Biology_of_Mustelids_Vol_1.pdf

111.
reptiles and insects occurred.
In the nests of the ermine containing young,
only remains of water
water rats were found.
The young ermine, when they reach independence, hunt mainly among
reedy marsh plains, and, for the most part, catch water rats.
During summer, autumn, and winter, water rat is a very important
prey of the ermine, despite the presence of other types offuod.
The so-
called "concentrations" of ermine, which occur in Western Siberia during the
second half of the winter, are observed in places where water rats are also
concentrated.
At this time, the ermine hunts actively under the snow,
catching its prey by following their tracks and entering their burrows.
The ermine, like other mustelid predators, kills many more prey than it
actually needs for food.
Surplus kills are dragged into burrows, under
turf or brushwood and, frequently, a whole store is so formed.
Sometimes
it drags the carcase only a little distance away, and bu~ieS it in the snow.
After the melt, in a season when small rodents are plentiful, such caches are
found frequently, suggesting that the ermine frequently does not make use
of its food reserves.
The prey of ermine is almost invariably caught under the snow during
winter time.
Kills on the surface are seen only very rarely.
In different regions of Western Siberia, the qualitative and
quantitative composition of the food of the ermine may very considerably,
depending upon the distribution end abundance of different species of rodents.
Zverev (1931), who analysed the gut contents of some 1600 ermine taken from
the Southern part of the Omsk region during 1929, found that water rats
accounted for 29.25% of the food of the ermine, whereas smaller rodents
accounted for 64.7%.
It should be mentioned that, in the Omsk region, the
population density of the water rat is considerably less than in the districts
[near Novosibirsk] which we have described.