Northern Prairie Wildlife Research Center
Interpreting Carnivore Scent-station Surveys
By
Glen A. Sargeant1, Douglas H. Johnson1, and William
E. Berg2
Abstract: The scent-station survey method has been widely used
to estimate trends in carnivore abundance. However, statistical properties of
scent-station data are poorly understood, and the relation between scent-station
indices and carnivore abundance has not been adequately evaluated. We assessed
properties of scent-station indices by analyzing data collected in Minnesota
during 1986-93. Visits to stations separated by <2 km were correlated for
all species because individual carnivores sometimes visited several stations
in succession. Thus, visits to stations had an intractable statistical distribution.
Dichotomizing results for lines of 10 stations (0 or ≥1 visits) produced
binomially distributed data that were robust to multiple visits by individuals.
We abandoned 2-way comparisons among years in favor of tests for population
trend, which are less susceptible to bias, and analyzed results separately for
biogeographic sections of Minnesota because trends differed among sections.
Before drawing inferences about carnivore population trends, we reevaluated
published validation experiments. Results implicated low statistical power and
confounding as possible explanations for equivocal or conflicting results of
validation efforts. Long-term trends in visitation rates probably reflect real
changes in populations, but poor spatial and temporal resolution, susceptibility
to confounding, and low statistical power limit the usefulness of this survey
method.
Key words: bias, carnivores, Minnesota, population index,
population trend, precision, scent-station survey, validation.
This resource is based on the following source (Northern Prairie Publication
1041):
Sargeant, Glen A., Douglas H. Johnson, and William E. Berg. 1998.
Interpreting carnivore scent-station surveys. Journal of
Wildlife Management 62(4):1235-1245.
This resource should be cited as:
Sargeant, Glen A., Douglas H. Johnson, and William E. Berg. 1998.
Interpreting carnivore scent-station surveys. Journal of
Wildlife Management 62(4). Jamestown, ND: Northern Prairie
Wildlife Research Center Online.
http://www.npwrc.usgs.gov/resource/mammals/scent/index.htm
(Version 20JAN99).
Table of Contents
1Northern Prairie Science Center, Biological Resources Division,
U.S. Geological Survey, 8711 37th Street SE, Jamestown, ND 58401, USA
2Minnesota Department of Natural Resources, 1201 East Highway 2,
Grand Rapids, MN 55744, USA
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