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102 intensity, potentially to avoid wetting their coat with raindrops left on vegetation by the rain. The fact that juveniles didn't modify the use of coyer outside of the den with changing temperature conditions suggests that coyer outside of the den was rather used as a hiding co ver, with juveniles retreating to dens wh en temperature decreased. Habitat use and survival Predation was the main cause of mortality in juvenile porcupines. Several predators hunt and kill porcupines more effectively in open habitats (coyotes: Keller 1935, mountain lions: Robinette et al. 1959, fishers: Powell & Brander 1977) and porcupines perceive open habitats as risky habitats (Sweitzer & Berger 1992). Consistent with the hypothesis that open habitats are more risky, we found that use of coyer (both at the microhabitat and local scales) enhanced survival. There were individual differences in the use of coyer and juveniles survived better when using habitat patches with high shrub coyer and, within those patch es, when using microhabitats with high protective coyer. Numerous studies have reported that ungulate fawns bed down in dense ground coyer (review in Mysterud & Ostbye 1999) but only a few studies have related habitat use to survival (Linnell et al. 1995, Aanes & Andersen 1996, Canon & Bryant 1997, Farrner et al. 2006). ln addition, studies on rodents (Moreno et al. 1996, Schooley et al. 1996, Ebensperger & Hurtado 2005) suggested that coyer may be obstructive rather than protective for small mammals. Here we exploited a multivariate and hierarchical analysis of habitat use by juvenile porcupines to show that use of coyer at both scales studied enhanced survival of one small-bodied animal. Use of coyer indeed has diverse ecological consequences depending probably partly on the size of the study animal, and on the limiting factors with which it is faced (Mysterud & Ostbye 1999). Besides individual differences in the use of coyer, we also found individual differences in the use of dens, ground and trees. Juveniles survived better when using trees than when using ground. We suggest that juveniles were more vulnerable to predators when they were on the ground th an when they were in trees. Use oftrees prevents attack by sorne predators (e.g. coyotes) but not from others (e.g. fishers, Powell & Brander 1977). According to the few signs of presence we found, fishers appeared to be the main predators of juvenile porcupines during the study period (results not shown) and the use of trees is therefore not expected to decrease risk of attack. However, use of trees may have decreased detectability by fishers, therefore leading to higher survival of juveniles. Our third prediction was suppOlted because
103 we found that most mortalities were due to predation and that use of coyer enhanced survival. Predation was therefore the main factor limiting survival of juveniles in our population, as supported by the evidence that habitat selection headed towards predator avoidance, even at fine scales of selection. Sex, body mass, mobility, distance ta the mother, and survival Juveniles were not sexually dimorphic and we found no effect ofsex or body mass on survival. Because predation was the main limiting factor in our population, we would expect increased body mass to enhance survival if larger (i.e. older) animaIs were less vulnerable to predators as in several other mammal species (white-tailed deer: Nelson & Woolf 1987, pronghorns: Fairbanks 1993). Even though males were not heavier than females, sex could also have intluenced survival because of sex-differences in behaviour (Webb 1993). We observed juvenile porcupines to stay still when approached, whatever their size and sex. Males and heavier (older) juveniles did not show higher escape speed or aggressiveness compared to other juveniles (G.M. personal observation). Therefore, it is not surprising they did not survive better. We also found no effect of mobility on survival of juveniles. Juveniles are often argued to suffer high predation risk during dispersal because of greater activity rates, lower familiarity with new habitats, or use of lower-quality habitats (Gaines & McClenaghan 1980, Yoder et al. 2004). We expected more active individuals to show decreased survival because of higher exposure to predation risk. As stated before, juvenile porcupines perfonned mainly small movements «20 m) on a daily basis. However, porcupines were sometimes observed to move longer distances (up to 500 m) that could have exposed them to the same risks as dispersing animaIs. However, in "hider" species, mothers initiate the changes in location and accompany their young during long moves (Lent 1974). They also ce11ainly intluenced the choice of the immigration area, even though the exact location of the new hiding site depends upon the infant (Lent 1974). One previous study (Stuart-Smith & Boutin 1995) investigated whether movements made by juvenile red squirrels (Tamiasciurus hudsonicus) before weaning (i.e. wh en they were still dependent on mother for food) intluenced survival. This work found no effect of total movements on survival but found that individuals that spend relatively more time offtheir natal territory were more likely to be depredated. We suggest that the presence of the mother in the vicinity of the juvenile and, for porcupines, the
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UNIVERSITÉ DU QUÉBEC À RIMOUSKI
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Remerciements Cette thèse n'aurait
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Table des matières LISTE DES TABLE
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Liste des tableaux Chapitre 3 Table
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VB Table 4.2 Power consumed (in Wat
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Liste des figures Chapitre 1 Figure
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XI Figure 2.3 Number oftimes ajuven
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Xlll Figure 4.3 Time spent outside
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Liste des annexes Annexe 1 Descript
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Chapitre 1 Introduction 1.1 Impact
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3 L ' importance relative des facte
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5 des populations ne donne qu' une
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7 (Tympanuchus pallidicinctus) les
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9 1940 1000 1960 139---------- c ~
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1 1 (Roze 1987). Ils perdent 10 à
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13 140 a) 1 20 - o -l- 2000 2001 20
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15 manipulations et la pose d'émet
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Chapitre 2 Handling North American
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19 information is lacking in the pu
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21 We searched for juvenile porcupi
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23 Switzerland). To check sex and r
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25 transmitters fo r larger units s
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27 8 a) 7 "0 c: :l 0 6 -If) ~ c: 5
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29 record sex, reproducti ve status
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Chapitre 3 Predation as a possible
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33 3.2. Introduction A growing numb
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35 predation risk. To do so, we tes
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37 Table 3.1 : Monitoring effort ac
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39 winter precipitation (total prec
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41 emaciated), road kills, dead fro
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43 Seasonal survival rates The sele
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45 >. 1.0 0.9 ..... 0.8 .c ta .c 0.
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47 Causes of mortality We assigned
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49 100 - 90 a) 80 1/) c: .2 iii ...
Page 69 and 70: 51 too simplistic to detect complex
Page 71 and 72: 53 correlated with winter survival
Page 73 and 74: 55 4.1. A bstract Because the clima
Page 75 and 76: 57 Ta, first because of the effects
Page 77 and 78: 59 Third, we evaluated the behaviou
Page 79 and 80: 61 pattern of den use over one or t
Page 81 and 82: 63 two modali ties, Table 4.1, mode
Page 83 and 84: 65 feeding behaviour for the popula
Page 85 and 86: 67 of Tc we considered. However, we
Page 87 and 88: 69 Calculating TefrOIn Ta, wind spe
Page 89 and 90: 71 Number and duration of activity
Page 91 and 92: 73 8 o _ --L-_ 0 Operative temperat
Page 93 and 94: 75 Beschta 2004). Predation rates w
Page 95 and 96: 77 in our population (chap. 3). Mal
Page 97 and 98: 79 Tableau 4.5 : Pourcentage d'obse
Page 99 and 100: 81 associées avec le temps de surv
Page 101 and 102: 83 5.1. Abstract ln many mammals, j
Page 103 and 104: 85 use of coyer influenced summer s
Page 105 and 106: 87 juvenile was moving to escape fr
Page 107 and 108: 89 individual (using approximations
Page 109 and 110: 91 den use (treated as a binary var
Page 111 and 112: 1 93 20 - 18 ~ a) DAvailable .Used
Page 113 and 114: 95 80 -, 70 l DAvailable .Used 60 -
Page 115 and 116: 97 Table 5.3: Use of coyer by juven
Page 117 and 118: 99 juveniles. At the microhabitat s
Page 119: 101 However, we think protection fr
Page 123 and 124: Chapitre 6 Conclusion Dans le cadre
Page 125 and 126: 107 porcs-épics fréquentent les c
Page 127 and 128: 109 épies, via un impact des condi
Page 129 and 130: II I Hiver E n hi ver, on montre qu
Page 131 and 132: 113 compromis auquel les animaux fo
Page 133 and 134: 11 5 En été, la mortalité des je
Page 135 and 136: 117 pékan dans la région. On mont
Page 137 and 138: 119 Annexe 2 Étalonnage des modèl
Page 139 and 140: 121 Références Aanes, R. , & R. A
Page 141 and 142: Bult, A., & C. B. Lynch. 1997. Nest
Page 143 and 144: 125 Creel, S. , 1. Winnie, B . Maxw
Page 145 and 146: 127 Fortin, D., & G. Gauthier. 2000
Page 147 and 148: 129 Hik, D. S. 1995. Does risk of p
Page 149 and 150: Lent, P. C. 1974. Mother-infant rel
Page 151 and 152: 133 Murray, D. L. , & S. Boutin. 19
Page 153 and 154: au Québec depuis 1984. Ministère
Page 155 and 156: 137 Proceedings of the Royal Societ
Page 157 and 158: 139 Tsiropoula, G. 2003. Signatures
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