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

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Survival was a function of age and season, with time-dependent w inter survival (Table
3.4). Juveniles exhibited lower survival than individuals 2: 1-yr-old, whatever the season
considered. Summer survival was hi gh and constant over the study period (mean monthly
survival ± SE: 0.86 ± 0.06 for juveniles and 0.97 ± 0.01 for individuals 2: 1-yr-old) while
winter survival was lower and variable from year to year (mean monthly survival: 0.53-0.83
fOl·j uveniies and 0.84-0.96 for individuals 2:1-yr-old, Fig. 3.2). Winter precipitation
eXp lained a large pa11 (r 2 = 0. 87, Tabl e 3.5) of the yearly variations in winter survival (i.e. to
include this covariate decreased Alec by 5 units, Table 3.5). Snowfall al one eXplained a
moderate amount of variation in winter survival whereas spring temperature explained little
variati on (Table 3.5). Winter survival was inversely related to winter precipitation (Fig. 3.2)
and, because of the in verse relationship between winter precipitati on and solar ilTadiance,
positively related to solar irradiance (Fig. 3.2). We found no evidence ofa lagged effect (one
and two years) of winter precipitation, snowfall, or spring temperature on winter survival
(Table 3.6).
Table 3.4 : Tests of the effects of sex, age (a, considering two age classes: juveni les and 2: 1-
yr-old), season (s) and year (y) on seasonal survival rates (~) in a popul ation of North
American porcupines, Parc National du Bic, Québec, May 2000-May 2005. We Llsed data on
159 individuals and modeled sighting probabilities following model selected in Table 3.3.
Model in bold represents the selected model
Biological meaning Notationt Deviance np* L'.A ICc**
Constant survival