Chapter 9:
Tigers Routes, Their Dependence on Natural and Anthropogenic Factors
During the characterization of the tigers' travels in previous chapters,
a question that was hardly mentioned at all was: how do the animals' journeys
correspond to the characteristics of topography and vegetation as well as
to the distribution of snow cover over the landscape. Nevertheless, this
is one of the key problems in the winter ecology of the Amur tiger. The
analysis of factors influencing the formation of the animals' routes is most
conveniently conducted by differentiating the route in accordance with the
factors that had previously been combined in the tracking data obtained from
single individuals (here we consider only the division of the data according
to the sex of the animals).
Associations Between Tigers' Routes and Various Types of Topography
| Sex of the Animals |
Total Distance of Tracked Footprints
(km) |
Flat River Bottoms,
Floodplains |
Elevated Terraces
and Foothills of Slopes |
||
| | | Absolute Distance |
Percentage |
Absolute Distance |
Percentage |
| Male Tigers |
764 | 256 | 33.5 | 56 | 7.3 |
| Tigresses |
407 | 85 | 20.9 | 40 | 9.8 |
| Sex of the Animals
|
Slopes |
Mountain
Ridges |
||||||||
| Total |
Southerly Exposures |
Easterly or Westerly Exposures | Northerly Exposures | |||||||
| Abs. |
% | Abs. |
% | Abs. |
% | Abs. |
% | Absolute Distance | Percentage | |
| Male Tigers
Tigresses |
330
215 |
43.2
52.8 |
154
108 |
20.2
26.5 |
85
64 |
11.1
15.7 |
91
43 |
11.9
10.6 |
122
67 |
16.0
16.5 |
The percentage of the distance that was walked by tigers along river valleys
is close to the percentage of the area occupied by valley habitats over
the entire territory of the long-term study site (Table
6). This means that tigers do not exhibit a clearly expressed preference
for sectors with level relief. However, if we examine the sum of all the
animals' journeys along floodplains, elevated terraces and foothill slopes,
then a certain degree of selectivity is revealed. This is especially true
in the case of males (more than 40% of their travels took place in areas
with these types of topography with the percentage of the area characterized
by these types of relief being not more than 25%).
Almost half of the movements of tigers on mountain slopes take place along
slopes with a southern exposure: doubtless, they attract the animals. Selectivity
with regard to routes along mountain ridges and spurs is especially strongly
expressed. These narrow sectors along the divides between rivers occupy
an insignificant percentage of the territory. However, approximately 16%
of all tracked movements of tigers take place across such places.
Tigers avoid very steep slopes, most readily utilizing convenient upgrades
and descents. They prefer to cross over mountain spurs at low saddle points,
which exhibit flattened relief, where it is possible to travel from one
valley into another by the shortest possible route. The animals rarely
ascend onto a mountain across its "brow" (crown or front of thrust), preferring
to gain height gradually. If it is impossible to avoid a section of a slope
of great steepness, tigers sometimes surmount such sections by leaping across
them.
Results of observations along a special-purpose profile laid along the
azimuth across the extreme points of a characteristic section (15 km in
length) of the route of a male tiger allow us to judge how tigers select
their path under conditions of highly differentiated topography (Fig. 11). The transect's length was 13 km; the corresponding
coefficient of sinuosity of the animal's path is 1.15 in the present case.
The footprints of the tiger were tracked here on March 19, and the observations
along the profile were carried out on March 21, 1972. The transect was oriented
from southwest to northeast. As is also the case with the route of the animal,
the transect lies across mountain spurs of the left bank of the Orekhovka
River, crossing the valleys of its tributaries, Bol'shoi and Khvoinyi Streams.
The initial point of the transect lies in a valley of Malyi Klyuch Stream,
and the endpoint lies in the valley of Kazachkov Stream near its confluence
with Bystryi Stream.
The elevational gradient along the profile reaches 280 m (from 280 m up
to 560 m above sea level). The average elevation of the divides is approximately
500 m here. The transect crosses eight mountain ridges (or their spurs).
There are a total of five such ridges or spurs on the tiger's path, a path
which did not deviate from the transect line by more than one kilometer.
This difference is explained by the fact that the animal went around several
spurs and "noski" (i.e., small promontories), unhesitatingly
finding the most convenient passage between them. The average elevational
gradient over a distance of 1 kilometer of the transect was 183 m, whereas,
on the tiger's path, this gradient turned out to less by a factor of 1.5,
equaling 120 m.
It is possible to judge the energy expenditures during the passages of tigers
across slopes of varying degrees of steepness by using the frequency of laying
sites used by the tiger for brief rests. On steep descents (11.5 km of our
tracking), this index is 1.2 rest stops, and on gently sloping descents (161
km of tracking) it was 6.5 rest stops. On gently sloping upgrades (225 km
of tracking) it was 8 rest stops, and on steep upgrades (21 km of tracking)
it was 41 rest stops per 10 km of the tiger's path (Yudakov & Nikolaev
1977).
The tigers manifest a selective relationship to the specific types of plant
communities that are represented in the long-term study site to a still lesser
degree than they exhibit in regard to various types of topography. The animals
clearly avoid only massifs of dark coniferous taiga, which are traversed by
tigers in a few relatively rare instances. In such cases, the tigers do
not linger when surmounting the very highest mountain spurs. Tigers are distributed
rather uniformly across Korean pine forests of different types. Korean pine-oak
stands on south-facing slopes are, however, especially attractive to them,
since they correspond to the distribution of possible prey.
Tigers relatively rarely penetrate into areas that are both overgrown by
thickets of vegetation and difficult to pass through, although in individual
instances the animals clearly seek shelter in dense thickets of, for example,
seedlings of dark coniferous tree species. Open sites are almost absent in
the long-term study site. Tigers cross the small clearings, glades, and the
open shingle spits of rivers that are present on the study site without attempting
to go around such places. Judging from available data, selective cutting
of Korean pine and ash, where a considerable proportion of the standing timber
remains untouched, does not have an unfavorable effect on the tigers. The
numbers of wild boar on such sectors remain relatively high, and the populations
of both Manchurian deer and roe deer even increase.
Figure 11. Route of the Tiger and the Transect Rectifying this Route
Between Points A and B.
1. Path of the Tiger
2. Transect Line
3. Drainage Basin
4. Ridges and Their Spurs
As far as logging roads are concerned, they serve as the favorite "highways"
for the tigers' travels (Table 7). Approximately 80%
of the lengths of the routes of male tigers are associated with those valleys
and streams where roads are laid down: here, the animals prefer public roads
to those rarely visited by humans and those that have been abandoned by people.
The tigers have developed a standard reaction, which is "to let the automobiles
pass by them", where the tiger moves to the verge of the road for a distance
of several tens of meters. Tigresses utilize roads to a lesser degree, which
is one of the manifestations of their more secretive way of life. Generally
speaking, roads attract tigers as both the most convenient and the shortest
paths that also have little or no snow (Fig. 12).
The animals also seek out conditions facilitating their travel on snow in
places where roads are absent (Table 8). Tigers make
not more than half of their journeys over virgin snow (Fig.
13), more often going along tracks made by wild boar, along their old
tracks or along tracks made by other tigers (Fig. 14).
In order to make travel easier, they can also even use tracks made by people,
who had walked across the snow without using skis. Although heavy snowfalls,
of course, worsen the conditions under which tigers must overwinter, a significant
increase in the frequency of rest stops--at laying sites that are used for
brief periods--is not observed in such a situation. Thus, if at the end of
the moderately snowy winter of 1971-1972, we noted 45 laying places used by
the "Empress" tigress for brief periods over a distance of 56 km (about 0.8
stops per 1 km of her path), then in deep snow at the end of February, 1973,
she briefly used 39 laying places over distance of 39 km (1 stop per 1 km
of her path).
Table 7.
Significance of Roads in the Travels of Tigers
| Sex of the Animals |
Total Distance of Tracked Footprints
in River Valleys and Streams That Had Roads Present (km) |
Path Length |
|||||||
| Outside Roads |
Along Derelict RoadsWith Virgin
Snow |
Along Roads Having a Few Tracks
Made by Vehicles or Humans |
Along Public Roads |
||||||
| km | % | km | % | km | % | km | % | ||
| Male Tigers | 257 | 51 | 19.8 | 15 | 5.8 | 68 | 26.5 | 123 | 47.9 |
| Tigresses | 64.7 | 34.7 | 53.6 | 5.4 | 8.4 | 7.0 | 10.8 | 17.6 | 27.2 |
Table 8.
Tigers' Use of Conditions Facilitating Movement in Snow
| Total Distance of
Tracked Footprints in Valleys Lacking Roads and Also on Mountain Slopes and
Ridges (km) |
Path Length |
|||||||
| On Virgin Snow |
On Tracks of Other
Animals |
On Tracks of Humans |
On Tracks of Other
Tigers and on Their Own Old Tracks |
|||||
| km | % | km | % | km | % | km | % | |
| 1028 | 532 | 51.8 | 275 | 26.8 | 10 | 0.9 | 211 | 20.5 |
Figure 12. Laying Place Used Briefly by the "Lazy" Tiger Next to his
Path Along a Road.
Figure 13. Footprints of the "Emperor" Tiger in Deep Snow
(depth = approximately 70 cm). Impressions of the Tail are Visible Alongside
the Footprints.
Figure 14. Footprints of the "Empress" Tigress Following in the Tracks of
the "Emperor" Tiger
(which had walked on virgin snow).
It is precisely the increase in the depth of the snow cover that causes
a change in the gait of the tiger--the transformation of a "twinned" chain
of footprints into a series of overlapping impressions, where the print of
the rear paw lies exactly in the depression made by the print of the front
paw (Matyushkin & Yudakov 1974).
The appearance of bleeding injuries on the weight-bearing surfaces of the
paws, which had already been described by N. M. Przhevalskii (1870), is apparently
associated with the movement of the tigers across snow. We observed footprints
with drops of blood in 12 instances and only in the case of males, such prints
being found after leaps toward prey with the bloody spots becoming larger
and more brightly colored after the prey had been seized. In the case of
the "Lazy" male tiger, the bleeding noticeably increased when he made an
unsuccessful attempt to surmount a high divide and became mired in deep and
dense snow.
Data obtained from the transect described above provide a very graphic
illustration of the reaction of tigers toward the factor in question (i.e.,
snow depth). The mean depth of the snow cover for the profile line was 38
cm, while the magnitude of this index for the comparable route of the tiger
amounted to only 26 cm.