Are sea otters the only tool using mammal?

Sea otters are indeed well-known for their tool use, including cracking open shellfish with rocks or pounding shellfish open on their chest with small smooth pebbles. However, they are definitely not the only tool using mammals. Various primate species, such as chimpanzees, use sticks as tools for obtaining termites or ants. Dolphins show some level of tool use by attaching sponges to their noses to protect them while foraging in rocky crevices. Other marine mammals show similar examples of tool use, making sea otters one of several tool using mammals, rather than the only one.