Yes, whales eat crabs. However, crabs do not form an exclusive part of their diet. The truth is whales consume a variety of sea creatures, including small schooling fishes, squid, other whale species, smaller shark species, as well as crabs. Some whales prefer consuming different types of plankton, mainly krill.

Blue whales are mammals that exist even today, whereas megalodons are shark species that went extinct around 3 to 4 million years ago. Megalodons were deadly animals who hunted indiscriminately and had a sharp, biting force to match up to their fierceness. On the other hand, blue whales are quite friendly and prefer feeding on krill. 

Orcas are dangerous since they are wild creatures who move around swiftly and hunt actively for food. However, they are relatively less dangerous to humans since they are not trained to view them as a source of food. They only attack humans out of curiosity or if they feel threatened. On the other hand, they actively hunt down other marine creatures. 

On average, whales can survive in the wild for 20 to 70 years or more. However, given the right circumstances, they may live up to 100 years. Several factors like the climate, living conditions, space, and diet affect the lifespan of a whale. Whales also need proper and regular nourishment and sufficient moving space. 

Whales do eat jellyfish, although it is not an essential part of their diet. Some whales eat quite indiscriminately and attack everything that comes their way in the ocean. As a result, jellyfishes often come under attack, but they are 95% water and do not carry any essential nutrients needed by the whale for sustenance.

Whales eat penguins, but only a few of them. Most whale species do not prey on penguins and prefer feeding on krill, fish, shrimp, crabs, and the like. Penguins are eaten by toothed whales such as killer whales and, to a certain extent, sperm whales. However, killer whales are their most fierce predators.

Whales do have ears. But, even though they have external auditory canals, their functionality is questionable, just as it is in the case of all cetaceans. It is believed that whales have an especially designed sound system that helps them hear sound underwater. As such, they can easily hear sounds underwater and also communicate with ease.

Whales sleep for about 30 minutes at a stretch. Some whale species sleep for no more than 10 to 15 minutes at one go. This is because sleeping for longer durations will lower the body temperatures of whales, which can be detrimental to their being. Moreover, whales need to keep swimming to breathe or to escape predators.