According to the search results, the average lifespan of a blue whale is estimated to be around 80 to 90 years. Scientists can estimate the age of whales by counting the layers of wax-like earplugs collected from deceased animals. The oldest blue whale determined using this method was 110 years old. The maximum age of a pygmy blue whale determined this way is 73 years. Blue whales generally reach sexual maturity at 8-15 years old, depending on their location. In the Northern Hemisphere, the length at which they reach maturity is 21-23 meters (69-75 ft) for females and 20-21 meters (66-69 ft) for males. In the Southern Hemisphere, the length of maturity is 22-24 meters (72-79 ft) for females and 22 meters (72 ft) for males.