Lagomorph ladders: Assessing a multi-host community and potential for spillover of rabbit hemorrhagic disease at Great Sand Dunes National Park and Preserve

Abstract

Rabbit hemorrhagic disease virus type 2 (RHDV2) has caused dramatic declines in rabbits and hares on several continents, with cascading effects on local ecology. Recent mortalities have been reported for several rabbit and hare species in the United States, suggesting broad susceptibility of lagomorphs. If this susceptibility extends to the American pika (Ochotona princeps), the most cold-adapted lagomorph, it could compound climate-mediated threats to this species. Due to climate change, American pikas are predicted to experience significant upslope range retraction during this century. Using an analogy borrowed from wildfire scenarios, other lagomorph species occurring at lower and mid-elevations could act as ?ladder fuels? to wick RHDV2 into high-elevation pika populations. To address this concern, we investigated spatial patterns of habitat use by pikas and other lagomorphs in Great Sand Dunes National Park and Preserve (GRSA), which borders several counties that have reported RHDV2. In 2022, we surveyed 115 plots from a spatially balanced sample of pika habitats in the park, including 48 legacy plots from a pika survey conducted in 2010-2012. Pika detections at the plot level were paired with topographic and environmental indices to estimate minimum habitat occupancy and determine its covariates. Leporid (rabbit and hare) detections at these same plots were used to model presence using similar covariates and correcting for imperfect detection. Our best-supported models of pika and leporid presence were then used to estimate the probability of contact between these taxa within the park. Our mean estimate of pika habitat occupancy was at least 95% during 2022 in GRSA, slightly higher than in 2010-2012, and effects of elevation and precipitation on pika occupancy were as expected from the previous study. Leporid presence at these same plots was 48% after correcting for imperfect detection. The best model of leporid presence supported a negative effect of elevation, in agreement with other studies of these taxa. The best pika and leporid models also included a positive effect of incoming solar radiation. Finally, we used our best models of pika habitat occupancy and leporid presence within the park to map the potential for areas of contact and RHDV2 transmission between these taxa. Our results indicate some potential for contact within subalpine forests, Specifically in the northern half of the park near the lower reach of the Sand Creek Trail and in the far south just north of California Peak.