It’s not unusual for parents and especially mothers to sacrifice their own future success for the sake of their offspring. Now a new study shows that killer whale mothers take this to a surprising extreme. They sacrifice their own reproductive success to care for their sons, even after those sons are full-fledged adults.It’s not unusual for parents and especially mothers to sacrifice their own future success for the sake of their offspring. Now a new study shows that killer whale mothers take this to a surprising extreme. They sacrifice their own reproductive success to care for their sons, even after those sons are full-fledged adults.