Modeling ecological minimum requirements for
distribution of greater sage-grouse leks: implications for
population connectivity across their western range, U.S.A.

Habitat similarity index (HSI) values
for greater sage-grouse across their western
range. HSI values represent the relationship of
environmental values at map locations to the
multivariate model of minimum requirements
for sage-grouse defined by land cover,
anthropogenic variables, soil, topography, and
climate.
Greater sage-grouse Centrocercus urophasianus (Bonaparte) currently occupy
approximately half of their historical distribution across western North America.
Sage-grouse are a candidate for endangered species listing due to habitat and
population fragmentation coupled with inadequate regulation to control development
in critical areas. Conservation planning would benefit from accurate
maps delineating required habitats and movement corridors. However, developing
a species distribution model that incorporates the diversity of habitats used
by sage-grouse across their widespread distribution has statistical and logistical
challenges. We first identified the ecological minimums limiting sage-grouse,
mapped similarity to the multivariate set of minimums, and delineated connectivity
across a 920,000 km2 region. We partitioned a Mahalanobis D2 model of
habitat use into k separate additive components each representing independent
combinations of species–habitat relationships to identify the ecological minimums
required by sage-grouse. We constructed the model from abiotic, land
cover, and anthropogenic variables measured at leks (breeding) and surrounding
areas within 5 km. We evaluated model partitions using a random subset of leks
and historic locations and selected D2 (k = 10) for mapping a habitat similarity
index (HSI). Finally, we delineated connectivity by converting the mapped HSI
to a resistance surface. Sage-grouse required sagebrush-dominated landscapes
containing minimal levels of human land use. Sage-grouse used relatively arid
regions characterized by shallow slopes, even terrain, and low amounts of forest,
grassland, and agriculture in the surrounding landscape. Most populations were
interconnected although several outlying populations were isolated because of
distance or lack of habitat corridors for exchange. Land management agencies
currently are revising land-use plans and designating critical habitat to conserve
sage-grouse and avoid endangered species listing. Our results identifying attributes
important for delineating habitats or modeling connectivity will facilitate
conservation and management of landscapes important for supporting current
and future sage-grouse populations.
Contact the Authors:
Steven T. Knick
USGS Forest and Rangeland Ecosystem Science Center
email: steve_knick@usgs.gov
telephone: 208-426-5208
Steven E. Hanser
USGS Forest and Rangeland Ecosystem Science Center
email: shanser@usgs.gov
telephone: 208-426-2892
Kristine L. Preston
Center for Conservation Biology
University of California, Riverside
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Habitat similarity index (HSI) values for greater sage-grouse across their western range.
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Estimated potential for sage-grouse movement
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