title: Disentangling direct and growth-mediated influences on early survival: a mechanistic approach.
abstract: 1. Early survival is a key life-history trait that often accounts for a large part of the variation in individual fitness and shapes population dynamics. The factors influencing early survival are multiple in large herbivores, including malnutrition, predation, cohort variation or maternal effects. However, the mechanistic pathways connecting these drivers to variation in early survival are much less studied. Indeed, whether these factors influence early survival directly or indirectly through early growth remains to be disentangled. 2. In this study, we used a path analysis to separate the direct and indirect (i.e. mediated by early growth) pathways through which sex, birth date, cohort and family effects influence early survival. We used a large data set of marked roe deer newborns collected from 1985 to 2010 in the intensively monitored population of Trois Fontaines (France). 3. We found that most drivers have indirect influences on early survival through early growth. Indeed, cohort effects influenced early survival through the indirect effect of precipitation around birth on early growth. Precipitation also had direct effects on early survival. Family effects indirectly influenced early survival. Twins from the same litter grew at about the same rate, so they had the same fate. Moreover, some factors, such as birth date, had both direct and indirect effects on roe deer early survival, with fawns born early in the season benefiting from high early survival both because they have more time to grow before the harsh season and because they grow faster during their first days of life than late-born fawns. 4. These findings suggest that most drivers of early survival previously identified in large mammalian herbivores may affect early survival primarily through their influence on early growth. Disentangling the direct and indirect pathways by which different factors influence early survival is of crucial importance to understand the mechanisms shaping this key component of individual fitness.
authors.affiliation: Université de Lyon, F-69000, Lyon, France.|Université Lyon 1, Lyon, France.|CNRS, UMR5558, Laboratoire de Biométrie et Biologie Evolutive, F-69622, Villeurbanne, France.
authors.forename: Floriane
authors.initials: F
authors.lastname: Plard
authors.affiliation: Department of Arctic and Marine Biology, Faculty of Biosciences, Fisheries and Economics, UiT, The Arctic University of Norway, 9037, Tromsø, Norway.
authors.forename: Nigel G
authors.initials: NG
authors.lastname: Yoccoz
authors.affiliation: Université de Lyon, F-69000, Lyon, France.|Université Lyon 1, Lyon, France.|CNRS, UMR5558, Laboratoire de Biométrie et Biologie Evolutive, F-69622, Villeurbanne, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Bonenfant
authors.affiliation: Centre National d'Études et de Recherches Appliquées sur les Cervidés et Sanglier, Office National de la Chasse et de la Faune Sauvage, 85 bis Avenue de Wagram, 75017, Paris, France.
authors.forename: François
authors.initials: F
authors.lastname: Klein
authors.affiliation: Centre National d'Études et de Recherches Appliquées sur les Cervidés et Sanglier, Office National de la Chasse et de la Faune Sauvage, 85 bis Avenue de Wagram, 75017, Paris, France.
authors.forename: Claude
authors.initials: C
authors.lastname: Warnant
authors.affiliation: Université de Lyon, F-69000, Lyon, France.|Université Lyon 1, Lyon, France.|CNRS, UMR5558, Laboratoire de Biométrie et Biologie Evolutive, F-69622, Villeurbanne, France.
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Gaillard
mesh_terms: D000818:Animals; D003670:Deer / Q000254:growth & development / Q000502:physiology*; D005260:Female; D020387:Food Chain; D005602:France; D008136:Longevity; D008297:Male; D011157:Population Dynamics; D012621:Seasons
keywords: birth mass; early growth; maternal effect; path analysis; population density