Den site selection by marmots
The underground structure of marmot dens is very complex, and digging a
complete burrow requires a lot of work. Animals tend to use the smallest
investment of energy to get the greatest return (Mcfarland 1993).
Marmots decide where to dig their dens only after careful consideration,
and, therefore, environmental factors (i.e., the terrain and plant
traits) have an important influence on their site selection behavior.
We found that den density on shady and sunny slopes was higher than that
in flat areas (Fig. 2; Fig. 10). Topographic characteristics directly
affect the moisture and thickness of the soil. Dens located on slopes
may allow a more extensive system of burrows to be excavated (Garrott et
al. 1983). A den must be dry and have clean underground shelters in
which marmots can live (Shi 2007). Although flat areas are conducive to
digging burrows, alpine meadow have frequent precipitation during the
warm season and rainwater can easy flow into the den. Therefore, the den
density is lower in flat areas. The soil layer on the shady slopes in
this region is thick (~1 m) relative to that on the
other two regions (He and Li 2016) and is therefore convenient for
marmots to build their underground den systems. In areas where the soil
is shallow and the lower layer is rocky, it is difficult for marmots to
excavate burrows. A study that looked at den site preference indicated
that Arctic foxes like to dig dens on slopes with thin permafrost (30
cm) (Garrott et al. 1983). Marmots like to excavate their burrows on
sunny slopes, in addition to their need for a dry and comfortable
habitat, they also benefit from basking in the sun and staying warm,
which is vital for avoiding cold temperatures and to avoid freezing in
winter after they hibernate (Shi 2007).