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

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However, we think protection from wind was not the main factor driving selection of covered
microhabitats by juveniles because selection for coyer did not vary according to wind
conditions (see below).
Effects ofmeteorological conditions on the use of cover
ln summer, use of co ver by animais usually results in a lower access to incoming
radiation and thus to exposure to lower temperatures (Cook et al. 1998). Our results
confirmed this pattern since air temperature was negatively correlated with protective cover
at a given site. As predation was expected to drive habitat selection by juvenile porcupines,
we predictedjuvenile porcupines would use open environments only under cold conditions
(prediction 2). We found that animais increased their use of dens when temperature decreased
and when rain intensity increased. It was not surprising that juveniles used their den when
rain intensity increased because a wet coat provides a poor insulation against cold
temperatures (Kreith & Black 1980) so porcupines used dens to avoid wetting their coat.
However, the fact that juveniles used dens under co Id tempe rature conditions does not
support our prediction that juveniles should use open areas on co Id days to maximize
radiative heat gain. We trust juveniles were able to warm up their dens when using them so
that dens constituted unique covered microhabitats that provided shelter against co Id
temperatures, rain, and predators. Juveniles therefore did not face a trade-off between use of
coyer and thennal exposure, but rather faced a trade-off between use of den and non-den
microhabitats. Dens provided hiding coyer and protection against harsh weather conditions
but no foraging Oppo11unities. As energy needs of juveniles increased (i.e. as their body mass
increased with Julian date), porcupines decreased their use of dens, possibly to increase the
time spent foraging. An alternate (non-exclusive) hypothesis would be that juveniles
decreased use oftheir dens because the thermal environment became more favourable or
because animais were able to thennoregulate better as the season advanced.
Wind also influenced the use of dens with juveniles being increasingly outside of their
den as wind speed increased. Biting insects are less abundant inside than outside dens
(Comtois & Berteaux 2005) so that juveniles may weil use dens on calm (i.e. non windy)
days to avoid biting flies when insect harassment is high (i .e. when there is no wind). Outside
of the den, we found no effect of air temperature on the use of coyer (at the microhabitat
scale). However, juveniles used open microhabitats more often with increasing past rain