influence du climat et de la prÃ©dation sur l'utilisation de l'habitat et la ...

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32 3.1. Abstract Understanding the effects of climate on population dynamics of mammals is plagued by experimental difficulties. One way to move ahead with climate research may be to alternate large and small-scale studies on a given system. ln such a "cyclical scaling", large-scale studies serve to generate hypotheses that can be challenged with small-scale studies. Klvana et al. (2004) showed that North American porcupine (Erethizon dorsatum) populations in eastern Québec have regularly fluctuated over the past 130 years in relation to fluctuations in the solar cycle and local weather variables. This generated the hypothesis that solar activity may affect porcupines' abundance through effects on weather variables. We used a smallscale study to challenge this hypothesis and shed light on the mechanism(s) linking porcupine abundance to weather conditions. We stalted in 2000 a capture-recapture study which implied systematically searching and capturing porcupines in May and August each year. This design allowed estimating "summer" (May to August) and "winter" (August to May) survival rates between 2000 and 2005. Summer survival was high and constant over the study period (mean monthly survival: 0.86 for juveniles and 0.97 for individuals ~1-yr-old) while winter survival was lower and variable from year to year (mean monthly survival: 0.53-0.83 for juveniles and 0.84-0.96 for individuals ~ l-yr-old). Local winter precipitation was negatively correlated to solar irradiance and explained a large part of the variation in winter survival (r 2 = 0.87) with winter survival being negatively influenced by winter precipitation. Predation rates were elevated in years of hi gh winter precipitation and 95% of depredated porcupines were killed when snow was covering the ground. Predation rates thus appeared strongly related to snow conditions, and variations of predation rates according to snow conditions may explain the observed relationship between winter precipitation and survival of porcupines. Key-words : capture-mark-recapture, climatic variations, mOitai ity causes, predator-prey, seasonal survival
33 3.2. Introduction A growing number of studies indicates that climate affects population dynamics of mammals (Krebs & Be11eaux 2006). Climate can have direct effects on individuals (for example winter weather influences population dynamics through effects on locomotion (Telfer & Kelsall 1984) or thermoregulation (Cook et al. 1998)); or indirect ones by affecting species interactions. For example, deep snow may influence predator-prey relationships (Post et al. 1999b, Hebblewhite 2005) and access to food resources (Turner et al. 1994, Post & Stenseth 1999). Obviously, the different ways in which climate influences population dynamics are complex and our understanding of mechanisms linking climate to population growth rate is limited (Owen-Smith & Mills 2006). Because we can hardly manipulate climate, testing specifically for changes driven by weather variations is plagued by experimental difficulties. The two main approaches that have been used are 1) small scale studies that aim at determining mechanisms linking weather variations and changes in biological processes; and 2) large scale studies (i.e. data collected over long time periods and/or large areas) that aim at correlating the observed climatic variability with changes in ecosystem functioning. Both approaches have important drawbacks and Root and Schneider (1995) suggested alternating studies performed on large and small scales to move ahead with climate research. ln such cycles of analysis, large-scale studies would generate hypotheses that wou Id be tested using small-scale studies. The solar cycle is known to have an impact on weather (Sinclair et al. 1993) with cascading effects on entire ecosystems (Verschuren et al. 2000, Hodell et al. 2001). For instance, the reproductive output of snowshoe hares in Yukon was found to be cyclic and highly correlated with sunspot numbers with a two years time lag (Stefan & Krebs 200 l, Krebs & Be11eaux 2006). Possible mechanisms involved in this relationship include an effect of solar activity on snow depth which might in turn affect food supplies (Krebs & Berteaux 2006) and lynx hunting success (Sten seth et al. 1999,2004). North American porcupine (Erethizon dorsatum) populations in the Bas St. Laurent region of eastern Québec seem also to be affected by the solar cycle. Klvana et al. (2004) found that an index of porcupine abundance (porcupine feeding scars) was related to fluctuations in the solar cycle, winter
Page 1 and 2: 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: Chapitre 3 Predation as a possible
Page 53 and 54: 35 predation risk. To do so, we tes
Page 55 and 56: 37 Table 3.1 : Monitoring effort ac
Page 57 and 58: 39 winter precipitation (total prec
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
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83 5.1. Abstract ln many mammals, j
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85 use of coyer influenced summer s
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87 juvenile was moving to escape fr
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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
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139 Tsiropoula, G. 2003. Signatures
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