Body Weight, Longevity and Reproductive Success in Red Squirrels (Sciurus vulgaris)

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Abstract
(1) Two populations of red squirrels were studied by capture-mark-recapture over a 3-year period in different habitats. (2) Survival was positively correlated with body weight in the second winter of life, independent of body length. (3) Females weighing less than 300 g did not come into oestrus. In a logistic regression model, female body weight and dominance were the best predictors of fertility. (4) In the coniferous habitat, body weight when lactating and the difference in weight over the lactation period predicted success in raising offspring. In the deciduous habitat body weight was the best predictor, while the probably of having young was negatively influenced by body length and age. (5) In the coniferous woodland, both body weight and longevity were significantly correlated with lifetime reproductive success of females. In the deciduous woodland, only body weight had a significant effect due to early breeding in some females with poor survival. (6) Squirrels of high rank weighed significantly more than those of lower rank. Dominance rank also increased with age. (7) Body length was weakly correlated with habitat quality, but there was a strong effect of habitat quality on body weight. Large squirrels settled in areas with the best seed-crop, and gained more weight than more those that settled in areas with a poorer seed-crop.