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

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Hornfeldt 1994, Gese et al. 1996a, Selas & Vik 2006). Prey living above the snow surface
usually suffer higher predation risk as snow deepens. We therefore expected winter predation
rates on porcupines to increase in years of high snowfall/winter precipitation.
3.3. Material and methods
Study population
We worked from May 2000 to May 2006 in a ca. 2 km 2 area of Parc National du Bic
(48°20'N, 68°46'W, elevation 0-150m), Québec, Canada. The study area is fragmented by
abandoned and cultivated fields and characterized by a rugged topography, abundance of
natural rock dens, and a mixed boreal forest. We captured porcupines in open fields during
intensive capture sessions in May and August every year from 2000 to 2004 and in May only
in 2005 and 2006 (Table 3.1). Each night ofsurvey involved one to six observers (usually
two) who patrolled the study area on foot or bicycle for one to nine hours (usually five). We
sexed, weighed, aged (as juvenile, subadult, or adult using body mass in May, Berteaux et al.
2005), and permanently marked porcupines upon capture with metal ear tags (Be11eaux et al.
•
2005, Morin et al. 2005). We also used telemetry to monitor individuals and fitted radio
collars (Lotek SMRC-5RB VHF transmitters, Lotek Wireless Inc. , Newmarket, ON, Canada,
L3Y 7B5) on 97 individuals for 23576 porcupine-days (Table 3.1).
Parturition period is mid-May to late June so we considered a population-year to start in
May (e.g. year 2000 extends from May 2000 to April 2001). We estimated minimum
population size for a given year as the number of different individuals observed between May
and April of the following year. Open fields are very attractive to porcupines for feeding in
summer and porcupines were easily observed when using fields. We are therefore confident
that vi11ually ail porcupines present in the study area were captured or observed at least once
each year. As a confirmation, we rarely found marked animais not observed one year and
later relocated (only three and four animais, respectively in 2001 and 2002, which we added
to the population size for the year that they had not been observed).