scholarly journals Out-of-sight or out-of-site? Forays and detection probabilities in single-season occupancy models

2021 ◽  
Author(s):  
André Desrochers ◽  
Pierre Blanchette ◽  
Marc J. Mazerolle
Keyword(s):  
Radio Telemetry ◽  
Empirical Relationship ◽  
Site Occupancy ◽  
Major Effect ◽  
Probability Of Detection ◽  
Occupancy Models ◽  
Detection Distance ◽  
Individual Level ◽  
Temporary Emigration ◽  
Detection Probabilities

Occupancy models have become popular in wildlife survey analyses because they account for the frequent failure to detect individuals of targeted species. Those individuals sometimes move outside sampling sites, i.e. exhibit temporary emigration. In such cases, occupancy models may become difficult to interpret or even misleading either at the species or the individual level, because they confound presence at the site, availability for detection given presence, and actual detection by the observer. We quantified the probabilities of these three components with spruce grouse (Falcipennis canadensis) in southern Quebec, Canada. We conducted call-response surveys of 24 grouse monitored by radio-telemetry. We defined sites empirically as circular areas of 83 m radius centered on the observer, corresponding to the maximum detection distance obtained. Based on telemetry locations, grouse were present at the site during 42 % of the surveys. Six stationary grouse were present during surveys, but were never detected. Thus, only individuals that moved in the presence of the observer (89 %) were considered available for detection. Individuals available for detection were detected in 51 % of the cases. We simulated detection histories and built single-season occupancy models, based on the empirical relationship between detection probability and the distance measured between observers and grouse. When temporary emigration was ignored, site occupancy was ψ = 0.89, and the associated probability of detection was p = 0.23. When instances of temporary emigration were dropped, estimates were ψ = 0.88 and p = 0.41. Using only grouse available for detection, estimates were ψ = 0.87 and p = 0.42. Disentangling the components of detection probabilities had little impact on occupancy estimates, but showed a major effect of temporary emigration on estimated detection probabilities.

scholarly journals Optimal sampling methods for modelling the occupancy of Arctic grayling (Thymallus arcticus) in the Canadian Barrenlands

2017 ◽  
Vol 74 (10) ◽  
pp. 1564-1574 ◽  
Author(s):  
Leanne F. Baker ◽  
Kyle J. Artym ◽  
Heidi K. Swanson
Keyword(s):  
Sampling Methods ◽  
Site Occupancy ◽  
Sampling Strategy ◽  
Cost Effective ◽  
Probability Of Detection ◽  
Occupancy Models ◽  
Arctic Grayling ◽  
Autocorrelated Data ◽  
Thymallus Arcticus ◽  
Better Than

In occupancy models, imperfect detectability of animals is usually corrected for by using temporally repeated surveys to estimate probability of detection. Substituting spatial replicates for temporal replicates could be an advantageous sampling strategy in remote Arctic regions, but may lead to serious violations of model assumptions. Using a case study of site occupancy of adfluvial young-of-year Arctic grayling (Thymallus arcticus) in Barrenland tundra streams, we assessed the reliability and efficiency of alternative sampling strategies: (i) randomly distributed versus sequential adjacent spatial replicates; (ii) visual versus electrofishing surveys; and (iii) spatial versus temporal replicates. Sequential, adjacent spatial replicates produced spatially autocorrelated data. Autocorrelation was relieved using randomly distributed spatial replicates, but using these randomly distributed spatial replicates introduced significant error into estimates of the probability of occupancy in streams. Models designed for spatially autocorrelated data could minimize this bias. Visual and electrofishing surveys produced comparable probabilities of detection. Spatially replicated surveys performed better than temporal replicates. The easiest and relatively most cost-effective sampling methods performed as well as, or better than, the more established, expensive, and logistically difficult alternatives for occupancy estimation.

Using multiple methods to assess detection probabilities of riparian-zone anurans: implications for monitoring

2014 ◽  
Vol 41 (3) ◽  
pp. 243 ◽  
Author(s):  
Jacquelyn C. Guzy ◽  
Steven J. Price ◽  
Michael E. Dorcas
Keyword(s):  
South Carolina ◽  
Riparian Zone ◽  
Survey Methods ◽  
Population Monitoring ◽  
Probability Of Detection ◽  
Occupancy Models ◽  
Specific Detection ◽  
Field Methods ◽  
Anuran Species ◽  
Detection Probabilities

Context Both manual call surveys (MCS) and visual encounter surveys (VES) are popular methods used to monitor anuran populations. Recent statistical developments, specifically the development of occupancy models that permit the use of data from various survey methods to assess method-specific detection probabilities, provide a rigorous framework for evaluating the effectiveness of field methods. Aim To compare species-specific detection probabilities generated by MCS and VES and to evaluate the effectiveness of these methods throughout the activity season of several riparian-zone anuran species. Methods During 2010 and 2011, we sampled 21 sites along the Broad and Pacolet Rivers, in South Carolina, USA, using MCS and VES. Anuran species were surveyed across three seasons (fall, spring and summer) each year. Key results For six species, MCS resulted in a higher mean probability of detection, whereas VES resulted in a higher mean probability of detection for four species. In addition, survey date was an important influence on detection probability of most anurans when using MCS, but largely unimportant when employing VES. Conclusions Our findings indicated that VES are as effective as MCS for detecting some species of anurans, and for others, VES represent a more effective method. Furthermore, when using VES outside the breeding window, some anurans can be reliably detected, and in some cases, detected more easily than by using MCS. Implications We suggest that VES is a complimentary technique to MCS and a potentially important tool for population monitoring of anurans. VES can provide more flexibility for anuran researchers, as robust estimates of detection and occupancy can be obtained outside a narrow breeding window.

scholarly journals Analysis of Low Probability of Detection Capability for Chaotic Standard Map-Based FH-OFDMA System

2021 ◽  
Vol 11 (5) ◽  
pp. 2198
Author(s):  
Junwoo Jung ◽  
Jaesung Lim ◽  
Sungyeol Park ◽  
Haengik Kang ◽  
Seungbok Kwon
Keyword(s):  
Detection Probability ◽  
Probability Of Detection ◽  
Lower Probability ◽  
Symbol Sequence ◽  
Ofdma System ◽  
Standard Map ◽  
Detection Probabilities ◽  
Low Probability ◽  
Transmitted Symbol ◽  
Basic Symbol

A frequency hopping orthogonal frequency division multiple access (FH-OFDMA) can provide low probability of detection (LPD) and anti-jamming capabilities to users against adversary detectors. To obtain an extreme LPD capability that cannot be provided by the basic symbol-by-symbol (SBS)-based FH pattern, we proposed two FH patterns, namely chaotic standard map (CSM) and cat map for FH-OFDMA systems. In our previous work, through analysis of complexity to regenerate the transmitted symbol sequence, at the point of adversary detectors, we found that the CSM had a lower probability of intercept than the cat map and SBS. It is possible when a detector already knows symbol and frame structures, and the detector has been synchronized to the FH-OFDMA system. Unlike the previous work, here, we analyze whether the CSM provides greater LPD capability than the cat map and SBS by detection probability using spectrum sensing technique. We analyze the detection probability of the CSM and provide detection probabilities of the cat map and SBS compared to the CSM. Based on our analysis of the detection probability and numerical results, it is evident that the CSM provides greater LPD capability than both the cat map and SBS-based FH-OFDMA systems.

Differences in microhabitat selection patterns between a remnant and constructed landscape following management intervention

2017 ◽  
Vol 44 (3) ◽  
pp. 248 ◽  
Author(s):  
Jose W. Valdez ◽  
Kaya Klop-Toker ◽  
Michelle P. Stockwell ◽  
Loren Fardell ◽  
Simon Clulow ◽  
...  
Keyword(s):  
Aquatic Vegetation ◽  
Management Strategies ◽  
Probability Of Detection ◽  
Microhabitat Use ◽  
Microhabitat Selection ◽  
Habitat Creation ◽  
Litoria Aurea ◽  
Use Of Resources ◽  
Detection Probabilities ◽  
Future Management

Context Achieving successful conservation outcomes in habitat creation and reintroductions requires an understanding of how species use their habitat and respond to these interventions. However, few initiatives directly compare microhabitat selection between remnant and managed habitats to measure effectiveness and evaluate outcomes. Probability of detection is also rarely included in studies on microhabitat use, which may lead to erroneous conclusions if detectability varies between variables. Methods In this study, we used the endangered green and golden bell frog (Litoria aurea) to compare differences in microhabitat-use patterns in both a remnant and a constructed habitat. A detectability study was also conducted to determine detection probabilities among microhabitats. Key results Aquatic vegetation was used more than expected in both the remnant and constructed habitats, and rock piles were utilised less than expected in the constructed habitat, despite their recommendation in most habitat templates. We found that detection probabilities altered the outcomes of abundance estimates for nearly all the measured microhabitat variables. Conclusions Future management for this species should focus on providing high proportions of aquatic vegetation. Furthermore, although rock piles have been utilised greatly in past L. aurea habitat creation, placing large rocks on a managed site is expensive and time consuming. Future management initiatives may need to focus on providing smaller proportion of rocks, which would be a more appropriate use of resources. Implications With conservation management projects increasing over the next few decades, understanding habitat use before implementing strategies should be a priority as it will provide important insights and inform decision-making for optimum habitat creation and restoration. Furthermore, accounting for detectability in microhabitat use studies is essential to avoid wrong conclusions that may negatively affect the success of ecological management strategies.

scholarly journals Use of site occupancy models for targeted monitoring of the cheetah

2014 ◽  
Vol 292 (3) ◽  
pp. 212-220 ◽  
Author(s):  
L. Andresen ◽  
K. T. Everatt ◽  
M. J. Somers
Keyword(s):  
Site Occupancy ◽  
Occupancy Models

Estimating detection probabilities of tagged fish migrating past fixed receiver stations using only local information

2010 ◽  
Vol 67 (4) ◽  
pp. 641-658 ◽  
Author(s):  
Michael C. Melnychuk ◽  
Carl J. Walters
Keyword(s):  
Detection Probability ◽  
Radio Telemetry ◽  
Model Parameters ◽  
Migration Routes ◽  
Mark Recapture ◽  
The Pacific ◽  
Detection Probabilities ◽  
Acoustic Tags ◽  
Attenuation Models ◽  
Local Detection

We developed a method to predict the probability of detecting acoustic tags crossing a receiver station using only detection information at that station. This method is suitable for acoustic or radio telemetry studies in which individually tagged animals migrate past fixed stations (where a station may consist of one or more receivers). It is based on fitting attenuation models to sequences of detections and missed transmissions of individually coded tags in fish migrating past stations of the Pacific Ocean Shelf Tracking Project (POST). We used estimated attenuation model parameters from detected fish at each station to predict the number of fish that crossed the station undetected, which in turn was used to calculate the local detection probability. This estimator was correlated (r = 0.54–0.81 in river and coastal habitats) with mark–recapture estimates of detection probability (pmr) that use nonlocal detection information at stations further along migration routes. This local detection probability estimate can be used as a covariate of pmr in mark–recapture models and can predict approximate values of pmr at final detection stations where pmr is not estimable because of the lack of recaptures further along migration routes.

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