A mechanistic home range model for optimal use of spatially distributed resources
Authored by MS Mitchell, RA Powell
Date Published: 2004
DOI: 10.1016/j.ecolmodel.2004.01.015
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Abstract
Home ranges of animals are associated with the spatial distribution of
limiting resources on a landscape, yet no mechanistic models
representing this relationship exist. We present models of how animals
might choose patches for their home ranges in ways that are optimal with
respect to spatially distributed resources. The models assume that
animals choose patches for their home ranges based on resource benefits
discounted for travel costs. Animals might select patches to maximize
resources within their home ranges over random use of the landscape
(resource maximization), or to satisfy a minimum resource threshold
needed for survival or reproduction (area minimization). We evaluated
how landscape configuration structures home ranges of animals by
performing individual-based, spatially explicit computer simulations
using each model on simulated landscapes that differed only in the
spatial continuity of resources among patches (from over-dispersed to
clumped). The most important factor determining quality, efficiency, resource content, and spatial distribution of home ranges was the extent
to which resources were clumped on a landscape. Characteristics of
resource-maximizing home ranges were determined only by the distribution
of resources, and differed from those of area-minimizing home ranges
depending upon the magnitude of the resource threshold required. An
increase in resource threshold increased area and total resource content
for area-minimizing home ranges, but did not change their quality or
efficiency. Because animals can consume or protect resources within
their home ranges, they can depress the value of resources available to
other animals and hence how those animals will choose their home ranges.
Depression of resource values on a landscape by animals should result in
different configuration and spatial distribution of home ranges on a
landscape than would be predicted in its absence. We modified the two
home range models to depress the value of resources available to other
animals within patches selected for each home range. We generated home
ranges with the new models on the simulated landscapes and evaluated how
home ranges with resource depression varied with landscape configuration
and with the number of home ranges on the landscape. We compared
characteristics and spatial distribution of home ranges with resource
depression to those of home ranges that do not. For the number of
simulations we performed, resource depression resulted in home ranges
that differed little in configuration and landscape interactions from
those without, except that they were distributed more evenly on the
landscapes and overlapped each other less. As the number of home ranges
on a landscape increased, resource distributions declined in quality and
heterogeneity, and home ranges became larger, less efficient, and of
lower quality. Our results suggest that, in addition to landscape
configuration, the extent to which animals depress resources included in
their home ranges should determine the evenness of spatial dispersion, overlap, and home range structure, especially where animals select home
ranges to satisfy a specific resource threshold and the density of
animals is high. Because resource depression sets a limit on the number
of home ranges a landscape with fixed resource levels can support, our
models provide a means of assessing carrying capacity of a landscape.
(C) 2004 Elsevier B.V. All rights reserved.
Tags
Animal movement
Habitat use
time
Density
Territory size
Small mammals
Population regulation
Hummingbirds
Spacing behavior
Black bears