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Author Durbach, I., Borchers, D., Sutherland, C., Sharma, K.
Title Fast, flexible alternatives to regular grid designs for spatial capture–recapture. Type Research Article
Year 2020 Publication Methods in Ecology and Evolution Abbreviated Journal
Volume Issue Pages 1-13
Keywords camera trap, population ecology,sampling, spatial capture-recapture, surveys
Abstract Spatial capture–recapture (SCR) methods use the location of

detectors (camera traps, hair snares and live-capture traps) and the

locations at which animals were detected (their spatial capture

histories) to estimate animal density. Despite the often large expense

and effort involved in placing detectors in a landscape, there has been

relatively little work on how detectors should be located. A natural

criterion is to place traps so as to maximize the precision of density

estimators, but the lack of a closed-form expression for precision has

made optimizing this criterion computationally demanding. 2. Recent

results by Efford and Boulanger (2019) show that precision can be well

approximated by a function of the expected number of detected

individuals and expected number of recapture events, both of which can

be evaluated at low computational cost. We use these results to develop

a method for obtaining survey designs that optimize this approximate

precision for SCR studies using count or binary proximity detectors, or

multi-catch traps. 3. We show how the basic design protocol can be

extended to incorporate spatially varying distributions of activity

centres and animal detectability. We illustrate our approach by

simulating from a camera trap study of snow leopards in Mongolia and

comparing estimates from our designs to those generated by regular or

optimized grid designs. Optimizing detector placement increased the

number of detected individuals and recaptures, but this did not always

lead to more precise density estimators due to less precise estimation

of the effective sampling area. In most cases, the precision of density

estimators was comparable to that obtained with grid designs, with

improvement in some scenarios where approximate CV(¬D) < 20% and density

varied spatially. 4. Designs generated using our approach are

transparent and statistically grounded. They can be produced for survey

regions of any shape, adapt to known information about animal density

and detectability, and are potentially easier and less costly to

implement. We recommend their use as good, flexible candidate designs

for SCR surveys when reasonable knowledge of model parameters exists. We

provide software for researchers to construct their own designs, in the

form of updates to design functions in the r package oSCR.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title (up)
Series Volume Series Issue Edition
ISSN ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number Serial 1618
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Author Bischof, R.,Hameed, S.,Ali, H.,Kabir, M.,Younas, M.,Shah, K. A.,Din, J. U.,Nawaz, M. A.
Title Using time-to-event analysis to complement hierarchical methods when assessing determinants of photographic detectability during camera trapping Type Journal Article
Year 2013 Publication Methods in Ecology and Evolution Abbreviated Journal
Volume Issue Pages
Keywords Cox proportional hazards model, cumulative incidence, Martes foina, Panthera Uncia, survival anaalysis, Vulpes Vulpes, weighted observations
Abstract 1. Camera trapping, paired with analytical methods for estimating occupancy, abundance and other ecological parameters, can yield information with direct consequences for wildlife management and conservation. Although ecological information is the primary target of most camera trap studies, detectability influences every aspect from design to interpretation.

2. Concepts and methods of time-toevent analysis are directly applicable to camera trapping, yet this statistical field has thus far been ignored as a way to analyze photographic capture data. to illustrate the use to time-to-event statistics and to better understand how photographic evidence accumulates, we explored patterns in tow related measure of detectability: Detection probability and time to detection. We analyzed camera trap data for three sympatric carnivores ( snow Leopard, red fox and stone marten) in the mountains of northern Pakistan and tested predictions about patterns in detectability across species, sites and time.

3. We found species-specific differences in the magnitude of detectability and the factors influencing it, reinforcing the need to consider determinants of detectability in study design and to account for them during analysis. Photographic detectability of snow leopard was noticeably lower than that of red fox, but comparable to detectability of stone marten. Site-specific attributes such as the presence of carnivore sign ( snow Leopard), terrain ( snow leopard and red fox) and application for lures ( red fox) influenced detectability. For the most part, detection probability was constant over time.

4. Species- specific differences in factors determining detectability make camera trap studies targeting multiple species particularly vulnerable to misinterpretation if the hierarchical origin of the data is ignored. Investigators should consider not only the magnitude of detectability, but also the shape of the curve describing the cumulative process of photographic detection, as this has consequences for both determining survey effort and the election of analytical models. Weighted time-to -event analysis can complement occupancy analysis and other hierarchal methods by providing additional tools for exploring camera trap data and testing hypotheses regarding the temporal aspect of photographic evidence accumulation.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title (up)
Series Volume Series Issue Edition
ISSN ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number SLN @ rakhee @ Serial 1405
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