Title
Modelling broad-scale wolverine occupancy in a remote boreal region using multi-year aerial survey data
Author(s)
Ray, J.C., Poley, L.G., Magoun, A.J., Chetkiewicz, C.B., Southee, F.M. , Dawson, F.N., Chenier, C. 2018.
Published
2018
Publisher
Journal of Biogeography 45: 1478-1489.
Abstract
Aim: We used data from aerial surveys of wolverine tracks collected in seven winters
over a 10-year period (2003–2012) within a 574,287 km2 study area to evaluate
the broad-scale pattern of wolverine occurrence across a remote northern
boreal forest region, identifying areas of high and low occupancy.
Location: Northern Ontario, Canada.
Taxon: Wolverine (Gulo gulo Linnaeus, 1758).
Methods: We collected wolverine tracks and observations in 100-km2 hexagonal
survey units, making a total of 6,664 visits to 3,039 units, visiting each 1–9 times.
We used hierarchical Bayesian occupancy modelling to model wolverine occurrence,
and included covariates with the potential to affect detection and/or occupancy
probability of wolverines.
Results: we detected wolverines on 946 visits, 14.2% of total visits. Probability of
detecting a wolverine varied among years and between the two ecozones in the
study area. Wolverine occupancy was negatively related to two important covariates,
the geographical coordinate Easting and thawing degree-days. A site occupancy
probability map indicated that wolverine occupancy probabilities were
highest, and standard error lowest, in the western and northern portions of the
study area.
Main conclusions: The occupancy framework enabled us to use observation data
from tracks of this elusive, wide-ranging carnivore over a vast, remote area while
explicitly considering detectability and spatial autocorrelation, yielding a map of
probable wolverine distribution in northern Ontario that would not be possible using
other methods of detection across a large region. With resource development pressures
increasing in this globally significant region in the face of a changing climate,
it is important to monitor changes in distribution of species like wolverines that
have low population growth rates, large spatial requirements and sensitivity to
human disturbance. This study demonstrates a relatively cost-effective and noninvasive
alternative to monitoring based on wolverine harvest records, which have
not been available since 2009 in Ontario due to changes in the provincial regulatory
regime for this threatened species.
Keywords
Aerial survey; conservation biogeography; fur harvest; Gulo gulo; hierarchical modelling; imperfect detection; northern Ontario; probability of occupancy; spatial autocorrelation; wolverine
Full Citation
Ray, J.C., Poley, L.G., Magoun, A.J., Chetkiewicz, C.B., Southee, F.M., Dawson, F.N., Chenier, C. 2018. Modelling broad-scale wolverine occupancy in a remote boreal region using multi-year aerial survey data. Journal of Biogeography 45: 1478-1489.
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