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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.


Conceptual examples of home range comparisons at 50 and 95% isopleth values in two‐ and three‐dimensional aspects. (A) and (B) represent the UDs being compared in each scenario. (I) Comparison between full home range estimates (95%) indicates little difference in home range size, but on closer inspection of the UD, the intensity of use shows a marked change in core area use (50%). (II) A scenario where the full extent and core home range sizes are nearly identical, but the intensity of use has shifted. (III) Extent of 95% home range indicates a marked expansion in space use, but on closer inspection of the UD, the majority of 50% core use area remains basically unchanged.
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ece31655-fig-0001: Conceptual examples of home range comparisons at 50 and 95% isopleth values in two‐ and three‐dimensional aspects. (A) and (B) represent the UDs being compared in each scenario. (I) Comparison between full home range estimates (95%) indicates little difference in home range size, but on closer inspection of the UD, the intensity of use shows a marked change in core area use (50%). (II) A scenario where the full extent and core home range sizes are nearly identical, but the intensity of use has shifted. (III) Extent of 95% home range indicates a marked expansion in space use, but on closer inspection of the UD, the majority of 50% core use area remains basically unchanged.

Mentions: The estimated values of intensity of use allocated to the cells within a UD can be used to create a three‐dimensional representation of the home range; a dynamic surface where the volume of the area under the plane is comprised of relative cell values that sum to 1. Comparisons among home ranges, particularly contrasting the extent of home ranges, are often conducted at chosen home range proportions of the volume of three‐dimensional utilization distributions. These isopleths, or contours of the UD, can also be used to determine core ranges (Börger et al. 2006). Isopleths are typically defined at 50% (core home range) and 95% (total home range extent) levels (e.g., Ostfeld 1986; Heupel et al. 2004; Kie et al. 2010; Garitano‐Zavala et al. 2013) for individual animals, or for all marked animals in a sample to gain population inference (Fieberg and Börger 2012). However, applying a home range estimator that quantifies intensity of use through a UD allows visual inspection across all proportional levels of the home range. It may be seen, then, that two‐dimensional comparisons of estimated home range extent conducted at chosen isopleths may overlook or exclude variability in the intensity of use across the entirety of the home range that is provided by the UD (Kernohan et al. 2001; Millspaugh et al. 2004; Kie et al. 2010). Conceptual examples of these ideas are provided in Figure 1. These exaggerated examples show obvious differences in intensity of use through various representations of home range comparisons at 50 and 95% isopleths. However, empirical high‐volume GPS data used to generate UDs often result in complex distributions with disconnected polygons that can make interpretation difficult.


Evaluating distributional shifts in home range estimates.

Clapp JG, Beck JL - Ecol Evol (2015)

Conceptual examples of home range comparisons at 50 and 95% isopleth values in two‐ and three‐dimensional aspects. (A) and (B) represent the UDs being compared in each scenario. (I) Comparison between full home range estimates (95%) indicates little difference in home range size, but on closer inspection of the UD, the intensity of use shows a marked change in core area use (50%). (II) A scenario where the full extent and core home range sizes are nearly identical, but the intensity of use has shifted. (III) Extent of 95% home range indicates a marked expansion in space use, but on closer inspection of the UD, the majority of 50% core use area remains basically unchanged.
© Copyright Policy - creativeCommonsBy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4588651&req=5

ece31655-fig-0001: Conceptual examples of home range comparisons at 50 and 95% isopleth values in two‐ and three‐dimensional aspects. (A) and (B) represent the UDs being compared in each scenario. (I) Comparison between full home range estimates (95%) indicates little difference in home range size, but on closer inspection of the UD, the intensity of use shows a marked change in core area use (50%). (II) A scenario where the full extent and core home range sizes are nearly identical, but the intensity of use has shifted. (III) Extent of 95% home range indicates a marked expansion in space use, but on closer inspection of the UD, the majority of 50% core use area remains basically unchanged.
Mentions: The estimated values of intensity of use allocated to the cells within a UD can be used to create a three‐dimensional representation of the home range; a dynamic surface where the volume of the area under the plane is comprised of relative cell values that sum to 1. Comparisons among home ranges, particularly contrasting the extent of home ranges, are often conducted at chosen home range proportions of the volume of three‐dimensional utilization distributions. These isopleths, or contours of the UD, can also be used to determine core ranges (Börger et al. 2006). Isopleths are typically defined at 50% (core home range) and 95% (total home range extent) levels (e.g., Ostfeld 1986; Heupel et al. 2004; Kie et al. 2010; Garitano‐Zavala et al. 2013) for individual animals, or for all marked animals in a sample to gain population inference (Fieberg and Börger 2012). However, applying a home range estimator that quantifies intensity of use through a UD allows visual inspection across all proportional levels of the home range. It may be seen, then, that two‐dimensional comparisons of estimated home range extent conducted at chosen isopleths may overlook or exclude variability in the intensity of use across the entirety of the home range that is provided by the UD (Kernohan et al. 2001; Millspaugh et al. 2004; Kie et al. 2010). Conceptual examples of these ideas are provided in Figure 1. These exaggerated examples show obvious differences in intensity of use through various representations of home range comparisons at 50 and 95% isopleths. However, empirical high‐volume GPS data used to generate UDs often result in complex distributions with disconnected polygons that can make interpretation difficult.

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.