First tunnel length
Across all dens, the average length of the first tunnel was 248.64 ± 23.67 cm. The first tunnel length of the dens on the shady slopes and sunny slopes and in flat areas was 257.50 ± 101.33, 226.67 ± 93.93, and 256.25 ± 76.15 cm, respectively, and the differences among them were significant (F2, 128 = 4.37, P< 0.05) (Fig. 4).