Fig. 2: Individuality is present at day one after birth and is not explained by differences in maternal identity or body size.

Repeatability of median swimming speed at hourly intervals on the first day after birth (A); each line represents one individual (N = 26). Maternal identity (B) did not explain variation in swimming speeds among individuals. Small and large points indicate the hourly (i.e. 11 data points per individual) and daily median swimming speeds, respectively, of individuals from each mother on day one after birth; see also Table 1. Behavior on day one after birth (C) was not related to an individual’s total length on their first day of life; see also Supplementary Table 3. Small and large points indicate hourly and daily median swimming speeds for each individual respectively; gray lines indicate posterior estimates for the effects of body size on behavior. Throughout, lines and points are colored according to the individual’s behavior in hour one on day one (yellow represents higher swimming speeds; purple indicates lower swimming speeds). Source Data are provided as a Source Data file.