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38 Study design We first tested if changes in abundance of porcupines conelated with solar irradiance during the study period. Second, we tested if solar irradiance conelated with local weather variables. Then, we estimated winter and summer survival of porcupines from May 2000 to May 2005 in order to test for an effect of local weather on survival. Because time-lag effects of weather on phenotypic and demographic traits can be important (Post & Stenseth 1999, Post 2005), we investigated for a direct and for a delayed influence of environmental covariates on survival (lags 1-2 years). Finally, to determine which age-class was the most sensitive to changes in local weather, and whether changes in survival were mainly due to changes in predation or starvation rates, we examined causes of mortality according to year, season and age classes. Relationship between abundance of porcupines and solar irradiance We used estimates of population size to calculate population growth rate as: r f = N f + 1 /N f (1) in which r f is population growth rate for year t, Nf is population size in year t and N f + / is population size in the following year. We used a Pearson correlation to test for an association between population growth rate and total solar irradiance monitored with absolute radiometers placed onboard satellites (daily irradiance in W/m 2 as calculated by Frohlich (2000), averaged over a year). We obtained solar irradiance data from the World Radiation Center (Physicalisch-Meteorologisches Observatorium Davos, PMOD/WRC, Switzerland, unpublished data from the VIRGO Experiment on the cooperative ESA/NASA Mission SoHO) and standardized it ((value - mean)/SD) before analyses. Solar irradiance is more likely to be a biologically and climatically explicative measure of the solar activity than the traditionally used sunspot number (Klvana et al. 2004). However, we also perfonned analyses using the sunspot number (obtained from the World Data Center for the Sunspot Index), given its widespread lise in the ecological literature. We found similar results using either measure so results using sunspot numbers are not shown. Below we use solar activity and solar inadiance as synonyms. Relationships between solar irradiance and local weather variables We used Pearson correlations to test for a correlation between solar irradiance and weather variables. Based on Klvana et al. (2004), we considered three weather variables:
39 winter precipitation (total precipitation in mm, between November and April), snowfall (in cm, between November and April) and spring temperature (mean monthly temperature in oC, averaged over May and June). We obtained weather records from the Environment Canada weather station at Rimouski, about 20 km from our study site (48°27'N, 68°31 'W). We examined relationships between solar irradiance and weather parameters for years 1998 to 2004 because we tested for effects of environmental covariates on survival with lags of up to two years (i.e. stalting in 1998) and because 2004 was the last population year we used in survival analyses (see below). We standardized weather data before analyses. Seasona! survival rates We detennined fates of porcupines through capture, visual and radio-telemetry observations (hereafter called porcupine observations). Survival analyses included only porcupines that died naturally (i .e. not from research related reasons, see below). Our dataset consisted in 82 females (12 captured for the first time as juveniles, 16 as subadults, and 54 as adults) and 77 males (16 captured for the first time as juveniles, seven as subadults, and 54 as adults). Preliminary analyses indicated that survival was similar for subadults and adults so that we only considered two age classes: juveniles and individuals 2: l-yr-old. We used methods detailed in Loison et al. (1994) to include different ages at capture in the estimation procedures. We estimated seasonal survival rates of porcupines from May 2000 to May 2005 (k = Il occasions of captures). We defined as "summer survival" the survival from May-June to August and as "winter survival" the survival from August to May-June. The lengths of our "summer" and "winter" periods were thus four and eight months, respectively. We used observations from May and June to determine presence at the beginning of summer because using only May would have reduced our sample size (n = 139 instead of 159), especially for juveniles (n = 18 instead of 28). lndeed, juveniles are born at the end of Mayor beginning of June so that many of them were observed for the first time in June and died during their first summer (i.e. were not observed in August). We performed survival analyses using capture-mark-recapture methods (Lebreton et al. 1992), using the program M-SURGE 1.7.1 (Choquet et al. 2004, 2005) which can take into account unequal interval lengths between capture occasions. The fit of our data to the Cormack-Jolly-Seber model was acceptable (Goodness of fit test using U-CARE 2.02 (Choquet et al. 2003, Pradel et al. 2003): Chi 2 = 39.620, df= 29, P = 0.090) so that we used
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UNIVERSITÉ DU QUÉBEC À RIMOUSKI
Page 3 and 4:
Remerciements Cette thèse n'aurait
Page 5 and 6: Table des matières LISTE DES TABLE
Page 7 and 8: Liste des tableaux Chapitre 3 Table
Page 9 and 10: VB Table 4.2 Power consumed (in Wat
Page 11 and 12: Liste des figures Chapitre 1 Figure
Page 13 and 14: XI Figure 2.3 Number oftimes ajuven
Page 15 and 16: Xlll Figure 4.3 Time spent outside
Page 17 and 18: Liste des annexes Annexe 1 Descript
Page 19 and 20: Chapitre 1 Introduction 1.1 Impact
Page 21 and 22: 3 L ' importance relative des facte
Page 23 and 24: 5 des populations ne donne qu' une
Page 25 and 26: 7 (Tympanuchus pallidicinctus) les
Page 27 and 28: 9 1940 1000 1960 139---------- c ~
Page 29 and 30: 1 1 (Roze 1987). Ils perdent 10 à
Page 31 and 32: 13 140 a) 1 20 - o -l- 2000 2001 20
Page 33 and 34: 15 manipulations et la pose d'émet
Page 35 and 36: Chapitre 2 Handling North American
Page 37 and 38: 19 information is lacking in the pu
Page 39 and 40: 21 We searched for juvenile porcupi
Page 41 and 42: 23 Switzerland). To check sex and r
Page 43 and 44: 25 transmitters fo r larger units s
Page 45 and 46: 27 8 a) 7 "0 c: :l 0 6 -If) ~ c: 5
Page 47 and 48: 29 record sex, reproducti ve status
Page 49 and 50: Chapitre 3 Predation as a possible
Page 51 and 52: 33 3.2. Introduction A growing numb
Page 53 and 54: 35 predation risk. To do so, we tes
Page 55: 37 Table 3.1 : Monitoring effort ac
Page 59 and 60: 41 emaciated), road kills, dead fro
Page 61 and 62: 43 Seasonal survival rates The sele
Page 63 and 64: 45 >. 1.0 0.9 ..... 0.8 .c ta .c 0.
Page 65 and 66: 47 Causes of mortality We assigned
Page 67 and 68: 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
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91 den use (treated as a binary var
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1 93 20 - 18 ~ a) DAvailable .Used
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95 80 -, 70 l DAvailable .Used 60 -
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97 Table 5.3: Use of coyer by juven
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99 juveniles. At the microhabitat s
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101 However, we think protection fr
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103 we found that most mortalities
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Chapitre 6 Conclusion Dans le cadre
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107 porcs-épics fréquentent les c
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109 épies, via un impact des condi
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II I Hiver E n hi ver, on montre qu
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113 compromis auquel les animaux fo
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11 5 En été, la mortalité des je
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117 pékan dans la région. On mont
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119 Annexe 2 Étalonnage des modèl
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121 Références Aanes, R. , & R. A
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Bult, A., & C. B. Lynch. 1997. Nest
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125 Creel, S. , 1. Winnie, B . Maxw
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127 Fortin, D., & G. Gauthier. 2000
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129 Hik, D. S. 1995. Does risk of p
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Lent, P. C. 1974. Mother-infant rel
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133 Murray, D. L. , & S. Boutin. 19
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au Québec depuis 1984. Ministère
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137 Proceedings of the Royal Societ
Page 157 and 158:
139 Tsiropoula, G. 2003. Signatures
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