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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.


Distributional comparisons of 16 bighorn sheep across home range contours before (2009–2011) and after (2011–2013) fire‐mediated habitat alterations. (A) Proportional change in home range size. Because the change in home range size was quantified by dividing postfire by prefire area, a metric equal to one indicates no change. (B) Proportion of postfire home ranges that overlapped pre‐fire distributions. (C) Joint‐space use calculated with utilization distribution overlap index (UDOI) between prefire and postfire UDs. (D) Bhattacharyya's affinity index (BA) showing overall similarity between distributions.
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ece31655-fig-0005: Distributional comparisons of 16 bighorn sheep across home range contours before (2009–2011) and after (2011–2013) fire‐mediated habitat alterations. (A) Proportional change in home range size. Because the change in home range size was quantified by dividing postfire by prefire area, a metric equal to one indicates no change. (B) Proportion of postfire home ranges that overlapped pre‐fire distributions. (C) Joint‐space use calculated with utilization distribution overlap index (UDOI) between prefire and postfire UDs. (D) Bhattacharyya's affinity index (BA) showing overall similarity between distributions.

Mentions: When summarizing comparative measures to gain population‐level inference, results from our example showed an approximate 200% increase in home range size consistently from the full home range extent (mean = 3.35, 95% CI = 1.16–5.53) to the highest intensity of use (mean = 2.58, 95% CI = 1.44–3.72) or core range areas (Fig. 5A). Because the change in home range size was quantified by dividing postfire by prefire area, a metric equal to 1 indicated no relative change, and confidence intervals did not overlap 1 at any home range contour. When comparing how much postfire home range area overlapped prefire area, at the 99% level home ranges averaged ~50% overlap (mean = 0.49, 95% CI = 0.33–0.65). This trend decreased to ~25% overlap (mean = 0.24, 95% CI = 0.10–0.37) at extreme core range levels (Fig. 5B). When examining similarity between UDs, we identified a sharp decrease in estimated joint‐space use (UDOI) ranging from the 99% contour (mean = 1.50, 95% CI = 0.83–2.16) until an apparent “threshold” was reached at approximately the 70% isopleth (mean = 0.48, 95% CI = 0.30–0.66) after which the decline slowed as UDOI moved toward an asymptote (Fig. 5C). Using the BA index, we found mean similarity in distributions exhibited a linear decrease at increasing core range contours (Fig. 5D). Mean BA values indicated ~60% similarity at the 99% contour, trending down to only ~30% at core home range levels.


Evaluating distributional shifts in home range estimates.

Clapp JG, Beck JL - Ecol Evol (2015)

Distributional comparisons of 16 bighorn sheep across home range contours before (2009–2011) and after (2011–2013) fire‐mediated habitat alterations. (A) Proportional change in home range size. Because the change in home range size was quantified by dividing postfire by prefire area, a metric equal to one indicates no change. (B) Proportion of postfire home ranges that overlapped pre‐fire distributions. (C) Joint‐space use calculated with utilization distribution overlap index (UDOI) between prefire and postfire UDs. (D) Bhattacharyya's affinity index (BA) showing overall similarity between distributions.
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Related In: Results  -  Collection

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ece31655-fig-0005: Distributional comparisons of 16 bighorn sheep across home range contours before (2009–2011) and after (2011–2013) fire‐mediated habitat alterations. (A) Proportional change in home range size. Because the change in home range size was quantified by dividing postfire by prefire area, a metric equal to one indicates no change. (B) Proportion of postfire home ranges that overlapped pre‐fire distributions. (C) Joint‐space use calculated with utilization distribution overlap index (UDOI) between prefire and postfire UDs. (D) Bhattacharyya's affinity index (BA) showing overall similarity between distributions.
Mentions: When summarizing comparative measures to gain population‐level inference, results from our example showed an approximate 200% increase in home range size consistently from the full home range extent (mean = 3.35, 95% CI = 1.16–5.53) to the highest intensity of use (mean = 2.58, 95% CI = 1.44–3.72) or core range areas (Fig. 5A). Because the change in home range size was quantified by dividing postfire by prefire area, a metric equal to 1 indicated no relative change, and confidence intervals did not overlap 1 at any home range contour. When comparing how much postfire home range area overlapped prefire area, at the 99% level home ranges averaged ~50% overlap (mean = 0.49, 95% CI = 0.33–0.65). This trend decreased to ~25% overlap (mean = 0.24, 95% CI = 0.10–0.37) at extreme core range levels (Fig. 5B). When examining similarity between UDs, we identified a sharp decrease in estimated joint‐space use (UDOI) ranging from the 99% contour (mean = 1.50, 95% CI = 0.83–2.16) until an apparent “threshold” was reached at approximately the 70% isopleth (mean = 0.48, 95% CI = 0.30–0.66) after which the decline slowed as UDOI moved toward an asymptote (Fig. 5C). Using the BA index, we found mean similarity in distributions exhibited a linear decrease at increasing core range contours (Fig. 5D). Mean BA values indicated ~60% similarity at the 99% contour, trending down to only ~30% at core home range levels.

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.