Clements, Peter Roy: Orca World

If humans were to go extinct, what would follow? Orcas are the ocean's top predator and as the land is essentially empty, they evolve to come on land. Many orcas believe they are the first sentient species on the land but one astute orca has other ideas. He has exceptional sonar abilities and can see the outline of a bunker left by the last human on earth. What will he find there? How will those who believe they were first handle this new information?