Biology_of_Mustelids_Vol_1.pdf

162.
In winter there is a substantial difference between the age structures
of northern and southern populations, but there is no such difference in
summer.
The proportion of first year ermine in the summer collection
(June to September) from the north of Tyumen t
province (n = 65) was 66.6 ±
5.7%, and the equivalent figures for Northern Kazakhstan (n = 126)(8) were
64.2 ± 4.2%.
There was no seasonal variation in age structure in the ermine
populations of Northern Kazakhstan (adult and ~ld:
35.8% in summer, 35.5% in
winter), but there were great variations in the north of Tyumen t
province
(adult and old: 33.5% in summer, 10.0% in winter). In the north, the ratio
of adults to first year animals is 1:2 in summer and 1:9 in winter.
The age structure also varies from year to year.
The percentage
of adults among specimens collected during nine seasons (1933~39-1946-47)
in the Pechora-Ilych game reserve were: 9.8, 19.0, 13.9, 13.7, 13.4, 5.0,
(b)
12.5 and 9.1 i.e., ranging from 5-19%. Table 3 shows the annual
variations in the age structure in North Tyumen r ;
compiled using more data, and so are more reliable.
these figures were
In 1959-60 and the
al!tumn of 1964, the ratio of adults to young was 1 :25;
in 1960-61 it was
1:16, in 1963-64 it was 1:14, and in 1961-62 it was 1:3. A difference was
also observed in the oldest age group:
in 1960-61 the ratio of old to
adult animals was 1:29, and in 1963-64 it was 1:4.
Table 2
Variation in the age structure of ermine populations with latitude.
Region Latitude Number of Percentage Ratio of
of region years of of adults ages (adult
obser­ and m, % and old to
vations (p% ± SE(p)% young)
North of Tyumen r
province 66-68 0 6 10.0 ± 0.4 2:18
Pechora-Ilych
game reserve
Povolzhre (Tatar ASSR)
Northern Kazakhstan
63-64 0
9
55-57 0
3
53-54 0 3
17.0±2.1
27.0 ± 3.9
35.5 + 2.1
2:10
2: 6
2: 4
(a) Kopein does not mention more than 65 specimens collected in summer on
p. 158 - Ed.
(b) 8 sets of figures given, but there should be 9 - Trans.