We found that adult females were more likely to lead group movement compared to adult males (permutation-based binomial regression on the number of times an adult whale was a leader in a given year relative to the number of times they were a follower, regression coefficient = 20.93, p < 0.0001; Table S2; Figure 1C). Among adult females, postreproductively aged whales (R35 years old, which is the mean age at last reproduction for Southern resident females that lived past the age of peak adult female mortality) were more likely to lead group movement compared to reproductively aged females (regression coefficient = 0.50, p < 0.001; Table S2; Figure 1D)