Fig. 3. Individuality increases gradually throughout the first 70 days of development.

The predicted values of median individual swimming speed diverge over time (A) leading to gradual increases in the among-individual variance and hence repeatability (B) of behavior. These models included only the 26 individuals on which we had complete data for the first 10 weeks of life to ensure that absolute levels of variation would remain comparable over time. Individual lines in (A) are colored according to their predicted behavior in week 1 with yellow indicating greater swimming speeds and purple indicating lower swimming speeds. In (B), shown are the posterior modes of each variance estimate and its 95% CI. Source Data are provided as a Source Data file.