Sperm whales, which are the largest of the toothed whales. and the largest toothed predators. They feed mostly on medium-sized squid, but also giant squid, colossal squid, octopuses, and fish such as demersal rays and sharks. Encounters between sperm whales and giant squid or colossal squid have never been observed by humans, however many sperm whales have scars which are believed to have been caused by such squids.