Disease and weather induce rapid shifts in a rangeland ecosystem mediated by a keystone species (Cynomys ludovicianus)

Authors: DUCHARDT, COURTNEY - Oklahoma State University; Augustine, David; Porensky, Lauren; BECK, JEFF - University Of Wyoming; HENNIG, JAKE - Us Geological Survey; PELLATZ, DAVE - Thunder Basin Grasslands Prairie Ecological Association; SCASTA, DEREK - University Of Wyoming; CONNELL, LAUREN - Bird Conservancy Of The Rockies; DAVIDSON, ANA - Colorado State University

Submitted to: Ecological Applications
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/6/2022
Publication Date: 11/29/2022
Citation: Duchardt, C., Augustine, D.J., Porensky, L.M., Beck, J., Hennig, J., Pellatz, D., Scasta, D., Connell, L., Davidson, A. 2022. Disease and weather induce rapid shifts in a rangeland ecosystem mediated by a keystone species (Cynomys ludovicianus). Ecological Applications. Article e2712. https://doi.org/10.1002/eap.2712.
DOI: https://doi.org/10.1002/eap.2712

Interpretive Summary: Black-tailed prairie dogs occur in grasslands throughout the western Great Plains, and are known to be a "keystone species" because they create habitat for many associated wildlife species, and also are a key prey source for many predators. However, few studies have quantified how the removal of prairie dogs from an extensive portion of a grassland landscape affects the overall abundance and composition of the wildlife community. We used a natural experiment where an outbreak of plague rapidly removed prairie dogs from an extensive landscape within the Thunder Basin National Grassland of Wyoming, to measure changes in wildlife before and after prairie dog removal. We documented a dramatic collapse in populations of ferruginous hawks, American badgers, and swift fox, as well as substantial shift in the bird community, including loss of mountain plovers and a concurrent proliferation of lark buntings. Our work illustrates how disease dynamics combined with variation in weather patterns can rapidly and drastically alter the composition of grassland wildlife communities.

Technical Abstract: Habitat loss and changing climate have direct impacts on native species but can also interact with disease pathogens to influence wildlife communities. In the North American Great Plains, black-tailed prairie dogs (Cynomys ludovicianus) are a keystone species that structure habitat for associated taxa, but lethal control driven by agricultural conflict has severely reduced their abundance. Novel disease dynamics caused by epizootic plague (Yersinia pestis) within prairie dog colonies have further destabilized associated wildlife communities. We capitalized on a natural experiment -- collecting data on prairie dog distributions, vegetation structure, avian abundance, and mesocarnivore and ungulate occupancy before (2015–2017) and after (2018–2019) a plague event in northeastern Wyoming, USA. Plague decimated black-tailed prairie dog populations in what was then the largest extant colony complex, reducing colony area from over 10,000 ha to less than 50 ha. We documented dramatic declines in mesocarnivore occupancy and raptor abundance post-plague, with probability of occupancy or abundance approaching zero in species that rely on prairie dogs for a high proportion of their diet (e.g., ferruginous hawk [Buteo regalis], American badger [Taxidea taxus], and swift fox [Vulpes velox]). Following the plague outbreak, abnormally high precipitation in 2018 hastened vegetation recovery on colonies where constant herbivory had formerly maintained shortgrass structure necessary for certain colony-associates. As a result, we observed large shifts in avian communities on former prairie dog colonies, including near-disappearance of mountain plover (Charadrius montanus) and increases in mid-grass associated songbirds (e.g., lark bunting [Calamospiza melanocorys]). Our research highlights how climate can interact with disease-induced loss of a keystone species to induce drastic and rapid shifts in wildlife communities. Although grassland taxa co-evolved with high spatiotemporal variation, fragmentation of remaining North American rangelands paired with higher-than-historical variability are likely to destabilize these systems in the future.