Orcas were spotted using kelp as a grooming tool on each other, the first known use of tools among cetaceans for something other than hunting prey.

The more we learn about orcas, the more remarkable they are. These giant dolphins are the ocean's true apex predator, preying on great white sharks and other lesser predators.

Over the years, orcas have been seen partaking in some peculiar practices, from sinking sailboats to wearing salmon "hats." Now, the apex predators have been observed engaging in a "remarkable" new behavior: fashioning tools from underwater plants to massage one another.