An integrated model decomposing the components of detection probability and abundance in unmarked populations

Hostetter, Nathan J.; Gardner, Beth; Sillett, T. Scott; Pollock, Kenneth H.; Simons, Theodore R.

doi:10.1002/ecs2.2586

Cited by 25 publications

(34 citation statements)

References 31 publications

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“…Our application of the hierarchal Bayesian model originally formulated for birds (Amundson et al 2014, Hostetter et al 2019) provided useful site-specific density estimates for this aquatic turtle. There was no overlap among credible intervals for low-and high-density estimates, suggesting the method could be used across large geographic areas to investigate species status and prioritize areas for conservation action.…”

Section: Discussionmentioning

confidence: 99%

“…The distribution of the total number of terrapins seen at a station summed for all four visits of terrapins. Future efforts could consider additional information (e.g., telemetry), modeling approaches that combine all four visits to estimate temporary emigration into a single model, and the development of density contour maps (K ery and Royle 2015, Hostetter et al 2019. Simple presence/absence surveys would otherwise be difficult to interpret because they lack information on sample effort, detection probabilities, and a definition of the area sampled (Efford and Dawson 2012).…”

Section: Discussionmentioning

confidence: 99%

“…Our implementation of availability in the Amundsen model addressed being at the surface and available to count, but not with movement in and out of the sample area. Future efforts could consider additional information (e.g., telemetry), modeling approaches that combine all four visits to estimate temporary emigration into a single model, and the development of density contour maps (K ery and Royle 2015, Hostetter et al 2019. Keeping track of individuals could be more difficult in areas with terrapin aggregations larger than we encountered and our future work includes investigating approaches that rely less on individual recognition.…”

Section: Discussionmentioning

confidence: 99%

“…Farnsworth et al (2005) integrated distance sampling with a time removal approach to account for availability because samples need to be long enough for animals to be sighted, but not too long that abundance changes during the sampling period. Amundson et al (2014) integrated Farnsworth et al (2005) distance-sampling and time-removal approach with Royle et al's (2004) hierarchical Bayesian N-mixture approach to allow site-specific covariate effects (models) separately for the availability, perceptibility, and abundance processes to improve estimation (Hostetter et al 2019).…”

Section: Introductionmentioning

confidence: 99%

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Sampling rare and elusive species: Florida east coast diamondback terrapin population abundance

et al. 2019

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The Florida east coast terrapin (Malaclemys terrapin tequesta) is a rare and potentially endangered species that is difficult to survey because of poor detection probability and a patchy distribution. Like many rare species sampling programs, we apply a density and multistate occupancy sampling approach that considered the impacts of imperfect detection. We separated the detection process into availability of the animal within the sampling area (e.g., coming to surface) and perceptibility (actually seeing it). Our study employed a density estimation approach originally developed for birds, which combined time to detection and distance sampling within a Bayesian N-mixture model. Our study also estimated two abundance occupancy states (few and many terrapins). We were able to estimate large differences in terrapin densities between sites through functions of site-specific environmental covariates (water depth, distance to mangrove, and distance to land). The detection probability was poor (0.28) for the few terrapin occupancy state, but was much greater for many (0.75). The time to detection and distance-sampling approach for this aquatic animal should be useful for other aquatic organisms that regularly surface. Terrapins were generally available to be sighted within four minutes but detection declined rapidly to a low probability of terrapin detection >30 m. The approach of estimating density as a function of habitat covariates to identify habitat associations can provide an effective method that combined with adaptive sampling should be useful to investigate the distribution of terrapins in open water.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Sampling rare and elusive species: Florida east coast diamondback terrapin population abundance

et al. 2019

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“…Another problem, which has received little attention, is that lek survey protocols do not ensure that an equal proportion of active leks are counted relative to the true (likely unknown or not estimated) population of leks (Sedinger 2007, Shyvers et al 2018). Additionally, lek detection probability (i.e., the product of the probability a lek is available for detection and the probability that an available lek is detected by an observer; Hostetter et al 2019) is typically unknown and not measurable with existing protocols. Lek detection probability may vary for several reasons.…”

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confidence: 99%

Aural and Visual Detection of Greater Sage‐Grouse Leks: Implications for Population Trend Estimates

et al. 2021

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Counts of greater sage‐grouse (Centrocercus urophasianus) at leks have been used in harvest management, Endangered Species Act listing decisions, and land management policies for over half a century. Lek count sampling methods focus on counting male sage‐grouse at known leks, primarily those observed visually from roads or vantage points, but leks are likely missed that are unknown prior to the survey and are difficult to detect while driving between known lek sites. One way to ameliorate this shortfall may be to conduct short point‐count surveys at multiple stops along lek‐survey routes or while driving between lek counts, thereby detecting newly established or unknown leks. To evaluate the feasibility of this approach, we estimated aural and visual detection probability of active sage‐grouse leks during 1‐minute point‐count surveys at known distances and examined the effects of environmental factors on aural lek detection in southern Idaho, USA, 2016–2017. Our results demonstrate that field observers can aurally detect sage‐grouse leks at approximately 3 times greater distances compared to detecting leks visually. The probability of hearing an active lek was highest near the peak of male and female attendance (8 Apr), within an hour of sunrise, on relatively calm and cold days, when the observer was at a higher elevation relative to the lek, and during conditions with no background noise. Detection probability declined with distance and the probability of aural detection was 0.59 at 1 km from a lek when other variables were held at their means. Hence, conducting ≥3 1‐minute surveys along a lek route would be expected to detect ≥93% of all leks within 1.5 km of each survey under the average environmental conditions in our study. Our results suggest that surveys could greatly improve detection of unknown or newly established leks and can facilitate a more accurate assessment of sage‐grouse population trends through lek counts. Moreover, our results demonstrate how environmental factors influence the detection of leks during surveys, and therefore which variables should be considered for inclusion in any future revisions of lek count protocols or in analyses of lek count data. © 2021 The Wildlife Society.

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Estimating abundance in unmarked populations of Golden Eagle (Aquila chrysaetos)

Stien

Tveraa

et al. 2022

Ecol Sol and Evidence

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1. Estimates of species abundance are of key importance in population and ecosystem level research but can be hard to obtain. Study designs using camera traps are increasingly being used for large-scale monitoring of species that are elusive and/or occur naturally at low densities. Golden eagle (Aquila chrysaetos) is one such species, and we investigate whether existing large-scale monitoring programs using baited camera traps can be used to estimate the abundance of golden eagles, as an alternative to traditional labour-intensive searches for active territories and nest sites during the breeding period.3. The camera-trap data allowed two measures of abundance to be estimated within each of four main study areas in mid and northern Norway; occupancy was measured as the probability of camera site use, and population size was measured as the number of individuals using camera sites within a study area. Spatial and temporal patterns in occupancy and population size were explored and evaluated against independent estimates of breeding pair density in the study areas.4. Annual estimates of golden eagle occupancy showed low precision, while estimates of population size were more precise in relation to both estimated and anticipated abundance fluctuations. Estimates of population size may therefore be suitable for monitoring within-study area temporal abundance trends, while estimates of occupancy seem unsuitable for such for golden eagles. Across study areas, patterns in both average occupancy and average population density estimated from population size were consistent with the spatial pattern in average breeding pair densities (r = 0.99, and r = 0.89, respectively). This suggests that camera-trap-based estimates of occupancy and population density, both reflect territory density at large spatial scales. In conclusion, our results suggest that baited camera traps can be a cost-effective strategy for monitoring the abundance of golden eagles.

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An integrated model decomposing the components of detection probability and abundance in unmarked populations

Cited by 25 publications

References 31 publications

Sampling rare and elusive species: Florida east coast diamondback terrapin population abundance

Sampling rare and elusive species: Florida east coast diamondback terrapin population abundance

Aural and Visual Detection of Greater Sage‐Grouse Leks: Implications for Population Trend Estimates

Estimating abundance in unmarked populations of Golden Eagle (Aquila chrysaetos)

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