A callosity, like a callus, is a patch of thick skin. So what makes callosities interesting? For starters only the three species of Right Whales - North Atlantic, North Pacific and Southern Right Whales - have callosities. They are found on the whale's head and form a unique pattern on each one making Right Whales easy to identify. What's more, these seemingly white patches are actually gray and not nearly as rough as they look. The cyamids, nicknamed whale lice, that live on Right Whale's skin make callosities look white and more bristly than they actually are.