The Giant Pacific octopus is the largest species of octopus and has been known to reach sizes of 20-28 feet across and can weigh more than 100 pounds. The average arms span of an adult Giant octopus is about 15 feet. Like other species of octopus, the Giant octopus can secrete an ink screen to deter a predator and can inflict a venomous bite. They can change colors instantly, which is believed to communicate emotion.