Time budgets for 17 behaviors were analyzed for cohort, day-period, season- period and interactions among the main effects for three colonies of yellowbellied marmots in the Upper East River Valley in western Colorado. These effects explained up to 79% of the variation in the behaviors. Marmots allocated more time (40-60%, 110-265 min daily) above-ground to sitting/lying than to any other activity. Foraging was the other major activity (12-23%, 37 to 94 min daily). Vigilance/alert varied from 1.1 to 14.5% and from 12.0 to 71.7 min daily. Social status affected the time budget, especially time allocated to vigilance/alert. All other behaviors averaged about 5% or less except for out-of-sight and enterburrow. The adult male cohort spent significantly more time above-ground than all other cohorts and reproductive females allocated significantly more time to foraging than the other cohorts. The amount of time spent above-ground decreased linearly from the down-river site to the up-river site. The proportion of time spent above-ground was significantly less at mid day than in the morning or afternoon. Above-ground activity was lowest during gestation, increased during lactation, remained high during early post-lactation, and declined during the final season-period. The following significant relationships common to the three colonies suggest species characteristics or common environmental influences: more time allocated to foraging and foraging-vigilance in the afternoon and more time allocated to foraging-alert, alert, and locomotion during gestation and lactation than during post-lactation. Marmots adjust their behaviors according to prevailing conditions. The remaining significant relationships can be attributed to specific age-sex cohorts or to habitat differences. Because marmots allocate so much time to sitting/lying, we suggest that energy budgets are not constrained by foraging time but by time required to process ingested food. Similarly, time spent vigilant/alert does not seem to constrain energy intake. Social behavior is not limited by time, but could easily be expanded by spending less time inactive. In general, there do not seem to be tradeoffs among activities. Among other species of ground-dwelling sciurids, social behavior occupies a small proportion of the time budget, but the amount of time allocated to foraging and sitting/lying varies widely.