PARENT SESSION

Population Ecology 3 -- Session Chair: Winston Smith-- Van Duzer Theater

PATTERNS OF EXTINCTION IN PRAIRIE-DOG METAPOPULATIONS: PLAGUE OUTBREAKS FOLLOW EL NIO EVENTS. Paul Stapp¹, Michael F. Antolin² and Mark Ball³. ¹ 1Department of Biological Science, California State University, Fullerton, CA, USA; ² Department of Biology, Colorado State University, Fort Collins, CO, USA; ³ USDA Forest Service Pawnee National Grasslands, Greeley, CO.

ABSTRACT- Outbreaks of many vector-borne human diseases are broadly correlated with climatic variation, but evidence of similar fluctuations in disease in natural host populations is rare. Here, we use 21 years of monitoring of black-tailed prairie-dog (Cynomys ludovicianus) colonies in northern Colorado to demonstrate a link between extinctions of colonies attributed to plague (Yersinia pestis) and climatic fluctuations associated with El Niño Southern Oscillation events that promote the growth of flea vector and rodent host populations. Logistic regression revealed that rates of extinction of the largest colonies (>16 ha) during epizootics were nearly as high (>60%) as for the smallest ones (<3 ha), whereas only a third of intermediate-sized colonies were extirpated. The probability of extinction was influenced by the size and fate of nearby colonies, but there was no predictable relationship between extinction probabilities and inter-colony distance, indicating that spatial isolation may not reduce the vulnerability of colonies to plague. By causing sporadic extinctions of colonies, plague creates a metapopulation structure that has altered the dynamics of prairie-dog colonies as they respond to a century of human persecution and habitat loss.

KEY WORDS: plague, climate, prairie dog, metapopulation