Landscape composition and anthropogenic development drive occupancy dynamics of pygmy rabbits (Brachylagus idahoensis)

Résumé fourni par la source

The pygmy rabbit (Brachylagus idahoensis) is a species of conservation interest because, in some portions of the Intermountain West, its sagebrush-dominated habitat is undergoing modification associated with industrial, residential, and agricultural development, and information on population status, trends, and distribution remains limited. We investigated initial state and subsequent trends in occupancy dynamics within pygmy rabbit populations in two southwestern Wyoming landscapes including the Pinedale Anticline Project Area (PAPA; hereafter developed area), managed largely for development of oil and gas energy resources, and the adjacent Boulder Reference Area (hereafter reference area) throughout which development was limited. We sampled 254 plots for live pygmy rabbits and fresh sign in the developed area and 136 in the reference area, visiting each plot twice per year from 2011 through 2020. Survey plots had higher initial occupancy rates when found in drier areas (39.8% increase in occupancy for a 1-unit decrease in wetness index) and with more vegetative cover (29.9% increase in occupancy for a 10% point decrease in bare ground). Amongst years, unoccupied plots were 81.4% less likely to become occupied for a ~25% increase in roughness within 1 km but were 476.8% more likely to become occupied for a 50% increase in roughness within 2.9 km. Occupied plots were 23.8% more likely to become extinct for every 10% point increase in bare ground, by 4.6% for every additional well within 2.9 km, and by 19.5% for every additional 1 km/km2 of two-track roads within 1 km of the plot. Plot proximity to development features was not associated with initial occupancy or occupancy dynamics, suggesting that pygmy rabbit populations would benefit from management focusing on total landscape-level development in aggregate rather than placement of individual anthropogenic features. Management of anthropogenic development is important because it occurs in the context of topographic and vegetative limits on the range of pygmy rabbits, including habitat conversion to invasive annual grasses, altered fire regimes, and conifer encroachment.

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