Cohort effects in red squirrels: the influence of density, food abundance and temperature on future survival and reproductive success

Authors

  • Sébastien Descamps,

    1. Chaire de Recherche du Canada en Conservation des Écosystèmes Nordiques et Centre d’Études Nordiques, Université du Québec à Rimouski, 300 allée des Ursulines, Rimouski, Québec G5L 3A1, Canada,
    2. Unité Mixte de Recherche 5558 ‘Biométrie et Biologie Evolutive’, Université Claude Bernard Lyon I, 43 boul. du 11 Novembre 1918, 69622 Villeurbanne Cedex, France,
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  • Stan Boutin,

    1. Department of Biological Sciences, CW405, Biological Sciences Center, University of Alberta, Edmonton, Alberta, T6G 2E9, Canada,
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  • Dominique Berteaux,

    Corresponding author
    1. Chaire de Recherche du Canada en Conservation des Écosystèmes Nordiques et Centre d’Études Nordiques, Université du Québec à Rimouski, 300 allée des Ursulines, Rimouski, Québec G5L 3A1, Canada,
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  • Andrew G. McAdam,

    1. Department of Fisheries and Wildlife, 13 Natural Resources Building, Michigan State University, East Lansing, MI 48824, USA
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  • Jean-Michel Gaillard

    1. Unité Mixte de Recherche 5558 ‘Biométrie et Biologie Evolutive’, Université Claude Bernard Lyon I, 43 boul. du 11 Novembre 1918, 69622 Villeurbanne Cedex, France,
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*Correspondence author. E-mail: dominique_berteaux@uqar.qc.ca

Summary

  • 1Environmental conditions experienced early in life may have long-lasting effects on individual performance, thereby creating ‘silver-spoon effects’.
  • 2We used 15 years of data from a North American red squirrel (Tamiasciurus hudsonicus Erxleben) population to investigate influences of food availability, density and spring temperature experienced early in life on reproduction and survival of female squirrels during adulthood.
  • 3We found that spring temperature and food availability did not affect female survival after 1 year of age, whereas higher squirrel densities led to lower survival, thereby affecting longevity and lifetime fitness.
  • 4In addition, both food availability experienced between birth and weaning, and spring temperature in the year of birth, had long-lasting positive effects on female reproductive success. These results emphasize the critical effect environmental conditions during the early life stages can have on the lifetime performance of small mammals.
  • 5These long-term effects of early food and temperature were apparent only once we controlled for conditions experienced during adulthood. This suggests that silver-spoon effects can be masked when conditions experienced early in life are correlated to some environmental conditions experienced later in life.
  • 6The general importance of silver-spoon effects for adult demographic performance might therefore be underestimated, and taking adult environment into account appears to be necessary when studying long-term cohort effects.

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