The article explains why orcas are fearful of sperm whales. It discusses how orcas are often seen as the apex predators of the ocean due to their hunting skills. However, sperm whales possess the ability to dive deeper and for longer periods, giving them an advantage over orcas. Sperm whales are known to fiercely defend themselves and have been known to attack orcas with their powerful jaws, causing significant injuries. This fear and respect for sperm whales make orcas wary of confrontation with them.