Pine marten copulation is prolonged, lasting 30-50 minutes, and may occur on the ground or in trees.
Adult male pine martens exhibit a distinct seasonal testicular cycle and can be sexually vigorous throughout their entire lives. Males complete testicular development a full month before estrous, and begin regression about the time females enter estrous. The first visible sign of estrous in females is an enlarged vulva.
Most pine marten matings occur within a 30- to 45-day period, during which females may exhibit one to four periods of sexual receptivity. These periods last for 1-4 days and have an interval of 6-17 days.
Copulation is prolonged, lasting 30-50 minutes, and may occur on the ground or in trees. In captivity, multiple copulations with one or more males can occur during each period of receptivity.