring hotspot.

Язык: Английский

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Species occurrence data reflect the magnitude of animal movements better than the proximity of animal space use

Ecosphere, Год журнала: 2018, Номер 9(2)

Опубликована: Фев. 1, 2018

Abstract Animal ecologists often use stationary point‐count surveys, such as camera traps, to collect presence–absence data and infer distribution, abundance, density of species. Rarely do these surveys explicitly consider variations in the magnitude animal movement despite assumptions being implicit their interpretation. For example, assume frequency species detections at a site is associated with intensity local space use, but it may be more indicative transit through that point en route other areas. This assumption remains untested, resolution critical accurate interpretation occurrence data. We compared fisher ( Pekania pennanti ) collected from trap array detailed Global Positioning System‐telemetry test whether, population level, spatial temporal patterns reflected proximity sampling sites, or variability across study area. also used an occupancy modeling framework quantify relative contributions estimated probabilities detectability. demonstrate that, detection estimates probability are closely around survey device than use. Variations within between should receive greater consideration when interpreting correctly ecological processes. Not accounting for movement, especially multi‐species bias inferences ecologic processes result misspecified management recommendations.

Язык: Английский

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Effects of camera‐trap placement and number on detection of members of a mammalian assemblage

Ecosphere, Год журнала: 2021, Номер 12(7)

Опубликована: Июль 1, 2021

Abstract A central goal in camera‐trapping (CT) studies is to maximize detection probability and precision of occupancy estimates while minimizing the number CTs reduce equipment labor costs. Few studies, however, have examined effect CT on probability. Moreover, historically, most focused a specific species design could be tailored toward maximizing this target species. Increasingly, such use data for all captured, non‐target, (by‐catch data) animal community‐level analyses. It remains unclear if, how, targeting one affects non‐target We paired from permanent grid (with 38 CTs) targeted at monitoring Eurasian lynx ( Lynx ) Innlandet County, Norway, with additional randomly placed two spatial scales (38 within same habitat patch 50‐km 2 cell as lynx‐targeted three months. combined multi‐scale models that enable separation large‐scale occupancy, CT‐scale site use, single‐scale models. This allowed us study effects placement (lynx) seven mammal (four carnivores, herbivores, rodent). found species, except moose Alces alces ), had highest CTs. Moose equal probabilities types. Adding extra generally increased probabilities. Consequently, combining or more CTs, accuracy cells compared single estimates. The underestimated grid‐cell known minimum were similar site‐use is, uncertain which extent these refer. therefore recommend multiple (targeted) estimate large interpret an, yet undefined, area surrounding CT.

Язык: Английский

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High‐density camera trap grid reveals lack of consistency in detection and capture rates across space and time

Ecosphere, Год журнала: 2021, Номер 12(2)

Опубликована: Фев. 1, 2021

Abstract Counts of independent photo events from camera traps are commonly used to make inference about species occupancy, the density unmarked populations, and relative abundance across time space. These applications rest on untested assumption that data collected individual cameras representative landscape location in which they placed, nearby would record similar when any additional micro‐site differences accounted for. We established a high‐density trapping grid (100 × 100 m; 27 cameras) Virginia, USA, explicitly test these assumptions, investigating variation capture rates detection probabilities for range terrestrial mammals during four 2‐month seasonal surveys. Despite controlling numerous habitat placement factors, we documented, all 5 focal species, large ranges coefficients both rate probabilities, were those seen 2 sets forest sampling sites larger, more typical trap design. also documented lack spatial autocorrelation at distance. Measured local covariates relevant viewshed (stem density, height, log presence, effective distance [EDD], total dbh oak trees) rarely explained significant portion observed or grid. The influence EDD, measured here first stations, was inconsistently important varied direction effect depending season. Our study indicates single‐camera stations may fail sample animal presence frequency use robust repeatable way, primarily resulting idiosyncrasies movement unknown characteristics. recommend replication within (e.g., small‐scale shifting multiple stations) should be considered minimize impacts characteristics, some difficult identify.

Язык: Английский

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Human impacts on mammals in and around a protected area before, during, and after COVID‐19 lockdowns

Conservation Science and Practice, Год журнала: 2022, Номер 4(7)

Опубликована: Июнь 7, 2022

The dual mandate for many protected areas (PAs) to simultaneously promote recreation and conserve biodiversity may be hampered by negative effects of on wildlife. However, reports these are not consistent, presenting a knowledge gap that hinders evidence-based decision-making. We used camera traps monitor human activity terrestrial mammals in Golden Ears Provincial Park the adjacent University British Columbia Malcolm Knapp Research Forest near Vancouver, Canada, with objective discerning relative various forms cougars (

Язык: Английский

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Population assessment without individual identification using camera-traps: A comparison of four methods

Basic and Applied Ecology, Год журнала: 2022, Номер 61, С. 68 - 81

Опубликована: Март 7, 2022

The use of camera traps to estimate population size when animals are not individually recognizable is gaining traction in the ecological literature, because its applicability conservation and management. We estimated synthetic with four trap sampling-based statistical models that do rely on individual recognition. Using a realistic model animal movement generate data, we compared random encounter model, staying time association time-to-event-model investigated impact violation assumptions estimates. While under ideal conditions these provide reliable estimates, movements were characterised by differences speed (due diverse behaviours such as locomotion, grazing resting) none provided both unbiased precise density results but tended overestimate size, while was less underestimate size. Lastly, unable results. found each tested very sensitive method used range field-of-view traps. Density estimates from also biases animals' speed. guidelines how get could be useful wildlife managers practitioners.

Язык: Английский

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Guidelines for estimating occupancy from autocorrelated camera trap detections

Methods in Ecology and Evolution, Год журнала: 2024, Номер 15(7), С. 1177 - 1191

Опубликована: Май 31, 2024

Abstract Site occupancy models (SOMs) are a common tool for studying the spatial ecology of wildlife. When observational data collected using passive monitoring field methods, including camera traps or autonomous recorders, detections animals may be temporally autocorrelated, leading to biased estimates and incorrectly quantified uncertainty. We presently lack clear guidance understanding mitigating consequences temporal autocorrelation when estimating with trap data. use simulations explore how gives rise overconfident occupancy. impact sampling design biological conditions on model performance in presence autocorrelation, investigate usefulness several techniques identifying bias compare SOM that explicitly autocorrelation. also conduct case study 22 North American mammals. show join count goodness‐of‐fit test previously proposed clustered is effective detecting across range conditions. find strong occurs estimated intercept survey durations short detection rates low. provide reference table assessing degree expected under all further discretizing larger windows decreases magnitude introduced by In our study, we most species autocorrelated demonstrate might mitigate resulting bias. Our findings suggest likely widespread many previous studies based have systematically underestimated probabilities. Moving forward, recommend ecologists from determine whether present their If it is, SOMs should large more accurately quantify uncertainty parameters. Ecologists not gaps between periods, which ineffective at structure discard useful

Язык: Английский

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The influence of movement on the occupancy–density relationship at small spatial scales

Ecosphere, Год журнала: 2019, Номер 10(8)

Опубликована: Авг. 1, 2019

Abstract The global decline of large carnivores demands effective and efficient methods to monitor population status, particularly using non‐invasive methods. Density is among the most useful metrics status because it directly comparable across space time. Unfortunately, density difficult measure reliably, especially for mobile, cryptic species. Recently, efforts have turned approximating based on its relationship more readily estimable indices occurrence. However, between such contingent several key assumptions that field studies often violate. Recent research has shown these relationships are unreliable where sampling units not independent, as case when estimating or occurrence carnivores. Here, we use largest data set thus far collected leopards ( Panthera pardus ) — 88 camera‐trap surveys undertaken in 24 protected areas 2013 2018—to explore how other characteristics relate parameter estimates occupancy Royle–Nichols abundance models. We show home‐range size confounds underlying relationships, with larger home ranges inflating proportion area used (PAU) resulting double counting Relativizing by improved their density, but remained weak largely uninformative management. Our findings illustrate pitfalls PAU implicit proxies highlight challenges assessing wide‐ranging, species fragmented landscapes.

Язык: Английский

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Assessing arrays of multiple trail cameras to detect North American mammals

PLoS ONE, Год журнала: 2019, Номер 14(6), С. e0217543 - e0217543

Опубликована: Июнь 17, 2019

Motion triggered camera traps are an increasingly popular tool for wildlife research and can be used to survey multiple species simultaneously. As with all techniques, it is crucial conduct trapping following study designs that include adequate spatial temporal replication, sufficient probability of detecting presence. The use configuration within a single site understudied considerations could have substantial impact on detection probability. Our objective was test the role number (one, two or three units), spacing along linear transect (100 m 150 m), given present. From January March, 2017 we collected data six mammal in Maine, USA: coyote (Canis latrans), fisher (Pekania pennanti), American marten (Martes americana), short-tailed weasel (Mustela erminea), snowshoe hare (Lepus americanus), red squirrel (Tamiasciurus hudsonicus). We multi-scale occupancy modelling compare pooled histories different five cameras deployed at same (n = 32), how would influence available site. Across species, found increases as increased from one (22 400 percent increase), regardless between cameras. For most magnitude increase less when adding third (4 85 showing pronounced effect. station features also varied by species. suggest using cost effective approach success over camera.

Язык: Английский

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