Boom and bust cycles of black-tailed prairie dog populations in the Thunder Basin grassland ecosystem

Abstract

AbstractBlack-tailed prairie dogs (Cynomys ludovicianus) exhibit boom and bust cycles in landscapes where they are affected by outbreaks of plague caused by the introduced bacterium Yersinia pestis. We examined spatiotemporal dynamics of black-tailed prairie dog colonies in the Thunder Basin National Grassland, Wyoming over a period of 21 years. The colony complex experienced three plague epizootics during that time, and consequently three boom and bust cycles. The entire prairie dog colony complex collapsed over a 1-year period during the first and third epizootics, and over a 3-year period during the second epizootic. The boom and bust cycles were characterized by relatively rapid contractions in total area occupied by prairie dogs during a plague outbreak (e.g., >99% decline from 10,604 ha to 47 ha over 1 year [2017–2018]) followed by much slower recovery times (e.g., an increase from 410 ha to 10,604 ha over 11 years [2006–2017]). Prairie dogs occupied a total of 10,604 ha during at least one survey within the study period, but much of the area was not continuously occupied over time. We found that each of the three plague outbreaks occurred in years with highly connected prairie dog colonies and slightly above-average temperatures and summer precipitation, which were preceded by a dry year. Although plague outbreaks were associated with climatic conditions, we were unable to detect a role of climate in driving colony expansion. Our results illustrate the cyclic and extreme nature of fluctuations in black-tailed prairie dog colony size and distribution in a landscape where plague occurs and illuminate some of the drivers of these cycles. Further, our work shows how introduced diseases can dramatically influence populations of a keystone species, with important consequences for the broader ecological system.