The long-tailed marmot is diurnal and feeds on plant material. It is most active in the morning when about 40% of the time is spent foraging. After emerging from the burrow, the marmot spreads out and do not forage as a group. Food is either collected from the ground by the mouth or plucked from taller plants. Between bouts of foraging, a marmot sometimes stands on its back legs and surveys its surroundings. Group members communicate with each other, emitting complex alarm calls when predators are spotted. They also react to alarm calls of neighbouring groups.