PARENT SESSION
Oral Session # 42: Mammal Ecology: From Mice to Elephants.
Presiding: H Howe
Wednesday, August 6. 8:00 AM to 11:30 AM, SITCC Meeting Room 104.
Demography of fluctuating populations: Temporal and phase-related changes in vital rates of prairie voles, Microtus ochrogaster.
Ozgul, Arpat*,1, Getz, Lowell2, Oli, Madan1, 1 University of Florida, Gainesville, FL2 University of Illinois, Urbana, IL
ABSTRACT- Small mammal population fluctuations have been an ecological puzzle and a source of heated debates among ecologists. Identifying the demographic parameters that closely covary with density changes can help elucidate the underlying causes of population fluctuations, but few studies have reported rigorous estimates of these parameters. We applied capture-mark-recapture analysis to biweekly trapping data from a long-term study of a fluctuating prairie vole, Microtus ochrogaster population in Illinois, USA to estimate overall and stage-specific survival and maturation probabilities. We also estimated population density, fecundity rates, age at maturity, and lifespans. Survival, maturation and fecundity rates exhibited phase-related changes during the major density fluctuations, but they showed density-independent temporal variations during the prolonged low-density phases. Among these variables, maturation and juvenile survival probabilities most closely covaried with population density. These results suggest that phase-related changes in maturation and juvenile survival probabilities are likely to be the main demographic factors driving the dynamics of our study population. Phase-related changes in maturation rates provide a plausible demographic explanation of density fluctuations. Because direct predation is unlikely to influence maturation rates, our results suggest that direct predation may not be necessary for large-scale fluctuations in prairie vole abundance.
Key words: density fluctuations, Microtus ochrogaster, population dynamics, capture-mark-recapture analysis