Development and Evaluation of Sightability Models for Summer Elk Surveys

Anderson, Charles R.; Moody, David S.; Smith, Bruce L.; Lindzey, Frederick G.; Lanka, Robert P.

doi:10.2307/3802558

Cited by 41 publications

(57 citation statements)

References 8 publications

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“…Here a measure of the area that incorporated species' vegetation preferences was calculated (see also Anderson et al, 1998). A nearly continuous record was independently made of the vegetation type (Table 1) on each side of the vehicle by noting changes in vegetation structure given that the vehicle had traversed 0.2 km or more.…”

Section: Methods Dmentioning

confidence: 99%

Conservation monitoring: estimating mammal densities in woodland habitats

1999

Animal Conservation

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Conservation and ecological monitoring programmes often estimate animal densities over time, but in wooded and forested areas practical techniques are still poorly developed. Here I have examined five simple methods of deriving densities of large and medium-sized mammals using line transects driven through miombo woodland habitat in Africa. These methods calculated area by dividing the number of individuals seen by (i) an average of each species' sighting distances, (ii) a fixed 200 m belt width, (iii) the area visible from the centre of the transect, (iv) visible area weighted by species ' vegetation preferences, and (v) by dividing the number of groups seen by area visible from the transect. Individual-based methods produced quite divergent estimates of species' densities and overall biomass with belt transects giving the lowest values. The group method and corresponding individual-based method gave similar values, however. Most of these calculations yielded considerably higher density estimates than aerial surveys conducted in the same area over a similar time period. Sightings of species were not distributed evenly across vegetation types although the majority of mammal species were observed more often in open habitat. These findings indicate that ground-based conservation monitoring programmes should set transects through several vegetation types, restrict comparisons to those studies that use the same methodology, and refrain from comparing ground and aerial surveys.

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Section: Methods Dmentioning

confidence: 99%

Conservation monitoring: estimating mammal densities in woodland habitats

1999

Animal Conservation

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“…During breeding, animals aggregate on high alpine plateaus devoid of trees. Given increased sightability of other ungulates in open versus forested habitats (e.g., Anderson et al 1998;Poole 2007) we assumed northern mountain caribou in the Yukon were also more visible during the breeding season in these open habitats. Further, a comparison between concurrent estimates of calf:cow ratios, of the same herd, from aerial survey (as used here) and ratios based on individually sampled radio-collared adult females indicated no significant difference (0.095 vs. 0.10, respectively; T. Hegel, unpublished data), suggesting minimal sampling error.…”

Section: Study Area and Caribou Recruitment Datamentioning

confidence: 99%

Spatial synchrony of recruitment in mountain‐dwelling woodland caribou

et al. 2011

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Spatial synchrony in population dynamics is a ubiquitous feature across a range of taxa. Understanding factors influencing this synchrony may shed light on important drivers of population dynamics. Three mechanisms influence the degree of spatial synchrony between populations: dispersal, shared predators, and spatial environmental covariance (the Moran effect). We assessed demographic spatial synchrony in recruitment (calf:cow ratio) of 10 northern mountain caribou herds in the Yukon Territory, Canada (1982Canada ( -2008. Shared predators and dispersal were ruled out as causal mechanisms of spatial recruitment synchrony in these herds and therefore any spatial synchrony should be due to the Moran effect. We also assessed the degree of spatial synchrony in April snow depth to represent environmental variability. The regional average spatial synchrony in detrended residuals of April snow depth was 0.46 (95% CI 0.37 to 0.55). Spatial synchrony in caribou recruitment was weak at 0.13 (95% CI -0.06 to 0.32). The spatial scale of synchrony in April snow depth and caribou recruitment was 330.2 km (95% CI 236.3 to 370.0 km) and 170.0 km (95% CI 69.5 to 282.8 km), respectively. We also investigated how the similarity in terrain features between herds influenced the degree of spatial synchrony using exponential decay models. Only the difference in elevation variability between herds during calving was supported by the data. Herds with more similar elevation variability may track snowmelt ablation patterns in a more similar fashion, which would subsequently result in more synchronized predation rates on calves and/or nutritional effects impacting juvenile survival. Interspecific interactions with predators and alternate prey may also influence spatial synchrony of recruitment in these herds.

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“…During the aerial survey the same covariates are recorded for each sighting and the sightability model is used to correct the counts for animals that were missed. This approach has been applied to elk surveys in the United States (Samuel et al 1987;Unsworth et al 1990;Otten et al 1993;Anderson et al 1998), moose (Anderson and Lindzey 1996), and also bighorn sheep (Ovis canadensis) (Bodie et al 1995). In each of these studies the sightability model was developed using radio-telemetry data Skalski et al (2005).…”

Section: Sightability Modelsmentioning

confidence: 99%

Theory and application of mark - recapture and related techniques to aerial surveys of wildlife

Barker¹

2008

Wildl. Res.

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The key difficulty in assessing animal numbers from the air is that not all animals are seen by the observers. Methods for estimating detection probabilities, or accounting for imperfect detection, are reviewed including double surveys, use of sightability models, mark-resight, and mark-recapture. The assumptions needed for each method are considered as well as issues concerning survey design. For closed-population mark-recapture modelling particular attention is given to multiple observer studies. An emphasis is that an assumption of complete independence in doubleobserver studies is rarely justifiable and that independent observers will generally only satisfy an assumption of conditional independence and not complete independence.

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Development and Evaluation of Sightability Models for Summer Elk Surveys

Cited by 41 publications

References 8 publications

Conservation monitoring: estimating mammal densities in woodland habitats

Conservation monitoring: estimating mammal densities in woodland habitats

Spatial synchrony of recruitment in mountain‐dwelling woodland caribou

Theory and application of mark - recapture and related techniques to aerial surveys of wildlife

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