COS 166-4 - Novel population cycles in a keystone species cause drastic community-level changes at a grassland-sagebrush ecotone

Abstract: Short or long-term cycles of wildlife population growth and decline are key trait of many systems, but increased climatic variation and disease prevalence may lead to novel patterns and periodicity of these fluctuations. Further, if these fluctuations are affecting a keystone species, the whole ecosystem may become destabilized. In the North American Great Plains, black-tailed prairie dogs (Cynomys ludovicianus) are a keystone species that create important grassland habitat for numerous species and serve as prey for predators, 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 reduced prairie dog abundances, in turn destabilizing associated wildlife communities. However, long-term community-level data on wildlife responses to cycles of prairie dog population growth and die-off are virtually non-existent. We here synthesize over two decades of population data on prairie dogs, nearly a decade of data on songbirds, shorebirds, and raptors, as well as ungulate, mesocarnivores, and invertebrate data from a population of prairie dogs in northeastern Wyoming, to identify patterns of response of associated wildlife to boom and bust cycles in black-tailed prairie dogs. During cycles of colony growth we observed increases in prairie dog predators (e.g., Ferruginous hawk [Buteo regalis], Swift fox [Vulpes velox]) as well as bird species that select for the short, sparse vegetation structure found on prairie dog colonies (Mountain plover [Charadrius montanus]). Following an extreme plague event that wiped out over 99% of prairie dogs in the region between 2017 and 2018, we noted rapid declines in associated species, but increased abundance of some species preferring less disturbed habitat (e.g., Lark bunting [Calamospiza melanocorys]). These responses were magnified by extreme precipitation in the year following plague, compounding the loss of disturbance to generate extremely tall and dense vegetation structure. As of 2022, prairie dog populations have not reached pre-plague levels but are comparable to levels observed in the mid-2010s, but associated wildlife responses are slow, indicating either a severe lag between this keystone species and associates, or potentially a state-change in this ecological system.