Nestling survival and population cycles in the prairie vole, Microtus ochrogaster

We live-trapped a population of the prairie vole, Microtus ochrogaster, occupying an alfalfa habitat twice weekly for 63 months. The population underwent four high-amplitude cycles during this time. The most consistent factor associated with population increases was an increase in the number of young animals recruited into the population. Recruitment of young was more a function of survival of offspring during the nestling period than of the proportion of pregnant females in the population. Increased adult survival and reproduction in the population only partly explained the increase phase of the cycles. The decline phases resulted from a combination of decreased reproduction and increased adult mortality. Precipitous declines were associated with major mortality episodes, some less than a week in duration.