Great Gray Owl Prey Inventory at Yosemite National Park

Blois, Jessica

The great gray owl (Strix nebulosa yosemitensis) is a genetically distinct and state endangered subspecies whose strongest remaining population occurs within Yosemite National Park. Because great gray owls rely heavily on meadow associated small mammals, particularly voles and pocket gophers, understanding prey dynamics is essential for ensuring the long-term persistence of this species. Yet despite extensive research on great gray owl ecology in Yosemite, little is known about the distribution, abundance, and habitat associations of their prey within the park. This information gap is especially critical considering the Ackerson Meadow Restoration Project, a major hydrologic restoration effort expected to substantially alter meadow conditions that influence prey availability. Restoring Ackerson Main Meadow from a degraded, deeply incised system to a functioning wet meadow may shift prey communities, with potential management implications for great gray owl foraging habitat. This study addresses these information needs by providing baseline data on vole and gopher populations in Ackerson Main Meadow during the early phases of restoration, using Ackerson South and Hodgdon Meadow as reference sites representing desired future conditions. We assessed prey presence and relative abundance across habitat types, sites, and years; evaluated relationships with vegetation and soil characteristics; and explored the feasibility of chew blocks as a low-cost method for monitoring vole populations over time. Results from this work support Yosemite’s ability to evaluate restoration effects, anticipate changes to owl foraging habitat, and guide adaptive management actions that protect great gray owl populations. Ultimately, this study establishes the foundation for long term monitoring of prey dynamics within a key conservation landscape.

Great Gray Owl Prey Inventory at Yosemite National Park

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