Unusually High Body Mass in Virginia Meadow Voles

We used monthly capture-mark-recapture information to determine growth rates and life spans for 2 populations of meadow voles studied for 28 and 29 months in eastern Virginia in order to learn whether the exceptionally large body masses of some voles were due to rapid growth, long lives, or both. On 1 study grid, 64 males (19%) and 43 nonpregnant females (11%) were ≥70 g, with the largest male being 89 g. Mostly positive growth rates (averaging 1.1-3.9 g/month) were recorded, even in autumn and winter months, times when meadow voles are losing mass in northern populations, where most studies of body growth have been conducted. Periods of low mean body mass were associated with low population density more than high body mass was associated with high population density. Patterns of body mass dynamics were related more to season than to density in our populations. We concluded that the large body masses we observed in some voles were due more to long field lives than to unusually high rates of body growth