Fig. 2

Cross-validation study of single-species epigenetic clocks for cetaceans for blood. Four epigenetic clocks that were trained on cetacean blood samples from individual species: (A) beluga whale, (B) pacific white-sided dolphin, (C) killer whale, (D) common bottlenose dolphin. Dots are colored by species. “LOO” sample denotes the leave-one-out cross validation estimates of DNA methylation age (DNAm, y-axis, in units of years). Each panel illustrates a linear regression (black dashed line), a diagonal line (y = x), sample size (N), Pearson correlation (cor) between DNAm and estimated age across all samples, and median value of the median absolute error (MAE) for residuals across all samples.