Assertion: arctic fox's den | /r/HasProperty | underground
Facets:
Source sentences:
text: Generally, the arctic foxes live in underground dens that can be centuries old and used by many generations of foxes.
text: Their dens are also underground and often the tunnels that they made end with their den.
text: Arctic foxes also stay warm by avoiding the wind and staying in their underground dens, which also serves the purpose of raising their young ones.