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Evaluating distributional shifts in home range estimates.

Clapp JG, Beck JL - Ecol Evol (2015)

Bottom Line: We describe an approach to gain additional insight into home range changes by comparing UDs across isopleths and summarizing comparisons into meaningful results.We found a consistent increase in bighorn sheep home range size when measured across home range levels, but that home range overlap and similarity values decreased when examined at increasing core levels.Our results highlight the benefit of conducting multiscale assessments when comparing distributions, and we encourage researchers to expand comparative home range analyses to gain a more comprehensive evaluation of distributional changes and to evaluate comparisons across home range levels.

View Article: PubMed Central - PubMed

Affiliation: Department of Ecosystem Science and Management University of Wyoming Dept. 3354 1000 East University Avenue Laramie Wyoming 82071 ; Wyoming Game and Fish Department 260 Buena Vista Drive Lander Wyoming 82520.

ABSTRACT
A variety of methods are commonly used to quantify animal home ranges using location data acquired with telemetry. High-volume location data from global positioning system (GPS) technology provide researchers the opportunity to identify various intensities of use within home ranges, typically quantified through utilization distributions (UDs). However, the wide range of variability evident within UDs constructed with modern home range estimators is often overlooked or ignored during home range comparisons, and challenges may arise when summarizing distributional shifts among multiple UDs. We describe an approach to gain additional insight into home range changes by comparing UDs across isopleths and summarizing comparisons into meaningful results. To demonstrate the efficacy of this approach, we used GPS location data from 16 bighorn sheep (Ovis canadensis) to identify distributional changes before and after habitat alterations, and we discuss advantages in its application when comparing home range size, overlap, and joint-space use. We found a consistent increase in bighorn sheep home range size when measured across home range levels, but that home range overlap and similarity values decreased when examined at increasing core levels. Our results highlight the benefit of conducting multiscale assessments when comparing distributions, and we encourage researchers to expand comparative home range analyses to gain a more comprehensive evaluation of distributional changes and to evaluate comparisons across home range levels.

No MeSH data available.


Example showing Brownian bridge utilization distribution rasters (A) and associated contour lines (B) before (2009–2011) and after (2011–2013) fire‐mediated habitat alterations for an individual female bighorn sheep. Color scales (A) represent the relative intensity of use estimated for cells within the UDs.
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ece31655-fig-0002: Example showing Brownian bridge utilization distribution rasters (A) and associated contour lines (B) before (2009–2011) and after (2011–2013) fire‐mediated habitat alterations for an individual female bighorn sheep. Color scales (A) represent the relative intensity of use estimated for cells within the UDs.

Mentions: We used the bbmm.contour function (package BBMM) to identify proportional contour levels for each UD ranging from 99% (most inclusive home range estimate) to 5% (highest core use areas) in 5% intervals (Fig. 2). We stored the relative probability threshold values that represented each contour level for each UD. We then overlaid each pair of utilization distributions for visual inspection (Fig. 3). Because variation in probability of use, home range size, overlap, and similarity depend largely on the chosen contour of the UD examined, we summarized data based on multiple contour levels of the home ranges. We quantified comparative metrics starting with the most inclusive home range contour (99% isopleth) for each experimental unit. After calculating metrics at the broadest home range level, we used the appropriate probability threshold values to reclassify both prefire and postfire UD rasters at the next sequential contour level (95% isopleth). We used a conditional statement to set cell values less than the 95% contour threshold to zero. Because the remaining cell values must sum to one to remain a relative utilization distribution, we reclassified cells by dividing each cell value by the sum of the remaining cell values within the UD. We then recalculated comparative metrics at this level.


Evaluating distributional shifts in home range estimates.

Clapp JG, Beck JL - Ecol Evol (2015)

Example showing Brownian bridge utilization distribution rasters (A) and associated contour lines (B) before (2009–2011) and after (2011–2013) fire‐mediated habitat alterations for an individual female bighorn sheep. Color scales (A) represent the relative intensity of use estimated for cells within the UDs.
© Copyright Policy - creativeCommonsBy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4588651&req=5

ece31655-fig-0002: Example showing Brownian bridge utilization distribution rasters (A) and associated contour lines (B) before (2009–2011) and after (2011–2013) fire‐mediated habitat alterations for an individual female bighorn sheep. Color scales (A) represent the relative intensity of use estimated for cells within the UDs.
Mentions: We used the bbmm.contour function (package BBMM) to identify proportional contour levels for each UD ranging from 99% (most inclusive home range estimate) to 5% (highest core use areas) in 5% intervals (Fig. 2). We stored the relative probability threshold values that represented each contour level for each UD. We then overlaid each pair of utilization distributions for visual inspection (Fig. 3). Because variation in probability of use, home range size, overlap, and similarity depend largely on the chosen contour of the UD examined, we summarized data based on multiple contour levels of the home ranges. We quantified comparative metrics starting with the most inclusive home range contour (99% isopleth) for each experimental unit. After calculating metrics at the broadest home range level, we used the appropriate probability threshold values to reclassify both prefire and postfire UD rasters at the next sequential contour level (95% isopleth). We used a conditional statement to set cell values less than the 95% contour threshold to zero. Because the remaining cell values must sum to one to remain a relative utilization distribution, we reclassified cells by dividing each cell value by the sum of the remaining cell values within the UD. We then recalculated comparative metrics at this level.

Bottom Line: We describe an approach to gain additional insight into home range changes by comparing UDs across isopleths and summarizing comparisons into meaningful results.We found a consistent increase in bighorn sheep home range size when measured across home range levels, but that home range overlap and similarity values decreased when examined at increasing core levels.Our results highlight the benefit of conducting multiscale assessments when comparing distributions, and we encourage researchers to expand comparative home range analyses to gain a more comprehensive evaluation of distributional changes and to evaluate comparisons across home range levels.

View Article: PubMed Central - PubMed

Affiliation: Department of Ecosystem Science and Management University of Wyoming Dept. 3354 1000 East University Avenue Laramie Wyoming 82071 ; Wyoming Game and Fish Department 260 Buena Vista Drive Lander Wyoming 82520.

ABSTRACT
A variety of methods are commonly used to quantify animal home ranges using location data acquired with telemetry. High-volume location data from global positioning system (GPS) technology provide researchers the opportunity to identify various intensities of use within home ranges, typically quantified through utilization distributions (UDs). However, the wide range of variability evident within UDs constructed with modern home range estimators is often overlooked or ignored during home range comparisons, and challenges may arise when summarizing distributional shifts among multiple UDs. We describe an approach to gain additional insight into home range changes by comparing UDs across isopleths and summarizing comparisons into meaningful results. To demonstrate the efficacy of this approach, we used GPS location data from 16 bighorn sheep (Ovis canadensis) to identify distributional changes before and after habitat alterations, and we discuss advantages in its application when comparing home range size, overlap, and joint-space use. We found a consistent increase in bighorn sheep home range size when measured across home range levels, but that home range overlap and similarity values decreased when examined at increasing core levels. Our results highlight the benefit of conducting multiscale assessments when comparing distributions, and we encourage researchers to expand comparative home range analyses to gain a more comprehensive evaluation of distributional changes and to evaluate comparisons across home range levels.

No MeSH data available.