What are the tractories of bighorn sheep and mountain goat populations in the GYA? We dive in to the data to find out.
Using new and rigorous methods to understand habitat selection and expansion of the non-native, invading mountain goat.
Watch Jesse DeVoe's M.Sc. defense "Occupancy Modeling of Non-native Mountain Goats in the GYA"
Occupancy Habitat Modeling
Using Occupancy Surveys to Model Habitat Selection and Range Expansion of Mountain Goats
Non-native species can have adverse impacts on native species. Predicting the potential extent of distributional expansion and abundance of an invading non-native species can inform appropriate conservation and management actions. Non-native mountain goats (Oreamnos americanus) in the greater Yellowstone area (GYA) have substantial potential to occupy similar habitats to native Rocky Mountain bighorn sheep (Ovis canadensis canadensis). To understand the potential for expansion of mountain goats in the GYA, this study evaluated detection-nondetection data from two study areas with established mountain goat populations collected over three summer seasons (2011-2013). Relationships between scale-specific habitat covariates and mountain goat selection were evaluated using a single-species, single-season analysis to model occupancy and detection probabilities based on 505 mountain goat detections from 53,098 surveyed sampling units.
Habitat selection was most strongly associated with terrain covariates, including mean slope and slope variance, at a spatial scale of 500 x 500 m, and canopy cover, heat load, and normalized difference vegetation index at a spatial scale of 100 x 100 m. These results provide new insight into multi-scale patterns of mountain goat habitat selection, as well as evidence that mean slope and slope variance are more informative terrain covariates than distance to escape terrain that has dominated published mountain goat habitat models.
The model predicted 10,745 km2 of suitable habitat within the GYA, of which 57% is currently un-colonized. Throughout the GYA, suitable habitat appears to generally overlap extensively with areas occupied by bighorn sheep. We also estimated the GYA may have the potential to support 5,372-8,918 mountain goats when all predicted habitat is occupied, or approximately 2.5-4.2 times the most recent abundance estimate of 2,104.
written by Jesse DeVoe
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Ongoing telemetry studies across the GYA are being used to understand population vital rates and dynamics, spatial ecology, and competition.
Annual and regional climate factors may impact recruitment of bighorn sheep across the GYA.
Combining historic observations of mountain goats and bighorn sheep obtained from regional biologists to see what we can learn from data we already have.
Predicted suitable mountain goat habitat across the GYA -- CLICK TO ENLARGE!