In males, dorsal fin growth is probably a secondary sex characteristic. Peak growth of the fin coincides with the onset of sexual maturity.

Observations of females in zoological parks indicate that killer whales undergo periods of multiple estrous cycling (polyestrus), interspersed with periods of noncycling. On average, females may have four estrous cycles during one polyestrus period. This period is highly variable, as is the period of noncycling, both for one whale over time, and between whales.