With a few exceptions, the primary threat to sperm whales, directed hunts, has all but ceased. However, lingering effects of these massive removals may still remain. The selective removal of large males may have depressed pregnancy rates, particualrly in the Pacific. While the removal of females may have resulted in the loss of socio-ecological knowledge as has been shown by the removal of older females in elephants, a terrestrial mammal with very similar social-structure and ecological success.