3.2 ǀ Differences in habitat utilization
The
density of breeding pairs was 72 pairs per km2 in the
high disturbance habitat, 50 pairs per km2 in the low
disturbance habitat, and 55 pairs per km2 in the
natural habitat (Figure 1B, 1C, 1D; Table 2), although none of the
differences in breeding pair density were detected among the three
habitats are statistically significant
(χ2 = 1.14, p =
0.285 between HDH and NH; χ2 = 1.99, p = 0.157 between
HDH and LDH; χ2 = 0.119, p = 0.729 between LDH and
NH). However, inter-group differences emerged in measurements related to
the burrows themselves, with a significant negative correlation between
the intensity of human activity and the number of burrows per breeding
pair: pairs in HDH dig far more
(twice as much as) pair-specific
burrows than pairs in LDH (t = 3.63, p=0.000, d.f. = 66) and NH (t =
4.21, p = 0.000, d.f. = 52), furthermore, though not significant (t =
1.83, p = 0.074, d.f. = 46), pairs in LDH also on average dig two more
extra burrows than their counterparts in NH (13.39
± 0.96 V.S. 10.82 ± 0.73). (Figure
3A).
Moreover,
average distance between burrows also differs between different
habitats: inter-burrow distance of reproductive burrows in the high
disturbance habitat is less than that of the other two habitats (t =
-3.22, p = 0.002, d.f. = 81 relative to natural habitat and t = -2.95, p
= 0.004, d.f. = 96 relative to low disturbance habitat), although no
significant difference was found between the low disturbance and natural
habitats (t = -0.18, p = 0.86, d.f. = 77) (Figure 3B). As for the
distances between all burrows in the habitat, relative to the natural
habitat, human activities led to the same decline in the inter-burrow
distance in two disturbed habitats (Figure 2; Figure 3C). Besides, the
FID of individuals in HDP derived from inter all burrow distance is
shortest among all three habitats as expected (Figure 4A), nevertheless,
though inter all burrow distances in LDP are the shortest among three
habitats (Figure 4), and the home range size of pairs in LDH is
significantly smaller than pairs in other two habitats (t = -3.34, p =
0.001, d.f. = 62 relative to HDH, and t = -4.02, p= 0.000, d.f. = 42
relative to NH) (Figure 4B), FID of individuals in the LDP are longer
than marmots in HDP (t = 5.05, p = 0.000, d.f. = 46) and no
differentiation emerged relative to individuals from NP (t = 1.36, p =
0.182, d.f. = 38) (Figure 4A).
Similarly,
the characteristics of sites selected for the digging of reproductive
burrows also differed depending on human activity levels.
Relative to pairs in the low
disturbance population, both reproductive pairs in the high disturbance
population
(χ2= 7.28, p = 0.007) and the natural population (χ2 =
5.89, p = 0.015) preferentially constructed their reproductive burrows
on mounds raised above the level of the surrounding ground (Figure 5A).
The volume of those mounds also differed between sites, with mounds used
for reproductive burrows in the high disturbance population being
significantly smaller than mounds in the natural habitat (t = -2.68, p =
0.014, d.f. = 19.7), and both of those habitats’ mounds being much
smaller than the mounds selected by pairs in the low disturbance
population (Figure 5B). Finally, the mean distance from reproductive
burrows to the nearest road in the high disturbance habitat is
significantly shorter than in the low disturbance habitat (t = -5.77, p
= 0.000, d.f. = 15.97) (Figure 5C).