Blue whales are not skilled at protecting themselves and rely primarily on their large size, as they do not have many predators in the ocean. The blue whale will grow anywhere between 70 to 100 feet in length and weigh anywhere from 100 to 200 tons.
The blue whale is considered to be the "largest creature ever to have lived on Earth" reports the OneKind organization. This extreme size makes it possible for the blue whale to avoid most predators simply because predators are unable to successfully attack, kill and then eat the mammal. The blue whale does have predators, however, and both killer whales and sharks will sometimes attack the whale though both species also hunt smaller animals. Blue whales are also often killed in boating accidents with large ships.
The blue whale is currently listed on the ICUN red list as endangered due to the hunting that began in the 1900s. The hunters wanted to kill the blue whales in order to get whale oil. It is estimated that there are 10,000 to 25,000 blue whales left in the ocean today. It is difficult for the blue whale to repopulate because female blue whales will only breed once in every 3 years and they only have one baby calf at a time.