THERMAL INFLUENCES ON THE ACTIVITY AND ENERGETICS OF YELLOW-BELLIED MARMOTS (MARMOTA-FLAVIVENTRIS)

The thermal environment (Tes) of microhabitats used by yellow-bellied marmots in the Elk Mountains, SW Colorado was characterized. Marmots typically used only two aboveground microhabitats - meadows, where they foraged, and rocks near the burrow, where they often sat. Tes's calculated for foraging areas were often <0°C before 0800 hr and often exceeded the upper limit of marmots' thermoneutral zone from late morning to midafternoon on clear days. Higher wind speeds over rocks produced Tes's up to 10°C less than in foraging areas. Marmots responded to stressfully high Tes's by reducing aboveground activity, reducing the length of foraging bouts, and tolerating transient increases in body temperature. Foraging activity during midday hours was greater on cloudy days and at a high elevation site with lower average Tes's. Young responded to stressfully low Tes's by timing daily activity to avoid the lowest Tes's. Marmots sometimes foraged at stressful Tes's when that option was necessary to meet daily energy demands and preferable to the alternative of forgoing foraging. -from Authors