| Summary: | Food limitation and habitat preference of northern flying squirrels (Glaucomys
sabrinus) and red squirrels (Tamiasciurus hudsonicus) were examined in the Montane Spruce
(MSdm2) and Engelmann-Spruce-Subalpine-Fir (ESSFdc2) (transition area) biogeoclimatic
zones (Meidinger and Pojar 1991) in the south-central interior of British Columbia. I tested
the hypotheses that: 1) flying squirrel and red squirrel populations are limited by food
availability, 2) flying squirrel abundance is positively related to the abundance of cavities for
nesting and, 3) second-growth stands are sub-optimal habitat for flying squirrels and red
squirrels. Populations were monitored on 6 study areas; 2 second-growth lodgepole pine
stands (controls), 2 second-growth stands with food supplementation (treatments: 25-ha blocks
with sunflower seeds aerially applied for 3 summers, starting in June 1991), and 2 old-growth
lodgepole pine stands. Northern flying squirrel and red squirrel populations were examined
for two summers, starting June in 1992.
From hypothesis 1, I predicted that population size, proportion of adults breeding,
body weight, recruitment, and survival would be higher in treatment stands that received
supplemental feeding than in control stands. Treatment stands had significantly more flying
squirrels than control stands (P < 0.00 1). Average densities of flying squirrels were twice as
high in treatment stands (1.38 and 1.50 squirrels/ha) than control stands (0.64 and 0.68
squirrels/ha). In 1992, the abundance of red squirrels was not significantly different between
control and treatment stands (P = 0.74). In 1993, treatment stands had significantly more red
squirrels (P = 0.008) than control stands. The average weight of adult males, survival rates,
and the proportions of female and male flying squirrels, and male red squirrels in breeding
condition were not significantly different in control and treatment stands. The proportion of
female red squirrels in breeding condition was significantly higher in control than treatment
stands. Consequently, population size of flying squirrels and red squirrels appeared to be limited by food availability, but individual squirrels did not appear to benefit from food
supplementation.
An intensive survey of cavities, coupled with subsequent cavity checks, indicated that
flying squirrels did not require cavities and their population size was not limited by the
availability of cavities. These results do not support the hypothesis that flying squirrel
abundance is positively related to the abundance of cavities.
Population size of flying squirrels, body weight, recruitment, and survival of flying
squirrels and red squirrels were not significantly different in second-growth and old-growth
stands. Population sizes for red squirrels were significantly higher in second-growth than old
growth stands. There was no consistent difference in the proportion of squirrels in breeding
condition between second-growth and old-growth stands. These results do not support the
hypothesis that second-growth stands are sub-optimal habitat for northern flying squirrels and
red squirrels.
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