Octopuses are not mammals. They are classified as cephalopods, a class of mollusk. Octopuses are invertebrates, meaning that they do not have a backbone; on the other hand, mammals are vertebrates.
Octopuses are known to be very intelligent, and they have been shown to use tools to aid against predators. Octopuses change their appearance to camouflage themselves from predators. In addition to camouflage, octopuses also have ink that they shoot at would-be attackers to blind them and potentially escape. If octopuses are attacked, they can lose limbs and regrow them with no permanent damage. They have also been observed solving puzzles, and they remember paths through mazes to get to food.