Size and growth characteristics of dispersing voles, Microtus townsendii.

In a peak population of Microtus townsendii, adults and subadults dispersed during the spring decline, and subadults and juveniles dispersed during the summer and fall. Voles born in the spring dispersed before the start of the next year's breeding season, whereas fall-born voles dispersed during the next year's breeding season. Voles under 50 g, when they dispersed, had faster growth rates than similar-sized residents, but voles over 59 g, when they dispersed, had slower growth rates than similar-sized residents. Dispersing and resident voles 50-59 g had no consistent trend in growth rates.