Browsing by Author "Willey, David"

Now showing 1 - 2 of 2

Modeling carnivore sign data: A case study with the carnivore guild in a ranch in eastern Montana
(2013-03) Bertin, Tor; Willey, David
Track deposition patterns by carnivores on a 54 km2 ranch in eastern Montana were recorded with a sand strip passive index survey method over the course of 33 days. Carnivore tracks identified included coyotes (n = 17), bobcats (n = 8), feral cats (n = 6), pumas (n = 1), and long-tailed weasels (n = 1). Using temporal, weather, and habitat covariates, coyote intrusions were modeled with generalized linear models using a negative binomial distribution and log link. An information theoretic approach, using the Akaike information criterion adjusted for sample size (AICc) to compare the relative support of multiple models, indicated that habitat type had a strong influence on coyote track deposition, and that weather and temporal covariates were comparatively poor descriptors of coyote track patterns. Autocorrelation functions revealed no evidence for daily temporal autocorrelation of coyote intrusion numbers in either habitat, and a Spearman’s rank correlation coefficient suggested little between-habitat daily intrusion correlation (r = -0.21). Use of open areas by coyotes has been well documented in the literature, and the data analyzed in this report are in agreement with said studies.
Multiscale habitat suitability modeling for a threatened raptor offers insight into ecological model transferability
(Elsevier BV, 2024-10) Nayeri, Danial; Cushman, Samuel; Ganey, Joseph; Hysen, Logan; Szykman Gunther, Micaela; Willey, David; Yi Wan, Ho
Habitat fragmentation and loss are major threats to species conservation worldwide. Studying species-habitat relationships is a crucial first step toward understanding species habitat requirements, which is necessary for conservation and management planning. However, some species inhabit a range of habitat types, potentially making the use of range-wide habitat models inappropriate due to non-stationarity in species-habitat preferences. The Mexican spotted owl (Strix occidentalis lucida) (MSO) is a species that inhabits both forests and rocky canyonlands, two habitats with large differences in environmental conditions. It is unclear whether the species uses habitat differently in these two habitat types or if previously-built habitat models for forest-dwelling owls can be used to understand MSO habitat use in rocky canyonlands. To explore this, we developed the first scale-optimized habitat suitability model for this subspecies of spotted owl in rocky canyonlands using an ensemble framework. We then compared our results with a previously-built habitat model for MSO in forested areas. In the rocky canyonland model, slope (800 m scale), cumulative degree days (1200 m scale), insolation (1000 m scale), and monsoon precipitation (100 m scale) were the most important environmental covariates. In contrast, in the forest model, percent canopy cover (100 m scale), percent mixed-conifer (5000 m scale), and slope (500 m scale) were the most important environmental covariates. The rocky canyonland model performed well, while the forest model performed poorly when projected to rocky canyonlands and predicted low suitability across the entire study area, including areas with known nesting locations. These results support the non-stationarity in habitat use for MSOs between rocky canyonland and forest habitats. Hence, when transferring habitat suitability models from one region to another, it is necessary to evaluate the transferability of the model by accounting for non-stationarity in species-habitat preferences.