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

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pattern of den use over one or two winter seasons (n = 14 individua1s followed from 23
January to 14 April 2004; n = 6 individuals followed from 05 January to 19 March 2005;
among which three individuals were followed both years). For that, we attached temperature
loggers (SmartButton Temperature Loggers, ACR systems Inc.) to their radio collar (total
weight of collar with temperature recorders = 74 g). We used abrupt changes in temperature
readings to estimate the timing of movements in and out of the dens. To complement data
from temperature loggers, we placed movement detectors (Vigil 650X, Circuitronique Estrie
Inc.) at the entrances of ail dens used. Combining information from temperature loggers and
movement detectors allowed us to determine wh en animais were inside or outside of a den
and therefore to ca\culate the time spent outside of the den, the number and duration of
activity bouts, and the nocturnality index. The nocturnality index ln (after Zalewski 2000)
reflects the relative distribution of activity between day and night, and is calculated as:
2Nal
1 = I N
Il (Nal +(Dal
I N) I D)
(2)
where Na and Da are total duration of porcupine activity during night and day, respectively,
and N and D are night and day lengths. Night started 30 min after sun set and ended 30 min
before sunrise. In varies from 0 (diurnal activity) to 2 (nocturnal activity).
Microhabitats used outside of the den
We measured habitat use by porcupines from 12 January to 16 April 2004 and Il January
to 12 March 2005. Twice a week, we precisely located the 26 radiocollared porcupines. For
that, we followed the telemetry signal to the animal (homing) instead of using triangulation.
Each time we located an individual, we assigned its position to one of the six microhabitats
(i.e. "den", "ground open", "ground covered" , "conifer open", "conifer covered" , or
"deciduous"). If the animal was in a tree, we recorded its position according to one of tluee
classes of height (Iower third, middle, higher third of the canopy) and to one of two classes of
distance to the trunk (base, tip of the branch). We also noted whether the porcupine was
feeding or resting. We characterized thermal conditions in the stand by measuring Tc using a
hand held thermocouple (HH Il with type K thermocouple input, Omega Engineering Inc.,
Stamford, Connecticut) inserted in a black bowl and placed 0.3 m ab ove ground.