Its destruction seems to be due to a sudden
great rise of the water after the ice has formed, so that the Rats
are drowned; or to a dry season followed by severe frost, freezing
most ponds to the bottom, so that the Rats are imprisoned and starve
to death, or are forced out to cross the country in winter, and so
are brought within the power of innumerable enemies.
How tremendously this operates may be judged by these facts. In
1900 along the Mackenzie I was assured one could shoot 20 Muskrats
in an hour after sundown. Next winter the flood followed the
frost and the Rats seemed to have been wiped out. In 1907 1 spent
6 months outdoors in the region and saw only 17 Muskrats the whole
time; in 1901 the H. B. Co. exported over 11 millions; in 1907,
407,472. The fact that they totalled as high was due, no doubt, to
their abundance in eastern regions not affected by the disaster.
Second. The group that increases till epidemic disease attacks
their excessively multiplied hordes. The Snowshoe-Rabbit is the
only well-known case today, but there is reason for the belief that
once the Beaver were subjected to a similar process. Concerning the
Mice and Lemmings, I have not complete data, but they are believed
to multiply and suffer in the same, way.
Third. The purely carnivorous, whose existence is dependent on the
Rabbits. This includes chiefly the Lynx and Fox, but in less degree
all the small carnivores.
In some cases such as the Marten, over-feeding seems as inimical
to multiplication as under-feeding, and it will be seen that each
year of great increase for this species coincided with a medium
year for Rabbits.
But the fundamental and phenomenal case is that of the Rabbits
themselves. And in solving this we are confronted by the generally
attested facts that when on the increase they have two or three
broods each season and 8 to 10 in a brood; when they are decreasing
they have but one brood and only 2 or 3 in that. This points to some
obscure agency at work; whether it refers simply to the physical
vigour of the fact, or to some uncomprehended magnetic or heliological
cycle, is utterly unknown.
The practical consideration for the collecting naturalist is this:
Beaver, Muskrat, Otter, Fisher, Raccoon, Badger, Wolverine, Wolf,
Marten, Fox reached the low ebb in 1904-5. All are on the upgrade;
presumably the same applies to the small rodents. Their decacycle
will be complete in 1914-15, so that 1910-11 should be the years
selected by the next collecting naturalist who would visit the
north.
For those who will enter before that there is a reasonable prospect
of all these species in fair numbers, except perhaps the Lynx and
the Caribou.
