Constraints on first reproduction in North American red squirrels [Tamiasciurus hudsonicus]

age alberta ardilla bosques cones conos croissance de la population ecologia ecologie ecology edad females femelle field experimentation food supply foraging forests graine de tournesol growth rate hembra pinus banksiana plant production population growth recherche de nourriture reproduction seasonal variation semilla de girasol squirrels suministro de alimentos sunflower seed supervivencia survie survival taux de croissance