influence du climat et de la prédation sur l'utilisation de l'habitat et la ...

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older and was dependent on meteorological conditions. PaIiicularly, juveniles used dens to
avoid low air tempe rature and rain. Outside of the den, juveniles used more open habitats
after it had rained. The main cause of mOliality was predation and habitat use, both at the
microhabitat and at the local scales, influenced survival. At the microhabitat scale, use of
protective coyer and use of trees compared to use of the ground enhanced survival, whereas
at the local scale, use of sites with high shrub coyer enhanced survival. We did not detect any
effect ofsex, body mass, mobility, and distance to the mother on survival ofjuveniles. We
now discuss these findings in order to evaluate our three original predictions.
Habitat selection
We predicted selection for coyer to occur at both the microhabitat and local scales
(prediction 1) because juvenile porcupines were found by Sweitzer and Berger (1992) to
avoid open areas in presence of predators, and because predation risk was high in our system
(chap. 3). Our study animais selected microhabitats with high protective coyer within habitat
patches showing low herb coyer and dominated by cedar trees. We could not detect selection
for high tree or shrub coyer (at the local scale), even though stands with low herb coyer were
typically dense in our study area, as illustrated by the negative relationship we found between
tree and herb coyer. We suggest some selection for coyer occurred at the scale of the stand
(not investigated in this study) because we always located juveniles in forested environments,
while our study area was fragmented by open fields that were used by adult porcupines for
feeding (Morin et al. 2005). Open areas therefore constituted exploitable areas for adults but
were not used by juveniles.
Our results support the hypothesis that predator avoidance was the main factor driving
habitat selection at the two scales studied. Indeed, use of covered microhabitats is likely to
decrease probability of detection by predators (Mysterud & Ostbye 1999) while use of areas
with low herb coyer should reduce likelihood of encountering predators since herb coyer in
forested environments is mainly associated with open or edge habitats, that are easily
accessible to predators (Bider 1968, Andren & Angelstam 1988). We found no evidence that
juveniles selected their microhabitat so as to increase access to radiative gain (i.e. they did
not select open microhabitats). Covered microhabitats that were selected by juveniles were
characterized by low air temperatures and low wind speeds. Besides providing protection
from predators, covered microhabitats therefore provided protection against high winds.