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

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Body temperature (Tb) of the mounts was regul ated at 37.5 ± 0.3°C, whi ch is the core
body temperature of winter acclimatized free-ranging porcupines (D.W. Thomas,
unpublished data). We moni tored temperature inside the copper mounts usmg a copperconstantan
thermocouple placed in the centre of the mount. We w rote a program for the
Campbell CR-2 1 X to regul ate Tb' Power was applied automatically as 24V pulse to maintain
body temperature. The datalogger measured voltage (Vm) every fi ve seconds, calcul ated the
power consumption (see below), and stored the me an power over fi ve minute intervals. We
calcul ated the power drawn by each mount (Pm) from Vm and the resistance of the heater wire
circuit (R) fo llowing equati on 1:
2
P _ v'n m- R (1)
with Pm expressed in Watts, Vm in Volts and R in Ohms.
We recorded meteorological conditions in the stand while mounts were functioning by
measuring Tc w ith a copper-constantan thelmocouple placed inside an anodi zed aluminium
sphere, Ta w ith a copper-constantan thenTIocouple placed in the shade, and wind speed with a
portable hot-wire anemometer (Seri es 440 Portable Air Velocity Meters, Kurz Instruments).
Measurements were made 0.3 m above ground, averaged over fi ve minute intervals, and
stored in the data logger. We obtained measures of net radiation from our automated weather
stati on. We used synchronous measurements of Tc, Ta, wind speed and net radi ation to
establish an equati on relating Tc to the other meteorological param eters (see below).
We placed mounts in six microhabitats: "den", "ground open", "ground covered,"
"conifer open", "conifer covered', and "deciduous"(see Appendix J fo r a detail ed description
of the mi crohabitats). We placed each mount fo r about 24 hours in one geographical site
corresponding to one of the six microhabitats, and subsequently moved it to a new site. Since
easily accessible sites were scarce in the study area, we used some sites on several occasions
but took this into account in our analyses (see data analyses).
Activity patterns
We captured 26 adult porcupines (10 males, 16 females) in summer and fall 2003 and
2004 . Individuals were immobilized fo llowing Morin & Bel1eaux (2003) and equipped with
radio tra nsmitters (Lotek SMRC-5RB VHF transmitter, Lotek W ireless Inc.) (see chap. 2 fo r
details). ln January 2004 and 2005, we recaptured radi ocollared porcupines to measure their