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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.


Examples of individual variation when comparing UDs across home range contours for bighorn sheep (n = 16) before (2009–2011) and after (2011–2013) fire‐mediated habitat alterations. (A) Trends in BA similarity across contours for individual bighorn sheep. Note the variability among individuals includes consistently high similarity (e.g., bolded individual trend with square markers), marked decreases in similarity at increasing core home range isopleths (e.g., circle markers), and an individual with no similarity measured across contours (triangle markers). (B) Box plots constructed at each contour showing variation in the proportional change in home range size for bighorn sheep. Box plots include the interquartile range (25th–75th percentile) of comparative values; horizontal lines within boxes are median values; whiskers are 1.5 times the interquartile range. Note individual outlier comparative values were consistently >1.5 times the interquartile range (connected circle markers).
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ece31655-fig-0004: Examples of individual variation when comparing UDs across home range contours for bighorn sheep (n = 16) before (2009–2011) and after (2011–2013) fire‐mediated habitat alterations. (A) Trends in BA similarity across contours for individual bighorn sheep. Note the variability among individuals includes consistently high similarity (e.g., bolded individual trend with square markers), marked decreases in similarity at increasing core home range isopleths (e.g., circle markers), and an individual with no similarity measured across contours (triangle markers). (B) Box plots constructed at each contour showing variation in the proportional change in home range size for bighorn sheep. Box plots include the interquartile range (25th–75th percentile) of comparative values; horizontal lines within boxes are median values; whiskers are 1.5 times the interquartile range. Note individual outlier comparative values were consistently >1.5 times the interquartile range (connected circle markers).

Mentions: By examining individual trends across home range contours, variation was identified among individual UD comparisons (Fig. 4A), providing insight into how individuals included in the sample may influence mean distributional changes. For example, some bighorn sheep completely shifted home ranges after fires, exhibiting no overlap or similarity during comparisons. In addition, it was evident that a few bighorn sheep showed extreme home range changes, with comparative values >1.5 times the interquartile range of the sample, and were identified as outliers shown in box plots plotted at each contour (Fig. 4B). However, without reason to suspect outliers were influenced differently from others in the sample, we retained all animals when summarizing population‐level changes.


Evaluating distributional shifts in home range estimates.

Clapp JG, Beck JL - Ecol Evol (2015)

Examples of individual variation when comparing UDs across home range contours for bighorn sheep (n = 16) before (2009–2011) and after (2011–2013) fire‐mediated habitat alterations. (A) Trends in BA similarity across contours for individual bighorn sheep. Note the variability among individuals includes consistently high similarity (e.g., bolded individual trend with square markers), marked decreases in similarity at increasing core home range isopleths (e.g., circle markers), and an individual with no similarity measured across contours (triangle markers). (B) Box plots constructed at each contour showing variation in the proportional change in home range size for bighorn sheep. Box plots include the interquartile range (25th–75th percentile) of comparative values; horizontal lines within boxes are median values; whiskers are 1.5 times the interquartile range. Note individual outlier comparative values were consistently >1.5 times the interquartile range (connected circle markers).
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ece31655-fig-0004: Examples of individual variation when comparing UDs across home range contours for bighorn sheep (n = 16) before (2009–2011) and after (2011–2013) fire‐mediated habitat alterations. (A) Trends in BA similarity across contours for individual bighorn sheep. Note the variability among individuals includes consistently high similarity (e.g., bolded individual trend with square markers), marked decreases in similarity at increasing core home range isopleths (e.g., circle markers), and an individual with no similarity measured across contours (triangle markers). (B) Box plots constructed at each contour showing variation in the proportional change in home range size for bighorn sheep. Box plots include the interquartile range (25th–75th percentile) of comparative values; horizontal lines within boxes are median values; whiskers are 1.5 times the interquartile range. Note individual outlier comparative values were consistently >1.5 times the interquartile range (connected circle markers).
Mentions: By examining individual trends across home range contours, variation was identified among individual UD comparisons (Fig. 4A), providing insight into how individuals included in the sample may influence mean distributional changes. For example, some bighorn sheep completely shifted home ranges after fires, exhibiting no overlap or similarity during comparisons. In addition, it was evident that a few bighorn sheep showed extreme home range changes, with comparative values >1.5 times the interquartile range of the sample, and were identified as outliers shown in box plots plotted at each contour (Fig. 4B). However, without reason to suspect outliers were influenced differently from others in the sample, we retained all animals when summarizing population‐level changes.

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.