POPULATIONS OF SMALL MAMMALS

a NE Vt PEA A

The trapping of small mammals was carried on at the following
localities between the dates noted: Baker Creek Valley, May 12 ~-
June 3; Bouchie Lake, June 13 - 18; Summit Lake, June 25 - July 8;
Nukko Lake, July 7 - 8; Rocher Deboule, July 20 - 22; Sixteen Mile
Lake, August 21 - 29; Tiltzarone Lake, August 31 - September 1. A
total of 400 small mammals was trapped. The species taken most
frequently were, in order of abundance, meadow vole Microtus penn-
sylvanicus, red-backed vole Clethrionomys gapperi, white-footed
mouse Peromyscus maniculatus, jumping mouse Zapus princeps and
dusky shrew Sorex obscurus.

The periodicity cycle of scarcity and abundance, common to
all small mammals, is perhaps most conspicuous in the meadow vole
that makes lasting runways and burrows which reveal the presence or
absence of the animal The summer's investigations suggest that
the cyclic rhythm in the meadow vole, and the red-backed vole also,
Operates not as a widespread and synchronized phenomenon but over
different time periods in different localities that may be adjacent.
For example, in the Baker Creek Valley meadow voles were beginning
to recover from a period of scarcity; at Bouchie Lake, 24 miles
distant to the east, the up-swing was at a more advanced stage, while
at Sixteen Mile Lake, 22 miles farther east and separated from the
other two localities by the Fraser River, the peak of abundance prob-
ably had been reached. The cyclic pattern of the red-backed vole
apparently was synchronous with that of the meadow vole at Baker
Creek Valley, Sixteen Mile Lake and Nukko Lake, At Bouchie Lake it
was at a low point in the population curve and at Summit Lake, where
meadow voles were scarce, it was nearing a peak (see Table IIT).

In the Baker Creek Valley trapping was done in dry, open,
lodgepole pine and aspen forest, in muskegs, dwarf birch thickets,
marshy lakeshore and dry meadows. The results obtained indicated
that while the meadow vole and red-backed vole were on the up-
swing of the cycle, as has been noted, the mice and shrew popula-
tions were at or near the minimum. The product of 641 trap-nights
was 52 specimens of which 37 were voles, all but six being adult

animals.

Trapping at Bouchie Lake in aspen woods, marshy meadows,
creek banks and dry meadows produced 30 meadow voles, 1 red-backed
vole and 25 mice and shrews, a total of 56 specimens in 216 trap-

nights

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