Plant characteristics near the den entrance
Vegetation characteristics (richness, height, and biomass) have an important influence on the den-selecting behavior of marmots (Li et al. 2017). We found that species richness in marmot activity areas was significantly higher than that near the den entrance (Fig. 9). The active area for these marmots was mainly concentrated within 2−100 m near the den entrance. Plants in the active area provide food and water for the marmots, as well as bedding for their nests in winter. Marmots like to feed on succulent and highly nutritious forage and can get enough water from their forage without additional water. Generally, marmots like to excavate burrows on sloped terrain, but we found that there were also some dens in flat areas (0.60/ha), and the species richness in those areas was significantly higher than that on sloped terrain. High species richness may be the reason why marmots are attracted to these places to dig dens (Shi 2007).
Plant height also has a significant influence on the activities of marmots (Li et al. 2017). We found that plant height within the activity area was significantly higher than that near the den entrance (Fig. 9). The low plants near the den entrance allow marmots to hide in their tunnels while observing the outside environment (Shi 2007), thus ensuring that there is no danger before they leave their dens. In addition, marmots often stand and observe their surroundings when feeding, and the exposed den entrance serves as a marker, which helps them return to their den quickly when danger is detected (Zhang et al. 2019).
Because marmots are active only near the entrance to their dens, the availability of food in those areas directly affects their den-selecting behavior and quality of life. We found that the aboveground biomass in the active area was significantly higher than that near the den entrance (Fig. 9). Abundant food sources ensure that marmots can reserve enough energy before hibernation to prepare for the 6-month hibernation period (October to April).